Fumigant pumped into tented houses to kill pests remains in atmosphere six to 10 times longer than previously thought, Scripps-led study shows


Tent fumigation

Sulfuryl fluoride (SO₂F₂), a gas commonly used to rid buildings of termites and other pests, is a greenhouse gas that remains in the atmosphere about 36 years, six to 10 times longer than previously thought, according to a research team led by Jens Mühle, an atmospheric chemist at Scripps Institution of Oceanography, UC San Diego.

The team found that the concentration of the gas rose at a rate of 4 to 6 percent per year between 1978 and 2007, to a global atmospheric abundance by the end of 2007 of about 1.5 parts per trillion. Its actual emissions into the atmosphere over this period were about one third less than estimated from industrial production data.

"It's extremely important to have independent verification of emissions," said Mühle. "You can't have regulation without verification, and you can't have verification without measurements."


Scripps atmospheric chemist Jens Mühle

The team will report the results of the first-ever measurements of SO₂F₂ in the Journal of Geophysical Research on March 12.

Mühle said he started detecting an unknown compound in air samples taken in early 2004 at the Scripps pier with a newly developed measurement instrument. He identified the compound as SO₂F₂ and concluded that the large fluctuations seen at the pier were likely related to the fumigation of local buildings. The team expanded the analysis to air samples routinely collected around the world at stations of the NASA-funded Advanced Global Atmospheric Gases Experiment (AGAGE) network and to old air samples archived in metal cylinders.

With the help of atmospheric computer models, the Scripps team and colleagues at the Massachusetts Institute of Technology (MIT) determined that the most important removal process of sulfuryl fluoride is dissolution into the ocean, where it is decomposed by chemical reactions. NOAA researchers working with the Scripps team calculated that one kilogram of SO₂F₂ emitted into the atmosphere has a global warming potential approximately 4,800 times greater than one kilogram of carbon dioxide. However, amounts of sulfuryl fluoride released into the atmosphere (about 2,000 metric tons per year) are far lower than those of carbon dioxide (about 30 billion metric tons per year) and thus the absolute effect of present SO₂F₂ emissions on global warming is comparably small.

Widespread use of sulfuryl fluoride began in the 1990s following the Montreal Protocol, an international treaty ratified in 1987 to protect the ozone layer by reducing the production of ozone-depleting chemicals. The protocol ordered the gradual discontinuation of methyl bromide, which has strong ozone-depleting characteristics, and sulfuryl fluoride became a preferred replacement for structural fumigation. Sulfuryl fluoride is regulated as a toxic substance but not currently as a greenhouse gas.

"Such fumigants are very important for controlling pests in the agricultural and building sectors," said Ron Prinn, director of MIT's Center for Global Change Science and a co-author on the new paper. But with methyl bromide being phased out, "industry had to find alternatives, so sulfuryl fluoride has evolved to fill the role."


The Medusa gas chromatograph/mass spectrometer is used to analyze amounts of gases in air. Mühle used the device to track amounts of the fumigant sulfuryl fluoride in the atmosphere.

"Unfortunately, it turns out that sulfuryl fluoride is a greenhouse gas with a longer lifetime than previously assumed," added Mühle. "This has to be taken into account before large amounts are emitted into the atmosphere."

Mühle credited the assistance of the chief manufacturer of sulfuryl fluoride in the United States, Dow AgroSciences, in the study.

"They've been very cooperative in sharing with us their estimates of global industrial sulfuryl fluoride production," he said.

The team's report follows closely on the announcement of a similar finding about the greater-than-expected prevalence of nitrogen trifluoride, a gas used as a cleaning agent during the manufacture of thin-film solar cells, flat panel monitors and other electronics. The first measurements of nitrogen trifluoride, reported in October, has led to calls for it to be included in the list of greenhouse gases whose emissions are regulated by international treaties. Similar discussions are underway for sulfuryl fluoride. Scripps geochemistry professor Ray Weiss and Scripps researchers Peter Salameh and Christina Harth contributed to the nitrogen trifluoride finding as well as the sulfuryl fluoride research.

Researchers from the Massachusetts Institute of Technology, the University of Bristol in the United Kingdom, and the Centre for Australian Weather and Climate Research are co-authors of the sulfuryl fluoride paper.

M.I.T. joins climate realists, doubles its projection of global warming by 2100 to 5.1°C

The Massachusetts Institute of Technology Joint Program on the Science and Policy of Climate Change has joined the climate realists. The realists are the growing group of scientists who understand that the business as usual emissions path leads to unmitigated catastrophe (see, for instance, “Hadley Center: “Catastrophic” 5-7°C warming by 2100 on current emissions path” and below).
http://climateprogress.org/2008/12/21/h ... strophic-5°c-warming-by-2100-on-current-emissions-path/

The Program issued a remarkable, though little-remarked-on, report in January, “Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters,” by over a dozen leading experts.
http://globalchange.mit.edu/pubs/abstra ... ion_id=990
They reanalyzed their model’s 2003 projections model using the latest data, and concluded:

The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model’s first projections were published in 2003 substantial improvements have been made to the model and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections, e.g., the median surface warming in 2091 to 2100 is 5.1°C compared to 2.4°C in the earlier study.

Their median projection for the atmospheric concentration of carbon dioxide in 2095 is a jaw-dropping 866 ppm.


Projected decadal mean concentrations of CO2. Red solid lines are median, 5% and 95% percentiles for present study: dashed blue line the same from their 2003 projection.

Why the change? The Program’s website explains:
http://globalchange.mit.edu/resources/g ... rison.html

There is no single revision that is responsible for this change. In our more recent global model simulatations, the ocean heat-uptake is slower than previously estimated, the ocean uptake of carbon is weaker, feedbacks from the land system as temperature rises are stronger, cumulative emissions of greenhouse gases over the century are higher, and offsetting cooling from aerosol emissions is lower. No one of these effects is very strong on its own, and even adding each separately together would not fully explain the higher temperatures. Rather than interacting additively, these different affects appear to interact multiplicatively, with feedbacks among the contributing factors, leading to the surprisingly large increase in the chance of much higher temperatures.

The carbon sinks are saturating, and the amplifying feedbacks are worse than previously thought — that, of course, is a central understanding of all climate realists (see Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius” for links to the various feedbacks that have been ignored by most climate models).
Andrew Freedman at washingtonpost.com has one of the very few stories on this important study and reprints this useful figure from MIT:


He explains:

Results of the studies are depicted online in MIT’s “Greenhouse Gamble” exercise that conveys the “range of probability of potential global warming” via roulette wheel graphics (shown above). The modeling output showed that under both a “no policy” scenario and one in which nations took action beginning in the next few years to reduce greenhouse gas emissions, the odds have shifted in favor of larger temperature increases.

For the no policy scenario, the researchers concluded that there is now a nine percent chance (about one in 11 odds) that the global average surface temperature would increase by more than 7°C (12.6°F) by the end of this century, compared with only a less than one percent chance (one in 100 odds) that warming would be limited to below 3°C (5.4°F).

To repeat, on our current emissions path, we have a 9% chance of an incomprehensibly catastrophic warming of 7°C by century’s end, but less than a 1% chance of under 3°C warming.

“The take home message from the new greenhouse gamble wheels is that if we do little or nothing about lowering greenhouse gas emissions that the dangers are much greater than we thought three or four years ago,” said Ronald G. Prinn, professor of atmospheric chemistry at MIT. “It is making the impetus for serious policy much more urgent than we previously thought.”

The time to act is now.

Sea levels are predicted to rise twice as fast as was forecast by the United Nations only two years ago, threatening hundreds of millions of people with catastrophe, scientists said yesterday in a dramatic new warning about climate change. Rapidly melting ice sheets in Greenland and Antarctica are likely to push up sea levels by a metre or more by 2100, swamping coastal cities and obliterating the living space of 600 million people who live in deltas, low-lying areas and small island states.


Low-lying countries with increasing populations, such as Bangladesh, Burma and Egypt, could see large parts of their surface areas vanish. Experts in Bangladesh estimate that a one-metre rise in sea levels would swamp 17 per cent of the country's land mass. Pacific islands such as Tuvalu, where 12,000 people live just a few feet above sea level, and the Maldives, would face complete obliteration.

Even Britain could face real challenges in lower-lying areas along the east coast, from Lincolnshire to the Thames estuary, with a much greater risk of catastrophic "storm surges" such as the great flood of 1953 that killed 307 people.

Yesterday's urgent wake-up call to governments about global warming – telling them the data on which they are basing their official advice is flawed – came from four scientists from the US, Australia, France and Germany, who gave a press conference at a scientific meeting on climate change in Copenhagen, Denmark.

Professor Konrad Steffen, from the University of Colorado, Dr John Church, of the Centre for Australian Weather and Climate Research in Tasmania, Dr Eric Rignot, of Nasa's jet propulsion laboratory in Pasadena, and Professor Stefan Rahmsdorf, from the Potsdam Institute for Climate Impact Research, are all experts in sea-level rise. Their views represent the mainstream opinion of researchers in the field, taking account of the most recent data.

Only two years ago, the UN's Intergovermental Panel on Climate Change (IPCC) said in its Fourth Assessment Report, or AR4, that the worst-case prediction for global sea-level rise was 59cm by 2100. But the scientists in Copenhagen suggested that the 2007 report was a drastic underestimation of the problem, and that oceans were likely to rise twice as fast.

Yesterday's meeting was a scientific overture to the global conference on climate change, which takes place in the Danish capital in December. The four researchers underlined how critical it is that world leaders act to slash the emission of carbon dioxide and other greenhouse gases from industry and transport which are causing the atmosphere to overheat.

Advance negotiations begin in three weeks in Bonn. On pages 20 and 21, we illustrate in detail just how great the task is, profiling the main emitters of CO2 and what they are doing – or not doing – to cut back. Yesterday's alarm call was clearly intended to inject more urgency into the process.

Rising sea levels are caused by the thermal expansion of the ocean – where water increases in volume as it warms. But although the melting of ice already floating in the sea does not add to the level, because it is already displacing its own mass, melting into the sea of land-based ice most definitely does.

It is the accelerated melting of the vast, land-based ice sheets in Greenland and Antarctica, caused by rapidly rising temperatures at high latitudes, which is now speeding up the increase beyond anything previously forecast. The Greenland ice sheet, in particular, is not simply melting but melting "dynamically" – that is, it is collapsing in parts as meltwater seeps down through crevices and speeds up its disintegration. Critically, the four scientists said, this process was not taken into account in the AR4 report, leading to estimates of sea-level increase which were far too low.

They revealed remarkable figures showing just how fast it is now happening. Professor Steffen said Greenland was losing 200 to 300 cubic-kilometres of ice into the sea each year – about the same amount as all the ice in Arctic Europe. This on its own is causing the global sea level to rise by more than a millimetre a year, he added, whereas a decade ago Greenland's contribution to sea level rise was non-existent.

Dr Church said that the most recent satellite and in situ data showed seas were now rising by more than 3mm a year – more than 50 per cent faster than the average for the 20th century.

"As a result of improved estimates of the observed rise, the thermal expansion, the melting of the glaciers and of the ice sheets, we now have a much better quantitive understanding of why sea level is rising," he said. "Without significant, urgent and sustained emissions reductions, we will cross a threshold which will lead to continuing sea level rise of metres."

Professor Steffen added: "What we have learnt in the past three or four years is that the ice dynamic is much stronger than the models indicated, and the prediction has to be revised up to a metre or more – which is enormous if you look at the impact."

Britain's Environment Agency was apparently unique when it discarded the IPCC's 2007 advice as flawed. Based on its own estimates, it is planning flood defences for 2100 on the basis of a one-metre rise in sea levels – with a "worst-case scenario" of 2.7 metres.

"These startling new predictions spell disaster for millions of the world's poorest people," said Rob Bailey, Oxfam's policy adviser on climate change. "Poor coastal communities in countries such as Bangladesh are already struggling to cope with a changing climate, and it can only get worse. This must be a wake-up call for rich countries who are not doing anywhere near enough to prevent these cataclysmic predictions from becoming a reality."

March 13, 2009
World leaders told to act on climate before it's too late


(Erik Malm/PA)

Recent observations of climatic trends showed that the worst-case trajectories highlighted by the Intergovernmental Panel on Climate Change in 2007 were being followed or exceeded on a range of measurements
Lewis Smith, Environment Reporter, in Copenhagen

Full text of the statement from the International Scientific Conference on Climate Change
http://climatecongress.ku.dk/newsroom/c ... _messages/

The world is on the brink of dangerous climate change and immediate action is needed to avert it, scientists said yesterday, issuing one of the bleakest assessments yet of the state of the planet.

A strongly worded communiqué marking the end of a specially convened conference in Copenhagen concluded that climate change and its impacts match or exceed the worst fears expressed by the Nobel prize-winning Intergovernmental Panel on Climate Change two years ago.

The statement, issued on behalf of 2,500 scientists from 80 countries, will be passed to world leaders in the coming months. Their summary of what global warming is doing to the planet warned policymakers: “There is no excuse for inaction.”

The demands and alerts contained in the statement were described as a defining moment in scientists’ relations with political leaders, represening a shift away from their traditional role of merely offering advice to telling politicians to act.

Professor Katherine Richardson, of the University of Copenhagen, who organised the conference, said: “We need the politicians to realise what a risk they are taking on behalf of their constituents, the world and, even more importantly, future generations.

“All of the signals from the Earth system and the climate system show us that we are on a path that will have enormous and unacceptable consequences.”

Findings from this week’s conference, designed to identify changes in scientific understanding of climate change, will be presented to world leaders and policymakers who will converge on the Danish capital in December to try to agree an international deal on bringing greenhouse gas emissions under control.

Recent observations of climatic trends, the new statement said, showed that the worst-case trajectories highlighted by the Intergovernmental Panel on Climate Change in 2007 were being followed or exceeded on a range of measurements.

“There is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts,” it said.

Scientists called for rapid, sustained and effective mitigation programmes to bring down greenhouse gas emissions.

They were particularly concerned that any significant delay in reducing emissions would lead to a range of tipping points being reached that would make it significantly more difficult to reduce greenhouse gas levels.

There was also a warning for politicians involved in negotiations over targets designed to reduce emissions. It was an implicit rebuff to Silvio Berlusconi and other European leaders who attempted last year to reduce the EU commitment to cutting emissions.

Despite the gloom, the scientists said that the tools to beat climate change already existed and if vigorously and widely implemented they would enable governments to bring about low-carbon economies across the world.

Sea Level Rise Due to Global Warming Poses Threat to New York City
March 13th, 2009 in Space & Earth / Earth Sciences



(PhysOrg.com) -- Global warming is expected to cause the sea level along the northeastern U.S. coast to rise almost twice as fast as global sea levels during this century, putting New York City at greater risk for damage from hurricanes and winter storm surge, according to a new study led by a Florida State University researcher.

Jianjun Yin, a climate modeler at the Center for Ocean-Atmospheric Prediction Studies (COAPS) at Florida State, said there is a better than 90 percent chance that the sea level rise along this heavily populated coast will exceed the mean global sea level rise by the year 2100. The rising waters in this region -- perhaps by as much as 18 inches or more -- can be attributed to thermal expansion and the slowing of the North Atlantic Ocean circulation because of warmer ocean surface temperatures.

Yin and colleagues Michael Schlesinger of the University of Illinois at Urbana-Champaign and Ronald Stouffer of Geophysical Fluid Dynamics Laboratory at Princeton University are the first to reach that conclusion after analyzing data from 10 state-of-the-art climate models, which have been used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. Yin’s study, “Model Projections of Rapid Sea Level Rise on the Northeast Coast of the United States,” will be published online March 15 in the journal Nature Geoscience.

“The northeast coast of the United States is among the most vulnerable regions to future changes in sea level and ocean circulation, especially when considering its population density and the potential socioeconomic consequences of such changes,” Yin said. “The most populous states and cities of the United States and centers of economy, politics, culture and education are located along that coast.”

The researchers found that the rapid sea-level rise occurred in all climate models whether they depicted low, medium or high rates of greenhouse-gas emissions. In a

medium greenhouse-gas emission scenario, the New York City coastal area would see an additional rise of about 8.3 inches above the mean sea level rise that is expected around the globe because of human-induced climate change.

Thermal expansion and the melting of land ice, such as the Greenland ice sheet, are expected to cause the global sea-level rise. The researchers projected the global sea-level rise of 10.2 inches based on thermal expansion alone. The contribution from the land ice melting was not assessed in this study due to uncertainty.

Considering that much of the metropolitan region of New York City is less than 16 feet above the mean sea level, with some parts of lower Manhattan only about 5 feet above the mean sea level, a rise of 8.3 inches in addition to the global mean rise would pose a threat to this region, especially if a hurricane or winter storm surge occurs, Yin said.

Potential flooding is just one example of coastal hazards associated with sea-level rise, Yin said, but there are other concerns as well. The submersion of low-lying land, erosion of beaches, conversion of wetlands to open water and increase in the salinity of estuaries all can affect ecosystems and damage existing coastal development.

Although low-lying Florida and Western Europe are often considered the most vulnerable to sea level changes, the northeast U.S. coast is particularly vulnerable because the Atlantic meridional overturning circulation (AMOC) is susceptible to global warming. The AMOC is the giant circulation in the Atlantic with warm and salty seawater flowing northward in the upper ocean and cold seawater flowing southward at depth. Global warming could cause an ocean surface warming and freshening in the high-latitude North Atlantic, preventing the sinking of the surface water, which would slow the AMOC.

Provided by Florida State University

Mighty Diatoms: Global Climate Feedback From Microscopic Algae



Diatoms in a variety of shapes. (Credit: iStockphoto/Nancy Nehring)

ScienceDaily (Mar. 17, 2009) — Tiny creatures at the bottom of the food chain called diatoms suck up nearly a quarter of the atmosphere’s carbon dioxide, yet research by Michigan State University scientists suggests they could become less able to “sequester” that greenhouse gas as the climate warms. The microscopic algae are a major component of plankton living in puddles, lakes and oceans.

Zoology professor Elena Litchman, with MSU colleague Christopher Klausmeier and Kohei Yoshiyama of the University of Tokyo, explored how nutrient limitation affects the evolution of the size of diatoms in different environments. Their findings underscore potential consequences for aquatic food webs and climate shifts.

“They are globally important since they ‘fix’ a significant amount of carbon,” Litchman explained of the single-cell diatoms. “When they die in the ocean, they sink to the bottom carrying the carbon from the atmosphere with them. They perform a tremendous service to the environment.”

Carbon dioxide buildup, due to a significant extent to burning fossil fuels and deforestation, is identified as the leading cause of climate change. Carbon dioxide is at its highest level in at least 650,000 years and rising, according to The National Academies, and only half of the CO2 produced now can be absorbed by plant life.

Litchman analyzed data from lakes and oceans across the United States, Europe and Asia and found a striking difference between the size of diatoms in freshwater and in marine environments. In oceans, diatoms grow to be 10 times larger on average than in freshwater and have a wider range of sizes.

One factor that affects growth is nutrient availability, Litchman said. The research shows that limitations by nitrogen and phosphorus exert different selective pressures on cell size. The availability of these nutrients depends on the mixing of water from greater depths. Using a mathematical model, Litchman and her colleagues found that when those nutrients are constantly limited and mixing is shallow, smaller diatoms thrive.

But when nitrate comes and goes, as often happens in roiling oceans, diatoms evolve larger to store nutrients for lean times. Deep mixing also benefits large diatoms. Depending on how intermittent the nitrate supply is and how deep the ocean mixes, there can be a wide range of diatom sizes. Size matters for the creatures that eat them and also for carbon sequestration, as large diatoms are more likely to sink when they die.

Changing climate could alter the mixing depths and delivery of nutrients to diatoms and their subsequent sizes with a cascade of consequences, Litchman said.

“On a global scale, increased ocean temperatures could make the ocean more stratified,” she explained. “This would cause less mixing and create stronger nutrient limitation and less frequent nutrient pulses. A change like this would select for different sizes of diatoms. If smaller sized diatoms dominate, then carbon sequestration becomes less efficient and there may be more CO2 remaining in the atmosphere, which would exacerbate global warming.”

Litchman and colleagues’ research was supported by the National Science Foundation and the J.S. McDonnell Foundation. Their findings were published Feb. 24 in the Proceedings of the National Academy of Sciences.

Climate Warming Affects Antarctic Ice Sheet Stability


An ANDRILL sediment core. (Credit: Peter West/NSF)

ScienceDaily (Mar. 22, 2009) — A five-nation scientific team has published new evidence that even a slight rise in atmospheric concentrations of carbon dioxide, one of the gases that drives global warming, affects the stability of the West Antarctic Ice Sheet (WAIS). The massive WAIS covers the continent on the Pacific side of the Transantarctic Mountains. Any substantial melting of the ice sheet would cause a rise in global sea levels.

The research, which was published in the March 19 issue of the journal Nature, is based on investigations by a 56-member team of scientists conducted on a 1,280-meter (4,100-foot)-long sedimentary rock core taken from beneath the sea floor under Antarctica's Ross Ice Shelf during the first project of the ANDRILL (ANtarctic geological DRILLing) research program--the McMurdo Ice Shelf (MIS) Project.

"The sedimentary record from the ANDRILL project provides scientists with an important analogue that can be used to help predict how ice shelves and the massive WAIS will respond to future global warming over the next few centuries," said Ross Powell, a professor of geology at Northern Illinois University.

"The sedimentary record indicates that under global warming conditions that were similar to those projected to occur over the next century, protective ice shelves could shrink or even disappear and the WAIS would become vulnerable to melting," Powell said. "If the current warm period persists, the ice sheet could diminish substantially or even disappear over time. This would result in a potentially significant rise in sea levels."

ANDRILL--which involves scientists from the United States, New Zealand, Italy and Germany--refines previous findings about the relationship between atmospheric carbon dioxide concentration, atmospheric and oceanic temperatures, sea level rise and natural cycles in Earth's orbit around the Sun, through the study of sediment and rock cores that are a geological archive of past climate.

The dynamics of ice sheets, including WAIS, are not well understood, and improving scientists' comprehension of the mechanisms that control the growth, melting and movements of ice sheets was one of NSF's research priorities during the International Polar Year (IPY). The IPY field campaign, which officially ended March 2009, has been an intense scientific campaign to explore new frontiers in polar science, improve our understanding of the critical role of the polar regions in global processes, and educate students, teachers, and the public about the polar regions and their importance to the global system. NSF was the lead agency for U.S. IPY efforts.

The cores retrieved by ANDRILL researchers have allowed them to peer back in time to the Pliocene era, roughly 2 million to 5 million years ago. During that era, the Antarctic was in a natural climate state that was warmer than today and atmospheric carbon dioxide levels were higher. Data from the cores indicate the WAIS advanced and retreated numerous times in response to forcing driven by these climate cycles.

Powell and Tim Naish, director of Victoria University of Wellington's Antarctic Research Centre, served as co-chief scientists of the 2006-2007 ANDRILL project that retrieved the data and are lead authors in one of two companion studies published in Nature.

Naish said the new information gleaned from the core shows that changes in the tilt of Earth's rotational axis has played a major role in ocean warming that has driven repeated cycles of growth and retreat of the WAIS for the period in Earth's history between 3 million and 5 million years ago.

"It also appears that when atmospheric carbon dioxide concentrations reached 400 parts per million around four million years ago, the associated global warming amplified the effect of the Earth's axial tilt on the stability of the ice sheet," he said.

"Carbon dioxide concentration in the atmosphere is again approaching 400 parts per million," Naish said. "Geological archives, such as the ANDRILL core, highlight the risk that a significant body of permanent Antarctic ice could be lost within the next century as Earth's climate continues to warm. Based on ANDRILL data combined with computer models of ice sheet behavior, collapse of the entire WAIS is likely to occur on the order of 1,000 years, but recent studies show that melting has already begun."

The second ANDRILL study in Nature--led by David Pollard of Pennsylvania State University and Rob DeConto from University of Massachusetts--reports results from a computer model of the ice sheets. The model shows that each time the WAIS collapsed, some of the margins of the East Antarctic Ice Sheet also melted, and the combined effect was a global sea level rise of 7 meters above present-day levels.

Whether the beginnings of such a collapse could start 100 years from now or within the next millennium is hard to predict and depends on future atmospheric CO2 levels, the researchers said. However, the new information from ANDRILL contributes a missing piece of the puzzle as scientists try to refine their predictions of the effects of global warming.

The most recent report of the Intergovernmental Panel on Climate Change (IPCC) noted that because so little is understood about ice sheet behavior it is difficult to predict how ice sheets will contribute to sea level rise in a warming world. The behavior of ice sheets, the IPCC report said, is one of the major uncertainties in predicting exactly how the warming of the globe will affect human populations.

"From these combined data modeling studies, we can say that past warming events caused West Antarctic ice shelves and ice grounded below sea level to melt and disappear. The modeling suggests these collapses took one to a few thousand years," Pollard said.

Pollard and DeConto also underscored the role of ocean temperatures in melting of the ice.

"It's clear from our combined research using geological data and modeling that ocean temperatures play a key role," DeConto said. "The most substantial melting of protective ice shelves comes from beneath the ice, where it is in contact with seawater. We now need more data to determine what is happening to the underside of contemporary ice shelves."

The National Science Foundation (NSF), which manages the U.S. Antarctic Program (USAP), provided about $20 million in support of the ANDRILL program. The other ANDRILL national partners contributed an additional $10 million in science and logistics support.

The ANDRILL Science Management Office, located at the University of Nebraska-Lincoln, supports science planning and the activities of the international ANDRILL Science Committee (ASC). Antarctica New Zealand is the ANDRILL project operator and has developed the drilling system in collaboration with Alex Pyne at Victoria University of Wellington and Webster Drilling and Exploration.

The U.S. Antarctic Program and Raytheon Polar Services Corporation (RPSC) supported the science team at McMurdo Station and in the Crary Science and Engineering Laboratory, while Antarctica New Zealand supported the drilling team at Scott Base.

ANDRILL scientific studies are jointly supported by: the U.S. National Science Foundation, the New Zealand Foundation for Research, the Italian Antarctic Research Program, the German Science Foundation and the Alfred Wegener Institute.

Adapted from materials provided by National Science Foundation.

Carbon Sinks Losing The Battle With Rising Emissions


Findings on the exchange of heat and CO2 between the atmosphere and deep ocean are being discussed in Copenhagen. (Credit: CSIRO)

ScienceDaily (Mar. 21, 2009) — The stabilising influence that land and ocean carbon sinks have on rising carbon emissions is gradually weakening, say scientists attending last week’s international Copenhagen Climate Change Conference.

“Forests, grasslands and oceans are absorbing carbon dioxide (CO2) from the atmosphere faster than ever but they are not keeping pace with rapidly rising emissions,” says CSIRO scientist and co-chair of the Global Carbon Project, Dr Mike Raupach.

“While these natural CO2 sinks are a huge buffer against climate change, which would occur about twice as fast without them, they cannot be taken for granted.”

Dr Raupach and Swiss scientist, Dr Nicolas Gruber, co-chaired one of 43 sessions at the conference – Climate Change, Vulnerability of Carbon Sinks.

Dr Raupach says concern about the vulnerability of carbon sinks is based on identifying several mechanisms that could cause the present stabilising role of oceans and land to be weakened or even reversed.

“Such a change would have drastic consequences for the predicted magnitude or speed of climate change occurring and scientists will meet in Copenhagen to review and question the latest research from which advice can ultimately be provided to decision-makers.”

Discussions will focus on:

* Changes in the carbon sink on land through shifts in atmospheric composition, temperature and rainfall changes, deforestation, fire frequency and insect attacks, all of which can slow or reverse sinks or initiate sources of CO2 to the atmosphere.
* Release of carbon presently locked in frozen soil, as both CO2 and methane (a more potent greenhouse gas than CO2).
* Shifts in large-scale agricultural production of food and fibre, potentially speeding up land clearing and tropical deforestation. This process currently contributes 15-20 per cent of anthropogenic carbon emissions.

Findings on the exchange of heat and CO2 between the atmosphere and deep ocean, which suggest that climate change is effectively irreversible in less than 1000 years.

Australian science is represented at the conference in sessions on; sea ice, sea level rise, ocean circulation, atmosphere and ocean tipping points, carbon sequestration, carbon capture and storage, changing the way we live and adapting future agricultural production.

Pancake ice takes over the Arctic

Researchers work to put changing ice types into climate models.
Nicola Jones


Pancake iceMore pancake ice is being spotted in the Arctic.Glenn Grant/National Science Foundation

Climate change is not only making Arctic sea ice disappear — it's also changing the type of ice that forms. Researchers are now trying to determine how an increase in 'pancake ice' is affecting the far north, including whether it's accelerating local warming.

In the past, Arctic waters have been dominated by thick slabs of sea ice that last from one year to the next. But sea-ice cover is diminishing and thick ice that lasts for several years is disappearing fast, with researchers seeing a greater proportion of thin, newly formed ice.

New ice can form in several different ways. When water is surrounded by ice packs, as has been common in the Arctic, areas of open water are small and there is little chance for wind to work up vigorous waves. In such calm conditions, ice forms in unbroken sheets called 'nilas'.

But now the Arctic has larger areas of open water, and more waves. "As soon as you introduce swell, you get an entirely different form of ice," says Jeremy Wilkinson of the Scottish Association for Marine Science in Oban, UK. Under these conditions, globs of ice crystals tossed about in the water combine to form first a soupy mixture called 'grease ice', and then 'pancakes' of thin ice a metre or two in diameter.

This can have all sorts of knock-on effects. Because the pancakes are round, for example, they have areas of open water between them when joined up, making the surface darker overall. This could have a warming effect as a result of less of the Sun's radiation being reflected. Water also slops up from these holes over the ice so that falling snow melts rather than settling, keeping the surface darker. "This whole cycle is not in models of the Arctic or the Antarctic. It's one of these conundrums that people haven't looked into," says Wilkinson.
Pancakes in the lab

Wilkinson and his colleagues this month completed a series of controlled experiments to measure the differences between nilas and pancake ice in the lab, including differences in ice thickness, water temperature, salinity and albedo — the fraction of incident sunlight that's reflected. The team used a wave tank 30 metres long and 1.5 metres deep at the Arctic Environmental Test Basin in Hamburg, Germany, to test ice formation in calm conditions compared with choppy water and storms1. The team could not replicate the metre-high waves that might be seen in the ocean, so to mimic stormy conditions they increased the frequency of waves tens of centimetres high.

Their tests confirmed that, as expected, pancake ice dominated when waves were around. Their as-yet unpublished quantitative data, which will take some months yet to analyse, will be incorporated into new climate models being developed by team member Dirk Notz and others at the Max Planck Institute for Meteorology in Hamburg to see how the changing ice type might affect future Arctic temperatures.

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There are effects other than a change in albedo. Ice accumulates on the bottom of a single sheet more slowly than it does around crystals bobbing up and down in the water, so pancake ice 0-15 cm thick can form in the same time as 1 cm thickness of nilas ice. As ice formation extracts fresh water from the ocean, faster ice formation should mean saltier seas, which could in turn have an impact on ocean circulation, ice growth and air temperature.

"Young ice isn't that well studied because there didn't used to be that much of it," says David Barber of the University of Manitoba in Winnipeg, Canada, who led an over-wintering project investigating sea ice conditions in the Arctic that ended last year. He says there is clearly more open water during the winter freeze-up now, causing cyclonic storms that bring wind and snow, and more pancake ice. "We had to take our ship out of the open water because the storms were too rough for us," says Barber. "We couldn't land our helicopters because there was too much snow." He notes that although the extent of the sea ice was greater in 2008 than during the record low of 2007, this was because of additional young ice; the multi-year ice had in fact declined from 2007 levels.

Such rare observations of the winter ice pack along with lab and modelling work should help to determine the likely future of the Arctic. "We're trying to work out what the net result of all these processes are," says Barber.

'Halo effect' explains brightest patches of sky

* 17:40 30 March 2009 by Nora Schultz


Every cloud has a silver lining, the saying goes, but as it turns out, it's more of a giant halo.

It was already known that clear sky up to several kilometres away from clouds appears brighter than cloud-free sky elsewhere. People had assumed that this was due to varying levels of tiny particles in the air – now research shows that the effect is actually mostly due to light reflected off the cloud and bouncing off the particles.

This seemingly innocuous finding could have a surprisingly big knock-on effect because it means there may be fewer cooling particles in the sky than previously thought. And that could change the way we model climate change.

To discover why the air near clouds appears so aglow, Tamas Varnai and Alexander Marshak at the NASA Goddard Space Flight Center in Greenbelt, Maryland, used MODIS satellite observations from a piece of sky above the Atlantic just south-west of the UK.
'Sun shield'

Previous studies had speculated that whilst some of the glare may be due merely to measurement artefacts, it might also be the case that more of the small airborne particles aggregate around clouds or swell in size as they absorb some of the cloud's water.

Because they reflect some sunlight back into space, such aerosol particles are thought to make an important contribution to keeping the planet coolMovie Camera. Spraying particles into the atmosphere has even been considered to build a "sun shield" to combat global warming, although that plan was scrapped due to concerns it could damage the ozone layer.

"Aerosols measure only about a tenth of a micron, which is really, really tiny compared to cloud droplets, which are often roughly 10 microns across," says Marshak.

Because of their small size, the sky appears clear even where aerosol particles abound. To work out the amount of particles suspended in the air, Marshak's team looked at the number of clear sky pixels picked up by MODIS and subtracted the reflection that was estimated to come from the planet's surface and air molecules.

"This leaves us with the remaining reflection bouncing off aerosol particles, and so we can estimate their density," explains Marshak.

Using this idea, it makes sense to assume that where the sky appears brighter, light must be being reflected off more or bigger aerosol particles – unless there is more light in the first place, of course.
Skewed models

In their current analysis, Marshak and Varnai found that the bright sky effect was stronger on the sunlit sides of clouds or when the clouds were denser.

Because more light reflects off a denser or sunlit cloud, this suggests that the clear sky brightness near clouds is caused by extra light reflecting off the clouds sideways and then scattering again between the particles in the clear sky area before reaching the satellite. "It's essentially extra energy bouncing off the clouds that enhances the glow of the clear sky," he says.

This effect – called 3D radiative interaction – had been previously identified as a factor cranking up the sky's brightness, but the new data elevates it to the most important factor. This, in turn, means that many estimates of aerosol density may be plain wrong, because most clear sky analyses are close enough to clouds to be affected by the effect, says Marshak.

"Overestimating aerosol density means that climate models will be wrong if they assume a certain amount of aerosol is needed, when in fact it is less," says Varnai. "Given how much climate modelling relies on satellite data such as this, it is important that we figure out how to interpret it correctly."

Journal reference: Geophysical Research Letters (DOI:10.1029/2008GL037089)

Rising Sea Levels Will Lead To 'Relocation, Relocation, Relocation': Math Could Address Climate Change Population Concerns

ScienceDaily (Apr. 1, 2009) — As sea levels rise in the wake of climate change and semi-arid regions turn to desert, people living in those parts of the world are likely to be displaced. A mathematical approach to planned relocation reported in the International Journal of Mathematics and Operational Research.

Decision scientist Sajjad Zahir at the University of Lethbridge, Alberta, Canada, and colleagues Ruhul Sarker of the University of New South Wales, Canberra, Australia and Ziaul Al-Mahmud of Lethbridge Community Network, have devised a mathematical algorithm to address the problem of population relocation.

The team's multi-objective optimization approach will help governments decide what fraction of a population would need to be relocated and how many people could stay behind for effective adaptation to climate change.

The "multi-objective" nature of the calculation takes into account people's preferences, various costs, and planning priorities with the ultimate aim of ensuring that the issue of relocation is addressed fairly and is economically viable.

Although mitigation measures are vitally important for controlling greenhouse gas emissions, there are limitations to such efforts novel approaches to allow us to adapt successfully to the effects of climate change are now needed, the researchers say. They point out that large-scale cross-border migrations may not be a feasible solution to land loss because of the societal costs and the effects on labor. An influx of environmental refugees from the worst affected parts of the developing world is also likely to face opposition from the developed world, they add.

The team's decision analysis factors in the "value" of new opportunities, lost opportunities, transportation costs, adaptation costs and other variables. This allows them to balance the books in terms of how migration would affect a population.

"To make adaptation a success, part of the population must be prepared to adapt to new or different work opportunities and living conditions and others may have to be relocated in a planned way to new locations that require accepting different working and environmental conditions," the researchers conclude, "Our methodology lets us find the fraction of people who would be relocated and who would stay in an optimal manner."

Journal reference:

1. Sajjad Zahir, Ruhul Sarker, and Ziaul Al-Mahmud. An interactive decision support system for implementing sustainable relocation strategies for adaptation to climate change: a multi-objective optimization approach. Int. J. Mathematics in Operational Research, 2009, 1, 329-350

Natural mechanism for medieval warming discovered

* 19:00 02 April 2009 by Nora Schultz

Europe basked in unusually warm weather in medieval times – so much so that wine was produced in England – but why has been open to debate. Now the natural climate mechanism that caused the mild spell seems to have been pinpointed.

The finding is significant today because, according to Valerie Trouetat the Swiss Federal Institute for Forest, Snow, and Landscape Research in Birmensdorf, the mechanism is not now of sufficient strength to explain current warming.

The finding scuppers one of the favourite arguments of climate-change deniers. If Europe had temperature increases before we started emitting large amounts of greenhouse gases, the theory goes, then maybe the current global warming isn't caused by humans, either.

To work out what the global climate was doing 1000 years ago during the so-called "Medieval Warm Period", Trouet and colleagues started by looking at the annual growth rings of Moroccan Atlas cedar trees and of a stalagmite that grew in a Scottish cave beneath a peat bog. This revealed how dry or wet it has been in those regions over the last 1000 years.

The weather in Scotland is highly influenced by a semi-permanent pressure system called the Icelandic Low, and that in Morocco by another called the Azores High. "So by combining our data, which showed a very wet medieval Scotland and very dry Morocco, we could work out how big the pressure difference between those areas was during that time," says Trouet.
Warm blast

This pressure difference in turn revealed that the medieval period must have experienced a strongly positive North Atlantic Oscillation (NAO) – the ocean current that drives winds from the Atlantic over Europe. The more positive the NAO is, the more warm air is blown towards the continent.

The idea to use growth rings to work out past climate change is not new, but Trouet's team is the first to look back beyond 1400 in the European record. They found that the strongly positive NAO lasted for about 350 years from 1050 to 1400.

By combining their data with information from other regions of the world during medieval times and plugging it into different models, the researchers have also come up with a hypothesis of what made the warm winds so persistent.

"It turns out that in the tropical Pacific, the El Niño system was in a negative La Niña mode, meaning it was colder than normal," says Trouet.
Climate loop

El Niño and the NAO are connected by a process called thermohaline circulation, which drives the "ocean conveyor belt" that shuttles sea water of different density around the world's oceans.

According to Trouet, a Pacific La Niña mode and a positive NAO mode could have reinforced each other in a positive feedback loop – and this could explain the stability of the medieval climate anomaly.

Trouet thinks external forces like abrupt changes in solar output or volcanism must have started and stopped the cycle, and hopes to pinpoint the most likely candidates in a workshop with other climatologists in May.
'Profound implications'

Michael Mann at Pennsylvania State University says that based on the analyses and modelling that he has done, increased solar output and a reduction in volcanoes spouting cooling ash into the atmosphere could have not only kicked off the medieval warming, but might also have maintained it directly.

Mann is also concerned that the dominance of medieval La Niña conditions now indicated by Trouet's work might make it more likely that the current man-made warming could also put the El Niño system back into a La Niña mode, although most climate models so far had predicted the opposite.

"If this happens, then the implications are profound, because regions that are already suffering from increased droughts as a result of climate warming, like western North America, will become even drier if La Niña prevails in the future", he says.

Journal Reference: Science (DOI: 10.1126/science.1166349)

Huge Antarctic Ice Shelf Headed for Collapse
Written by Jake Richardson
Published on April 3rd, 2009



The Wilkins Ice Shelf has been cracking in new places recently and images released by
the European Space Agency show that it will probably very soon break off entirely. A 62 square mile piece broke off in May 2008.

Angelika Humbert of Muenster University stated, “During the last year the ice shelf has lost about 1800 square kilometers (694 square miles), or about 14 percent of its size.” The Wilkins Ice Shelf is currently about the size of Jamaica, though it has already been diminished by about 30 percent. In January the British Antarctic Survey found that an array of very large ice chunks were breaking off and separating from the area. “The cracks in the Wilkins ice shelf and the chunks of ice that are splitting away from the ice-shelf….they’re kind of shopping mall chunks of ice and some are floating off into the ocean.” About 8 other such ice shelves there have been lost. At least one of them had been intact for approximately 10,000 years. In addition to raising ocean levels, recent research has indicated that the loss of Antarctic ice shelves could actually shift the axis of the earth.

The Wilkins shelf is held together by a narrower strip of ice that has been thinning and growing weaker due to melting. Reportedly shaped like an hour glass, with the narrowest portion being the connecting bridge for the larger end pieces, the shelf is now estimated to collapse entirely very soon. The narrower part of the shelf has been estimated at 40 km wide down to 500 meters at the thinnest section. In 1950 the narrow connecting strip was 100 km wide. The disintegration of such enormous masses of ice is thought to be indicative of the power of global warming to cause very disruptive, if not catastrophic change to the natural environment. One measurement that is tied to the loss of the ice shelves is the temperature increase in the area over the last fifty years of 5 degrees Fahrenheit.

Image Credit: National Ice and Snow Data Center

Ice-free Arctic Ocean possible in 30 years, not 90 as previously estimated
April 2nd, 2009



The heavy red line is the sea-ice extent observed since the 1950s. Six models that most accurately depict that ice extent are shown with thin colored lines. The heavy blue line is the average of those six models and projects ice-free Septembers in 20 to 30 years. In contrast, the heavy yellow line is the average sea-ice extent of all 23 models including outliers unable to reproduce current sea-ice conditions. University of Washington/NOAA

The latest data from NASA and the University of Colorado at Boulder's National Snow and Ice Data Center show the continuation of a decade-long trend of shrinking sea ice extent in the Arctic, including new evidence for thinning ice as well.

The researchers, who have been tracking Arctic sea ice cover with satellites since 1979, found that the winter of 2008-09 was the fifth lowest maximum ice extent on record. The six lowest maximum events in the satellite record have all occurred in the past six years, according to CU-Boulder researcher Walt Meier of NSIDC.


Data from NASA satellites show younger, thinner Arctic sea ice is replacing multi-year ice. Credit: James Maslanik, University of Colorado

The new measurements by CU-Boulder's NSIDC show the maximum sea ice extent for 2008-09 reached on Feb. 28 was 5.85 million square miles, which is 278,000 square miles below the average extent for 1979 to 2000, an area slightly larger than the state of Texas, said Meier.

In addition, a team of CU-Boulder researchers led by Research Associate Charles Fowler of the Colorado Center for Astrodynamics Research, or CCAR, has found that younger, thinner ice has replaced older, thicker ice as the dominant type over the past five years, making it more prone to summer melt.

"Ice extent is an important measure of the health of the Arctic, but it only gives us a two dimensional view of the ice cover," said Meier. "Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it becomes more vulnerable to summer melt."

Until recent years, measurements have shown most Arctic ice has survived at least one summer and often several, said Meier. But the balance has now flipped, and seasonal ice -- which melts and re-freezes every year -- now comprises about 70 percent of Arctic sea ice in winter, up from 40 to 50 percent in the 1980s and 1990s, he said. Thicker ice that has survived two or more years now comprises just 10 percent of ice cover, down from 30 to 40 percent in years past.

Scientists believe Arctic sea ice functions like an air conditioner for the global climate system by naturally cooling air and water masses, playing a key role in ocean circulation and reflecting solar radiation back into space.

In a related study led by Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif., researchers have demonstrated a way to estimate ice thickness over the entire Arctic Ocean. Using two years of data from NASA's Ice, Cloud and Land Elevation Satellite, or ICESat, the team made the first basin-wide estimate of the thickness and volume of the Arctic Ocean ice cover for 2005 and 2006.

"With the new data on the area and thickness of Arctic sea ice, we can now better understand the sensitivity and vulnerability of the ice cover to changes in climate," Kwok said.

A recent study by a team from CU-Boulder's CCAR concluded there has been a near complete loss of the oldest, thickest Arctic ice, and that 58 percent of perennial ice was only two to three years old. In the mid-1980s, only 35 percent of that sea ice was that young and that thin, according to aerospace engineering sciences department Research Professor James Maslanik, who led the 2008 study published in Geophysical Research Letters.

"Heading into the 2009 summer melt season, the potential continues for extensive ice retreat due to the trend toward younger, thinner ice that has accelerated in recent years," said Maslanik, also a member of the Cooperative Institute for Research in Environmental Sciences. "A key question will be whether this second year ice is thick enough to survive summer melt," said Maslanik.

"If it does, this might start a trend toward recovery of the perennial sea ice pack," Maslanik said. "If it doesn't, then this would be further evidence of the difficulty of re-establishing the ice conditions that were typical of 20 or 30 years ago."

The Arctic ice cap grows each winter as the sun sets for several months and intense cold sets in. The total volume of winter Arctic ice is equal to the volume of fresh water in Lake Superior and Lake Michigan combined.

While some sea ice is naturally pushed out of the Arctic by winds, much of it melts in place. First-year sea ice usually reaches 6 feet in thickness, while ice that has lasted through more than one summer averages 9 feet and can grow much thicker in some locations near the coast.

For more information visit http://nsidc.org/arcticseaicenews.

Though greenhouse gases are invariably at the center of discussions about global climate change, new NASA research suggests that much of the atmospheric warming observed in the Arctic since 1976 may be due to changes in tiny airborne particles called aerosols.

Emitted by natural and human sources, aerosols can directly influence climate by reflecting or absorbing the sun's radiation. The small particles also affect climate indirectly by seeding clouds and changing cloud properties, such as reflectivity.

A new study, led by climate scientist Drew Shindell of the NASA Goddard Institute for Space Studies, New York, used a coupled ocean-atmosphere model to investigate how sensitive different regional climates are to changes in levels of carbon dioxide, ozone, and aerosols.

The researchers found that the mid and high latitudes are especially responsive to changes in the level of aerosols. Indeed, the model suggests aerosols likely account for 45 percent or more of the warming that has occurred in the Arctic during the last three decades. The results were published in the April issue of Nature Geoscience.

Though there are several varieties of aerosols, previous research has shown that two types -- sulfates and black carbon -- play an especially critical role in regulating climate change. Both are products of human activity.

Sulfates, which come primarily from the burning of coal and oil, scatter incoming solar radiation and have a net cooling effect on climate. Over the past three decades, the United States and European countries have passed a series of laws that have reduced sulfate emissions by 50 percent. While improving air quality and aiding public health, the result has been less atmospheric cooling from sulfates.

At the same time, black carbon emissions have steadily risen, largely because of increasing emissions from Asia. Black carbon -- small, soot-like particles produced by industrial processes and the combustion of diesel and biofuels -- absorb incoming solar radiation and have a strong warming influence on the atmosphere.

In the modeling experiment, Shindell and colleagues compiled detailed, quantitative information about the relative roles of various components of the climate system, such as solar variations, volcanic events, and changes in greenhouse gas levels. They then ran through various scenarios of how temperatures would change as the levels of ozone and aerosols -- including sulfates and black carbon -- varied in different regions of the world. Finally, they teased out the amount of warming that could be attributed to different climate variables. Aerosols loomed large.

The regions of Earth that showed the strongest responses to aerosols in the model are the same regions that have witnessed the greatest real-world temperature increases since 1976. The Arctic region has seen its surface air temperatures increase by 1.5 C (2.7 F) since the mid-1970s. In the Antarctic, where aerosols play less of a role, the surface air temperature has increased about 0.35 C (0.6 F).

That makes sense, Shindell explained, because of the Arctic's proximity to North America and Europe. The two highly industrialized regions have produced most of the world's aerosol emissions over the last century, and some of those aerosols drift northward and collect in the Arctic. Precipitation, which normally flushes aerosols out of the atmosphere, is minimal there, so the particles remain in the air longer and have a stronger impact than in other parts of the world.

Since decreasing amounts of sulfates and increasing amounts of black carbon both encourage warming, temperature increases can be especially rapid. The build-up of aerosols also triggers positive feedback cycles that further accelerate warming as snow and ice cover retreat.

In the Antarctic, in contrast, the impact of sulfates and black carbon is minimized because of the continent's isolation from major population centers and the emissions they produce.

"There's a tendency to think of aerosols as small players, but they're not," said Shindell. "Right now, in the mid-latitudes of the Northern Hemisphere and in the Arctic, the impact of aerosols is just as strong as that of the greenhouse gases."

The growing recognition that aerosols may play a larger climate role can have implications for policymakers.

"We will have very little leverage over climate in the next couple of decades if we're just looking at carbon dioxide," Shindell said. "If we want to try to stop the Arctic summer sea ice from melting completely over the next few decades, we're much better off looking at aerosols and ozone."

Aerosols tend to be quite-short lived, residing in the atmosphere for just a few days or weeks. Greenhouses gases, by contrast, can persist for hundreds of years. Atmospheric chemists theorize that the climate system may be more responsive to changes in aerosol levels over the next few decades than to changes in greenhouse gas levels, which will have the more powerful effect in coming centuries.

"This is an important model study, raising lots of great questions that will need to be investigated with field research," said Loretta Mickley, an atmospheric chemist from Harvard University, Cambridge, Mass. who was not directly involved in the research. Understanding how aerosols behave in the atmosphere is still very much a work-in-progress, she noted, and every model needs to be compared rigorously to real life observations. But the science behind Shindell's results should be taken seriously.

"It appears that aerosols have quite a powerful effect on climate, but there's still a lot more that we need to sort out," said Shindell.

NASA's upcoming Glory satellite is designed to enhance our current aerosol measurement capabilities to help scientists reduce uncertainties about aerosols by measuring the distribution and microphysical properties of the particles.

http://www.nasa.gov/topics/earth/featur ... osols.html

Climate Change Leads To Major Decrease In Carbon Dioxide Storage

ScienceDaily (Apr. 10, 2009) — The North Atlantic Ocean is one of the Earth’s tools to offset natural carbon dioxide emissions. In fact, the ‘carbon sink’ in the North Atlantic is the primary gate for carbon dioxide (CO2) entering the global ocean and stores it for about 1500 years. The oceans have removed nearly 30 per cent of anthropogenic (man-made) emissions over the last 250 years. However, several recent studies show a dramatic decline in the North Atlantic Ocean's carbon sink.

Concerned by this decline, a group of international scientists, including Helmuth Thomas, professor of oceanography at Dalhousie University, spent the last two years investigating the world’s largest carbon sink. They weren’t sure what was causing the decrease, whether it was man-made or natural reasons.

“There were massive changes in the coastal carbon cycle, and it was similar throughout the ocean,” says Dr. Thomas, who wrote about the study in Global Biogeochemical Cycles.

Recent observational studies found that the North Atlantic carbon uptake has decreased by 50 per cent over the last ten years. While many are quick to blame anthropogenic climate change, Dr. Thomas and his colleagues found different results.

They believe the decrease is a natural phenomenon as a result of the North Atlantic Oscillation (NAO), which causes weather patterns to change. “The next phase should once again increase in carbon uptake,” says Dr. Thomas. These natural phenomenons have the potential to mask the effects of anthropogenic climate change.

These findings are crucial in understanding how this natural system is reacting to climate change and dealing with increased man-made carbon emissions. Dr. Thomas says more research must be done; including enhanced observational efforts and developing models for analysis to fully understand the long-term effects, such as how the oceanic sink will deal with increased carbon emissions from humans. However, he hopes the study, reported on in the March edition of Nature, will help all climate change scientists with their research.

“This research is the foundation for research in ocean acidification which has implications on marine life and corals,” explains Dr. Thomas.

He also cautions against misinterpreting the findings. “There are natural systems that deal with and react to natural climate change. We have to understand these to assess how anthropogenic climate change is affecting them.”

Climate Change and Atmospheric Circulation Will Make for Uneven Ozone Recovery
April 10th, 2009 in Space & Earth / Earth Sciences



This plot of ozone concentration by latitude and altitude shows the net gain (oranges and reds) and net loss of ozone from years 1975-84 to 2060-69. Credit: Feng Li et al, NASA, published in Atmospheric Chemistry and Physics

(PhysOrg.com) -- Earth's ozone layer should eventually recover from the unintended destruction brought on by the use of chlorofluorocarbons (CFCs) and similar ozone-depleting chemicals in the 20th century. But new research by NASA scientists suggests the ozone layer of the future is unlikely to look much like the past because greenhouse gases are changing the dynamics of the atmosphere.

Previous studies have shown that while the buildup of greenhouse gases makes it warmer in troposphere - the level of atmosphere from Earth’s surface up to 10 kilometers (6 miles) altitude - it actually cools the upper stratosphere - between 30 to 50 kilometers high (18 to 31 miles). This cooling slows the chemical reactions that deplete ozone in the upper stratosphere and allows natural ozone production in that region to outpace destruction by CFCs.

But the accumulation of greenhouse gases also changes the circulation of stratospheric air masses from the tropics to the poles, NASA scientists note. In Earth's middle latitudes, that means ozone is likely to "over-recover," growing to concentrations higher than they were before the mass production of CFCs. In the tropics, stratospheric circulation changes could prevent the ozone layer from fully recovering.

"Most studies of ozone and global change have focused on cooling in the upper stratosphere," said Feng Li, an atmospheric scientist at the Goddard Earth Sciences and Technology Center at the University of Maryland Baltimore County, Baltimore, Md. and lead author of the study. "But we find circulation is just as important. It's not one process or the other, but both."

This simulation shows the seasonal rise and fall of ozone over the northern hemisphere from 1974 to 2065. Note how the geographic extent and the concentrations of ozone -- deep reds are the highest levels -- decrease around the turn of the century, then rise again. Credit: Trent Schindler, NASA's Goddard Space Flight Center
The findings are based on a detailed computer model that includes atmospheric chemical effects, wind changes, and solar radiation changes. Li's experiment is part of an ongoing international effort organized by the United Nations Environment Programme's Scientific Assessment Panel to assess the state of the ozone layer. Li and colleagues published their analysis in March in the journal Atmospheric Chemistry and Physics.

Working with Richard Stolarski and Paul Newman of NASA's Goddard Space Flight Center, Greenbelt, Md., Li adapted the Goddard Earth Observing System Chemistry-Climate Model (GEOS-CCM) to examine how climate change will affect ozone recovery. The team inserted past measurements and future projections of ozone-depleting substances and greenhouse gases into the model. Then the model projected how ozone, the overall chemistry, and the dynamics of the stratosphere would change through the year 2100.

"In the real world, we have observed statistically significant turnaround in ozone depletion, which can be attributed to the banning of ozone-depleting substances," said Richard Stolarski, an atmospheric chemist at Goddard and a co-author of the study. "But making that connection is complicated by the response of ozone to greenhouse gases."

The researchers found that greenhouse gases alter a natural circulation pattern that influences ozone distribution. Brewer-Dobson circulation is like a pump to the stratosphere, moving ozone from the lower parts of the atmosphere, into the upper stratosphere over the tropics. Air masses then flow north or south through the stratosphere, away from the tropics toward the poles.

In Li’s experiment, this circulation pump accelerated to a rate where the ozone flowing upward and outward from the tropics created a surplus at middle latitudes. Though the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre-1980 levels until 2060, the ozone layer over middle latitudes recovered to pre-1980 levels by 2025.

The Arctic - which is better connected to mid-latitude air masses than the Antarctic -- benefitted from the surplus in the northern hemisphere and from the overall decline of ozone-depleting substances to recover by 2025. Globally averaged ozone and Antarctic concentrations catch up by 2040, as natural atmospheric production of ozone resumes.

This recovery in the middle and polar latitudes has mixed consequences, Li noted. It might have some benefits, such as lower levels of ultraviolet radiation reaching the Earth's surface and correspondingly lower rates of skin cancer. On the other hand, it could have unintended effects, such as increasing ozone levels in the troposphere, the layer of atmosphere at Earth’s surface. The model also shows a continuing ozone deficit in the stratosphere over the tropics. In fact, when the model run ended at year 2100, the ozone layer over the tropics still showed no signs of recovery.

In February, researchers from Johns Hopkins University, Baltimore, teamed with Stolarski and other NASA scientists on a similar paper suggesting that increasing greenhouse gases would delay or even postpone the recovery of ozone levels in the lower stratosphere over some parts of the globe. Using the same model as Li, Stolarski, and Newman, the researchers found that the lower stratosphere over tropical and mid-southern latitudes might not return to pre-1980s levels of ozone for more than a century, if ever.

Provided by NASA Earth Science Team

Key role of forests 'may be lost'
By Mark Kinver
Science and environment reporter, BBC News



Forests' role as massive carbon sinks is "at risk of being lost entirely", top forestry scientists have warned.

The International Union of Forest Research Organizations (IUFRO) says forests are under increasing degrees of stress as a result of climate change.

Forests could release vast amounts of carbon if temperatures rise 2.5C (4.5F) above pre-industrial levels, it adds.

The findings will be presented at the UN Forum on Forests, which begins on Monday in New York.

Compiled by 35 leading forestry scientists, the report provides what is described as the first global assessment of the ability of forests to adapt to climate change.

“ The fact remains that the only way to ensure that forests do not suffer unprecedented harm is to achieve large reductions in greenhouse gas emissions ”
Professor Andreas Fischlin, Assessment co-author

"We normally think of forests as putting the brakes on global warming," observed Professor Risto Seppala from the Finnish Forest Research Institute, who chaired the report's expert panel.

"But over the next few decades, damage induced by climate change could cause forests to release huge quantities of carbon and create a situation in which they do more to accelerate warming than to slow it down."

Debate defining

The scientists hope that the report, called Adaption of Forests and People to Climate Change - A Global Assessment, will help inform climate negotiators.

The international climate debate has focused primarily on emissions from deforestation, but the researchers say their analysis shows that attention must also be paid to the impacts of climate change on forests.

While deforestation is responsible for about 20% of greenhouse gas emissions from human activities, forests currently absorb more carbon than they emit.

But the problem is that the balance could shift as the planet warms, the report concludes, and the sequestration service provided by the forest biomes "could be lost entirely if the Earth heats up by 2.5C or more".

The assessment says higher temperatures - along with prolonged droughts, more pest invasions, and other environmental stresses - would trigger considerable forest destruction and degradation.

This could create a dangerous feedback loop, it adds, in which damage to forests from climate change would increase global carbon emissions that then exacerbate global warming.

The report's key findings include:

• Droughts are projected to become more intense and frequent in subtropical and southern temperate forests

• Commercial timber plantations are set to become unviable in some areas, but more productive in others

• Climate change could result in "deepening poverty, deteriorating public health, and social conflict" among African forest-dependent communities

The IUFRO assessment will be considered by delegates at the eighth session of the UN Forum on Forests, which has the objective of promoting the "management, conservation and sustainable development of all types of forest".

Co-author Professor Andreas Fischlin from the Swiss Federal Institute of Technology commented: "Even if adaption measures are fully implemented, unmitigated climate change would - during the course of the current century - exceed the adaptive capacity of many forests.

"The fact remains that the only way to ensure that forests do not suffer unprecedented harm is to achieve large reductions in greenhouse gas emissions."

Did lead cause global cooling?

* 18:00 19 April 2009 by Jeff Hecht
*

Previous generations unwittingly found a way to cool the Earth, but it's an approach we won't want to reprise. Research suggests that particles of lead from gasoline exhaust may have offset warming in the 20th century.

It's well known that particles in the atmosphere such as mineral dust, pollen, heavy metals and even bacteria can act as seeds for the nucleation of ice crystals. These crystals form clouds that can affect the Earth's energy balance by reflecting the sun's rays back into space, for example.

Dan Cziczo and colleagues of the Pacific Northwest National Laboratory in Richland, Washington, created artificial clouds in the laboratory to explore the ice nucleation efficiency of various particles. Over a third of the ice nuclei generated contained lead, suggesting it is a highly-efficient nucleator. They found similar proportions of lead in atmospheric mineral dust samples collected in Switzerland.

Cziczo argues that lead "supercharges" ice-nucleating dust particles in the atmosphere. According to his calculations, global infrared emission would be 0.8 watts per square metre higher if all atmospheric ice crystals contained lead compared with none.

Before leaded fuel was phased out from road vehicles last century, the atmosphere contained substantially more leaded particulates than today, says Cziczo. This may have helped offset greenhouse warming from about 1940 to 1980, when global temperatures rose little before rising steeply.

Journal reference: Nature Geoscience (DOI:10.1038/NGEO499) (in press)

Ice ages are the greatest natural climate changes in recent geological times. Their rise and fall are caused by slight changes in the Earth's orbit around the Sun due to the influence of the other planets. But we do not know the exact relationship between the changes in the Earth's orbit and the changes in climate. New research from the Niels Bohr Institute indicates that there can be changes in the CO2 levels in the atmosphere that suddenly reach a critical turning point and with that trigger the dramatic climate changes. The results are published in the American journal Paleoceanography.

The Earth's climate is essentially contolled by three different cycles (Milankovitch). All three cycles are caused by the pull of the other planets in the solar system on the Earth, and one could say that they control the Earth's climate by causing changes in the Sun's radiation.

1: The Earth's orbit around the sun is not completely circular, but slightly elliptical. The orbit is 'elastic' and contracts and expands in a cycle of 100.000 years. And the closer we are to the Sun, the more solar radiation and the more heat we receive.

2: The Earth's axis has a tilt in relation to the Sun and that is why we have summer and winter. But the tilt is not constant, it swings between 22 degrees and 24 degrees, and the greater the tilt, the greater the difference between summer and winter. This cycle takes 40.000 years.

3: The Earth rotates around on its axis like a top - this gives day and night. But due to the tilt of the Earth and the elliptical orbit the direction changes with a cycle of 20.000 years. This results in varation in to whether the Earth is nearest the Sun during the summer or during the winter.

Solar radiation varies in the two hemispheres during the summer due to these cycles in the Earth's tilt and the elliptical orbit and this has profound implications for whether ice caps can build up in the northern hemisphere, where the largest land areas are.

Mysterious changes in ice ages

The ice ages have come and gone the last 20 million years and for the last few million years we know with reasonable accuracy how often they come. In the period before about 1 million years ago the ice ages occured around every 40.000 years, then it happened suddenly that the period changed so that it became circa 100.000 years between ice ages. It is a mystery because nothing changed in the behaviour of the Earth's orbit 1 million years ago. It is therefore due to a change that comes from the climate itself.

The conventional wisdom around the 100.000 year cycle of the last 10 ice ages is that the 100.000 years variation in the Earth's orbital eccentricity (the measure for how elliptical the orbit is and the half-yearly variation in the Earth's distance from the sun). This variation is still weaker than the variation that occurs with the 40.000 year cycle, so that in itself is a mystery.

Warm, half cold, ice cold

With completely new research results geophysicist Peter Ditlevsen, Centre for Ice and Climate at the Niels Bohr Institute, has found part of the explanation for the mystery of the sudden change of the ice ages. He has made model calculations of the climate of the past and compared it to the concrete data from seabed cores, which tell us about the climatic fluctuations of the past.

From the results he has been able to construct a diagram over the possible climatic conditions resulting from the variation in solar radiation. It appears that the ice ages and interglacial periods are not a gradual fluctuation between cold and warm climates.

What happened 1 million years ago was that the climate system went from a situation where it fluctuated between two states (cold and warm) with a 40.000 year cycle, corresponding to the dominant change in the Sun's radiation. After this period the dynamic changed so that the climate jumped between 3 states, that is to say between a warm interglacial climate like our present climate, a colder climate and a very cold ice age climate. It is still the 40.000 year variation in solar radiation which controls our current fluctuations, but it results in changing climate periods of 80.000 and 120.000 years.

Chaotic dynamic climate
The climate does not become gradually colder or warmer - it jumps from the one state to the other. That which gets the climate to jump is that when the solar radiation changes and reaches a certain threshold - a 'tipping point', the existing climate state, e.g. an ice age, is no longer viable and so the climate jumps over into another state, e.g. a warm interglacial period. In chaos dynamics this phenomenon is called a bifurcation or a 'catastrophe'.

In addition to the change in solar radiation there can be random changes in the Earth's weather variations, that contribute to triggering the bifurcation or the 'catastrophe'. Such variations are called 'noise', and a theory is, that the atmosphere's CO2 level can be an important noise-factor. This means that there is the possibility that the 'noise' is a decisive factor for very large climate changes, which can therefore be unpredictable.

There is still no explanation for the change in the climate system 1 million years ago, but one theory is that the atmosphere's CO2-level fell to the lowest level ever. If so, the manmade increase in CO2 may result in a return to 40.000 year ice age cycles.

"The new results are an important piece of the puzzle for understanding the ice ages and their climate dynamics. In the manmade climate changes, that we are possibly in the middle of now, one worries a lot about the possible so-called 'tipping points'. The bifurcations that are now identified in the natural climate fluctuations are tipping points, so this is of course an important step in our understanding of climate changes", explains Peter Ditlevsen.

"The bifurcation structure and noise assisted transitions in the Pleistocene glacial cycles": http://www.agu.org/journals/pa/papersin ... 08PA001673

New research suggests intertwining of tropical cyclones, climate change

CAMBRIDGE, Mass., April 20, 2009 -- Scientists at Harvard University have found that tropical cyclones readily inject ice far into the stratosphere, possibly feeding global warming.

The finding, published in Geophysical Research Letters, provides more evidence of the intertwining of severe weather and global warming by demonstrating a mechanism by which storms could drive climate change. Many scientists now believe that global warming, in turn, is likely to increase the severity of tropical cyclones.

"Since water vapor is an important greenhouse gas, an increase of water vapor in the stratosphere would warm the Earth's surface," says David M. Romps, a research associate in Harvard's Department of Earth and Planetary Science. "Our finding that tropical cyclones are responsible for many of the clouds in the stratosphere opens up the possibility that these storms could affect global climate, in addition to the oft-mentioned possibility of climate change affecting the frequency and intensity of tropical cyclones."

Romps and co-author Zhiming Kuang, assistant professor of climate science in Harvard's Faculty of Arts and Sciences, were intrigued by earlier data suggesting that the amount of water vapor in the stratosphere has grown by roughly 50 percent over the past 50 years. Scientists are currently unsure why this increase has occurred; the Harvard researchers sought to examine the possibility that tropical cyclones might have contributed by sending a large fraction of their clouds into the stratosphere.

Using infrared satellite data gathered from 1983 to 2006, Romps and Kuang analyzed towering cloud tops associated with thousands of tropical cyclones, many of them near the Philippines, Mexico, and Central America. Their analysis demonstrated that in a cyclone, narrow plumes of miles-tall storm clouds can rise so explosively through the atmosphere that they often push into the stratosphere.

Romps and Kuang found that tropical cyclones are twice as likely as other storms to punch into the normally cloud-free stratosphere, and four times as likely to inject ice deep into the stratosphere.

"It is ... widely believed that global warming will lead to changes in the frequency and intensity of tropical cyclones," Romps and Kuang write in Geophysical Research Letters. "Therefore, the results presented here establish the possibility for a feedback between tropical cyclones and global climate."

Typically, very little water is allowed passage through the stratosphere's lower boundary, known as the tropopause. Located some 6 to 11 miles above the Earth's surface, the tropopause is the coldest part of the Earth's atmosphere, making it a barrier to the lifting of water vapor into the stratosphere: As air passes slowly through the tropopause, it gets so cold that most of its water vapor freezes out and falls away.

But if very deep clouds, such as those in a tropical cyclone that can rise through the atmosphere at speeds of up to 40 miles per hour, can punch through the tropopause too quickly for this to happen, they can deposit their ice in the warmer overlying stratosphere, where it then evaporates.

"This suggests that tropical cyclones could play an important role in setting the humidity of the stratosphere," Romps and Kuang write.

Romps and Kuang's research was funded by the Eppley Foundation and NASA.

11 April 2009
Breaking the silence about Spring

Did you know that in 1965 the U.S. Department of Agriculture planted a particular variety of lilac in more than seventy locations around the U.S. Northeast, to detect the onset of spring — in turn to be used to determine the appropriate timing of corn planting and the like? The records the USDA have kept show that those same lilacs are blooming as much as two weeks earlier than they did in 1965. April has, in a very real sense, become May. This is one of the interesting facts that you’ll read about in Amy Seidl’s book, Early Spring, a hot-off-the-press essay about the impacts of climate change on the world immediately around us – the forest, the birds, the butterflies in our backyards.

The brilliant title of Seidl’s book was one of the reasons that it caught my attention. The other was that I have realized I need to better educate myself about the impact of climate change on everyday life. I’ve been dismissive of the idea that the average person can really detect the impacts of recent warming on, for example, the timing of the apple-blossom season, but I’ve been taken to task by several of RealClimate’s readers for this. If you are paying attention, they have argued, the changes are actually rather obvious.

Of course, Amy Seidl is not the average person. Rather, she’s a trained ecologist with a Ph.D. (as well as an avid gardener) and she’s clearly paying extremely close attention. Her book is the first one I have read that effectively brings home the tangible impacts that global warming will have – is having – on our everyday lives. “We are increasingly familiar,” she writes, of images of melting glaciers, “but how do we give them relevance in our lives? From my window I see no glaciers.” She answers her own question with a series of vignettes, some from her own experiences, many more from her extensive research (well referenced throughout the book).

Cardinals, robins and cowbirds are all arriving earlier in Vermont than they did a century ago. Kingfishes, fox sparrows and towhees are not. Why the difference? The answer, as Seidl explains, is that the former group has the ability to respond ecologically to the changes, because these birds cue their arrival to temperature. The latter, it appears, respond more directly to temporal cues, that won’t change even as climate does. It’s obvious from this example that the make up of bird life in Vermont – the species distribution – will change over time. This may not necessarily be a bad thing of course. On the other hand, it turns out that the robins are the most important host for West Nile virus; the early bird gets the worm, so to speak, and passes it along to humans.

Maple seedlings need about 100 days of below-freezing weather. As this becomes rarer, fewer maples will populate the forests. This, Seidl explains, is why species-range models predict the decline and eventual loss of sugar maple (at least in New England) in the future. But, she notes, the models don’t take into account the full complexity of the system, such as the impact of competition among different species. So we don’t really know what will happen, or how fast. What we do know is that maple-sugar farmers have noticed – and documented – an earlier maple sugaring season over the last few decades.

There are many other examples in Early Spring both of clear climate-related changes (such as the early arrival of robins), and of less clear-cut changes (the maple sugaring season). Seidl doesn’t make the common mistake of assuming that the more ambiguous examples are necessarily due to climate change. For example, she quotes a maple-sugarer who points out that technological changes have allowed them to tap maples earlier, and hence that the timing of sugaring is a weak measure of climate change. The point though, is that even rather minor changes are, after all, being noticed. And if much larger changes do occur, as predicted, they will most certainly have impacts we can’t ignore, even if we don’t live in the Arctic or in Bangladesh. In other words, Seidl tells us, listen to the farmers and gardeners, and the observations of regular people: they are meaningful.

The soberness of Seidl’s approach to the subject of climate change impacts contrasts starkly with that of many books before it. It couldn’t be further, for example, from Mark Lynas’s book, Six Degrees, which is a truly alarming read. In my comments on Six Degrees, I said that it wasn’t an alarmist book. I stand by that characterization, because – and this is what I liked about it – it doesn’t go beyond what is in the scientific literature. However, while Lynas’s book is a straightforward reading of the scientific literature, it is a somewhat uncritical one, and hence tends to emphasize what might happen in the future over what will happen; this is a point that many readers of my review seem to have missed. Seidl’s book, on the other hand, is focused on the more certain – and often less dramatic — things, and on the impacts we are likely to see in our own lifetimes.

The calm demeanor of Seidl’s book, and the very personal nature of it, could lead one to think that it is primarily just a philosophical reflection on the climate change story. Indeed, Bill McKibben, in his introduction to Early Spring, says that in the face of changes we may not be able to prevent, “one of our tasks is simply to bear witness”. Certainly, the book is partly that. But Seidl’s voice, like Rachel Carson’s before her, has the authentic and authoritative voice of a scientist, made all the more compelling for being very much rooted in the author’s own story and experiences. And she doesn’t pull punches when she has something definitive to say: “One thing is clear:” she writes, “we will not be able to manage the climate”.

Early Spring has the potential to be immensely influential, a real turning point in the popular appreciation of climate change impacts among laypersons and scientists alike. Read it.

saxman wrote:Over 900 large rivers studied over 50 yrs show decline in river discharge overall, climate change implicated.

http://news.yahoo.com/s/livescience/200 ... g9rA8PLBIF

BOULDER—Rivers in some of the world's most populous regions are losing water, according to a new comprehensive study of global stream flow. The study, led by scientists at the National Center for Atmospheric Research (NCAR), suggests that in many cases the reduced flows are associated with climate change. The process could potentially threaten future supplies of food and water.

The results will be published May 15 in the American Meteorological Society's Journal of Climate. The research was supported by the National Science Foundation, NCAR's sponsor.

The scientists, who examined stream flow from 1948 to 2004, found significant changes in about one-third of the world's largest rivers. Of those, rivers with decreased flow outnumbered those with increased flow by a ratio of about 2.5 to 1.


This map shows the change in runoff inferred from streamflow records worldwide between 1948 and 2004, with bluish colors indicating more streamflow and reddish colors less. In many heavily populated regions in the tropics and midlatitudes, rivers are discharging reduced amounts into the oceans. In parts of the United States and Europe, however, there is an upward trend in runoff. The white land areas indicate inland-draining basins or regions for which there are insufficient data to determine the runoff trends. (Graphic courtesy Journal of Climate, modified by UCAR.)

Several of the rivers channeling less water serve large populations, including the Yellow River in northern China, the Ganges in India, the Niger in West Africa, and the Colorado in the southwestern United States. In contrast, the scientists reported greater stream flow over sparsely populated areas near the Arctic Ocean, where snow and ice are rapidly melting.

"Reduced runoff is increasing the pressure on freshwater resources in much of the world, especially with more demand for water as population increases," says NCAR scientist Aiguo Dai, the lead author. "Freshwater being a vital resource, the downward trends are a great concern."

Many factors can affect river discharge, including dams and the diversion of water for agriculture and industry. The researchers found, however, that the reduced flows in many cases appear to be related to global climate change, which is altering precipitation patterns and increasing the rate of evaporation. The results are consistent with previous research by Dai and others showing widespread drying and increased drought over many land areas.

The study raises wider ecological and climate concerns. Discharge from the world's great rivers results in deposits of dissolved nutrients and minerals into the oceans. The freshwater flow also affects global ocean circulation patterns, which are driven by changes in salinity and temperature and which play a vital role in regulating the world's climate. Although the recent changes in the freshwater discharge are relatively small and may only have impacts around major river mouths, Dai said the freshwater balance in the global oceans needs to be monitored for any long-term changes.

Conflicting studies
Scientists have been uncertain about the impacts of global warming on the world's major rivers. Studies with computer models show that many of the rivers outside the Arctic could lose water because of decreased precipitation in the mid- and lower latitudes and an increase in evaporation caused by higher temperatures. Earlier, less comprehensive analyses of major rivers had indicated, however, that global stream flow was increasing.

Dai and his co-authors analyzed the flows of 925 of the planet's largest rivers, combining actual measurements with computer-based stream flow models to fill in data gaps. The rivers in the study drain water from every major landmass except Antarctica and Greenland and account for 73 percent of the world's total stream flow.


Aiguo Dai. (©UCAR, photo by Carlye Calvin.)

Overall, the study found that, from 1948 to 2004, annual freshwater discharge into the Pacific Ocean fell by about 6 percent, or 526 cubic kilometers--approximately the same volume of water that flows out of the Mississippi River each year. The annual flow into the Indian Ocean dropped by about 3 percent, or 140 cubic kilometers. In contrast, annual river discharge into the Arctic Ocean rose about 10 percent, or 460 cubic kilometers.

In the United States, the Columbia River's flow declined by about 14 percent during the 1948-2004 study period, largely because of reduced precipitation and higher water usage in the West. The Mississippi River, however, has increased by 22 percent over the same period because of greater precipitation across the Midwest since 1948.

The impacts of melting
Some rivers, such as the Brahmaputra in South Asia and the Yangtze in China, have shown stable or increasing flows. But they could lose volume in future decades with the gradual disappearance of the Himalayan glaciers feeding them, the authors warned.

"As climate change inevitably continues in coming decades, we are likely to see greater impacts on many rivers and water resources that society has come to rely on," says NCAR scientist Kevin Trenberth, a co-author of the study.

Increased growth in Antarctic sea ice during the past 30 years is a result of changing weather patterns caused by the ozone hole according to new research published this week (Thurs 23 April 2009).

Reporting in the journal Geophysical Research Letters scientists from British Antarctic Survey (BAS) and NASA say that while there has been a dramatic loss of Arctic sea ice, Antarctic sea ice has increased by a small amount as a result of the ozone hole delaying the impact of greenhouse gas increases on the climate of the continent.

Sea ice plays a key role in the global environment – reflecting heat from the sun and providing a habitat for marine life. At both poles sea ice cover is at its minimum during summer. However, during the winter freeze in Antarctica this ice cover expands to an area roughly twice the size of Europe. Ranging in thickness from less than a metre to several metres, the ice insulates the warm ocean from the frigid atmosphere above. Satellite images show that since the 1970s the extent of Antarctic sea ice has increased at a rate of 100,000 square kilometres a decade.

The new research helps explain why observed changes in the amount of sea-ice cover are so different in both polar regions.

Lead author Professor John Turner of BAS says,

“Our results show the complexity of climate change across the Earth. While there is increasing evidence that the loss of sea ice in the Arctic has occurred due to human activity, in the Antarctic human influence through the ozone hole has had the reverse effect and resulted in more ice. Although the ozone hole is in many ways holding back the effects of greenhouse gas increases on the Antarctic, this will not last, as we expect ozone levels to recover by the end of the 21st Century. By then there is likely to be around one third less Antarctic sea ice.”

Using satellite images of sea ice and computer models the scientists discovered that the ozone hole has strengthened surface winds around Antarctica and deepened the storms in the South Pacific area of the Southern Ocean that surrounds the continent. This resulted in greater flow of cold air over the Ross Sea (West Antarctica) leading to more ice production in this region. Satellite images and computer models reveal that the ozone hole has strengthened surface winds around the Southern Ocean

The satellite data reveal the variation in sea ice cover around the entire Antarctic continent. Whilst there has been a small increase of sea ice during the autumn around the coast of East Antarctica, the largest changes are observed in West Antarctica. Sea ice has been lost to the west of the Antarctic Peninsula – a region that has warmed by almost 3ºC in the past 50 years. Further west sea ice cover over the Ross Sea has increased.

Turner continues,
“Understanding how polar sea ice responds to global change – whether human induced or as part of a natural process – is really important if we are to make accurate predictions about the Earth’s future climate. This new research helps us solve some of the puzzle of why sea-ice is shrinking is some areas and growing in others.”

Notes to Editors:
The paper ‘Non-annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent’ by J Turner, JC Comiso, G J Marshall, T A Lachlan-Cope, T Bracegirdle, T Maksym, MP Meredith, Z Wang, and A Orr (2009), is published in
Geophysical Research Letters doi:10.1029/2009GL037524, [23 April 2009].

Floating sea ice caps the ocean around the Antarctic and although it is mostly only 1-2 m thick, it provides effective insulation between the frigid Antarctic atmosphere and the relatively warm ocean below. The ice extent has a minimum in autumn, but by the end of the winter covers an area of 19 million square kilometres, essentially doubling the size of the continent. Instruments flown on polar orbiting satellites have been able to map the distribution and concentration of sea ice since the late 1970s and this study used a new data set of Antarctic sea ice extent created by NASA.

The ozone hole was discovered by BAS scientists in the mid-1980s and found to be a result of CFCs in the stratosphere that destroyed the ozone above the continent each spring. The loss of the ozone resulted in marked cooling in the Antarctic stratosphere, which increased the winds around the continent at that level. The effects of the ozone hole propagate down through the atmosphere during the summer and autumn so that the greatest increase in surface winds over the Southern Ocean has been during the autumn. CFCs have a long lifetime in the atmosphere and despite the Montreal Protocol, which has banned the use of CFCs, there is currently no indication of a recovery of springtime ozone concentrations. However, over approximately the next half century there is expected to be a return to the pre-ozone hole concentrations of ozone.

Strong winds are a major feature of the Southern Ocean with the remoteness of the Antarctic from other landmasses allowing active depressions to ring the continent. The Antarctic continent is slightly off-pole, which results in a large number of storms over the Amundsen Sea (the Amundsen Sea Low) giving average northerly winds down the Antarctic Peninsula and cold, southerly winds off the Ross Ice Shelf. The stronger winds around the continent in Autumn as a result of the ozone hole have deepened the Amundsen Sea Low, giving the positive and negative trends in sea ice over the Ross Sea and to the west of the Antarctic Peninsula respectively. Although there has been a loss of some sea ice to the west of the Antarctic Peninsula, this is negated by the larger increase of ice in the Ross Sea, giving a net increase in the amount of ice around the Antarctic.

There has been contrasting climate change across the Antarctic in recent decades. The Antarctic Peninsula has warmed as much as anywhere in the Southern Hemisphere, with loss of ice shelves and changes in the terrestrial and marine biota. The warming during the summer, which has the greatest impact on the stability of the ice shelves, has been linked to the ozone hole and increasing greenhouse gases. Recent research has suggested that the warming extends into West Antarctica. In contrast, East Antarctic has shown little change or even a small cooling around the coast, which is consistent with the small increase in sea ice extent off the coast. The increase in storm activity over the South Pacific sector is also consistent with the pattern of temperature change observed, with warming down the Antarctic Peninsula in the stronger northerly flow.

The Cambridge-based British Antarctic Survey (BAS) is a world leader in research into global environmental issues. With an annual budget of around £40 million, five Antarctic Research Stations, two Royal Research Ships and five aircraft BAS undertakes an interdisciplinary research programme and plays an active and influential role in Antarctic affairs. BAS has joint research projects with over 40 UK universities and has more than 120 national and international collaborations. It is a component of the Natural Environment Research Council. More information about the work of the Survey can be found at: http://www.antarctica.ac.uk

Climate Change Means Shortfalls In Colorado River Water Deliveries


Scheduled deliveries of water from Lake Mead, created by Hoover Dam, could be missed 60 to 90 percent of the time by midcentury if human-caused climate change continues to make the region drier. (Credit: US Bureau of Reclamation)

ScienceDaily (Apr. 27, 2009) — The Colorado River system supplies water to tens of millions of people and millions of acres of farmland, and has never experienced a delivery shortage. But if human-caused climate change continues to make the region drier, scheduled deliveries will be missed 60-90 percent of the time by the middle of this century, according to a pair of climate researchers at Scripps Institution of Oceanography, UC San Diego.

"All water-use planning is based on the idea that the next 100 years will be like the last 100," said Scripps research marine physicist Tim Barnett, a co-author of the report. "We considered the question: Can the river deliver water at the levels currently scheduled if the climate changes as we expect it to. The answer is no."

Even under conservative climate change scenarios, Barnett and Scripps climate researcher David Pierce found that reductions in the runoff that feeds the Colorado River mean that it could short the Southwest of a half-billion cubic meters (400,000 acre feet) of water per year 40 percent of the time by 2025. (An acre foot of water is typically considered adequate to meet the annual water needs of two households.) By the later part of this century, those numbers double.

The paper, "Sustainable water deliveries from the Colorado River in a changing climate," appears in the April 20 edition of the journal Proceedings of the National Academy of Sciences.

The analysis follows a 2008 study in which Barnett and Pierce found that Lake Mead, the reservoir on the Colorado River created by Hoover Dam, stood a 50-percent chance of going dry in the next 20 years if the climate changed and no effort was made to preserve a minimum amount of water in the reservoir. The new study assumes instead that enough water would be retained in the reservoir to supply the city of Las Vegas, and examines what delivery cuts would be required to maintain that level.

"People have talked for at least 30 years about the Colorado being oversubscribed but no one ever put a date on it or an amount. That's what we've done," said Barnett. "Without numbers like this, it's pretty hard for resource managers to know what to do."

Barnett and Pierce also point out that lakes Mead and Powell were built during and calibrated to the 20th century, which was one of the wettest in the last 1,200 years. Tree ring records show that typical Colorado River flows are substantially lower, yet 20th Century values are used in most long-term planning of the River. If the Colorado River flow reverts to its long-term average indicated by the tree rings, then currently scheduled water deliveries are even less sustainable.

Barnett and Pierce show that the biggest effects of human-induced climate change will probably be seen during dry, low-delivery years. In most years, delivery shortfalls will be small enough to be manageable through conservation and water transfers, they estimate. But during dry years there is an increasing chance of substantial shortages.

"Fortunately, we can avoid such big shortfalls if the river's users agree on a way to reduce their average water use," said Pierce. "If we could do that, the system could stay sustainable further into the future than we estimate currently, even if the climate changes."

Note to broadcast and cable producers: UC San Diego provides an on-campus satellite uplink facility for live or pre-recorded television interviews. Please phone or e-mail the media contact listed above to arrange an interview.
Adapted from materials provided by University of California - San Diego, via EurekAlert!, a service of AAAS.

Fire Influences Global Warming More Than Previously Thought


Forest fire in Siberia. (Credit: Laboratory of Tree-Ring Research, The University of Arizona)

ScienceDaily (Apr. 29, 2009) — Fire's potent and pervasive effects on ecosystems and on many Earth processes, including climate change, have been underestimated, according to a new report.

"We've estimated that deforestation due to burning by humans is contributing about one-fifth of the human-caused greenhouse effect -- and that percentage could become larger," said co-author Thomas W. Swetnam of The University of Arizona in Tucson.

"It's very clear that fire is a primary catalyst of global climate change," said Swetnam, director of UA's Laboratory of Tree-Ring Research.

"The paper is a call to arms to earth scientists to investigate and better evaluate the role of fire in the Earth system," he said.

The team also reports that all fires combined release an amount of carbon dioxide into the atmosphere equal to 50 percent of that coming from the combustion of fossil fuels.

"Fires are obviously one of the major responses to climate change, but fires are not only a response -- they feed back to warming, which feeds more fires," Swetnam said.

When vegetation burns, the resulting release of stored carbon increases global warming. The more fires, the more carbon dioxide released, the more warming -- and the more warming, the more fires.

The very fine soot, known as black carbon, that is released into the atmosphere by fires also contributes to warming.

"The scary bit is that, because of the feedbacks and other uncertainties, we could be way underestimating the role of fire in driving future climate change," Swetnam said.

The report's 22 authors call for the Intergovernmental Panel on Climate Change, or IPCC, to recognize the overarching role of fire in global climate change and to incorporate fire better into future models and reports about climate change.

David Bowman, a lead co-author, said, "We're most concerned that fire has not been rigorously and adequately incorporated in the climate models. It's remarkable that such an integral part of the landscape has been so sidelined."

Swetnam, Bowman of the University of Tasmania in Hobart, Australia, the other lead co-author Jennifer K. Balch of the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif. and their colleagues will publish their paper, "Fire in the Earth System," in the April 24 issue of the journal Science. A complete list of authors is at the end of this release.

Because fire on Earth predates humans, its ubiquitous activity is simultaneously accepted and overlooked. Bowman says, "Fire is extraordinarily obvious, but deeply subtle."

The article ties together various threads of knowledge about fire from disparate fields including ecology, global modeling, physics, anthropology, environmental history, medicine and climatology.

A more complete understanding of how the Earth works requires recognizing how fire is intertwined with and also a driver of human history and the Earth's history, the authors write.

Balch said of the article, "This synthesis is a prerequisite for adaptation to the apparent recent intensification of fire feedbacks, which have been exacerbated by climate change, rapid land-cover transformation, and exotic species introductions."

She commented about "fires where we don't normally see fires," and pointed to the occurrence of bigger and more frequent fires from the western U.S. to the tropics.

Swetnam said that, in addition to the burning in the tropics, huge tracts of the boreal forests of Siberia, Canada and northern Europe burn each year.

"The role of fire in forests in the boreal zone is unappreciated," he said.

"Russian forests alone contain more than 50 percent of the carbon stored on land in the Northern Hemisphere," Swetnam wrote in an e-mail, adding that warming is happening fastest at high latitudes.

In some recent years, the acreage burned in the forests of Siberia exceeded the size of the U.S. state of Virginia, he said. As the world warms, more of those regions are likely to burn, accelerating the warming.

Calling for a holistic fire science, Balch said, "We don't think about fires correctly."

"Fire is as elemental as air or water. We live on a fire planet. We are a fire species. Yet, the study of fire has been very fragmented. We know lots about the carbon cycle, the nitrogen cycle, but we know very little about the fire cycle, or how fire cycles through the biosphere."

The article is a result of a workshop supported by the Kavli Institute for Theoretical Physics and the National Center for Ecological Analysis and Synthesis, both based at the University of California, Santa Barbara and both funded by the National Science Foundation.
Journal reference:

1. Bowman et al. Fire in the Earth System. Science, 2009; 324 (5926): 481-484 DOI: 10.1126/science.1163886

Adapted from materials provided by University of Arizona.

Scientists Surprised By Unexpected Emergence Of Periodical Cicadas -- Four Years Early



Scientists are reporting a four-year acceleration of the periodical cicada Brood II. (Credit: Image courtesy of College of Mount St. Joseph)
ScienceDaily (May 8, 2009) — Periodical cicadas, insects best known for their 17-year long life cycle, are emerging four years early in several Atlantic states. The emergence was first noticed in Greensboro, NC, on Monday and has since been reported in Maryland.

“This appears to be a four-year acceleration of the periodical cicada Brood II,” said Dr. Gene Kritsky, Ph.D., professor of biology at the College of Mount St. Joseph. Kritsky is an expert on these four-year early emergences being the first to predict an early appearance of the cicadas in 2000.

“It is thought that the timing of the emergence is determined during the first five years of the underground development of the juvenile cicadas.” Kritsky and his students monitor the cicada growth by digging up the insects each year. “We discovered that many cicadas were growing faster than expected, which led the prediction of their early emergence in 2000,” he said.

The emergence this year is the fifth 17-year cicada brood to appear early. Kritsky described the early appearance of Brood I in 1995 in eastern Ohio and predicted the early appearance of Brood X. Brood XIII appeared early in parts of Chicago in 2003 and Brood XIV accelerated in parts of Indiana and Ohio in 2004. This year’s acceleration is overlapping with the distribution of Brood II.

The cause of these early emergences is unknown, but Kritsky, in a paper to be published in the Proceedings of the Indiana Academy of Science, has found evidence suggesting that mild winters can affect the trees that young cicadas feed upon which in turn interferes with the cicadas’ timekeeping resulting in their emerging early. “This phenomenon might be another biological response to increasing temperatures,” Kritsky said.

People witnessing cicadas this year are encouraged to report their cicadas on mapping websites, at http://www.msj.edu/cicada.

Cold Water Ocean Circulation Doesn't Work As Expected


This model of North Atlantic currents has been called into question by new data from Duke University and the Woods Hole Oceanographic Institution. (Credit: Archana Gowda, Duke)

ScienceDaily (May 14, 2009) — The familiar model of Atlantic ocean currents that shows a discrete "conveyor belt" of deep, cold water flowing southward from the Labrador Sea is probably all wet.

New research led by Duke University and the Woods Hole Oceanographic Institution relied on an armada of sophisticated floats to show that much of this water, originating in the sea between Newfoundland and Greenland, is diverted generally eastward by the time it flows as far south as Massachusetts. From there it disburses to the depths in complex ways that are difficult to follow.

A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.

"Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn't hold anymore," said Duke oceanographer Susan Lozier. "So it's going to be more difficult to measure these climate change signals in the deep ocean."

And since cold Labrador seawater is thought to influence and perhaps moderate human-caused climate change, this finding may affect the work of global warming forecasters.

"To learn more about how the cold deep waters spread, we will need to make more measurements in the deep ocean interior, not just close to the coast where we previously thought the cold water was confined," said Woods Hole's Amy Bower.

Lozier, a professor of physical oceanography at Duke's Nicholas School of the Environment and Bower, a senior scientist in the department of physical oceanography at the Woods Hole Institution, are co-principal authors of a report on the findings to be published in the May 14 issue of the research journal Nature.

Their research was supported by the National Science Foundation.

Climatologists pay attention to the Labrador Sea because it is one of the starting points of a global circulation pattern that transports cold northern water south to make the tropics a little cooler and then returns warm water at the surface, via the Gulf Stream, to moderate temperatures of northern Europe.

Since forecasters say effects of global warming are magnified at higher latitudes, that makes the Labrador Sea an added focus of attention. Surface waters there absorb heat-trapping carbon dioxide from the atmosphere. And a substantial amount of that CO2 then gets pulled underwater where it is no longer available to warm Earth's climate.

"We know that a good fraction of the human caused carbon dioxide released since the Industrial revolution is now in the deep North Atlantic" Lozier said. And going along for the ride are also climate-caused water temperature variations originating in the same Labrador Sea location.

The question is how do these climate change signals get spread further south? Oceanographers long thought all this Labrador seawater moved south along what is called the Deep Western Boundary Current (DWBC), which hugs the eastern North American continental shelf all the way to near Florida and then continues further south.

But studies in the 1990s using submersible floats that followed underwater currents "showed little evidence of southbound export of Labrador sea water within the Deep Western Boundary Current (DWBC)," said the new Nature report.

Scientists challenged those earlier studies, however, in part because the floats had to return to the surface to report their positions and observations to satellite receivers. That meant the floats' data could have been "biased by upper ocean currents when they periodically ascended," the report added.

To address those criticisms, Lozier and Bower launched 76 special Range and Fixing of Sound floats into the current south of the Labrador Sea between 2003 and 2006. Those "RAFOS" floats could stay submerged at 700 or 1,500 meters depth and still communicate their data for a range of about 1,000 kilometers using a network of special low frequency and amplitude seismic signals.

But only 8 percent of the RAFOS floats' followed the conveyor belt of the Deep Western Boundary Current, according to the Nature report. About 75 percent of them "escaped" that coast-hugging deep underwater pathway and instead drifted into the open ocean by the time they rounded the southern tail of the Grand Banks.

Eight percent "is a remarkably low number in light of the expectation that the DWBC is the dominant pathway for Labrador Sea Water," the researchers wrote.

Studies led by Lozier and other researchers had previously suggested cold northern waters might follow such "interior pathways" rather than the conveyor belt in route to subtropical regions of the North Atlantic. But "these float tracks offer the first evidence of the dominance of this pathway compared to the DWBC."

Since the RAFOS float paths could only be tracked for two years, Lozier, her graduate student Stefan Gary, and German oceanographer Claus Boning also used a modeling program to simulate the launch and dispersal of more than 7,000 virtual "efloats" from the same starting point.

"That way we could send out many more floats than we can in real life, for a longer period of time," Lozier said.

Subjecting those efloats to the same underwater dynamics as the real ones, the researchers then traced where they moved. "The spread of the model and the RAFOS float trajectories after two years is very similar," they reported.

"The new float observations and simulated float trajectories provide evidence that the southward interior pathway is more important for the transport of Labrador Sea Water through the subtropics than the DWBC, contrary to previous thinking," their report concluded.

"That means it is going to be more difficult to measure climate signals in the deep ocean," Lozier said. "We thought we could just measure them in the Deep Western Boundary Current, but we really can't.

Journal reference:

1. Amy S. Bower, M. Susan Lozier, Stefan F. Gary & Claus W. Böning. Interior pathways of the North Atlantic meridional overturning circulation. Nature, 2009; 459 (7244): 243 DOI: 10.1038/nature07979

Adapted from materials provided by Duke University.

Gruelling' Arctic mission ends
By David Shukman
Environment Correspondent, BBC News, Eureka, Canadian Arctic

The Catlin Arctic Survey, a gruelling 10-week expedition to measure the thickness of sea-ice, has ended.

At 1750 BST on Wednesday, two planes landed safely on the floating Arctic ice to collect Pen Hadow, Ann Daniels and Martin Hartley.

Their data will help study the impacts of global warming in the region.

It also reinforces a new forecast, by a leading UK scientist, who says that the Arctic sea-ice could vanish in summertime far sooner than predicted.

The Catlin survey ended slightly ahead of schedule to ensure a safe pick up.

Speaking on a live link from the Arctic landing strip, Mr Hadow said that it had been a difficult but successful expedition.

"In our time here we have captured around 16,000 observations and [taken] 1,500 measurements of the thickness of the ice and snow as well as its density," he said.

He added that his team was now handing its valuable data, collected primarily through drilling following the failure of a mobile radar unit, over to the scientists.

"[The data] seems to suggest it was almost all first-year ice," Mr Hadow said.

He revealed that over the length of the survey the average thickness of the sea ice was 1.774m.

"Our science advisors had told us to expect thicker, older ice on at least part of the route, so it is something of a mystery where that older ice has gone. It'll be interesting to see what scientists think about this."

At the same time, Peter Wadhams, head of the polar ocean physics group at the University of Cambridge has brought forward his estimate for the demise of summer sea-ice in the Arctic.

He believes the ice, which has been a permanent feature for at least 100,000 years, is now so thin that almost all of it will disappear in about a decade.

He says it will become seasonal, forming only during the winter.

He told the BBC: "By 2013, we will see a much smaller area in summertime than now; and certainly by about 2020, I can imagine that only one area will remain in summer."

Although this bleak forecast is reinforced by the survey team's data, Professor Wadham's new assessment is based on analysis of nearly 40 years of sonar data gathered on Royal Navy submarines patrolling beneath the ice - the first, HMS Dreadnought, was in 1971.

Until recently, most climate forecasts suggested that the Arctic Ocean would have ice-free summers only towards the end of the century.

The most extreme scenario was for the ice to retreat as soon as 2013, but that was dismissed by many as far too soon.

Now Professor Wadhams, who has studied the Arctic for the past 40 years, says that there is "almost a breakdown" in the ice-cover.
“ It's like the Arctic is covered with an egg shell and the egg shell... is now just cracking completely ”
Peter Wadhams University of Cambridge

Over most of the Arctic, there has been a massive decline in the amount of so-called multi-year ice - ice that is tough enough to withstand the summer warmth.

Much of what is left of this ice accumulates in an area north of Greenland and Ellesmere Island in Canada, and may form what he calls "a last holdout, a kind of Alamo".

Professor Wadhams said: "The change is happening so fast. It's the result of this steady thinning over four decades that has brought it to a state where its summer melt is causing it to disappear.


"It's like the Arctic is covered with an egg shell and the egg shell has been thinning to the point where it is now just cracking completely."

His prediction comes as the Canadian Ice Service prepares to issue its annual summer forecast.

After a record melt in 2007, and an above-average melt last year, this coming summer is seen as crucial for determining the rate at which the sea-ice will disappear.

An ice service analyst, Dr Trudi Wohlleben, said that the ice was likely to retreat as much as it had in the past two years.

Typically, about 40% of the Arctic Ocean is covered with older, thicker ice, but that has been greatly reduced.

Referring to the direct measurements taken by the Catlin team, Dr Wohlleben said: "It is very nice to have 'ground-truthing' of what you're interpreting from the satellite data.

"So when we look at the imagery, we're expecting the first year ice to be between 1m and 2m thick and it's nice to have those numbers confirmed."

Climate Change Odds Much Worse Than Thought


The wheel on the right depicts researchers' estimation of the range of probability of potential global temperature change over the next 100 years if no policy change is enacted on curbing greenhouse gas emissions. The wheel on the left assumes that aggressive policy is enacted. (Credit: Image courtesy / MIT Joint Program on the Science and Policy of Global Change)

ScienceDaily (May 20, 2009) — The most comprehensive modeling yet carried out on the likelihood of how much hotter the Earth's climate will get in this century shows that without rapid and massive action, the problem will be about twice as severe as previously estimated six years ago - and could be even worse than that.

The study uses the MIT Integrated Global Systems Model, a detailed computer simulation of global economic activity and climate processes that has been developed and refined by the Joint Program on the Science and Policy of Global Change since the early 1990s. The new research involved 400 runs of the model with each run using slight variations in input parameters, selected so that each run has about an equal probability of being correct based on present observations and knowledge. Other research groups have estimated the probabilities of various outcomes, based on variations in the physical response of the climate system itself. But the MIT model is the only one that interactively includes detailed treatment of possible changes in human activities as well - such as the degree of economic growth, with its associated energy use, in different countries.

Study co-author Ronald Prinn, the co-director of the Joint Program and director of MIT's Center for Global Change Science, says that, regarding global warming, it is important "to base our opinions and policies on the peer-reviewed science," he says. And in the peer-reviewed literature, the MIT model, unlike any other, looks in great detail at the effects of economic activity coupled with the effects of atmospheric, oceanic and biological systems. "In that sense, our work is unique," he says.

The new projections, published this month in the American Meteorological Society's Journal of Climate, indicate a median probability of surface warming of 5.2 degrees Celsius by 2100, with a 90% probability range of 3.5 to 7.4 degrees. This can be compared to a median projected increase in the 2003 study of just 2.4 degrees. The difference is caused by several factors rather than any single big change. Among these are improved economic modeling and newer economic data showing less chance of low emissions than had been projected in the earlier scenarios. Other changes include accounting for the past masking of underlying warming by the cooling induced by 20th century volcanoes, and for emissions of soot, which can add to the warming effect. In addition, measurements of deep ocean temperature rises, which enable estimates of how fast heat and carbon dioxide are removed from the atmosphere and transferred to the ocean depths, imply lower transfer rates than previously estimated.

Prinn says these and a variety of other changes based on new measurements and new analyses changed the odds on what could be expected in this century in the "no policy" scenarios - that is, where there are no policies in place that specifically induce reductions in greenhouse gas emissions. Overall, the changes "unfortunately largely summed up all in the same direction," he says. "Overall, they stacked up so they caused more projected global warming."

While the outcomes in the "no policy" projections now look much worse than before, there is less change from previous work in the projected outcomes if strong policies are put in place now to drastically curb greenhouse gas emissions. Without action, "there is significantly more risk than we previously estimated," Prinn says. "This increases the urgency for significant policy action."

To illustrate the range of probabilities revealed by the 400 simulations, Prinn and the team produced a "roulette wheel" that reflects the latest relative odds of various levels of temperature rise. The wheel provides a very graphic representation of just how serious the potential climate impacts are.

"There's no way the world can or should take these risks," Prinn says. And the odds indicated by this modeling may actually understate the problem, because the model does not fully incorporate other positive feedbacks that can occur, for example, if increased temperatures caused a large-scale melting of permafrost in arctic regions and subsequent release of large quantities of methane, a very potent greenhouse gas. Including that feedback "is just going to make it worse," Prinn says.

The lead author of the paper describing the new projections is Andrei Sokolov, research scientist in the Joint Program. Other authors, besides Sokolov and Prinn, include Peter H. Stone, Chris E. Forest, Sergey Paltsev, Adam Schlosser, Stephanie Dutkiewicz, John Reilly, Marcus Sarofim, Chien Wang and Henry D. Jacoby, all of the MIT Joint Program on the Science and Policy of Global Change, as well as Mort Webster of MIT's Engineering Systems Division and D. Kicklighter, B. Felzer and J. Melillo of the Marine Biological Laboratory at Woods Hole.

Prinn stresses that the computer models are built to match the known conditions, processes and past history of the relevant human and natural systems, and the researchers are therefore dependent on the accuracy of this current knowledge. Beyond this, "we do the research, and let the results fall where they may," he says. Since there are so many uncertainties, especially with regard to what human beings will choose to do and how large the climate response will be, "we don't pretend we can do it accurately. Instead, we do these 400 runs and look at the spread of the odds."

Because vehicles last for years, and buildings and powerplants last for decades, it is essential to start making major changes through adoption of significant national and international policies as soon as possible, Prinn says. "The least-cost option to lower the risk is to start now and steadily transform the global energy system over the coming decades to low or zero greenhouse gas-emitting technologies."

This work was supported in part by grants from the Office of Science of the U.S. Dept. of Energy, and by the industrial and foundation sponsors of the MIT Joint Program on the Science and Policy of Global Change.

<sub>Journal reference:

1. A.P. Sokolov, P.H. Stone, C.E. Forest, R. Prinn, M.C. Sarofim, M. Webster, S. Paltsev, C.A. Schlosser, D. Kicklighter, S. Dutkiewicz, J. Reilly, C. Wang, B Felzer, H.D. Jacoby. Probabilistic forecast for 21st century climate based on uncertainties in emissions (without policy) and climate parameters. Journal of Climate, 2007; preprint (2009): 1 DOI: 10.1175/2009JCLI2863.1

Adapted from materials provided by Massachusetts Institute of Technology.</sub>

Origin of Antarctic ice revealed
By Victoria Gill
Science reporter, BBC News


The Gamburtsev mountains have been preserved under the ice sheet

Incredible peaks and valleys, buried beneath ice for 14 million years, have revealed evidence of how the East Antarctic ice sheet first formed.

Scientists used radar to map an area of the Gamburtsev mountains - believed to be the point of origin of the ice.

The region would have been cold enough for the first glacier to form.

Writing in the journal Nature, the researchers say their findings provide important clues about how the ice sheet will behave as our climate changes.

"This is the largest reservoir of ice on Earth, and the most poorly understood place on our planet," said the British Antarctic Survey's Fausto Ferraccioli, a scientist involved in a separate international project to study the region.

He explained that the elevation and location of the Gamburtsev Mountains - in the centre of the ice sheet - made them an "ideal place" for the formation of the very first ice.

Icy unknown

Sun Bo from the Polar Research Institute of China, who led this study, has now provided further insight into the evolution of the ice sheet.

He and his colleagues travelled 1,235km (767 miles) by tractor train from a research station at the edge of East Antarctica, to the summit of Dome A of the Gamburtsev range, near the centre.

Tractor train in Antarctica (Sun Bo)

Peering down at the ice sheet underneath your feet, you just don't know what's under there
Martin Siegert
University of Edinburgh

Dr Sun's team then attached radar equipment to the tractor and drove around, meticulously surveying a 30km by 30km square of the glacial region.

Their radar revealed a landscape that, 14 million years ago, looked similar to the European Alps.

"This is true scientific exploration," said Martin Siegert, head of the school of geosciences at Edinburgh University, who was also involved in the study.

"There's nothing to guide you really. Peering down at the ice sheet beneath your feet, you just don't know what's under there."

And for this type of exploration, the use of radio waves is very powerful.

When the waves reach the interface between ice and rock they bounce back, because of the difference in electrical properties between the two.

Antarctica

"You just measure the two-way travel time as they go down and come back up again," explained Dr Siegert. "Then you can convert that to ice thickness, because you know the velocity at which [the radio waves] are travelling."

Dr Siegert said the research team was "very lucky" to see such a clear image of the underlying landscape. They discovered a whole valley system - with mountains at the edge of the survey region and the valley in the middle.

"That's perfect, because it allows us to work out how the valley would have worked when it was filled with ice, and how the water would have flowed when there was no ice there at all," said Dr Siegert.

Frozen in time

By looking at ancient climate patterns, scientists have previously estimated that the East Antarctic ice sheet formed around 14 million years ago, burying and preserving the Gamburtsev mountain landscape under ice that is now up to 3km thick.

"You need a mean annual temperature of about 3C for the glaciers to form the way they did," Dr Siegert told BBC News.

"The mean annual temperature in this region now is -60 C. So we believe that these mountains are relics of [glacial erosion] in Antarctica before the ice sheet was in place."

He added that the findings provided an insight into the stability of the ice.
A glaciated valley in Snowdonia (Martin Siegert)

Antarctica's landscape was mountainous before the ice formed

"It is a critical part of our Earth's system," said Dr Ferraccioli. "If the whole ice sheet collapsed, sea levels would rise by 60m."

"There's been a lot of climate change over the last 14 million years," Dr Siegert said. "And what we can say about this place in the middle of the Antarctic is that nothing has changed."

But, he warned, if levels of atmospheric carbon dioxide continued to rise, in around 1,000 years they will approach the same levels that existed "before there was persistent ice sheet in Antarctica".

"This puts the ice sheet into the context of global climate and what conditions are needed to grow an ice sheet," explained Dr Siegert. "The worrying thing is that we seem to be going back to carbon dioxide concentrations consistent with there being a lot less ice around."

African farms becoming too hot to handle


Further climate change could make life even harder for struggling African farmers _{(Image: Daniel Berehulak/National Geographic/Getty)}

* 15:43 17 June 2009 by Bob Holmes
* For similar stories, visit Climate Change Topic Guides
http://www.newscientist.com/topic/climate-change

African farmers will soon face growing seasons hotter than any in their experience. To cope with this rapid climate change, they – and the plant breeders who supply their crops – will need to make big changes, and soon.

Agricultural experts have predicted for some time that farmers are likely to face problems as climates become hotter and drier than they are today. Indeed, some farmers in South Africa are already reporting difficulties (pdf).

To see how fast, and how broadly, this will strike, Marshall Burke, an agricultural economist at Stanford University, and colleagues, averaged the results from 18 global climate models to forecast likely temperature and rainfall conditions in 2025, 2050 and 2075 in regions of Africa where maize, millet and sorghum are grown today. Then, assuming that year-to-year variability would remain the same as today – perhaps a conservative assumption – they asked how much these future climates would overlap with existing climates.

They found that farmers in Africa will face average temperatures outside the current range of experience in their locality in 42% of years by 2025 – and 97% by 2075. Since temperature strongly affects crop yields, farmers will need to find new varieties adapted to these higher temperatures, Burke says. Future rainfall showed more overlap with current conditions, largely because rainfall already varies more from year to year.
Maize trap

The researchers then looked to see whether the warmer temperatures forecast for 2050 can be found anywhere in Africa today. If so, they reasoned, these analogous conditions might yield crop varieties already adapted for the future conditions. A few lucky countries, such as Tanzania, Ethiopia and South Africa, have diverse enough climates today that they can find climates analogous to the potential conditions of 2050 within their own borders today, Burke's team found.

At the opposite extreme, Sahelian countries such as Chad, Mali and Niger may have nowhere to turn. "By 2050, they're going to be hotter than any current growing season in any maize country in the world," says Burke. Most countries, however, will be able to find analogous climates in other countries today.

That would be good news, except that plant breeders have done very little collecting of locally adapted varieties from some of the most likely analog countries, such as Cameroon, Sudan and Nigeria, Burke's team found. To cope with future climates, genetic prospectors must sample much more of the genetic diversity of crops in these countries – and those nations must then do a better job of sharing these genetic resources, says Burke.

"We've got to do something serious about agriculture and we've got to start now," agrees Gerald Nelson, an agricultural economist who heads research on agriculture and climate change at the International Food Policy Research Institute in Washington DC.

Climate Change Already Having Impact On U.S., Expected To Worsen



Precipitation map developed by Berkeley Lab's Michael Wehner shows, among other things, a substantial reduction in springtime rains in California, and summertime rains in the Pacific Northwest. (Credit: Image courtesy of DOE/Lawrence Berkeley National Laboratory)

ScienceDaily (June 17, 2009) — Extreme weather, drought, heavy rainfall and increasing temperatures are a fact of life in many parts of the US as a result of human-induced climate change, researchers report. These and other changes will continue and likely increase in intensity into the future, the scientists found. For the southwest region of the United States, which includes California, the report forecasts a hotter, drier climate with significant effects on the environment, agriculture and health.

Researchers representing 13 U.S. government science agencies, major universities and research institutes produced the major report entitled "Global Climate Change Impacts in the United States." Two researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), Evan Mills and Michael Wehner, contributed to the analysis in the study, released June 16 by the multi-agency U.S. Global Change Research Program.

For the southwest region of the United States, which includes California, the report forecasts a hotter, drier climate with significant effects on the environment, agriculture and health.

“Global Climate Change Impacts in the United States” covers such effects as changes in rainfall patterns, drought, wildfire, Atlantic hurricanes, and effects on food production, fish stocks and other wildlife, energy, agriculture, water supplies, and coastal communities.

“This is the most thorough and up-to-date review ever assembled of climate-change impacts observed to date as well as those anticipated in the future across the United States,” says Evan Mills, one of the Berkeley Lab scientists who contributed to the report. While the report paints an ominous picture of potential impacts, “the good news is that the harshest impacts of future climate change can be avoided if the nation takes deliberate action soon. This can be done through a balanced mix of activities to reduce greenhouse-gas emissions and adaptation to the otherwise unavoidable impacts,” says Mills.

The report addresses nine zones of the United States (Southwest, Northwest, Great Plains, Midwest, Southeast, Northeast, Alaska, U.S. islands, and coasts), and describes potential climate change effects in each. California is part of the southwest zone, as well as a coastal zone.

Wehner, who is a climate researcher in the Scientific Computing Group of Berkeley Lab’s Computational Research Division, developed projections of future climate change for the report chapters covering global and national impacts of climate change. One of Wehner’s research interests is extreme weather conditions resulting from climate change.

The precipitation map shown is one of the projections developed by Wehner. It shows, among other things, a substantial reduction in springtime rains in California, and summertime rains in the Pacific Northwest.

“Even in areas where precipitation is projected to increase, higher temperatures will cause greater evaporation leading to a future where drought conditions are the normal state. In the southwest United States, water resource issues will become a major issue,” says Wehner.

Another of Wehner’s graphics shows past and future projections of the global mean surface air temperature, an indicator of the magnitude of the effects of global climate change. The three different trajectories after 2009 show low emissions, and two high emissions scenarios of how the temperature increase caused by greenhouse gas emissions could play out. The projections are based on the most sophisticated climate models available.

“These and similar projections reveal that actions taken today would take several decades to make any noticeable change in the rate of warming. This is one of the factors that makes climate change a difficult policy issue. There is no instant gratification,” says Wehner.

Mills, who studies climate change and the insurance industry in the Environmental Energy Technologies Division of Berkeley Lab, worked on the report’s sections addressing impacts on society and on the energy sector. The insurance industry has been one of the early responders to the threats posed by climate change, because the industry has been a leader in preventive education against catastrophes such as fire and windstorm hazards. Extreme weather conditions, and the resulting damage, will probably impact the industry’s bottom line, possibly severely, as well as that of government provided insurance programs for floods and crops.

“Insurance is one of the industries particularly vulnerable to increasing extreme weather events such as severe storms, but it also is beginning to help society manage the risks,” says Mills. “Insurance, the world’s largest industry, will be one of the primary mechanisms through which the costs of climate change are distributed across society. Some insurers are emerging as partners in climate science and the formulation of public policy and adaptation strategies. Others have recognized that mitigation and adaptation can work hand in hand in a coordinated climate risk-management strategy and are offering “green” insurance products designed to capture these dual benefits.”

A Drier California

Decline in precipitation and water supplies will likely be one of the most prominent effects of climate change in California and other states of the southwest (Nevada, Arizona, Utah, Colorado, and New Mexico). The report suggests that runoff will decline from 10 to 40 percent in 2040 to 2060 relative to the 1901-1970 baseline, and warns that scarce water supplies will call for trade-offs among competing uses.

“Floods and droughts are likely to become much more common and intense as regional and seasonal precipitation patterns change and rainfall is more concentrated into heavy events with longer dry periods in between,” it states.

There will likely be less snow, with more winter precipitation falling as rain, and the wet areas will get wetter as dry areas get dryer. The region will likely see declines in the mountain snowpack, and runoff will shift to earlier in spring, reducing water flows later in the year in the summer. California is strongly dependent on spring and summer runoff to supply water for residential, commercial and agricultural uses.

Agriculture in California will likely face increasing stress from the decline in runoff and drought, as well as increasing air temperatures, and the probable rise in agricultural pests and weeds expected in a warmer climate. Flooding and storm surges are threats to coastal regions.

Forest growth in the west will decrease because of the decreasing availability of water. This will also put additional stress on salmon, trout and other coldwater fish. Superinfestations of insects will cause ecological and economic damages to timberlands.

A Hotter California

Increasing air temperatures attributed to global warming are expected to cause a rise in the number of heat-related illnesses in the 2080 to 2099 timeframe. In parts of southern California, the state’s southern Central Valley, and western Arizona, for instance, the number of days in which the temperature exceeds 100°F could exceed 120 under the report’s higher emissions scenario.

Changes in the nation’s population and distribution could combine to amplify the probability of increasing heat-related disease. As the nation ages, its older members move to warmer areas of the country including the desert southwest.

Another effect of these higher temperatures will be increased energy demand. The report predicts “increases in demand for cooling energy” in California as well as elsewhere, which will result in “significant increases in electricity use and higher peak demand in most regions.” Mills contributed analysis to the report of the strongly rising role of extreme weather events in causing electric power disruptions, while non-weather-related events show no upward trend.

The full report, “Global Climate Change Impacts in the United States” is available at: http://www.globalchange.gov/usimpacts
Adapted from materials provided by DOE/Lawrence Berkeley National Laboratory.

Some Particles Cool Climate, Others Add To Global Warming



Aerosols. Aerosols like sulfur, nitrate, and organic carbon are formed in the atmosphere and cause global cooling. Thereby they contribute to mask parts of the human induced global warming. On the other hand, black carbon absorbs radiation and thereby has a warming effect on the earth’s climate. (Credit: iStockphoto/Daniel Stein)

ScienceDaily (June 19, 2009) — There is large scientific agreement that human made emissions of CO2 and other gasses give global warming. But human activity doesn’t just cause gas emissions. Burning of fossil fuels and biomass also causes emissions of the particle black carbon. Other kinds of particles are formed in the atmosphere as a cause of human made emissions.

Particles, also named aerosols, are today one of the main reasons for the uncertainty about how humans affect the global climate. Aerosols like sulfur, nitrate, and organic carbon are formed in the atmosphere and cause global cooling. Thereby they contribute to mask parts of the human induced global warming. On the other hand, black carbon absorbs radiation and thereby has a warming effect on the earth’s climate.

Models and observations

The average climate effect from particles is a cooling effect. But to which extent particles cool down the climate, has remained an unanswered question for scientists.

“An important reason for this uncertainty is that estimates of the climate effect based on observations and models have not coincided”, Gunnar Myhre explained.

“For scientists, this has been frustrating. It has given us less faith in our understanding of the models and in our understanding of the direct aerosol effect”.

Defect in the estimates

Based on satellite observations, estimates are made of the climate effect from aerosols. If these estimates were correct, aerosols would have had a stronger cooling effect than the models show and thereby to an even larger extent have masked the global warming. Some estimates even show that aerosols have masked as much as 50 percent of the warming from CO2.

But Myhre’s article now points at what might have been a defect in these estimates. By doing this, he brings scientists a big step closer to the explanation of the discrepancy between models and estimates from observations.

“The estimates are not able to consider that the share of black carbon particles has increased by a much faster rate than the total number of particles. This can explain the main discrepancy we have seen between estimates from observations and models”, Myhre said.

Weaker cooling effect

According to Myhre’s article, the models have until now given the best picture of the climate effect from aerosols. The cooling effect from aerosols looks like being a bit weaker than the estimates from observations would say.

“What I have done, is a small contribution to our understanding of the human influence on climate change. The more we understand, the better prognoses can we give for future temperatures”, Myhre said.

Even though particles until now have masked part of the global warming, they will not do this to the same extent in the future.

”Particles only stay in the atmosphere for a few days. If the production of particles should remain constant in the future, the amount of particles in the atmosphere would also be constant”, Myhre said.

”CO2 is different. CO2 stays in the atmosphere for several hundred years. With constant CO2 emissions, the concentration continues to increase and the warming will accelerate strongly in the future. The aereosols will then be able to mask a relatively smaller part of the global warming”, Gunnar Myhre said.

<sub>Journal reference:

1. Myhre et al. Consistency Between Satellite-Derived and Modeled Estimates of the Direct Aerosol Effect. Science, 2009; DOI: 10.1126/science.1174461</sub>

Dolphin 'super pod' seen in firth


Some of the short-beaked common dolphins which were seen in the Moray Firth

Hundreds of dolphins more commonly found in warmer seas have been seen in the Moray Firth while making a "massive migration" into the North Sea.

The environmental charity Earthwatch Institute said more than 400 short-beaked common dolphins were sighted off the north east coast.

It said the "super pod" was a sign of how climate change was pushing some wildlife further north.

The firth is famous for its bottlenose dolphins.

An Earthwatch team headed by Dr Kevin Robinson, director and co-founder of the Cetacean Research and Rescue Unit (CRRU), saw the pod 10 miles off land.

There were older animals doing back-flips, and there were even newborn calves swimming along with the group
Christina Gore
Earthwatch volunteer

He said the dolphins' appearance in the firth was hugely significant.

Dr Robinson said: "Firstly, the sheer number of dolphins was astounding - there were common dolphin everywhere around us over a two-mile radius.

"Furthermore, this was only the second sighting in the past few years of such a 'super-pod' of this species in these waters. The first sighting in 10 years was recorded here in July 2007 when we were joined by more than 300 animals in the outer Moray Firth.

"Since then we have not seen them, although smaller groups have been identified by co-workers from the Whale and Dolphin Conservation Society on opportunistic boat surveys."

He said "super pods" were known to exist in other parts of the UK. There have been sightings in the Western Isles, but few in the firth.

The scientist added: "This is further scientific evidence that populations of dolphins are moving further north because of climate change."

'Wall-to-wall'

Christina Gore, a 61-year-old Earthwatch volunteer who was also on the boat trip, said the water was "boiling with animals".

She said: "It was incredibly exciting. They were swimming under the boat and leaping alongside us. There were older animals doing back-flips, and there were even newborn calves swimming along with the group."

Charlie Phillips, of the WDCS, said common dolphins could be seen in the Inner Moray Firth where the stretch of water narrows in the summer.

He said the numbers in the group seen by Dr Robinson off Fraserburgh were amazing.

Mr Phillips said: "To see wall-to-wall dolphins is something to behold."

Large sand eel and mackerel shoals off the Caithness coast may see the "super pod" move into the Pentland Firth, he added.

Particulate Pollution Combined With Airborne Soot Adds To Global Warming



Los Angeles. Particulate pollution thought to be holding climate change in check by reflecting sunlight instead enhances warming when combined with airborne soot, a new study has found. (Credit: iStockphoto/Daniel Stein)

ScienceDaily (June 30, 2009) — Particulate pollution thought to be holding climate change in check by reflecting sunlight instead enhances warming when combined with airborne soot, a new study has found.

Like a black car on a bright summer day, soot absorbs solar energy. Recent atmospheric models have ranked soot, also called black carbon, second only to carbon dioxide in potential for atmospheric warming. But particles, or aerosols, such as soot mix with other chemicals in the atmosphere, complicating estimates of their role in changing climate.

"Until now, scientists have had to assume how soot is mixed with other chemical species in individual particles and estimate how that ultimately impacts their warming potential," said Kimberly Prather, professor in the Department of Chemistry and Biochemistry and the Scripps Institution of Oceanography at the University of California, San Diego. "Our measurements show that soot is most commonly mixed with other chemicals such as sulfate and this mixing happens very quickly in the atmosphere. These are the first direct measurements of the optical properties of atmospheric soot and allow us to better understand the role of soot in climate change."

Prather and Ryan Moffet, a former graduate student at UC San Diego who is now at the Lawrence Berkeley National Laboratory, measured atmospheric aerosols over Riverside, California and Mexico City. Using an instrument that measures the size, chemical composition and optical properties of aerosols in real time, they showed that jagged bits of fresh soot quickly become coated with a spherical shell of other chemicals, particularly sulfate, nitrate, and organic carbon, through light-driven chemical reactions.

Within several hours of sunrise, most of the atmospheric carbon they measured had been altered in this way, they report in the Proceedings of the National Academy of Sciences online the week of June 29.

Particles of sulfate or nitrate alone reflect light, and some have proposed pumping sulfate aerosols into the atmosphere to slow climate change. But these chemicals play a different role when they mix with soot.

"The coating acts like a lens and focuses the light into the center of the particle, enhancing warming," Prather said. "Many people think sulfate aerosols are a good thing because they are highly reflective and cool our planet. However we are seeing that sulfate is commonly mixed with soot in the same particles, which means in some regions sulfate could lead to more warming as opposed to more cooling as one would expect for a pure sulfate aerosol."

Their measurements showed that in the atmosphere the lens-like shell of sufate and nitrate enhances absorption of light by coated soot particles 1.6 times over pure soot particles.

Soot comes from fires, including those used to cook food and clear agricultural fields, as well as burning of diesel fuel in trucks and ships. Simple measures such as providing better cook stoves with more complete combustion to those in developing countries would help reduce atmospheric soot levels.

Efforts to reduce soot would pay off soon. Unlike carbon dioxide, which lingers in the atmosphere for centuries, soot falls from the sky in a matter of days to weeks, making the reduction of soot a quicker option for slowing down climate change.

"While reducing CO2 concentrations is extremely important, changes we make today will not be felt for quite a while, whereas changes we make today on soot and sulfate could affect our planet on timescales of months," Prather said. "This could buy us time while we grapple with the problems of reducing carbon dioxide and other greenhouse gases."
_{Adapted from materials provided by University of California - San Diego, via EurekAlert!, a service of AAAS.}

Palo Alto, CA— When glaciers advanced over much of the Earth's surface during the last ice age, what kept the planet from freezing over entirely? This has been a puzzle to climate scientists because leading models have indicated that over the past 24 million years geological conditions should have caused carbon dioxide levels in the atmosphere to plummet, possibly leading to runaway "icehouse" conditions. Now researchers writing in the July 2, 2009, Nature report on the missing piece of the puzzle – plants.

"Atmospheric CO2 concentrations have been remarkably stable over the last 20 or 25 million years despite other changes in the environment," says co-author Ken Caldeira of the Carnegie Institution's Department of Global Ecology. "We can look to land plants as the primary buffering agent that's held CO2 in such a narrow range during this time."

The research team, led by Mark Pagani of Yale University, found that the critical role of plants in the chemical breakdown and weathering of rocks and soil gave them a strong influence on carbon dioxide levels. It was a link that earlier studies had missed.

Over geologic time, large volumes of carbon dioxide have been released into the atmosphere by volcanoes. This would cause CO2 to build up in the atmosphere were it not for countervailing geologic processes of sedimentation, which bury carbon-containing minerals in the crust, sequestering it from the atmosphere. The overall rate of sedimentation is controlled by the upthrust of mountains and the erosion and chemical breakdown of their rocks. The rise of the Andes, Himalayas, Tibetan Plateau, and mountain ranges in western North America over the past 25 million years would have been expected to have cause faster weathering and erosion, and therefore a faster burial of carbon drawn from the atmosphere. But the stability of carbon dioxide levels indicate that this didn't happen. Why not?

This is where the plants come in. "The rates of weathering reactions are largely controlled by plants. Their roots secrete acids that dissolve minerals, they hold soils, and they increase the amount of carbon dissolved in groundwater," says Caldeira. "But when levels of carbon dioxide get too low, the plants basically suffocate and the weathering slows down. That means less sediment is eroded from the uplands and less carbon can be buried. It's a negative feedback on the system that has kept carbon dioxide levels from dropping too low."

Extremely low carbon dioxide levels would have reduced the atmosphere's ability to retain heat, putting the planet into a deep freeze. "So you could say that by limiting the drawdown of CO2 by chemical weathering and sedimentation, plants saved the planet from freezing over," says Caldeira.

Could plants save us from rising carbon dioxide from human emissions and harmful greenhouse warming? No, says Caldeira. "We are releasing CO2 to the atmosphere about 100 times faster than all the volcanoes in the world put together. While these weathering processes will eventually remove the CO2 we are adding to the atmosphere, they act too slowly to help us avoid dangerous climate change. It will take hundreds of thousands of years for these rock weathering processes to remove our fossil fuel emissions from the atmosphere."

The Carnegie Institution (http://www.CIW.edu) has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments throughout the U.S. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science. The Department of Global Ecology, located in Stanford, California, was established in 2002 to help build the scientific foundations for a sustainable future. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.

New Haven, Conn. — Fifty million years ago, the North and South Poles were ice-free and crocodiles roamed the Arctic. Since then, a long-term decrease in the amount of CO2 in the atmosphere has cooled the Earth. Researchers at Yale University, the Carnegie Institution of Washington and the University of Sheffield now show that land plants saved the Earth from a deep frozen fate by buffering the removal of atmospheric CO2 over the past 24 million years.

While the upper limit for atmospheric CO2 levels has been a focus for discussions of global warming and the quality of life on Earth, this study points to the dynamics that maintain the lower sustainable limits of atmospheric CO2.

Volcanic gases naturally add CO2 to the atmosphere, and over millions of years CO2 is removed by the weathering of silica-based rocks like granite and then locked up in carbonates on the floor of the world's oceans. The more these rocks are weathered, the more CO2 is removed from the atmosphere.


As plants become starved for CO2, rock weathering diminishes. Credit: David Beerling

"Mountain building in places like Tibet and South America during the past 25 million years created conditions that should have sucked nearly all the CO2 out of the atmosphere, throwing the Earth into a deep freeze," said senior author Mark Pagani, associate professor of geology and geophysics and a member of the Yale Climate and Energy Institute's executive committee. "But as the CO2 concentration of Earth's atmosphere decreased to about 200 to 250 parts per million, CO2 levels stabilized."


Mark Pagani is a researcher at Yale University. Credit: Pagani.

The study, published in the XX issue of Nature, looked for a possible explanation. They used simulations of the global carbon cycle and observations from plant growth experiments to show that as atmospheric CO2 concentrations began to drop towards near-starvation levels for land plants, the capacity of plants and vegetation to weather silicate rocks greatly diminished, slowing the draw-down of atmospheric CO2.

"When CO2 levels become suffocatingly low, plant growth is compromised and the health of forest ecosystems suffer," said Pagani. "When this happens, plants can no longer help remove CO2 from the atmosphere faster than volcanoes and other sources can supply it."

"Ultimately, we owe another large debt to plants" said co-author Ken Caldeira from the Carnegie Institution of Washington at Stanford University. "Aside from providing zesty dishes like eggplant parmesan, plants have also stabilized Earth's climate by inhibiting critically low levels of CO2 that would have thrown Earth spinning into space like a frozen ice ball."

Co-author David Beerling from Sheffield University adds, "Our research supports the emerging view that plants should be recognized as a geologic force of nature, with important consequences for all life on Earth"

Robert Berner, professor emeritus of geology and geophysics at Yale, is also an author on the study. The Yale Climate and Energy Institute; the National Science Foundation; the Department of Energy; the Leverhulme Trust and a Royal Society-Wolfson Research Merit Award supported the research.

The Yale Climate and Energy Institute (YCEI) is a newly established interdisciplinary institute focused on bridging research and policy around climate and energy issues so that practical solutions can be implemented in both the developing and developed world.

An interview with Mark Pagani is available at http://tinyurl.com/yale-pagani-052909

Citation: Nature, (doi:10.1038/nature08133)

New research, which reconstructs the extent of ice in the sea between Greenland and Svalbard from the 13th century to the present indicates that there has never been so little sea ice as there is now. The research results from the Niels Bohr Institute, among others, are published in the scientific journal, Climate Dynamics.

There are of course neither satellite images nor instrumental records of the climate all the way back to the 13th century, but nature has its own 'archive' of the climate in both ice cores and the annual growth rings of trees and we humans have made records of a great many things over the years - such as observations in the log books of ships and in harbour records. Piece all of the information together and you get a picture of how much sea ice there has been throughout time.


There has never been so little sea ice in the area between Svalbard and Greenland in the last 800 years. Credit: NASA/GSFC.

Modern research and historic records
"We have combined information about the climate found in ice cores from an ice cap on Svalbard and from the annual growth rings of trees in Finland and this gave us a curve of the past climate" explains Aslak Grinsted, geophysicist with the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen.

In order to determine how much sea ice there has been, the researchers needed to turn to data from the logbooks of ships, which whalers and fisherman kept of their expeditions to the boundary of the sea ice. The ship logbooks are very precise and go all the way back to the 16th century. They relate at which geographical position the ice was found. Another source of information about the ice are records from harbours in Iceland, where the severity of the winters have been recorded since the end of the 18th century.

By combining the curve of the climate with the actual historical records of the distribution of the ice, researchers have been able to reconstruct the extent of the sea ice all the way back to the 13th century. Even though the 13th century was a warm period, the calculations show that there has never been so little sea ice as in the 20th century.

In the middle of the 17th century there was also a sharp decline in sea ice, but it lasted only a very brief period. The greatest cover of sea ice was in a period around 1700-1800, which is also called the 'Little Ice Age'.

"There was a sharp change in the ice cover at the start of the 20th century," explains Aslak Grinsted. He explains, that the ice shrank by 300.000 km2 in the space of ten years from 1910-1920. So you can see that there have been sudden changes throughout time, but here during the last few years we have had some record years with very little ice extent.

"We see that the sea ice is shrinking to a level which has not been seen in more than 800 years", concludes Aslak Grinsted.

Link: http://dx.doi.org/10.1007/s00382-009-0610-z

New Type Of El Nino Could Mean More Hurricanes Make Landfall


The 2008 hurricane season was one of the most active on record. In this image, taken on August 28, 2008, three storms can be seen in various stages: Fay, Gustav and Hannah. (Credit: National Oceanic and Atmospheric Administration)

ScienceDaily (July 3, 2009) — El Niño years typically result in fewer hurricanes forming in the Atlantic Ocean. But a new study suggests that the form of El Niño may be changing potentially causing not only a greater number of hurricanes than in average years, but also a greater chance of hurricanes making landfall, according to climatologists at the Georgia Institute of Technology. The study appears in the July 3, 2009, edition of the journal Science.

"Normally, El Niño results in diminished hurricanes in the Atlantic, but this new type is resulting in a greater number of hurricanes with greater frequency and more potential to make landfall," said Peter Webster, professor at Georgia Tech's School of Earth and Atmospheric Sciences.

That's because this new type of El Niño, known as El Niño Modoki (from the Japanese meaning "similar, but different"), forms in the Central Pacific, rather than the Eastern Pacific as the typical El Niño event does. Warming in the Central Pacific is associated with a higher storm frequency and a greater potential for making landfall along the Gulf coast and the coast of Central America.

Even though the oceanic circulation pattern of warm water known as El Niño forms in the Pacific, it affects the circulation patterns across the globe, changing the number of hurricanes in the Atlantic. This regular type of El Niño (from the Spanish meaning "little boy" or "Christ child") is more difficult to forecast, with predictions of the December circulation pattern not coming until May. At first glance, that may seem like plenty of time. However, the summer before El Niño occurs, the storm patterns change, meaning that predictions of El Niño come only one month before the start of hurricane season in June. But El Niño Modoki follows a different prediction pattern.

"This new type of El Niño is more predictable," said Webster. "We're not sure why, but this could mean that we get greater warning of hurricanes, probably by a number of months."

As to why the form of El Niño is changing to El Niño Modoki, that's not entirely clear yet, said Webster.

"This could be part of a natural oscillation of El Niño," he said. "Or it could be El Niño's response to a warming atmosphere. There are hints that the trade winds of the Pacific have become weaker with time and this may lead to the warming occurring further to the west. We need more data before we know for sure."

In the study, Webster, along with Earth and Atmospheric Sciences Chair Judy Curry and research scientist Hye-Mi Kim used satellite data along with historical tropical storm records and climate models.

The research team is currently looking at La Niña, the cooling of the surface waters in the Eastern and Central Pacific.

"In the past, La Nina has been associated with a greater than average number of North Atlantic hurricanes and La Nina seems to be changing its structure as well," said Webster. "We're vitally interested in understanding why El Niño-La Niña has changed. To determine this we need to run a series of numerical experiments with climate models."

_{Adapted from materials provided by Georgia Institute of Technology, via EurekAlert!, a service of AAAS.}

Super-size deposits of frozen carbon threat to climate change
June 30th, 2009 in Space & Earth / Earth Sciences

The vast amount of carbon stored in the arctic and boreal regions of the world is more than double that previously estimated, according to a study published this week.

The amount of carbon in frozen soils, sediments and river deltas (permafrost) raises new concerns over the role of the northern regions as future sources of greenhouse gases.

"We now estimate the deposits contain over 1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere", said Dr. Charles Tarnocai, Agriculture and Agri-Food Canada, Ottawa, and lead author.

Dr. Pep Canadell, Executive Director of the Global Carbon Project at CSIRO, Australia, and co-author of the study says that the existence of these super-sized deposits of frozen carbon means that any thawing of permafrost due to global warming may lead to significant emissions of the greenhouse gases carbon dioxide and methane.

Carbon deposits frozen thousands of years ago can easily break down when permafrost thaws releasing greenhouse gases to the atmosphere, according to another recent study by some of the same authors.

"Radioactive carbon dating shows that most of the carbon dioxide currently emitted by thawing soils in Alaska was formed and frozen thousands of years ago. The carbon dating demonstrates how easily carbon decomposes when soils thaw under warmer conditions," said Professor Ted Schuur, University of Florida and co-author of the paper.

The authors point out the large uncertainties surrounding the extent to which permafrost carbon thawing could further accelerate climate change.

"Permafrost carbon is a bit of a wildcard in the efforts to predict future climate change," said Dr Canadell. "All evidence to date shows that carbon in permafrost is likely to play a significant role in the 21st century climate given the large carbon deposits, the readiness of its organic matter to release greenhouse gases when thawed, and the fact that high latitudes will experience the largest increase in air temperature of all regions."

Carbon in permafrost is found largely in northern regions including Canada, Greenland, Kazakhstan, Mongolia, Russia, Scandinavia and USA.

The carbon assessment is published this week in the journal of "Global Biogeochemical Cycles" of the American Geophysical Union, and the radiocarbon study was recently published in the journal of Nature.

Source: Global Carbon Project

NASA Satellite Shows 'Dramatically Thinned' Arctic Ice

WASHINGTON (AFP) – Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thick older ice shrinking by the equivalent of Alaska's land area, a study using data from a NASA satellite showed Tuesday.

Using information from NASA's Ice, Cloud and Land Satellite (ICESat), scientists from the US space agency and the University of Washington in Seattle estimated both the thickness and volume of the Arctic Ocean's ice cover.

ICESat allows scientists to measure changes in the thickness and volume of Arctic ice, whereas previously scientists relied only on measurements of area to determine how much of the Arctic Ocean is covered in ice.

Scientists found that Arctic sea ice thinned some seven inches (17.8 centimeters) a year, or 2.2 feet (67 centimeters) over four winters, according to the study by NASA and the University of Washington, published in the Journal of Geophysical Research-Oceans.

They also found that thicker, older ice, which has survived one or more summers, shrank by 42 percent.

"Between 2004 and 2008, multi-year ice cover shrank 595,000 square miles (1.5 million square kilometers) -- nearly the size of Alaska's land area," a report of the study's findings said.

The Arctic ice cap grows each winter, when the northerly region grows intensely cold as the sun sets for several months.

Then, in the summer, wind and ocean currents cause some of the ice to flow out of the Arctic, while warmer temperatures make much of it melt in place.

Thicker, older ice is less vulnerable than thinner ice to melting in the summer months.

But in recent years, the amount of ice replaced in the winter has not been sufficient to offset summer ice losses, the ICESat study showed.

That makes for more open water in summer, which absorbs more heat, warming the ocean and further melting the ice, the report of the scientists' findings said.

The research team attributed the changes in the overall thickness and volume of Arctic Ocean sea ice to recent warming and anomalies in patterns of sea ice circulation.

"The near-zero replenishment of the multi-year ice cover, combined with unusual exports of ice out of the Arctic after the summers of 2005 and 2007, have both played significant roles in the loss of Arctic sea ice volume," said Ron Kwok of NASA's Jet Propulsion Laboratory in California who led the study.

Data from the study will help scientists to better understand how fast the volume of Arctic ice is decreasing and how soon the region might be "nearly ice-free in the summer," said Kwok.

A study published in April by the Colorado-based National Snow and Ice Data Center (NSIDC) also showed that the Arctic ice cap is thinner than ever and the maximum extent of Arctic ice was at an all-time low.

The same month, US researchers warned that the Arctic could be almost ice-free within 30 years, not 90 as scientists had previously estimated.

Warming Arctic could teem with life by 2030

* 19:01 08 July 2009 by Catherine Brahic



"Teeming with life" may not be the description that springs to mind when thinking of the Arctic Ocean, but that could soon change as global warming removes the region's icy lid.

A study of what the Arctic looked like just before dinosaurs were wiped off the planet has provided a glimpse of what could be to come within decades.

Alan Kemp of the UK National Oceanography Centre in Southampton and colleagues used powerful microscopes to inspect cores of mud extracted from the bottom of the Arctic Ocean. They found successive layers of tiny algae called diatoms. The pattern of the layers and the distribution of the diatoms provides strong evidence that the Arctic was free of ice during the summer and, contrary to recent studies, frequently covered in ice during the winter.
Hot summer

Ice-free summers and icy winters are precisely what glaciologists fear could happen in the Arctic within decades. Over the past few years, wind pattern and warm temperatures have been gradually thinning Arctic sea ice, making it less and less likely to survive the summer. Some believe the Arctic could be ice-free during the summer as soon as 2030.

The researchers say that the sheer number of diatoms locked in the mud suggests that when the dinosaurs roamed the Earth the Arctic Ocean was biologically very rich during the summer, on a par with the most productive regions of the Southern Ocean today. Since diatoms are at the very bottom of the food chain, waters rich in diatoms can support a lot of larger life forms as well.

"On the basis of our findings, we can say that it is likely that a future Arctic Ocean free of summer sea ice will also be highly productive," says Kemp. Arctic fauna today is limited by the region's harsh conditions. The ocean is home to very few species of fish – such as the Arctic cod – which in turn support seals, whales and polar bears.
Summer migration

While more diatoms during the summer does not mean that larger animals will spontaneously appear in the Arctic over the coming decades, it could give species that currently live further south an incentive to move into the region by providing them with food. The most likely scenario is one in which larger species migrate to the Arctic in the summer to feed on the enriched summer food chain, then move back south during the dark winters.

"The outcome would depend on organisms at all levels of the food chain moving in to exploit this potential," says Kemp. "What is unpredictable is what species from elsewhere may migrate in to fill the new ecological niches."

A study of fossils and fossilised faeces carried out around Devon Island in the Canadian Arctic, suggested last year that the regions may once have been home to a rich gathering of larger fish and possibly even sharks during the late Cretaceous (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2008.0801). Presumably, these animals would have been supported by Kemp's diatoms.

Journal reference: Nature (DOI: 10.1038/nature08141)

Arctic glacier to lose Manhattan-sized 'tongue'

* 17:34 14 July 2009 by Catherine Brahic


http://brightcove.newscientist.com/serv ... 9419261001

Video: Researcher Alun Hubbard discusses the break up of the ice

The biggest glacier in the Arctic is on the verge of losing a chunk of ice the size of Manhattan. A group of scientists and climate change activists who are closely monitoring the Petermann glacier's ice tongue believe the rapid flow of ice is in part due to warm ocean currents moving up along the coast of Greenland, fuelled by global warming.

During the summer of last year, Jason Box of Ohio State University in Columbus noticed a huge crack in the glacier's floating ice tongue, which acts as a conveyor belt, pushing the glacier's ice through a fjord and out to sea. The crack extended almost completely from one side of the fjord to the other, 16 kilometres away.

This prompted Box and colleagues to return this year on the Arctic Sunrise, a Greenpeace vessel. The researchers are equipped with an arsenal of cameras and sensors, which they have been setting up on surrounding cliffs as well as on the ice itself.
Break imminent

Stitched together, the pictures they are taking will provide a blow-by-blow animation of the event. "We're looking on a minute by minute basis at what it's doing, how it's moving in relation to the rest of the glacier, and looking for that critical point where it fractures and breaks off," says Alun Hubbard, a glaciologist at the University Of Wales, UK.

The team believes this will happen within weeks. Only yesterday, a 3-square-kilometre chunk broke away. There are now more than 10 cracks in the ice, some 500 metres wide. The researchers expect the ice tongue to break up within the coming weeks.

When this happens, an island of ice the size of Manhattan, spanning 100 km2 holding 5 billion tonnes of ice, will break free and drift out to sea.
Melt concerns

As with all glaciers that terminate over water, big chunks of ice regularly break off the Petermann ice tongue, a process which is normally compensated for by the snow that falls on the upper reaches of the glacier. But the sheer amount of ice that could break away in a single event is concerning the scientists – five billion tonnes of ice is equivalent to nearly half of the glacier's usual annual flow.

The researchers are unsure what exactly is causing the break-up. A chunk of 1 million tonnes of ice broke off last year and there has been an acceleration in the flow of ice over the past few years. They think a number of factors are involved including warmer ocean currents that are melting the ice from below and warmer air temperatures that are melting it from above.

"Ocean warming currents are circulating around the fjord and eroding the underbelly of Petermann glacier at an incredible rate," says Hubbard.
Driller thriller

Melting at the surface of the ice forms huge whirlpools of relatively warm fresh water that bore holes into the floating sheet. The scientists believe this process is accelerating the ice's demise.

In places, the meltwater bores holes through the ice right down to the bottom of the ice tongue. Surfacing seals are proof that some of the holes – called moulins – pierce to bottom of the ice.

Box, who in addition to posting his instruments on the ground is surveying the ice by helicopter, says the view from above is one of "innumerable turquoise pools, from puddles to lakes – thousands of them".

When the huge section of ice breaks off, it could be like uncorking a bottle. A smaller ice tongue will provide less resistance for the glacier as it flows out to sea, which ultimately will accelerate sea level rise.

Indian Ocean: Gatekeeper to climate extremes?

Some glacial periods in the Earth’s more recent geological past have been cooler and more severe than others, despite very similar greenhouse gas concentrations and orbital parameters. What is it that decouples global temperature from carbon dioxide levels and the solar heat?

Changes in ocean circulation, particularly in the climatically crucial North Atlantic region, are the most likely candidate. A paper in Nature (subscription required) now suggests that some of these changes originate more than 10,000 kilometres away in the subtropical Indian Ocean.



Edouard Bard and Rosalind Rickaby analysed an 800,000-year record of sea surface temperature and ocean productivity from an ocean sediment core retrieved off the southeastern coast of South Africa (Editor's summary). This is the region where a portion of the warm and salty water carried southwards by the Agulhas current, the Indian Ocean equivalent to the Gulf Stream, leaks into the South Atlantic. The inflow compensates for the export of cold Atlantic deep water to other ocean basins. More importantly, it fuels the Atlantic overturning circulation which carries warm tropical surface water towards the poles, and cold deep water back towards the equator.

The strength of this heat conveyor depends on the position of ocean fronts, boundaries between water masses of different temperature and salinity, which are known to intermittently shift northwards and southwards.

Bard and Rickaby suggest that the Agulhas current between Madagascar and the African coast has almost come to a halt during times when the subtropical front in the Indian Ocean migrated northwards by up to 1,000 kilometres. Isotopic data from the sediment record suggest this has happened at least twice, namely during glacial stadials around 340,000 and 420,000 years ago. The closure of the Agulhas ‘valve’ might explain why these glacial periods have been severely colder than most others before and thereafter.

The “persuasive” study makes “a compelling case that, at times in the past, severely reduced water transport between the Indian and Atlantic oceans may have caused climate to cool beyond typical ice-age conditions,” writes Barcelona-based oceanographer Rainer Zahn in a News & Views piece (subscription required).

There’s a tempting afterthought: If in warm climates such as ours more Indian Ocean water leaks into the Atlantic it could help stabilize the Atlantic overturning circulation, safeguarding us against drastic climate disruptions caused by the heat conveyor’s hypothesized failure.

But as is often the case in Earth system studies, it is hard to distinguish the forces that push from those that pull on the causal chain to mode shifts. It is not quite clear, for example, what might have caused the subtropical Indian Ocean front to move this far northwards in the first place.

How the Agulhas current might behave if temperatures continue to rise is even more uncertain. “Let’s keep an eye on what the leakage does next,” says Zahn.

<sub>Quirin Schiermeier

Image: The Agulhas current carries warm Indian Ocean water around the Cape of Good Hope.
Credit: SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE</sub>

Scientists Expect Wildfires To Increase As Climate Warms In Coming Decades


This graph shows the percentage increase in area burned by wildfires, from the present-day to the 2050s, as calculated by the model of Spracklen et al. [2009] for the May-October fire season. The model follows a scenario of moderately increasing emissions of greenhouse gas emissions and leads to average global warming of 1.6 degrees Celsius (3 degrees Fahrenheit) by 2050. Warmer temperatures can dry out underbrush, leading to more serious conflagrations in the future climate. (Credit: Loretta Mickley, Harvard School of Engineering and Applied Sciences)

ScienceDaily (July 29, 2009) — As the climate warms in the coming decades, atmospheric scientists at Harvard's School of Engineering and Applied Sciences (SEAS) and their colleagues expect that the frequency of wildfires will increase in many regions. The spike in the number of fires could also adversely affect air quality due to the greater presence of smoke.

The study, led by SEAS Senior Research Fellow Jennifer Logan, was published in the June 18th issue of Journal of Geophysical Research. In their pioneering work, Logan and her collaborators investigated the consequences of climate change on future forest fires and on air quality in the western United States. Previous studies have probed the links between climate change and fire severity in the West and elsewhere. The Harvard study represents the first attempt to quantify the impact of future wildfires on the air we breathe.

"Warmer temperatures can dry out underbrush, leading to a more serious conflagration once a fire is started by lightening or human activity," says Logan. "Because smoke and other particles from fires adversely affect air quality, an increase in wildfires could have large impacts on human health."

Using a series of models, the scientists predict that the geographic area typically burned by wildfires in the western United States could increase by about 50% by the 2050s due mainly to rising temperatures. The greatest increases in area burned (75-175%) would occur in the forests of the Pacific Northwest and the Rocky Mountains. In addition, because of extra burning throughout the western U.S., one important type of smoke particle, organic carbon aerosols, would increase, on average, by about 40 percent during the roughly half-century period.

To conduct the research, the team first examined a 25-year record of observed meteorology and fire statistics to identify those meteorological factors that could best predict area burned for each ecosystem in the western United States. To see how these meteorological factors would change in the future, they then next ran a global climate model out to 2055, following the A1B scenario in greenhouse gas emissions. This scenario, one of several devised by the Intergovernmental Panel on Climate Change, describes a future world with rapid economic growth and balanced energy generation from fossil and alternative fuels. Relative to the other scenarios, it leads to a moderate warming of the earth's average surface temperature, about 3oF (1.6 oC) by 2050.

"By hypothesizing that the same relationships between meteorology and area burned still hold in the future, we then could predict wildfire activity and emissions from 2000 to the 2050's," explains Logan.

As a last step, the researchers used an atmospheric chemistry model to understand how the change in wildfire activity would affect air quality. This model, combining their predictions of areas burned with 2050's meteorology data, shows the emissions and fate of the smoke and other particles emitted by the future wildfires. The resulting diminished air quality could lead to smoggier skies and adversely affect those suffering from lung and heart conditions such as asthma and chronic bronchitis.

The authors expect the work will help policymakers gauge the "climate penalty" related to ongoing efforts to reduce air pollution across the United States. In addition, the study underscores the need for a vigorous fire management plan.

The team next plans to focus on future wildfires and air quality over the densely populated areas in California and in the southwest United States.

_{Logan's collaborators included SEAS Research Associate Loretta Mickley and former postdocs Dominick Spracklen (now at University of Leeds), Rynda Hudman, and Rosemarie Yevich; Michael D. Flannigan, Canadian Forest Service; and Anthony. L. Westerling, University of California, Merced. The authors acknowledge the support of a STAR (Science to Achieve Results) grant from National Center for Environmental Research of the U.S. Environmental Protection Agency and a grant from the National Aeronautics and Space Administration.}

Sahara Desert Greening Due to Climate Change?
James Owen
for National Geographic News
July 31, 2009

Desertification, drought, and despair—that's what global warming has in store for much of Africa. Or so we hear.



Emerging evidence is painting a very different scenario, one in which rising temperatures could benefit millions of Africans in the driest parts of the continent.

Scientists are now seeing signals that the Sahara desert and surrounding regions are greening due to increasing rainfall.

If sustained, these rains could revitalize drought-ravaged regions, reclaiming them for farming communities.

This desert-shrinking trend is supported by climate models, which predict a return to conditions that turned the Sahara into a lush savanna some 12,000 years ago.

Green Shoots

The green shoots of recovery are showing up on satellite images of regions including the Sahel, a semi-desert zone bordering the Sahara to the south that stretches some 2,400 miles (3,860 kilometers).

Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences.

The study suggests huge increases in vegetation in areas including central Chad and western Sudan.

The transition may be occurring because hotter air has more capacity to hold moisture, which in turn creates more rain, said Martin Claussen of the Max Planck Institute for Meteorology in Hamburg, Germany, who was not involved in the new study.

"The water-holding capacity of the air is the main driving force," Claussen said.

He added that the greening trend is supported by other satellite data.

(See a map of global warming's impacts.)

Not a Single Scorpion

While satellite images can't distinguish temporary plants like grasses that come and go with the rains, ground surveys suggest recent vegetation change is firmly rooted.

Throughout North Africa, new trees, such as acacias, are flourishing, according to Stefan Kröpelin, a climate scientist at the University of Cologne's Africa Research Unit in Germany.

"Shrubs are coming up and growing into big shrubs. This is completely different from having a bit more tiny grass."

In 2008 Kröpelin—not involved in the new satellite research—visited Western Sahara, a disputed territory controlled by Morocco.

"The nomads there told me there was never as much rainfall as in the past few years," Kröpelin said. "They have never seen so much grazing land."

He explained it's a similar story in the eastern Sahara area of southwestern Egypt and northern Sudan, a remote desert region that he has studied for two decades.

"Before, there was not a single scorpion, not a single blade of grass," he said.

"Now you have people grazing their camels in areas which may not have been used for hundreds or even thousands of years. You see birds, ostriches, gazelles coming back, even sorts of amphibians coming back," he said.

"The trend has continued for more than 20 years. It is indisputable."

Uncertain Future

An explosion in plant growth has been predicted by some climate models.

For instance, in 2005 a team led by Reindert Haarsma of the Royal Netherlands Meteorological Institute in De Bilt, the Netherlands, forecast significantly more future rainfall in the Sahel.

The study in Geophysical Research Letters predicted that rainfall in the July to September wet season would rise by up to two millimeters a day by 2080.

Satellite data shows "that indeed during the last decade, the Sahel is becoming more green," Haarsma said.

Even so, climate scientists don't agree on how future climate change will affect the Sahel: Some studies simulate a decrease in rainfall.

"This issue is still rather uncertain," Haarsma said.

Max Planck's Claussen said North Africa is the area of greatest disagreement among climate change modelers.

Forecasting how global warming will affect the region is complicated by its vast size and the unpredictable influence of high-altitude winds that disperse monsoon rains, Claussen added.

"Half the models follow a wetter trend, and half a drier trend."

Role Of Solar Radiation In Climate Change


Clouds and aerosols influence the solar radiation on the earth’s surface and therefore the climate. (Credit: iStockphoto/Jaap Hart)

ScienceDaily (Aug. 11, 2009) — A special volume of the Journal of Geophysical Research reviews the growing research field of “global dimming” and “global brightening” in over 20 articles. These phenomena, supposedly human-induced, control solar radiation incident at the Earth’s surface and thus influence climate.

Special instruments have been recording the solar radiation that reaches the Earth’s surface since 1923. However, it wasn’t until the International Geophysical Year in 1957/58 that a global measurement network began to take shape. The data thus obtained reveal that the energy provided by the sun at the Earth’s surface has undergone considerable variations over the past decades, with associated impacts on climate.

Investigating which factors reduce or intensify solar radiation and thus cause “global dimming” or “global brightening” is still very much a nascent field of research. The American Geophysical Union (AGU) has now published a special volume on the subject which presents the current state of knowledge in detail and makes a considerable contribution to climate science. “Only now, especially with the help of this volume, is research in this field really taking off”, stresses Martin Wild, senior scientist at the Institute for Atmospheric and Climate Science of ETH Zurich, who is a specialist on the subject.

Decrease in solar radiation discovered

The initial findings, which revealed that solar radiation at the Earth’s surface is not constant over time but rather varies considerably over decades, were published in the late 1980s and early 1990s for specific regions of the Earth. Atsumu Ohmura, emeritus professor at ETH Zurich, for example, discovered at the time that the amount of solar radiation over Europe decreased considerably between the 1950s and the 1980s. It wasn’t until 1998 that the first global study was conducted for larger areas, like the continents Africa, Asia, North America and Europe for instance. The results showed that on average the surface solar radiation decreased by two percent per decade between the 1950s and 1990.

In analyzing more recently compiled data, however, Wild and his team discovered that solar radiation has gradually been increasing again since 1985. In a paper published in “Science” in 2005, they coined the phrase “global brightening” to describe this new trend and to oppose to the term “global dimming” used since 2001 for the previously established decrease in solar radiation.

Only recently, an article in the journal Nature, which Wild was also involved in, brought additional attention to the topic of global dimming/brightening.

Air pollution favors photosynthesis

In this study, for the first time, the scientists examined the connection between global dimming/brightening and the carbon cycle. They demonstrated that more scattered light is present during periods of global dimming due to the increased aerosol- and cloud-amounts, enabling plants to absorb CO2 more efficiently than when the air is cleaner and thus clearer. According to the scientists, this is because scattered light penetrates deeper into the vegetation canopy than direct sunlight, which means the plants can use the light more effectively for photosynthesis. Consequently, there was around 10 percent more carbon stored in the terrestrial biosphere between 1960 and 1999.

The special volume, which appears in the AGU’s Journal of Geophysical Research, provides an overview of the current state of knowledge. Almost half of the publications in the volume were either completely or partially written by ETH Zurich scientists. Wild is the guest editor, and author or co-author of ten of these articles.

The articles provide the first indication of the magnitude of these effects, how they vary in terms of time and space and what the possible consequences might be for climate change. They also discuss in detail the underlying causes and mechanisms, which are still under debate.

Many questions left open

It is particularly unclear as to whether it is the clouds or the aerosols that trigger global dimming/brightening, or even interactions between clouds and aerosols, as aerosols can influence the “brightness” and lifetime of the clouds. The investigation of these relations is complicated by the fact that insufficient – if any – observational data are available on how clouds and aerosol loadings have been changing over the past decades. The recently launched satellite measurement programs should help to close this gap for the future from space, however.

“There is still an enormous amount of research to be done as many questions are still open”, explains Wild. This includes the magnitude of the dimming and brightening effects on a global level and how greatly the effects differ between urban and rural areas, where fewer aerosols are released into the atmosphere. Another unresolved question is what happens over the oceans, as barely any measurement data are available from these areas.

A further challenge for the researchers is to incorporate the effects of global dimming/brightening more effectively in climate models, to understand their impact on climate change better. After all, studies indicate that global dimming masked the actual temperature rise – and therefore climate change – until well into the 1980s. Moreover, the studies published also show that the models used in the Intergovernmental Panel on Climate Change’s (IPCC) fourth Assessment Report do not reproduce global dimming/brightening adequately: neither the dimming nor the subsequent brightening is simulated realistically by the models. According to the scientists, this is probably due to the fact that the processes causing global dimming/brightening were not taken into account adequately and that the historical anthropogenic emissions used as model input are afflicted with considerable uncertainties.

“This is why at ETH Zurich we are working with a research version of a global climate model, which contains much more detailed aerosol and cloud microphysics and can reproduce global dimming/brightening more effectively”, says Wild. For him, the studies so far constitute “initial” estimates that need to be followed up with further research.

_{Global Dimming and Brightening, Special Issue of Journal of Geophysical Research, vol. 114, no. , 2009.}

The warming of an Arctic current over the last 30 years has triggered the release of methane, a potent greenhouse gas, from methane hydrate stored in the sediment beneath the seabed.

Scientists at the National Oceanography Centre Southampton working in collaboration with researchers from the University of Birmingham, Royal Holloway London and IFM-Geomar in Germany have found that more than 250 plumes of bubbles of methane gas are rising from the seabed of the West Spitsbergen continental margin in the Arctic, in a depth range of 150 to 400 metres.

Methane released from gas hydrate in submarine sediments has been identified in the past as an agent of climate change. The likelihood of methane being released in this way has been widely predicted.

The data were collected from the royal research ship RRS James Clark Ross, as part of the Natural Environment Research Council's International Polar Year Initiative. The bubble plumes were detected using sonar and then sampled with a water-bottle sampling system over a range of depths.

The results indicate that the warming of the northward-flowing West Spitsbergen current by 1° over the last thirty years has caused the release of methane by breaking down methane hydrate in the sediment beneath the seabed.

Professor Tim Minshull, Head of the University of Southampton's School of Ocean and Earth Science based at that the National Oceanography Centre, says: "Our survey was designed to work out how much methane might be released by future ocean warming; we did not expect to discover such strong evidence that this process has already started."

Methane hydrate is an ice-like substance composed of water and methane which is stable in conditions of high pressure and low temperature. At present, methane hydrate is stable at water depths greater than 400 metres in the ocean off Spitsbergen. However, thirty years ago it was stable at water depths as shallow as 360 metres.

This is the first time that such behaviour in response to climate change has been observed in the modern period.

While most of the methane currently released from the seabed is dissolved in the seawater before it reaches the atmosphere, methane seeps are episodic and unpredictable and periods of more vigorous outflow of methane into the atmosphere are possible. Furthermore, methane dissolved in the seawater contributes to ocean acididfication.

Graham Westbrook Professor of Geophysics at the University of Birmingham, warns: "If this process becomes widespread along Arctic continental margins, tens of megatonnes of methane per year – equivalent to 5-10% of the total amount released globally by natural sources, could be released into the ocean."

The team is carrying out further investigations of the plumes; in particular they are keen to observe the behaviour of these gas seeps over time.

Publication: Westbrook, G. K. et al. Escape of methane gas from the seabed along the West Spitsbergen continental margin. Geophysical Research Letters doi:10.1029/2009GL039191, 2009

The authors are Graham Westbrook (Birmingham), Kate Thatcher (Birmingham), Eelco Rohling (NOCS), Alexander Piotrowski (Cambridge), Heiko Palike (NOCS), Anne Osborne (Bristol), Euan Nisbet (Royal Holloway, London), Tim A. Minshull (NOCS), Mathias Lanoiselle (Royal Holloway, London), Rachael James (NOCS),Veit Huehnerbach (NOCS), Darryl Green (NOCS), Rebecca Fisher (Royal Holloway, London), Anya Crocker (NOCS), Anne Chabert (NOCS), Clara Bolton (NOCS), Agnieszka Beszczynska-Moeller (Alfred Wegener Institute, Bremerhaven), Christian Berndt (NOCS, and Kiel) & Alfred Aquilina (Bristol).

The research was supported by the Natural Environment Research Council.

The National Oceanography Centre, Southampton is the UK's focus for ocean science. It is one of the world's leading institutions devoted to research, teaching and technology development in ocean and earth science. Over 500 research scientists, lecturing, support and seagoing staff are based at the centre's purpose-built waterside campus in Southampton along with over 700 undergraduate and postgraduate students.

The National Oceanography Centre, Southampton is a collaboration between the University of Southampton and the Natural Environment Research Council. The NERC royal research ships RRS James Cook and RRS Discovery are based at NOCS as is the National Marine Equipment Pool which includes Autosub and Isis, two of the world's deepest diving research vehicles.

The thinning of a gigantic glacier in Antarctica is accelerating, scientists warned today.

The Pine Island Glacier in West Antarctica, which is around twice the size of Scotland, is losing ice four times as fast as it was a decade years ago.

The research, published in the journal Geophysical Research Letters, also reveals that ice thinning is now occurring much further inland. At this rate scientists estimate that the main section of the glacier will have disappeared in just 100 years, six times sooner than was previously thought.

The Pine Island Glacier is located within the most inaccessible area of Antarctica – over 1000 km from the nearest research base – and was for many years overlooked. Now, scientists have been able to track the glacier's development using continuous satellite measurements over the past 15years.

"Accelerated thinning of the Pine Island Glacier represents perhaps the greatest imbalance in the cryosphere today, and yet we would not have known about it if it weren't for a succession of satellite instruments," says Professor Andrew Shepherd, a co-author of the research from the School of Earth and Environment at the University of Leeds.

"Being able to assemble a continuous record of measurements over the past 15 years has provided us with the remarkable ability to identify both subtle and dramatic changes in ice that were previously hidden," he adds.

Scientists believe that the retreat of glaciers in this sector of Antarctica is caused by warming of the surrounding oceans, though it is too early to link such a trend to global warming.

The 5,400 km squared region of the Pine Island Glacier affected today is big enough to impact the rate at which sea level rise around the world.

"Because the Pine Island Glacier contains enough ice to almost double the IPCC's best estimate of 21st century sea level rise, the manner in which the glacier will respond to the accelerated thinning is a matter of great concern " says Professor Shepherd.

The research was led by Professor Duncan Wingham at University College London, and was funded by the UK Natural Environment Research Council.

The 2008 Research Assessment Exercise showed the University of Leeds to be the UK's eighth biggest research powerhouse. The University is one of the largest higher education institutions in the UK and a member of the Russell Group of research-intensive universities. The University's vision is to secure a place among the world's top 50 by 2015. http://www.leeds.ac.uk

The School of Earth and Environment at the University of Leeds is has more than 90 academic staff, over 60 research staff and 140 postgraduate researchers. It focuses on a multidisciplinary approach to understanding our environment, studying the Earth from its core to its atmosphere and examining the social and economic dimensions of sustainability. http://www.see.leeds.ac.uk/index.htm

The Natural Environment Research Council is the UK's main agency for funding and managing research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, environmental influences on human health, and the genetic make-up of life on earth.

Physicists at the University of Rochester have combed through data from satellites and ocean buoys and found evidence that in the last 50 years, the net flow of heat into and out of the oceans has changed direction three times.

These shifts in the balance of heat absorbed from the sun and radiated from the oceans correlate well with past anomalies that have been associated with abrupt shifts in the earth's climate, say the researchers. These anomalies include changes in normal storm intensities, unusual land temperatures, and a large drop in salmon populations along the western United States.

The physicists also say these changes in ocean heat-flow direction should be taken into account when predicting global climate because the oceans represent 90 percent of the total heat in the earth's climate system.

The study, which will appear in an upcoming issue of Physics Letters A, differs from most previous studies in two ways, the researchers say. First, the physicists look at the overall heat content of the Earth's climate system, measuring the net balance of radiation from both the sun and Earth. And second, it analyzes more completely the data sets the researchers believe are of the highest quality, and not those that are less robust.

"These shifts happened relatively abruptly," says David Douglass, professor of physics at the University of Rochester, and co-author of the paper. "One, for example, happened between 1976 and 1977, right when a number of other climate-related phenomenona were happening, such as significant changes in U. S. precipitation."

Douglass says the last oceanic shift occurred about 10 years ago, and that the oceans are currently emitting slightly more radiation than they are receiving.

The members of the team, which includes Robert Knox, emeritus professor of physics at the University, believe these heat-flux shifts had previously gone unnoticed because no one had analyzed the data as thoroughly as the Rochester team has.

The team believes that the oceans may change how much they absorb and radiate depending on factors such as shifts in ocean currents that might change how the deep water and surface waters exchange heat. In addition to the correlation with strange global effects that some scientists suspect were caused by climate shifts, the team says their data shows the oceans are not continuously warming—a conclusion not consistent with the idea that the oceans may be harboring "warming in the pipeline." Douglass further notes that the team found no correlation between the shifts and atmospheric carbon dioxide concentration.

"An interesting aspect of this research is that no reference to the surface temperature itself is needed," says Knox. "The heat content data we used, gathered by oceanographers, was gleaned from temperature measurements at various ocean depths up to 750 meters." The team also found that the radiative imbalance was sufficiently small that it was necessary to consider the effect of geothermal heating. Knox believes this is the first time this additional source of heat has been accounted for in such a model.

The team notes that it's impossible to predict when another shift might occur, but they suspect future shifts might be similar to the three observed. Both Douglass and Knox are continuing to analyze various climate-related data to find any new information or correlations that may have so far gone unnoticed.

The University of Rochester (http://www.rochester.edu) is one of the nation's leading private universities. Located in Rochester, N.Y., the University gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty through its unique cluster-based curriculum. Its College, School of Arts and Sciences, and Hajim School of Engineering and Applied Sciences are complemented by the Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, Schools of Medicine and Nursing, and the Memorial Art Gallery.

Highest Ever Winter Water Temperatures Recorded Off Tasmania


NOAA polar orbiting satellites obtain the data generating sea surface temperature images. This is a composite 15-day image showing the extension of the Leeuwin Current around Tasmania. (Credit: CSIRO)

ScienceDaily (Aug. 20, 2009) — Tasmania’s east coast is recording its highest-ever winter water temperatures of more than 13ºC – up to 1.5ºC above normal – due to a strengthening of an ocean current originating north of Australia.

Satellites have given oceanographers an insight into a remarkable phenomenon – a significant extension of the Leeuwin Current curling around the southern tip of Tasmania and reaching as far north as St Helens.

Remote sensing specialists at CSIRO's Wealth from Oceans Flagship have been observing the current in recent days using satellite data, and ocean measurements made near Maria Island on Tasmania’s east coast.

CSIRO oceanographers Katy Hill, David Griffin and George Cresswell study ocean behaviour in the Australian region. Dr Cresswell says that scientists use ocean observations from satellite, ocean instruments and research vessels – such as the Marine National Facility, RV Southern Surveyor – to track the currents but there are also other indicators such as tropical species reaching Tasmania.

“It’s important for us to monitor these changes in the ocean, as they can have consequences for marine ecosystems, fisheries, aquaculture, coastal communities and more,” Dr Cresswell says.

The Leeuwin Current forms north of Australia and flows right around the western half of the country, meeting its better known cousin, the East Australian Current (EAC), at Tasmania. The exact location of this meeting point varies both seasonally and from year-to-year, depending on how strongly each current is flowing.

Oceanographers believe the EAC has gradually been getting stronger, and the Leeuwin Current weaker. Changes in the EAC are among the most significant in the global ocean, with a continuous record of monthly measurements one of Australian oceanography’s most valuable indicators for climate and environmental monitoring.

Observations of temperature, salinity and nutrients have been collected monthly just east of Maria Island since 1944, showing how the influence of both the EAC and Leeuwin Current systems varies in Tasmanian waters. As part of the Integrated Marine Observing System (IMOS), a National Reference Station mooring has been deployed at the same site, and data is now available online every 10 minutes. Monthly samples are taken by boat to measure nutrients, phytoplankton, and zooplankton (biomass and species composition).

Satellite images indicate the surface water temperature over the continental shelf current is around 13 degrees, a degree or two warmer than at this time in recent years. The EAC has been a research focus for Katy Hill since 2005 as part of her PhD in the Quantitiative Marine Science program – a joint initiative of CSIRO and the University of Tasmania.

The St Helens-based Chief Executive of the Tasmanian Rock Lobster Association, Rodney Treloggen, said he was not aware of any reports of Indian Ocean species but he said fishers were concerned at what he described as a “bad year” for the industry in the south-east and east coast.

"We know the warmer waters have an impact but we're not sure how much," Mr Treloggen said.

In hot water: World sets ocean temperature record (Update)
August 20th, 2009 in Space & Earth / Environment
In hot water: World sets ocean temperature record (AP)



Luis Torres, right, plays with his son Angel, 6, in the waters off Pine Point Beach Wednesday, Aug. 19, 2009 in Scarborough, Maine. The world's oceans this summer are heating up to their warmest on record. (AP Photo/Joel Page)

(AP) -- Steve Kramer spent an hour and a half swimming in the ocean this week - in Maine.

The water temperature was 72 degrees - more like Ocean City, Md., this time of year. And Ocean City's water temp hit 88 degrees, toasty even by Miami Beach standards.

Kramer, 26, who lives in the seaside town of Scarborough, said it was the first time he's ever swam so long in Maine's coastal waters.

It's not just the ocean off the Northeast coast that is super-warm this summer. July was the hottest the world's oceans have been in almost 130 years of record-keeping.

The average water temperature worldwide was 62.6 degrees, according to the National Climatic Data Center, the branch of the U.S. government that keeps world weather records. June was only slightly cooler, while August could set another record, scientists say. The previous record was set in July 1998 during a powerful El Nino.

Meteorologists said there's a combination of forces at work: A natural El Nino weather pattern just getting started on top of worsening man-made global warming, and a dash of random weather variations. The resulting ocean heat is already harming threatened coral reefs. It could also hasten the melting of Arctic sea ice and help hurricanes strengthen.

The Gulf of Mexico, where warm water fuels hurricanes, has temperatures dancing around 90. Most of the water in the Northern Hemisphere has been considerably warmer than normal. The Mediterranean is about three degrees warmer than normal. Higher temperatures rule in the Pacific and Indian Oceans.

The phenomena is most noticeable near the Arctic, where water temperatures are as much as 10 degrees above average. The tongues of warm water could help melt sea ice from below and even cause thawing of ice sheets on Greenland, said Waleed Abdalati, director of the Earth Science and Observation Center at the University of Colorado.

Breaking heat records in water is more ominous as a sign of global warming than breaking temperature marks on land, because water takes longer to heat up and does not cool off as easily as land.

"This warm water we're seeing doesn't just disappear next year; it'll be around for a long time," said climate scientist Andrew Weaver of the University of Victoria in British Columbia. It takes five times more energy to warm water than land.

The warmer water "affects weather on the land," Weaver said. "This is another yet really important indicator of the change that's occurring."

Georgia Institute of Technology atmospheric science professor Judith Curry said water is warming in more places than usual, something that has not been seen in more than 50 years.

Add to that an unusual weather pattern this summer where the warmest temperatures seem to be just over oceans, while slightly cooler air is concentrated over land, said Deke Arndt, head of climate monitoring at the climate data center.

The pattern is so unusual that he suggested meteorologists may want to study that pattern to see what's behind it.

The effects of that warm water are already being seen in coral reefs, said C. Mark Eakin, coordinator of the National Oceanic and Atmospheric Administration's coral reef watch. Long-term excessive heat bleaches colorful coral reefs white and sometimes kills them.

Bleaching has started to crop up in the Florida Keys, Puerto Rico and the Virgin Islands. Typically, bleaching occurs after weeks or months of prolonged high water temperatures. That usually means September or even October in the Caribbean, said Eakin. He found bleaching in Guam Wednesday. It's too early to know if the coral will recover or die. Experts are "bracing for another bad year," he said.

The problems caused by the El Nino pattern are likely to get worse, the scientists say.

An El Nino occurs when part of the central Pacific warms up, which in turn changes weather patterns worldwide for many months. El Nino and its cooling flip side, La Nina, happen every few years.

During an El Nino, temperatures on water and land tend to rise in many places, leading to an increase in the overall global average temperature. An El Nino has other effects, too, including dampening Atlantic hurricane formation and increasing rainfall and mudslides in Southern California.

Warm water is a required fuel for hurricanes. What's happening in the oceans "will add extra juice to the hurricanes," Curry said.

Hurricane activity has been quiet for much of the summer, but that may change soon, she said. Hurricane Bill quickly became a major storm and the National Hurricane Center warned that warm waters are along the path of the hurricane for the next few days.

Hurricanes need specific air conditions, so warmer water alone does not necessarily mean more or bigger storms, said James Franklin, chief hurricane specialist at the National Hurricane Center in Miami.

Climate change doubles tundra plant life

Updated Sun. Aug. 23 2009 8:29 AM ET

The Canadian Press

Climate change is already having a dramatic effect on plants in the High Arctic, turning the once rocky tundra a deep shade of green and creating what could be another mechanism speeding up global warming.

In a new study to be published in the November issue of the journal Ecology, University of British Columbia geographer Greg Henry has, for the first time, confirmed that rapidly rising temperatures in the Arctic are creating major changes in the plants that live there.

"It's happening so quickly," says Henry.

Henry first came to Alexandra Fiord on the east coast of Ellesmere Island in the 1980s to examine plants growing there. He found a harsh landscape covered with tiny Arctic willows, heather, dryas and blueberries, none taller than 10 centimetres.

Since those days, the average temperature in the area has increased by about 2.5 C - "an extremely rapid change," says Henry.

Those warmer temperatures are making a difference.

Henry says the total amount of plant material above the ground has doubled. In wetlands, that mass is at least three times what it was in the early 1980s. Plants that barely reached researchers' ankles now tickle their shins.

Below ground in wetland areas, researchers found 10 times as much biomass.

"That's an extremely rapid change," says Henry. "That's just unbelievable."

The changes were even more apparent where the land had been disturbed by erosion and sinkholes caused by melting permafrost.

Other evidence corresponds with his findings. The burgeoning shrub population can be spotted on satellite photos. And Dene and Inuit have been saying for years that the tundra is growing bushier.

There are other effects as well.

"If you increase the temperature, the plants respond by growing faster," Henry says. "The leaves come out earlier, the flowers come out earlier, they set seeds earlier. The timing of things is sped up."

The consequences of those changes, however, are still unclear.

"What's going to be the end point here?" Henry asks. "(Are) all parts of the system going to be able to adapt to the extremely rapid change in temperature?"

The range for large grazing animals such as muskox and caribou is almost certain to change.

They may welcome the more luxuriant summer growth. But taller shrubs may crowd out lichens and mosses, which muskox and caribou depend on for winter browse.

There could also be more ominous results.

Henry's study is restricted to Alexander Fiord. But his findings there closely match results from a global experiment that Henry co-ordinated on how warmer temperatures would affect tundra.

That means what's happening on Ellesmere Island could well be happening on tundra around the circumpolar world.

And if that is the case, Henry said the new, denser, shrubbier tundra could speed up global warming even further simply because that vegetation is darker and absorbs more solar energy. Previous studies have suggested that a global spread of thicker plant growth on the tundra could have the same effect as doubling the amount of carbon dioxide in the atmosphere.

Henry said he expects other researchers to soon start reporting results from similar experiments in other parts of the world.

Reports on how global warming is shrinking the Arctic ice cap are increasingly common. Henry said it could be just as important to keep track of how the climbing temperatures at the top of the world are affecting landscapes.

"There's lots of press every September when NASA comes out with the latest minimum sea ice measurements and assessments. That gets big play, but no one ever hears about tundra."

World's Last Great Forest Under Threat: New Study



Canadian pine tree forest. (Credit: iStockphoto/Stacey Newman)

ScienceDaily (Aug. 25, 2009) — The world's last remaining "pristine" forest -- the boreal forest across large stretches of Russia, Canada and other northern countries -- is under increasing threat, a team of international researchers has found.

The researchers from the University of Adelaide in Australia, Memorial University of Newfoundland in Canada and the National University of Singapore have called for the urgent preservation of existing boreal forests in order to secure biodiversity and prevent the loss of this major global carbon sink.

The boreal forest comprises about one-third of the world's forested area and one-third of the world's stored carbon, covering a large proportion of Russia, Canada, Alaska and Scandinavia.

To date it has remained largely intact because of the typically sparse human populations in boreal regions. That is now changing says researchers and co-authors Associate Professor Corey Bradshaw, University of Adelaide, Associate Professor Ian Warkentin, Memorial University, and Professor Navjot Sodhi, National University of Singapore.

"Much world attention has focused on the loss and degradation of tropical forests over the past three decades, but now the boreal forest is poised to become the next Amazon," says Associate Professor Bradshaw, from the University of Adelaide's Environment Institute.

"Historically, fire and insects have driven the natural dynamics of boreal ecosystems," says Associate Professor Warkentin. "But with rising demand for resources, human disturbances caused by logging, mining and urban development have increased in these forests during recent years, with extensive forest loss for some regions and others facing heavy fragmentation and exploitation."

The findings have been published online in Trends in Ecology and Evolution in a paper called "Urgent preservation of boreal carbon stocks and biodiversity". The findings include:

* Fire is the main driver of change and increased human activity is leading to more fires. There is also evidence that climate change is increasing the frequency and possibly the extent of fires in the boreal zone.
* Few countries are reporting an overall change in the coverage by boreal forest but the degree of fragmentation is increasing with only about 40% of the total forested area remaining "intact".
* Russian boreal forest is the most degraded and least "intact" and has suffered the greatest decline in the last few decades.
* Countries with boreal forest are protecting less than 10% of their forests from timber exploitation, except for Sweden where the figure is about 20%.
_{Adapted from materials provided by University of Adelaide.}

Small Fluctuations In Solar Activity, Large Influence On Climate

ScienceDaily (Aug. 28, 2009) — Subtle connections between the 11-year solar cycle, the stratosphere, and the tropical Pacific Ocean work in sync to generate periodic weather patterns that affect much of the globe, according to research appearing this week in the journal Science. The study can help scientists get an edge on eventually predicting the intensity of certain climate phenomena, such as the Indian monsoon and tropical Pacific rainfall, years in advance.

An international team of scientists led by the National Center for Atmospheric Research (NCAR) used more than a century of weather observations and three powerful computer models to tackle one of the more difficult questions in meteorology: if the total energy that reaches Earth from the Sun varies by only 0.1 percent across the approximately 11-year solar cycle, how can such a small variation drive major changes in weather patterns on Earth?

The answer, according to the new study, has to do with the Sun's impact on two seemingly unrelated regions. Chemicals in the stratosphere and sea surface temperatures in the Pacific Ocean respond during solar maximum in a way that amplifies the Sun's influence on some aspects of air movement. This can intensify winds and rainfall, change sea surface temperatures and cloud cover over certain tropical and subtropical regions, and ultimately influence global weather.

"The Sun, the stratosphere, and the oceans are connected in ways that can influence events such as winter rainfall in North America," says NCAR scientist Gerald Meehl, the lead author. "Understanding the role of the solar cycle can provide added insight as scientists work toward predicting regional weather patterns for the next couple of decades."

The study was funded by the National Science Foundation, NCAR's sponsor, and by the Department of Energy. It builds on several recent papers by Meehl and colleagues exploring the link between the peaks in the solar cycle and events on Earth that resemble some aspects of La Nina events, but are distinct from them. The larger amplitude La Nina and El Nino patterns are associated with changes in surface pressure that together are known as the Southern Oscillation.

The connection between peaks in solar energy and cooler water in the equatorial Pacific was first discovered by Harry Van Loon of NCAR and Colorado Research Associates, who is a co-author of the new paper.

Top down and bottom up

The new contribution by Meehl and his colleagues establishes how two mechanisms that physically connect changes in solar output to fluctuations in the Earth's climate can work together to amplify the response in the tropical Pacific.

The team first confirmed a theory that the slight increase in solar energy during the peak production of sunspots is absorbed by stratospheric ozone. The energy warms the air in the stratosphere over the tropics, where sunlight is most intense, while also stimulating the production of additional ozone there that absorbs even more solar energy. Since the stratosphere warms unevenly, with the most pronounced warming occurring at lower latitudes, stratospheric winds are altered and, through a chain of interconnected processes, end up strengthening tropical precipitation.

At the same time, the increased sunlight at solar maximum causes a slight warming of ocean surface waters across the subtropical Pacific, where Sun-blocking clouds are normally scarce. That small amount of extra heat leads to more evaporation, producing additional water vapor. In turn, the moisture is carried by trade winds to the normally rainy areas of the western tropical Pacific, fueling heavier rains and reinforcing the effects of the stratospheric mechanism.

The top-down influence of the stratosphere and the bottom-up influence of the ocean work together to intensify this loop and strengthen the trade winds. As more sunshine hits drier areas, these changes reinforce each other, leading to less clouds in the subtropics, allowing even more sunlight to reach the surface, and producing a positive feedback loop that further magnifies the climate response.

These stratospheric and ocean responses during solar maximum keep the equatorial eastern Pacific even cooler and drier than usual, producing conditions similar to a La Nina event. However, the cooling of about 1-2 degrees Fahrenheit is focused farther east than in a typical La Nina, is only about half as strong, and is associated with different wind patterns in the stratosphere.

Earth's response to the solar cycle continues for a year or two following peak sunspot activity. The La Nina-like pattern triggered by the solar maximum tends to evolve into a pattern similar to El Nino as slow-moving currents replace the cool water over the eastern tropical Pacific with warmer water. The ocean response is only about half as strong as with El Nino and the lagged warmth is not as consistent as the La Nina-like pattern that occurs during peaks in the solar cycle.

Enhancing ocean cooling

Solar maximum could potentially enhance a true La Nina event or dampen a true El Nino event. The La Nina of 1988-89 occurred near the peak of solar maximum. That La Nina became unusually strong and was associated with significant changes in weather patterns, such as an unusually mild and dry winter in the southwestern United States.

The Indian monsoon, Pacific sea surface temperatures and precipitation, and other regional climate patterns are largely driven by rising and sinking air in Earth's tropics and subtropics. Therefore the new study could help scientists use solar-cycle predictions to estimate how that circulation, and the regional climate patterns related to it, might vary over the next decade or two.

Three views, one answer

To tease out the elusive mechanisms that connect the Sun and Earth, the study team needed three computer models that provided overlapping views of the climate system.

One model, which analyzed the interactions between sea surface temperatures and lower atmosphere, produced a small cooling in the equatorial Pacific during solar maximum years. The second model, which simulated the stratospheric ozone response mechanism, produced some increases in tropical precipitation but on a much smaller scale than the observed patterns.

The third model contained ocean-atmosphere interactions as well as ozone. It showed, for the first time, that the two combined to produce a response in the tropical Pacific during peak solar years that was close to actual observations.

"With the help of increased computing power and improved models, as well as observational discoveries, we are uncovering more of how the mechanisms combine to connect solar variability to our weather and climate," Meehl says.
<sub>The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation.

Journal reference:

1. Gerald Meehl, Julie Arblaster, Katja Matthes, Fabrizio Sassi, and Harry van Loon. Amplifying the Pacific climate system response to a small 11 year solar cycle forcing. Science, August 28, 2009</sub>

Climate trouble may be bubbling up in Far North
Updated Mon. Aug. 31 2009 8:03 AM ET

The Associated Press

MACKENZIE RIVER DELTA, Northwest Territories -- Only a squawk from a sandhill crane broke the Arctic silence -- and a low gurgle of bubbles, a watery whisper of trouble repeated in countless spots around the polar world.


Canadian researcher Rob Bowen paddles his small rubber boat up beside a methane seep on the remote, boggy fringe of North America, 2,200 kilometers from the North Pole on Aug. 10, 2009. (AP / Rick Bowmer

"On a calm day, you can see 20 or more `seeps' out across this lake," said Canadian researcher Rob Bowen, sidling his small rubber boat up beside one of them. A tossed match would have set it ablaze.

"It's essentially pure methane."

Pure methane, gas bubbling up from underwater vents, escaping into northern skies, adds to the global-warming gases accumulating in the atmosphere. And pure methane escaping in the massive amounts known to be locked in the Arctic permafrost and seabed would spell a climate catastrophe.

Is such an unlocking under way?

Researchers say air temperatures here in northwest Canada, in Siberia and elsewhere in the Arctic have risen more than 2.5 C (4.5 F) since 1970 -- much faster than the global average. The summer thaw is reaching deeper into frozen soil, at a rate of 4 centimeters (1.5 inches) a year, and a further 7 C (13 F) temperature rise is possible this century, says the authoritative, U.N.-sponsored Intergovernmental Panel on Climate Change (IPCC).

In 2007, air monitors detected a rise in methane concentrations in the atmosphere, apparently from far northern sources. Russian researchers in Siberia expressed alarm, warning of a potential surge in the powerful greenhouse gas, additional warming of several degrees, and unpredictable consequences for Earth's climate.

Others say massive seeps of methane might take centuries. But the Russian scenario is disturbing enough to have led six U.S. national laboratories last year to launch a joint investigation of rapid methane release. And IPCC Chairman Rajendra Pachauri in July asked his scientific network to focus on "abrupt, irreversible climate change" from thawing permafrost.

The data will come from teams like one led by Scott Dallimore, who with Bowen and others pitched tents here on the remote, boggy fringe of North America, 2,200 kilometers (1,400 miles) from the North Pole, to learn more about seeps in the 25,000 lakes of this vast river delta.

A "puzzle," Dallimore calls it.

"Many factors are poorly studied, so we're really doing frontier science here," the Geological Survey of Canada scientist said. "There is a very large storehouse of greenhouse gases within the permafrost, and if that storehouse of greenhouse gases is fluxing to the surface, that's important to know. And it's important to know if that flux will change with time."

Permafrost, tundra soil frozen year-round and covering almost one-fifth of Earth's land surface, runs anywhere from 50 to 600 meters (160 to 2,000 feet) deep in this region. Entombed in that freezer is carbon -- plant and animal matter accumulated through millennia.

As the soil thaws, these ancient deposits finally decompose, attacked by microbes, producing carbon dioxide and -- if in water -- methane. Both are greenhouse gases, but methane is many times more powerful in warming the atmosphere.

Researchers led by the University of Florida's Ted Schuur last year calculated that the top 3 meters (10 feet) of permafrost alone contain more carbon than is currently in the atmosphere.

"It's safe to say the surface permafrost, 3 to 5 meters, is at risk of thawing in the next 100 years," Schuur said by telephone from an Alaska research site. "It can't stay intact."

Methane also is present in another form, as hydrates -- ice-like formations deep underground and under the seabed in which methane molecules are trapped within crystals of frozen water. If warmed, the methane will escape.

Dallimore, who has long researched hydrates as energy sources, believes a breakdown of such huge undersea formations may have produced conical "hills" found offshore in the Beaufort Sea bed, some of them 40 meters (more than 100 feet) high.

With underwater robots, he detected methane gas leaking from these seabed features, which resemble the strange hills ashore here that the Inuvialuit, or Eskimos, call "pingos." And because the coastal plain is subsiding and seas are rising from warming, more permafrost is being inundated, exposed to water warmer than the air.

The methane seeps that the Canadians were studying in the Mackenzie Delta, amid grassy islands, steel-gray lakes and summertime temperatures well above freezing, are saucer-like indentations just 10 meters (30 feet) or so down on the lake bed.

The ultimate source of that gas -- hydrates, decomposition or older natural gas deposits -- is unclear, but Dallimore's immediate goal is quantifying the known emissions and finding the unknown.

With tent-like, instrument-laden enclosures they positioned over two seeps, each several meters (yards) wide, the researchers have determined they are emitting methane at a rate of up to 0.6 cubic meters (almost 1 cubic yard) per minute.

Dallimore's team is also monitoring the seeps with underwater listening devices, to assess whether seasonal change -- warming -- affects the emissions rate.

Even if the lake seeps are centuries old, Bowen said, the question is, "Will they be accelerated by recent changes?"

A second question: Are more seeps developing?

To begin answering that, Dallimore is working with German and Canadian specialists in aerial surveying, teams that will fly over swaths of Arctic terrain to detect methane "hot spots" via spectrometric imagery, instruments identifying chemicals by their signatures on the light spectrum.

Research crews are hard at work elsewhere, too, to get a handle on this possible planetary threat.

"I and others are trying to take field observations and get it scaled up to global models," said Alaska researcher Schuur. From some 400 boreholes drilled deep into the tundra worldwide, "we see historic warming of permafrost. Much of it is now around 2 below zero (28 F)," Schuur said.

A Coast Guard C-130 aircraft is overflying Alaska this summer with instruments sampling the air for methane and carbon dioxide. In parts of Alaska, scientists believe the number of "thermokarst" lakes -- formed when terrain collapses over thawing permafrost and fills with meltwater -- may have doubled in the past three decades. Those lakes then expand, thawing more permafrost on their edges, exposing more carbon.

Off Norway's Arctic archipelago of Svalbard last September, British scientists reported finding 250 methane plumes rising from the shallow seabed. They're probably old, scientists said, but only further research can assess whether they're stable. In March, Norwegian officials did say methane levels had risen on Svalbard.

Afloat above the huge, shallow continental shelf north of Siberia, Russian researchers have detected seabed "methane chimneys" sending gas bubbling up to the surface, possibly from hydrates.

Reporting to the European Geophysical Union last year, the scientists, affiliated with the University of Alaska and the Russian Academy of Sciences, cited "extreme" saturation of methane in surface waters and in the air above. They said up to 10 percent of the undersea permafrost area had melted, and it was "highly possible" that this would open the way to abrupt release of an estimated 50 billion tons of methane.

Depending on how much dissolved in the sea, that might multiply methane in the atmosphere several-fold, boosting temperatures enough to cause "catastrophic greenhouse warming," as the Russians called it. It would be self-perpetuating, melting more permafrost, emitting more methane.

Some might label that alarmism. And Stockholm University researcher Orjan Gustafsson, a partner in the Russians' field work, acknowledged that "the scientific community is quite split on how fast the permafrost can thaw."

But there's no doubt the north contains enough potential methane and carbon dioxide to cause abrupt climate change, Gustafsson said by telephone from Sweden.

Canada's pre-eminent permafrost expert, Chris Burn, has trekked to lonely locations in these high latitudes for almost three decades, meticulously chronicling the changes in the tundra.

On a stopover at the Aurora Research Institute in the Mackenzie Delta town of Inuvik, the Carleton University scientist agreed "we need many, many more field observations." But his teams have found the frozen ground warming down to about 80 meters, and he believes the world is courting disaster in failing to curb warming by curbing greenhouse emissions.

"If we lost just 1 percent of the carbon in permafrost today, we'd be close to a year's contributions from industrial sources," he said. "I don't think policymakers have woken up to this. It's not in their risk assessments."

How likely is a major release?

"I don't think it's a case of likelihood," he said. "I think we are playing with fire."

Early Warning Signals Of Change: 'Tipping Points' Identified Where Sudden Shifts To New Conditions Occur
enlarge

Early warning indicators have been found in Wisconsin's side-by-side Peter and Paul Lakes. (Credit: Steve Carpenter, University of Wisconsin)

ScienceDaily (Sep. 5, 2009) — What do abrupt changes in ocean circulation and Earth's climate, shifts in wildlife populations and ecosystems, the global finance market and its system-wide crashes, and asthma attacks and epileptic seizures have in common?

According to a paper published this week in the journal Nature, all share generic early-warning signals that indicate a critical threshold of change dead ahead.

In the paper, Martin Scheffer of Wageningen University in The Netherlands and co-authors, including William Brock and Stephen Carpenter of the University of Wisconsin at Madison and George Sugihara of the Scripps Institution of Oceanography in La Jolla, Calif., found that similar symptoms occur in many systems as they approach a critical state of transition.

"It's increasingly clear that many complex systems have critical thresholds -- 'tipping points' -- at which these systems shift abruptly from one state to another," write the scientists in their paper.

Especially relevant, they discovered, is that "catastrophic bifurcations," a diverging of the ways, propel a system toward a new state once a certain threshold is exceeded.

Like Robert Frost's well-known poem about two paths diverging in a wood, a system follows a trail for so long, then often comes to a switchpoint at which it will strike out in a completely new direction.

That system may be as tiny as the alveoli in human lungs or as large as global climate.

"These are compelling insights into the transitions in human and natural systems," says Henry Gholz, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which supported the research along with NSF's Division of Ocean Sciences.

"The information comes at a critical time -- a time when Earth's and, our fragility, have been highlighted by global financial collapses, debates over health care reform, and concern about rapid change in climate and ecological systems."

It all comes down to what scientists call "squealing," or "variance amplification near critical points," when a system moves back and forth between two states.

"A system may shift permanently to an altered state if an underlying slow change in conditions persists, moving it to a new situation," says Carpenter.

Eutrophication in lakes, shifts in climate, and epileptic seizures all are preceded by squealing.

Squealing, for example, announced the impending abrupt end of Earth's Younger Dryas cold period some 12,000 years ago, the scientists believe. The later part of this episode alternated between a cold mode and a warm mode. The Younger Dryas eventually ended in a sharp shift to the relatively warm and stable conditions of the Holocene epoch.

The increasing climate variability of recent times, state the paper's authors, may be interpreted as a signal that the near-term future could bring a transition from glacial and interglacial oscillations to a new state -- one with permanent Northern Hemisphere glaciation in Earth's mid-latitudes.

In ecology, stable states separated by critical thresholds of change occur in ecosystems from rangelands to oceans, says Carpenter.

The way in which plants stop growing during a drought is an example. At a certain point, fields become deserts, and no amount of rain will bring vegetation back to life. Before this transition, plant life peters out, disappearing in patches until nothing but dry-as-bones land is left.

Early-warning signals are also found in exploited fish stocks. Harvesting leads to increased fluctuations in fish populations. Fish are eventually driven toward a transition to a cyclic or chaotic state.

Humans aren't exempt from abrupt transitions. Epileptic seizures and asthma attacks are cases in point. Our lungs can show a pattern of bronchoconstriction that may be the prelude to dangerous respiratory failure, and which resembles the pattern of collapsing land vegetation during a drought.

Epileptic seizures happen when neighboring neural cells all start firing in synchrony. Minutes before a seizure, a certain variance occurs in the electrical signals recorded in an EEG.

Shifts in financial markets also have early warnings. Stock market events are heralded by increased trading volatility. Correlation among returns to stocks in a falling market and patterns in options prices may serve as early-warning indicators.

"In systems in which we can observe transitions repeatedly," write the scientists, "such as lakes, ranges or fields, and such as human physiology, we may discover where the thresholds are.

"If we have reason to suspect the possibility of a critical transition, early-warning signals may be a significant step forward in judging whether the probability of an event is increasing."

<sub>Other co-authors of the paper are Jordi Bascompte and Egbert van Nes of the Consejo Superior de Investigaciones Scientificas, Sevilla, Spain; Victor Brovkin of the Max Planck Institute for Meteorology in Hamburg, Germany; Vasilis Dakos of the Potsdam Institute for Climate Research in Potsdam, Germany; and Max Rietkerk of Utrecht University in The Netherlands.

The research also was funded by the Institute Para Limes and the South American Institute for Resilience and Sustainability Studies, as well as the Netherlands Organization of Scientific Research and the European Science Foundation, among others.

Journal reference:

1. Marten Scheffer, Jordi Bascompte, William A. Brock, Victor Brovkin, Stephen R. Carpenter, Vasilis Dakos, Hermann Held, Egbert H. van Nes, Max Rietkerk and George Sugihara. Early-warning signals for critical transitions. Nature, 2009; 461 (7260): 53 DOI: 10.1038/nature08227</sub>

Adapted from materials provided by National Science Foundation.

Dramatic Biological Responses To Global Warming In The Arctic



The Arctic as we know it may soon be a thing of the past, according to the research of a large, international team led by Eric Post, associate professor of biology at Penn State University. The team carried out ecosystem-wide studies of the biological response to Arctic warming, and documented a wide range of responses by the plants, birds, animals, insects and humans living there. The team's results will be reported on Sept. 11, 2009, in the journal Science. This image, taken by Post, shows an adult female muskox and two calves in Greenland during 2008-2009. (Credit: Eric Post, Penn State University)

ScienceDaily (Sep. 10, 2009) — "The Arctic as we know it may soon be a thing of the past," says Eric Post, associate professor of biology at Penn State University. Post leads a large, international team that carried out ecosystem-wide studies of the biological response to Arctic warming during the fourth International Polar Year, which ended in 2008. The team's results will be reported on 11 September 2009 in the journal Science.

The team's research documents a wide range of responses by plants, birds, animals, insects, and humans to the warming trend. The scientists found that the increase in mean annual surface temperature in the Arctic over the last 150 years has had dramatic effects. In the last 20 to 30 years, for example, the seasonal minimal sea ice coverage has declined by a staggering 45,000 square kilometers per year. Similarly, the extent of terrestrial snow cover has declined steadily, with earlier melting and breaking up and an earlier start to the growing season.

"Species on land and at sea are suffering adverse consequences of human behavior at latitudes thousands of miles away," declares Post. "It seems no matter where you look -- on the ground, in the air, or in the water -- we're seeing signs of rapid change."

The study led by Post shows that many iconic Arctic species that are dependent upon the stability and persistence of sea ice are faring especially badly. Loss of polar ice habitat is causing a rapid decline in the numbers of ivory gull, Pacific walrus, ringed seal, hooded seal, narwhal, and polar bear. The researchers found that Polar bears and ringed seals, both of which give birth in lairs or caves under the snow, lose many newborn pups when the lairs collapse in unusually early spring rains. These species may be headed for extinction.

The research also reveals that species once confined to more southerly ranges now are moving northward. Among the most visible invaders are red foxes, which are displacing Arctic foxes from territories once too cold for red foxes. Some of the less showy invaders that the scientists found also are moving northward include the winter moth, which defoliates mountain birch forests, and species of Low Arctic trees and shrubs, which affect the dynamics of trace-gas exchange. The presence of more shrubs and trees promotes deeper snow accumulation, increasing soil temperatures during the winter, and more microbial activity in the soil, which in turn makes the habitats more suitable for shrubs. Increasing the shrub cover may lengthen the period during the plant growing season when the tundra acts as a carbon-dioxide sink.

Countering this change, the research reveals, are musk oxen and reindeer, which browse on shrubs, limiting their carbon-soaking capacity and northward expansion to the High Arctic. Grazing, trampling, and defecation by these herbivores promote the growth and spread of grasses, which further attract geese. The geese in turn influence the productivity of lakes, where they rest and graze. The research indicates that complex aquatic and marine food webs like these are extremely vulnerable to alteration due to changes in temperature, precipitation, and nutrient load from the land.

The paper by Post's research team shows that the effects of Arctic warming have been dramatic so far, especially since the warming amounts to only about 1-degree Celsius over the last 150 years. Post said it is difficult to predict what will happen with the anticipated 6-degree warming over the next century.

"The results of our studies so far reveal widespread changes, but also a surprising heterogeneity in biological responses to warming," comments Post. For example, the study shows that wild reindeer on the Norwegian archipelago of Svalbard actually have benefited from melting of snow during winter, and perhaps also from the earlier seasonal loss of snow cover. With less snow cover and a longer growing season, these nonmigratory reindeer have taken advantage of the increased plant abundance, with the result that reindeer populations and their ability to reproduce are up, while mortality is down.

In contrast, migratory caribou in Low Arctic Greenland and elsewhere are declining in numbers, the study found. The caribou have not been able to adjust their calving season to keep it synchronized with changes in plant growth. Thus, the research shows, the time when the females need the most food no longer matches the time of maximum food availability, so fewer calves survive. The research suggests that hotter summers may result in more insects and parasites to prey on the caribou, which in turn may reduce the annual caribou harvest by local indigenous peoples. "Inuit hunters at my study site in Greenland have all but given up on hunting caribou there. What will be the next component to disappear from their traditional lifestyle, a lifestyle that has worked for thousands of years?" wonders Post.

Many questions remain unanswered as scientists wrestle with forecasting future events and developing plans to conserve the fragile Arctic ecosystems. Because there are relatively few species in the Arctic, ecosystems in this region may be more vulnerable to changes in its climate. "There is little functional redundancy among species in Arctic ecosystems," explains Post. "Therefore, relatively small shifts in species ranges or abundances may cause fundamental changes in a unique ecosystem that also is important for tourism and traditional cultures."

Why do some parts of the ecosystem appear to be unaffected by rising temperatures, while others seem to be heading for collapse? For example, despite heavy harvest and changing environmental conditions, sockeye salmon production in Bristol Bay, Alaska, has remained relatively stable or even increased over the last century. Though hundreds of salmon populations are scattered throughout a range of habitats, the system somehow has compensated for these serious demands.

It has long been assumed that the most important biological activities in the Arctic occur during the growing season, but the work highlighted by Post's team suggests otherwise. One natural winter warming episode in the sub-Arctic led to vegetation damage so extensive that plant productivity in the following summer was reduced by 26 percent over an area of at least 1400 square kilometers. In a different area, there was an unexpectedly large release of methane into the atmosphere at the onset of autumn soil freezing. Though working in the Arctic in the autumn and winter poses logistical problems, the findings indicate the importance of monitoring the dynamics of the ecosystem year-round.

"People have thought of the Arctic as a relatively simple ecosystem that is easily understood, but in fact it is very complex," explains Post. "Not all populations within a given species respond similarly to warming because physical and landscape features that interact with climate can vary tremendously from site to site. I think response heterogeneity is going to be one of the keys to species persistence, community integrity, and ecosystem function as the Arctic continues to warm."

Post's team calls for establishing a pan-Arctic series of integrated baseline studies to monitor the physical drivers of climate change and the biological responses to them over the long term. "We've seen a great deal of emphasis recently on the melting of Arctic ice," Post says. "The broad, rapid, and in some cases devastating changes documented in this paper remind us of why it's important to give consideration to the consequences of rising temperatures."

In addition to Eric Post at Penn State University, the team he led was comprised of biologists, ecologists, geographers, botanists, anthropologists, and fish and wildlife experts from the University of Alberta and the Canadian Wildlife Service in Canada; Aarhus University and the University of Copenhagen in Denmark; the University of Helsinki in Finland; the Arctic Ecology Research Group in France; the Greenland Institute of Natural Resources in Greenland; the University Centre on Svalbard, the University of Tromsø, and the Centre for Saami Studies in Norway; the University of Aberdeen and the University of Stirling in Scotland; Lund University and the Abisko Scientific Research Station in Sweden; the University of Sheffield in the UK; and the Institute of Arctic Biology and the U.S. Geological Service at the University of Alaska-Fairbanks, the Environment and Natural Resources Institute of the University of Alaska-Anchorage, and the University of Washington in the United States.
<sub>Support was provided by Aarhus University, The Danish Polar Center, and the U.S. National Science Foundation.

Journal reference:

1. Eric Post, Mads C. Forchhammer, M. Syndonia Bret-Harte, Terry V. Callaghan, Torben R. Christensen, Bo Elberling, Anthony D. Fox, Olivier Gilg, David S. Hik, Toke T. Høye, Rolf A. Ims, Erik Jeppesen, David R. Klein, Jesper Madsen, A. David McGuire, Søren Rysgaard, Daniel E. Schindler, Ian Stirling, Mikkel P. Tamstorf, Nicholas J.C. Tyler, Rene van der Wal, Jeffrey Welker, Philip A. Wookey, Niels Martin Schmidt, and Peter Aastrup. Ecological Dynamics Across the Arctic Associated with Recent Climate Change. Science,, 11 September 2009: 1355-1358\ DOI: 10.1126/science.1173113

Adapted from materials provided by Penn State.</sub>

As climate shifts, birds follow
Most bird species in California’s Sierra Nevadas have altered their ranges during the last century in response to changes in temperature and rainfall
By Sid Perkins
Web edition : Monday, September 14th, 2009


On the moveThe mountain bluebird (left) and Bullock’s oriole (right) are two of the dozens of bird species whose breeding ranges in California’s Sierra Nevadas have shifted over the past century due to climate change.M. Tingley

Climate has become warmer and wetter in parts of the Sierra Nevada mountains over the past century, and the vast majority of the birds there have shifted their range accordingly, a new study suggests.

Over many generations, some plant and animal species can adapt to a slowly changing climate. When climate changes suddenly and dramatically, however, creatures generally shift their range, moving to new areas that offer suitable conditions, says Morgan Tingley, an ecologist at the University of California, Berkeley. Most previous studies have focused on species’ responses only to temperature changes. But the new study by Tingley and his colleagues — reported online and in an upcoming Proceedings of the National Academy of Sciences — shows that birds respond to changes in precipitation as well.

The researchers tallied all the species of perching birds present during breeding season at 82 sites along four transects, which stretch from low foothill elevations up to Sierra peaks topping out at more than 3,600 meters (12,000 feet). Then, they compared the results of their field studies, conducted from 2003 through 2008, with results of similar surveys at the same sites conducted from 1911 through 1929. In the intervening decades, the average temperature at the sites has risen by about 0.8 degrees Celsius and average annual precipitation has risen almost 6 millimeters, says Tingley.

In general, each species was present only in a rather narrow band of elevation — a sign that the creatures were adapted to a specific range of environmental conditions. Of the 53 species that were common at several sites both in the early 1900s and today, 90 percent had moved to a new breeding range during that time, says Tingley.

While most of those species had shifted to follow only one environmental factor — either increased temperature or increased rainfall — about 16 percent had shifted their range according to both. Birds that breed at low elevations tended to follow the rainfall, moving to wetter areas, while those that breed at higher mountain elevations tended to shift their ranges to follow the temperature most suitable for them, the researchers note. “That segregation in behavior surprised us,” says Tingley. The researchers speculate that this pattern may occur because some species, particularly those in lowland areas, are more constrained by food availability than they are by temperature.

“This is a landmark paper,” says A. Townsend Peterson, an evolutionary biologist at the University of Kansas in Lawrence. “It’s easy to note range changes for one species, but it’s quite different when most of the species are responding,” he says.

The five bird species that didn’t show any shift in range between surveys, such as Anna’s hummingbird and the western scrub jay, are species that have adapted to thrive around humans. Those species may be staying near areas where gardens and birdfeeders are common. The few species that shifted their breeding ranges in counterintuitive ways may be responding to other factors, such as extremes in temperature rather than averages, says Tingley.

Techniques used in the new analysis, as well as the findings, may help conservationists better estimate how species will respond to future climate change, Tingley says.

But because species didn’t respond to the climate changes in a consistent way, such ecological planning will be a challenge, says Peterson. “If everything moved in the same way, planning for conservation would be easy,” he notes.

NASA data: Greenland, Antarctic ice melt worsening
Updated Thu. Sep. 24 2009 7:18 AM ET

The Associated Press


An iceberg melts in Kulusuk, Greenland near the Arctic circle in this photo taken Tuesday, Aug. 16, 2005. (AP / John McConnico)

WASHINGTON -- New satellite information shows that ice sheets in Greenland and western Antarctica continue to shrink faster than scientists thought and in some places are already in runaway melt mode.

British scientists for the first time calculated changes in the height of the vulnerable but massive ice sheets and found them especially worse at their edges. That's where warmer water eats away from below. In some parts of Antarctica, ice sheets have been losing 30 feet a year in thickness since 2003, according to a paper published online Thursday in the journal Nature.

Some of those areas are about a mile thick, so they've still got plenty of ice to burn through. But the drop in thickness is speeding up. In parts of Antarctica, the yearly rate of thinning from 2003 to 2007 is 50 percent higher than it was from 1995 to 2003.

These new measurements, based on 50 million laser readings from a NASA satellite, confirm what some of the more pessimistic scientists thought: The melting along the crucial edges of the two major ice sheets is accelerating and is in a self-feeding loop. The more the ice melts, the more water surrounds and eats away at the remaining ice.

"To some extent it's a runaway effect. The question is how far will it run?" said the study's lead author, Hamish Pritchard of the British Antarctic Survey. "It's more widespread than we previously thought."

The study doesn't answer the crucial question of how much this worsening melt will add to projections of sea level rise from man-made global warming. Some scientists have previously estimated that steady melting of the two ice sheets will add about 3 feet, maybe more, to sea levels by the end of the century. But the ice sheets are so big it would probably take hundreds of years for them to completely disappear.

As scientists watch ice shelves retreat or just plain collapse, some thought the problem could slow or be temporary. The latest measurements eliminate "the most optimistic view," said Penn State University professor Richard Alley, who wasn't part of the study.

The research found that 81 of the 111 Greenland glaciers surveyed are thinning at an accelerating, self-feeding pace.

The key problem is not heat in the air, but the water near the ice sheets, Pritchard said. The water is not just warmer but its circulation is also adding to the melt.

"It is alarming," said Jason Box of Ohio State University, who also wasn't part of the study.

Worsening data, including this report, keep proving "that we're underestimating" how sensitive the ice sheets are to changes, he said

Global Warming May Dent El Niño's Protective Shield From Atlantic Hurricanes, Increase Droughts



El Niño, the periodic eastern Pacific phenomenon credited with shielding the United States and Caribbean from severe hurricane seasons, may be overshadowed by its brother in the central Pacific due to global warming, according to an article in the journal Nature. (Credit: Ben Kirtman/UM)

ScienceDaily (Sep. 24, 2009) — El Niño, the periodic eastern Pacific phenomenon credited with shielding the United States and Caribbean from severe hurricane seasons, may be overshadowed by its brother in the central Pacific due to global warming, according to an article in the September 24 issue of the journal Nature.

"There are two El Niños, or flavors of El Niño," said Ben Kirtman, co-author of the study and professor of meteorology and physical oceanography at the University of Miami's Rosentstiel School of Marine and Atmospheric Science. "In addition to the eastern Pacific El Niño which we know and love, a second El Niño in the central Pacific is on the increase."

El Niño is a recurring warm water current along the equator in the Pacific Ocean that affects weather circulation patterns in the tropics. The eastern El Niño increases wind sheer in the Atlantic that may hamper the development of major hurricanes there. The central Pacific El Niño, near the International Dateline, has been blamed for worsening drought conditions in Australia and India as well as minimizing the effects of its beneficial brother to the east.

Led by Sang-Wook Yeh of the Korea Ocean Research & Development Institute, a team of scientists applied Pacific Ocean sea surface temperature data from the past 150 years to 11 global warming models developed by the Intergovernmental Panel on Climate Change. Eight of the models showed that global warming conditions will increase the incidence of the central Pacific El Niño. Over the past 20 years, according to the data, the frequency of an El Niño event in the central Pacific has increased from one out of every five to half of all El Niño occurrences.

"The results described in this paper indicate that the global impacts of El Niño may significantly change as the climate warms," said Yeh.

Though the centers of the central and eastern areas are roughly 4,100 miles apart, El Niños historically have not simultaneously occurred in both places. An increase in central Pacific El Niño events may reduce the hurricane-shielding effects of the eastern Pacific event.

"Currently, we are in the middle of a developing eastern Pacific El Niño event," said Kirtman, "which is part of why we're experiencing such a mild hurricane season in the Atlantic. We also anticipate the southern United States to have a fairly wet winter, and the northeast may be dry and warm."

Kirtman expects the current El Niño event to end next spring, perhaps followed by a La Niña, which he expects may bode for a more intense Atlantic hurricane season in 2010.

Growing up in southern California, Kirtman frequently had to man the sump pump in his family's basement during the rainy season, which he learned later was caused by El Niño.

"We're finally learning about how ocean current flows and increases in sea surface temperature influence weather patterns, which affect every one of us, including the kid manning the sump pump," he said. "I have devoted much of my career to studying El Niño because of how it affects people and their lives."

Kirtman works with various meteorological organizations around the world to help developing countries respond to climate extremes.

"We provide them with the forecasts," he said, "and the countries use the results to develop their response."

<sub>Journal reference:

1. Sang-Wook Yeh, Jong-Seong Kug, Boris Dewitte, Min-Ho Kwon, Ben P. Kirtman & Fei-Fei Jin. El Niño in a changing climate. Nature, 2009; DOI: 10.1038/nature08316

Adapted from materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science, via EurekAlert!, a service of AAAS</sub>.

Four degrees of warming 'likely'
By David Shukman

In a dramatic acceleration of forecasts for global warming, UK scientists say the global average temperature could rise by 4C (7.2F) as early as 2060.

The Met Office study used projections of fossil fuel use that reflect the trend seen over the last 20 years.

Their computer models also factored in new findings on how carbon dioxide is absorbed by the oceans and forests.

The finding was presented at an Oxford University conference exploring the implications of a 4C rise.

The results show a "best estimate" of 4C being reached by 2070, with a possibility that it will come as early as 2060.

Previously we haven't looked at the impact of burning fossil fuels so intensely
Richard Betts

Richard Betts of the Met Office Hadley Centre described himself as "shocked" that so much warming could occur within the lifetimes of people alive today.

"If greenhouse gas emissions are not cut soon then we could see major climate changes within our own lifetimes," he said.

"Four degrees of warming averaged over the globe translates into even greater warming in many regions, along with major changes in rainfall."

Big burn

The model finds wide variations, with the Arctic possibly seeing a rise of up to 15C (27F) by the end of the century.

Western and southern parts of Africa could warm by up to 10C, with other land areas seeing a rise of 7C or more.

In its 2007 assessment, the Intergovernmental Panel on Climate Change (IPCC) said the average warming by the end of the century would probably lie between 1.8C and 4C (3.2-7.2F), though it did not rule out the possibility of larger rises.

Key to the Met Office calculations was the use of projections showing fossil fuel use continuing to increase as it has done for the last couple of decades.

"Previously we haven't looked at the impact of burning fossil fuels so intensely," said Dr Betts.

"But it's quite plausible we could get a rise of 4C by 2070 or even 2060."

Dr Betts and his colleagues emphasise the uncertainties inherent in the modelling, particularly the role of the carbon cycle.

But he said he was confident the findings were significant and would serve as a useful guide to policymakers.

The presentation at Oxford's Environmental Change Institute came as negotiators from 192 countries were gathering in Bangkok for the latest set of prepatory talks in the run-up to December's UN climate summit.

Major governments of developing and industrialised nations are committed to a deal that would keep the global temperature rise to 2C, which many regard as a threshold for "dangerous" climate change

UW Madison Climate Study: Biggest warming near Minnesota?

Posted at 8:46 AM on September 22, 2009 by Paul Huttner (2 Comments)


Wisconsin Initiative on Climate Change Impacts (WICCI) study projects average annual temperatures in Wisconsin will rise 4 to 9 degrees Fahrenheit by 2055.

A new climate change study released last week by the Wisconsin Initiative on Climate Change Impacts (WICCI) group at the University of Wisconsin-Madison should catch the eye of Minnesotans. According to the study, the biggest impacts from climate change may occur during the winter season in northwest Wisconsin near the Twin Cities.

That's just one of the conclusions of the study, which was run on supercomputers using 14 different global climate models. The study is raising eyebrows in Wisconsin; where it is being used by various state agencies to plan ways to adapt to climate change.

Among the study's findings:

Observed historical data:

-Average annual temperatures in Wisconsin have increased +1.1°F, with a peak warming of 2-2.5°F across northwest Wisconsin, closest to Minnesota.

-Observed warming since 1950 has been greatest in winter, with an average increase of 2.5°F across Wisconsin. Winter temperatures in northwest Wisconsin (near Minnesota) have increased by 3.5-4.5°F.


Observed warming since 1950.

-Wisconsin as a whole has become wetter, with an increase in annual precipitation of 3.1 inches. This observed increase in annual precipitation has primarily occurred in southern and western Wisconsin.

Future climate projections:

-Average annual temperatures in Wisconsin will increase 4 to 9 degrees by 2055. That's four times the already observed increase since 1950.

-The warming is projected to be largest in winter, with projected increases of 5-11°F by the mid-21st century across Wisconsin, with the greatest warming across northwest Wisconsin (again, near the Twin Cities and Minnesota).


Projected warming in the winter season.

-Typically, daily high temperatures exceed 90°F roughly 12 times per year in southern Wisconsin and only 5 times per year in northern Wisconsin. Based on one emission scenario, by the mid-21st century, the frequency of such hot days may double to about 25 times per year in the south and triple to about 12 times per year in the north. This consists of 1.5 to 4 more weeks each year with daily high temperatures exceeding 90°F.

Near the Twin Cities, the average annual number of 90 degree days could reach 20.

This peer reviewed study is largely consistent with the IPCC reports on climate change and the effects on the Upper Midwest. Some of the projected effects are already being observed in the landscape around Minnesota.

If the study's finding verify and winters are as much as 8 degrees warmer in the Twin Cities, that could have huge effects on the amount of snow cover we would see and be able to maintain during the winter. We could also see increased fire and disease activity in our forests and a transition from forest to prairie in the Twin Cities area and to the north.

This will study no doubt raise some eyebrows in Minnesota as well as Wisconsin. Milder winters have both positive and negative effects. The most striking prediction to me is the rate of predicted temperature changes in the next 45 years compared to the past 50 years.

eering Under The Ice Of Collapsing Polar Coast



Antarctica' Larsen Ice Shelf has deteriorated in recent years, and it is one target of the flights. (Credit: NASA)

ScienceDaily (Oct. 7, 2009) — Starting this month, a giant NASA DC-8 aircraft loaded with geophysical instruments and scientists will buzz at low level over the coasts of West Antarctica, where ice sheets are collapsing at a pace far beyond what scientists expected a few years ago. The flights, dubbed Operation Ice Bridge, are an effort by NASA in cooperation with university researchers to image what is happening on, and under, the ice, in order to estimate future sea-level rises that might result.

Since 2003, laser measurements of ice surfaces from NASA's ICESat satellite have shown that vast ice masses in Greenland and West Antarctica are thinning and flowing quickly seaward. Last month, a report in the journal Nature based on the satellite's measurements showed that some parts of the Antarctic area to be surveyed have been sinking 9 meters (27) feet a year; in 2002, one great glacial ice shelf jutting from land over the ocean on the Antarctic Peninsula simply disintegrated and floated away within days. NASA's satellite reaches the end of its life this year, and another will not go up until 2015; in the interim, Operation Ice Bridge flights will continue and expand upon the satellite mission.

In addition to lasers, the plane will carry penetrating radars to measure snow cover and the thickness of ice to bedrock, and a gravity-measuring system run by Columbia University's Lamont-Doherty Earth Observatory that will, for the first time, plot the geometry and depth of ocean waters under the ice shelves. The gravity study is seen as key because many scientists believe warm ocean currents may be the main force pulling the ice sheets seaward, melting the undersides of ice shelves and thus removing the buttresses that hold back the far greater masses of ice on land.

"What our colleagues see from modeling of these glaciers is that warm ocean water is providing the thermal energy to melt the ice," said Lamont geophysicist Michael Studinger, a co-leader of the gravity team who will be on some of the flights. "To really understand how the glaciers are going to behave, we need the firsthand measurements of water shape and depth." Earlier this year, an icebreaker cruise co-led by another Lamont scientist, Stan Jacobs, sent an automated submarine to look under the region's Pine Island Glacier, which has been moving forward rapidly in recent years. Its bed, where the ice contacts rock, is below sea level, and scientists are concerned about what would happen if a sudden large movement were to introduce seawater underneath. The plane flights, over some six weeks starting Oct. 15, are aimed at providing a wider-scale picture of Pine Island and other targets.

For each of some 17 flights, the 157-foot DC-8--too big for runways on Antarctic bases--will make an 11-hour round trip from Punta Arenas, Chile, with two-thirds of each trip spent getting to Antarctica. There, the plane will fly survey lines as low as 1,000 feet, some of them along sinuous glacial valleys that may test the nerves of both pilots and scientists. Some flights will investigate the region's open sea ice, which also seems to be in decline. The campaign will cost about $7 million.

"We learned how fast the ice sheets are changing from NASA satellites," said Lamont geophysicist Robin Bell, who is helping lead the project. "These flights are a unique opportunity to see through the ice, and address the question of why the ice sheets are changing."

"A remarkable change is happening on Earth, truly one of the biggest changes in environmental conditions since the end of the ice age," said Tom Wagner, cryosphere program scientist at NASA headquarters in Washington. "It's not an easy thing to observe, let alone predict what might happen next. Studies like this one are key."

Investigators from the University of Washington and University of Kansas will run their own suites of instruments.
_{Adapted from materials provided by The Earth Institute at Columbia University.}

Current Arctic heat wave as rare as any in 200,000 years, study says



A husky stands near a boat being repaired along the waterfront of Iqaluit, Nunavut, on Baffin Island on Aug. 16, 2009. REUTERS

Researchers studied remains of ancient flora and fauna in Baffin Island lake sediment

The Canadian Arctic is experiencing a heat wave that has seldom been matched in the past 200,000 years, says a new scientific paper based on the study of sediments found at the bottom of a remote lake on Baffin Island.

Scientists looking at the remains of microscopic plants and insects preserved in the lake's crusty bottom say a comparison of flora and fauna found in the remote past and in recent decades suggest temperatures are now so elevated they've rarely occurred.

Over the 200,000 years in question, the sediments revealed a natural ebbing and rising of various species that either favoured warmer or colder climate conditions. But recently there have been unprecedented increases of some algae types dependent on warmer conditions that were almost never found during the pre-industrial era.

“Our findings show that the last several decades have been the most ecologically unique in 200,000 years,” said Neil Michelutti, a research scientist at Queen's University in Kingston, Ont., and one of the members of the team that conducted the study, which is appearing this week in the online edition of the Proceedings of the National Academy of Sciences.

According to the study, the only times that summer temperatures were similar to current readings were just after the last ice age ended about 10,000 years ago, and also during an exceptionally warm period before the last glaciation.

The research also extends far back into time reconstructions of previous climate conditions in the Arctic. Up until now, past climates have been inferred from Greenland's ice cores and the 120,000 years of records they provide. But the data derived from the lake sediments predate the creation of Greenland's massive ice sheets by 800 centuries, allowing scientists to peer that much further back into the remote past.

The new finding is adding to the flurry of research suggesting dramatic and far reaching changes are under way in the Arctic, considered the part of the world most at risk from climate change. Last week, a team of British researchers said the Arctic Ocean is undergoing a swift melting that they predicted will leave it largely free of summertime ice in as little as 20 years.

Earlier this year, there was another report that suggested global warming in the decades ahead would allow for tree growth as far north as Baffin Island.

In the new research, scientists conducted a painstaking reconstruction of life at the site by looking at the fossilized remains of tiny algae and insects preserved in the sediments at the water body, located in an isolated part of the eastcoast of Baffin Island facing Greenland. The algae are microscopic, with hundreds fitting onto the head of a pin, and the insects are primarily midges, small two-winged gnats.

While the composition of the insect and plant communities varied over time, depending on the climate, recently the species have switched to those that thrive in ice free conditions, to a degree unlike anything previously seen.

“The lake has followed a trajectory through the 20th century toward increasingly exceptional environmental conditions with no natural analogues in the past 200,000 years,” the study said.

Over the period tracked by the researchers, there were two ice ages and three warmer so-called interglacial eras, highlighting the rarity of modern climate conditions.

“This historical record shows that we are dramatically affecting the ecosystems on which we depend. We have started uncontrolled experiments on this planet,” said Dr. John Smol, a biologist at Queen's University.

The lake was small and unremarkable by most standards – with less than a square kilometre in surface area and a maximum depth of only 10 metres. But scientists say it had one rare attribute that made it into a major scientific find: during previous ice ages, it wasn't covered with moving glaciers, but rather frozen solid. That meant the sediments at its bottom were preserved. They weren't scoured up and deposited elsewhere, bulldozer fashion, like lake bottoms throughout the rest of the area covered by the glaciers.

The study was conducted by researchers at five U.S. and Canadian universities, including the University of Alberta in Edmonton and the University of Colorado in Boulder.

eering Under The Ice Of Collapsing Polar Coast



Antarctica' Larsen Ice Shelf has deteriorated in recent years, and it is one target of the flights. (Credit: NASA)

ScienceDaily (Oct. 7, 2009) — Starting this month, a giant NASA DC-8 aircraft loaded with geophysical instruments and scientists will buzz at low level over the coasts of West Antarctica, where ice sheets are collapsing at a pace far beyond what scientists expected a few years ago. The flights, dubbed Operation Ice Bridge, are an effort by NASA in cooperation with university researchers to image what is happening on, and under, the ice, in order to estimate future sea-level rises that might result.

Since 2003, laser measurements of ice surfaces from NASA's ICESat satellite have shown that vast ice masses in Greenland and West Antarctica are thinning and flowing quickly seaward. Last month, a report in the journal Nature based on the satellite's measurements showed that some parts of the Antarctic area to be surveyed have been sinking 9 meters (27) feet a year; in 2002, one great glacial ice shelf jutting from land over the ocean on the Antarctic Peninsula simply disintegrated and floated away within days. NASA's satellite reaches the end of its life this year, and another will not go up until 2015; in the interim, Operation Ice Bridge flights will continue and expand upon the satellite mission.

In addition to lasers, the plane will carry penetrating radars to measure snow cover and the thickness of ice to bedrock, and a gravity-measuring system run by Columbia University's Lamont-Doherty Earth Observatory that will, for the first time, plot the geometry and depth of ocean waters under the ice shelves. The gravity study is seen as key because many scientists believe warm ocean currents may be the main force pulling the ice sheets seaward, melting the undersides of ice shelves and thus removing the buttresses that hold back the far greater masses of ice on land.

"What our colleagues see from modeling of these glaciers is that warm ocean water is providing the thermal energy to melt the ice," said Lamont geophysicist Michael Studinger, a co-leader of the gravity team who will be on some of the flights. "To really understand how the glaciers are going to behave, we need the firsthand measurements of water shape and depth." Earlier this year, an icebreaker cruise co-led by another Lamont scientist, Stan Jacobs, sent an automated submarine to look under the region's Pine Island Glacier, which has been moving forward rapidly in recent years. Its bed, where the ice contacts rock, is below sea level, and scientists are concerned about what would happen if a sudden large movement were to introduce seawater underneath. The plane flights, over some six weeks starting Oct. 15, are aimed at providing a wider-scale picture of Pine Island and other targets.

For each of some 17 flights, the 157-foot DC-8--too big for runways on Antarctic bases--will make an 11-hour round trip from Punta Arenas, Chile, with two-thirds of each trip spent getting to Antarctica. There, the plane will fly survey lines as low as 1,000 feet, some of them along sinuous glacial valleys that may test the nerves of both pilots and scientists. Some flights will investigate the region's open sea ice, which also seems to be in decline. The campaign will cost about $7 million.

"We learned how fast the ice sheets are changing from NASA satellites," said Lamont geophysicist Robin Bell, who is helping lead the project. "These flights are a unique opportunity to see through the ice, and address the question of why the ice sheets are changing."

"A remarkable change is happening on Earth, truly one of the biggest changes in environmental conditions since the end of the ice age," said Tom Wagner, cryosphere program scientist at NASA headquarters in Washington. "It's not an easy thing to observe, let alone predict what might happen next. Studies like this one are key."

Investigators from the University of Washington and University of Kansas will run their own suites of instruments.
_{Adapted from materials provided by The Earth Institute at Columbia University.}

Current Arctic heat wave as rare as any in 200,000 years, study says



A husky stands near a boat being repaired along the waterfront of Iqaluit, Nunavut, on Baffin Island on Aug. 16, 2009. REUTERS

Researchers studied remains of ancient flora and fauna in Baffin Island lake sediment

The Canadian Arctic is experiencing a heat wave that has seldom been matched in the past 200,000 years, says a new scientific paper based on the study of sediments found at the bottom of a remote lake on Baffin Island.

Scientists looking at the remains of microscopic plants and insects preserved in the lake's crusty bottom say a comparison of flora and fauna found in the remote past and in recent decades suggest temperatures are now so elevated they've rarely occurred.

Over the 200,000 years in question, the sediments revealed a natural ebbing and rising of various species that either favoured warmer or colder climate conditions. But recently there have been unprecedented increases of some algae types dependent on warmer conditions that were almost never found during the pre-industrial era.

“Our findings show that the last several decades have been the most ecologically unique in 200,000 years,” said Neil Michelutti, a research scientist at Queen's University in Kingston, Ont., and one of the members of the team that conducted the study, which is appearing this week in the online edition of the Proceedings of the National Academy of Sciences.

According to the study, the only times that summer temperatures were similar to current readings were just after the last ice age ended about 10,000 years ago, and also during an exceptionally warm period before the last glaciation.

The research also extends far back into time reconstructions of previous climate conditions in the Arctic. Up until now, past climates have been inferred from Greenland's ice cores and the 120,000 years of records they provide. But the data derived from the lake sediments predate the creation of Greenland's massive ice sheets by 800 centuries, allowing scientists to peer that much further back into the remote past.

The new finding is adding to the flurry of research suggesting dramatic and far reaching changes are under way in the Arctic, considered the part of the world most at risk from climate change. Last week, a team of British researchers said the Arctic Ocean is undergoing a swift melting that they predicted will leave it largely free of summertime ice in as little as 20 years.

Earlier this year, there was another report that suggested global warming in the decades ahead would allow for tree growth as far north as Baffin Island.

In the new research, scientists conducted a painstaking reconstruction of life at the site by looking at the fossilized remains of tiny algae and insects preserved in the sediments at the water body, located in an isolated part of the eastcoast of Baffin Island facing Greenland. The algae are microscopic, with hundreds fitting onto the head of a pin, and the insects are primarily midges, small two-winged gnats.

While the composition of the insect and plant communities varied over time, depending on the climate, recently the species have switched to those that thrive in ice free conditions, to a degree unlike anything previously seen.

“The lake has followed a trajectory through the 20th century toward increasingly exceptional environmental conditions with no natural analogues in the past 200,000 years,” the study said.

Over the period tracked by the researchers, there were two ice ages and three warmer so-called interglacial eras, highlighting the rarity of modern climate conditions.

“This historical record shows that we are dramatically affecting the ecosystems on which we depend. We have started uncontrolled experiments on this planet,” said Dr. John Smol, a biologist at Queen's University.

The lake was small and unremarkable by most standards – with less than a square kilometre in surface area and a maximum depth of only 10 metres. But scientists say it had one rare attribute that made it into a major scientific find: during previous ice ages, it wasn't covered with moving glaciers, but rather frozen solid. That meant the sediments at its bottom were preserved. They weren't scoured up and deposited elsewhere, bulldozer fashion, like lake bottoms throughout the rest of the area covered by the glaciers.

The study was conducted by researchers at five U.S. and Canadian universities, including the University of Alberta in Edmonton and the University of Colorado in Boulder.

Arctic Sediments Show That 20th Century Warming Is Unlike Natural Variation



Since the mid-20th century, changes seen in Arctic sediments retrieved by UB geologist Jason Briner and his colleagues, are unprecedented in the last 200,000 years. (Credit: Image courtesy of University at Buffalo)

ScienceDaily (Oct. 25, 2009) — The possibility that climate change might simply be a natural variation like others that have occurred throughout geologic time is dimming, according to evidence in a Proceedings of the National Academy of Sciences paper published October 19.

The research reveals that sediments retrieved by University at Buffalo geologists from a remote Arctic lake are unlike those seen during previous warming episodes.

The UB researchers and their international colleagues were able to pinpoint that dramatic changes began occurring in unprecedented ways after the midpoint of the twentieth century.

"The sediments from the mid-20th century were not all that different from previous warming intervals," said Jason P. Briner, PhD, assistant professor of geology in the UB College of Arts and Sciences. "But after that things really changed. And the change is unprecedented."

The sediments are considered unique because they contain rare paleoclimate information about the past 200,000 years, providing a far longer record than most other sediments in the glaciated portion of the Arctic, which only reveals clues to the past 10,000 years.

"Since much of the Arctic was covered by big ice sheets during the Ice Age, with the most recent glaciations ending around 10,000 years ago, the lake sediment cores people get there only cover the past 10,000 years," said Briner.

"What is unique about these sediment cores is that even though glaciers covered this lake, for various reasons they did not erode it," said Briner, who discovered the lake in the Canadian Arctic while working on his doctoral dissertation. "The result is that we have a really long sequence or archive of sediment that has survived arctic glaciations, and the data it contains is exceptional."

Working with Briner and colleagues at UB who retrieved and analyzed the sediments, the paper's co-authors at the University of Colorado and Queens University, experts in analyzing fossils of bugs and algae, have pooled their expertise to develop the most comprehensive picture to date of how warming variations throughout the past 200,000 years have altered the lake's ecology.

"There are periods of time reflected in this sediment core that demonstrate that the climate was as warm as today," said Briner, "but that was due to natural causes, having to do with well-understood patterns of the Earth's orbit around the sun. The whole ecosystem has now shifted and the ecosystem we see during just the last few decades is different from those seen during any of the past warm intervals."

Yarrow Axford, a research associate at the University of Colorado, and the paper's lead author, noted: "The 20th century is the only period during the past 200 millennia in which aquatic indicators reflect increased warming, despite the declining effect of slow changes in the tilt of the Earth's axis which, under natural conditions, would lead to climatic cooling."

<sub>Co-authors with Briner and Axford are Colin A. Cooke and Alexander P. Wolfe of the University of Alberta; Donna R. Francis of the University of Massachusetts; John P. Smol, Cheryl R. Wilson and Neal Michelutti at Queens University; Gifford H. Miller of the University of Colorado and Elizabeth K. Thomas, who did this work at UB for her master's degree in geology.

Journal reference:

1. Axford et al. Recent changes in a remote Arctic lake are unique within the past 200,000 years. Proceedings of the National Academy of Sciences, October 19, 2009; DOI: 10.1073/pnas.0907094106</sub>

Arctic Lake Sediments Show Warming, Unique Ecological Changes In Recent Decades



The adjacent foothills hold lakes that were not scoured by glaciers during late Quaternary glaciations, and thus preserve exceptionally long sedimentary records of climate change. (Credit: Jason Briner, Courtesy Queen's University)

ScienceDaily (Oct. 27, 2009) — An analysis of sediment cores indicates that biological and chemical changes occurring at a remote Arctic lake are unprecedented over the past 200,000 years and likely are the result of human-caused climate change, according to a new study led by the University of Colorado at Boulder.

While environmental changes at the lake over the past millennia have been shown to be tightly linked with natural causes of climate change -- like periodic, well-understood wobbles in Earth's orbit -- changes seen in the sediment cores since about 1950 indicate expected climate cooling is being overridden by human activity like greenhouse gas emissions. The research team reconstructed past climate and environmental changes at the lake on Baffin Island using indicators that included algae, fossil insects and geochemistry preserved in sediment cores that extend back 200,000 years.

"The past few decades have been unique in the past 200,000 years in terms of the changes we see in the biology and chemistry recorded in the cores," said lead study author Yarrow Axford of CU-Boulder's Institute of Arctic and Alpine Research. "We see clear evidence for warming in one of the most remote places on Earth at a time when the Arctic should be cooling because of natural processes."

The study was published Oct. 19 in the Proceedings of the National Academy of Sciences. The study included researchers from CU-Boulder, the State University of New York's University at Buffalo, the University of Alberta, the University of Massachusetts and Queen's University in Kingston, Ontario.

The sediment cores were extracted from the bottom of a roughly 100-acre, 30-foot-deep lake near the village of Clyde River on the east coast of Baffin Island, which is several hundred miles west of Greenland. The lake sediment cores go back in time 80,000 years beyond the oldest reliable ice cores from Greenland and capture the environmental conditions of two previous ice ages and three interglacial periods.

The sediment cores showed that several types of mosquito-like midges that flourish in very cold climates have been abundant at the lake for the past several thousand years. But the cold-adapted midge species abruptly began declining in about 1950, matching their lowest abundances of the last 200,000 years. Two of the midge species adapted to the coldest temperatures have completely disappeared from the lake region, said Axford.

In addition, a species of diatom, a lake algae that was relatively rare at the site before the 20th century, has undergone unprecedented increases in recent decades, possibly in response to declining ice cover on the Baffin Island lake.

"Our results show that the human footprint is overpowering long-standing natural processes even in remote Arctic regions," said co-author John Smol of Queen's University. "This historical record shows that we are dramatically affecting the ecosystems on which we depend."

"The 20th century is the only period during the past 200 millennia in which aquatic indicators reflect increased warming, despite the declining effect of slow changes in the tilt of the Earth's axis which, under natural conditions, would lead to climatic cooling," notes the University of Colorado's Dr. Axford.

The ancient lake sediment cores are the oldest ever recovered from glaciated parts of Canada or Greenland. Massive ice sheets during ice ages generally scour the underlying bedrock and remove previous sediments.

"What is unique about these sediment cores is that even though glaciers covered this lake, for various reasons they did not erode it," said study co-author Jason Briner of the University at Buffalo. The result is that we have a really long sequence of sediment that has survived Arctic glaciations."

The study was funded by the National Science Foundation, the Natural Sciences and Engineering Research Council of Canada and the Geological Society of America.

A study published in the journal Science last month that involved CU-Boulder researchers and reconstructed past temperatures in the Arctic using ice cores, tree rings and lake sediments concluded that recent warming around the Arctic is overriding a cooling trend caused by Earth's periodic wobble. Earth is now about 0.6 million miles further from the sun during the Northern Hemisphere summer solstice than it was in 1 B.C. -- a trend that has caused overall cooling in the Arctic until recently.

_{INSTAAR researcher and CU-Boulder geological sciences Professor Gifford Miller was a co-author on both the PNAS study and the recent Science study}.

Record High Temperatures Far Outpace Record Lows Across US



This graphic shows the ratio of record daily highs to record daily lows observed at about 1,800 weather stations in the 48 contiguous United States from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio now about two-to-one for the 48 states as a whole. (Credit: Copyright UCAR, graphic by Mike Shibao)

ScienceDaily (Nov. 12, 2009) — Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows. The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb.

"Climate change is making itself felt in terms of day-to-day weather in the United States," says Gerald Meehl, the lead author and a senior scientist at the National Center for Atmospheric Research (NCAR). "The ways these records are being broken show how our climate is already shifting."

The study, by authors at NCAR, Climate Central, The Weather Channel, and the National Oceanic and Atmospheric Administration (NOAA), has been accepted for publication in Geophysical Research Letters. It was funded by the National Science Foundation, NCAR's sponsor, the Department of Energy, and Climate Central.

If temperatures were not warming, the number of record daily highs and lows being set each year would be approximately even. Instead, for the period from January 1, 2000, to September 30, 2009, the continental United States set 291,237 record highs and 142,420 record lows, as the country experienced unusually mild winter weather and intense summer heat waves.

A record daily high means that temperatures were warmer on a given day than on that same date throughout a weather station's history. The authors used a quality control process to ensure the reliability of data from thousands of weather stations across the country, while looking at data over the past six decades to capture longer-term trends.

This decade's warming was more pronounced in the western United States, where the ratio was more than two to one, than in the eastern United States, where the ratio was about one-and-a-half to one.

The study also found that the two-to-one ratio across the country as a whole could be attributed more to a comparatively small number of record lows than to a large number of record highs. This indicates that much of the nation's warming is occurring at night, when temperatures are dipping less often to record lows. This finding is consistent with years of climate model research showing that higher overnight lows should be expected with climate change.

More records ahead

In addition to surveying actual temperatures in recent decades, Meehl and his co-authors turned to a sophisticated computer model of global climate to determine how record high and low temperatures are likely to change during the course of this century.

The modeling results indicate that if nations continue to increase their emissions of greenhouse gases in a "business as usual" scenario, the U.S. ratio of daily record high to record low temperatures would increase to about 20-to-1 by mid-century and 50-to-1 by 2100. The mid-century ratio could be much higher if emissions rose at an even greater pace, or it could be about 8-to-1 if emissions were reduced significantly, the model showed.

The authors caution that such predictions are, by their nature, inexact. Climate models are not designed to capture record daily highs and lows with precision, and it remains impossible to know future human actions that will determine the level of future greenhouse gas emissions. The model used for the study, the NCAR-based Community Climate System Model, correctly captured the trend toward warmer average temperatures and the greater warming in the West, but overstated the ratio of record highs to record lows in recent years.

However, the model results are important because they show that, in all likely scenarios of future greenhouse gas emissions, record daily highs should increasingly outpace record lows over time.

"If the climate weren't changing, you would expect the number of temperature records to diminish significantly over time," says Claudia Tebaldi, a statistician with Climate Central who is one of the paper's co-authors. "As you measure the high and low daily temperatures each year, it normally becomes more difficult to break a record after a number of years. But as the average temperatures continue to rise this century, we will keep setting more record highs."

An expanding ratio

The study team focused on weather stations that have been operating since 1950. They found that the ratio of record daily high to record daily low temperatures slightly exceeded one to one in the 1950s, dipped below that level in the 1960s and 1970s, and has risen since the 1980s. The results reflect changes in U.S. average temperatures, which rose in the 1950s, stabilized in the 1960s, and then began a warming trend in the late 1970s.

Even in the first nine months of this year, when the United States cooled somewhat after a string of unusually warm years, the ratio of record daily high to record daily low temperatures was more than three to two.

Despite the increasing number of record highs, there will still be occasional periods of record cold, Meehl notes.

"One of the messages of this study is that you still get cold days," Meehl says. "Winter still comes. Even in a much warmer climate, we're setting record low minimum temperatures on a few days each year. But the odds are shifting so there's a much better chance of daily record highs instead of lows."

Millions of readings from weather stations across the country

The study team analyzed several million daily high and low temperature readings taken over the span of six decades at about 1,800 weather stations across the country, thereby ensuring ample data for statistically significant results. The readings, collected at the National Oceanic and Atmospheric Administration's National Climatic Data Center, undergo a quality control process at the data center that looks for such potential problems as missing data as well as inconsistent readings caused by changes in thermometers, station locations, or other factors.

Meehl and his colleagues then used temperature simulations from the Community Climate System Model to compute daily record highs and lows under current and future atmospheric concentrations of greenhouse gases.

<sub>Journal reference:

1. Gerald A. Meehl, Claudia Tebaldi, Guy Walton, David Easterling, and Larry McDaniel. The relative increase of record high maximum temperatures compared to record low minimum temperatures in the U.S.. Geophysical Research Letters, (in press)

Adapted from materials provided by National Center for Atmospheric Research/University Corporation for Atmospheric Research</sub>.