Data compiled by the University of East Anglia finds evidence of warming in Antarctica that can for the first time be directly attributed to human emissions
David Adam, guardian.co.uk 30 Oct 08;
No corner of the Earth is immune from the effects of global warming, according to a new study that confirms manmade temperature rises in both the Arctic and Antarctic regions. Temperature records over the last century show that warming in the planet's coldest and most remote wildernesses is caused by human emissions of greenhouse gases.
The study, published today in Nature Geoscience, is the first to find the fingerprints of manmade global warming on the Antarctic, where a shortage of data makes it hard to be sure.
Last year's report, from the Intergovernmental Panel on Climate Change (IPCC), said human influence could be detected on every continent, except Antarctica. Climate sceptics have exploited this omission to question the science of global warming.
In the new study, Nathan Gillett, then working at the Climatic Research Unit at the University of East Anglia, though now at Environment Canada, compiled, with colleagues, climate data across the Arctic and Antarctic regions since 1900, and compared the patterns with those produced by computer simulations with and without human activity.
They say only the models that included human influences – such as emissions of carbon dioxide and chlorofluorocarbons (CFCs) – were able to reproduce the observed temperature trends.
Gillett said: "The main message is that for the first time we are able to directly attribute warming in both the Arctic and Antarctica to human influence. Melting of ice shelves has implications for sea-level rises."
Peter Stott, head of climate monitoring and attribution at the Met Office, who worked on the study, said: "In both polar regions, the observed warming can only be reproduced in our models by including human influences, natural forces alone are not enough.
For a long time climate scientists have known that Arctic areas would be expected to warm most strongly because of feedback mechanisms. But the results from this work demonstrate the part man has already played in the significant warming that we've observed in both polar regions."
The polar regions have seen some of the most dramatic impacts of climate change on the planet in recent years. The Arctic is warming twice as fast as the global average, which has contributed to record melting of sea ice in the Arctic summer and thinning in the winter.
The picture in Antarctica is more complex, but the rocky Antarctic peninsula has experienced temperature rises of 3C over the past 50 years – among the largest recorded. Other parts, including the vast east-Antarctic ice sheet, have seen less change.
Man-Made Climate Change Seen In Antarctica, Arctic
Alister Doyle, PlanetArk 31 Oct 08;
OSLO - Both Antarctica and the Arctic are getting less icy because of global warming, scientists said on Thursday in a study that extends evidence of man-made climate change to every continent.
Detection of a human cause of warming at both ends of the earth also strengthens a need to understand ice sheets on Antarctica and Greenland that would raise world sea levels by about 70 metres (230 ft) if they all melted, they said.
"We're able for the first time to directly attribute warming in both the Arctic and the Antarctic to human influences," said Nathan Gillett of England's University of East Anglia of a study he led with colleagues in the United States, Britain and Japan.
The Arctic has warmed sharply in recent years and sea ice shrank in 2007 to a record low. But Antarctic trends have been confusing -- some winter sea ice has expanded in recent decades, leaving doubts for some about whether warming was global.
The UN Climate Panel, which draws on work by 2,500 experts, said last year that the human fingerprint on climate "has been detected in every continent except Antarctica", which has insufficient observational coverage to make an assessment.
The scientists, writing in the journal Nature Geoscience, said the new findings filled that gap.
The study, comparing temperature records and four computer climate models, found a warming in both polar regions that could be best explained by a buildup of greenhouse gases, mainly from burning fossil fuels, rather than natural shifts.
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The link with human activities had been elusive in the polar regions because there are fewer than 100 temperature stations in the Arctic and just 20 in Antarctica, they said.
The scientists said temperatures had risen about 2 Celsius (3.6 Fahrenheit) in the past 40 years in the Arctic.
Temperatures in Antarctica, an icy deep freeze bigger than the United States, had gained by a few tenths of a degree. The Arctic is warming fast because darker water and ground soak up ever more heat than ice and snow that reflect the sun's rays.
The study also formally linked greenhouse gas emissions to rising temperatures in the Arctic, where big natural variations included a sharp temperature rise in the 1930s and 1940s.
The human cause had been hinted at by the UN Climate Panel last year, which said a human impact "has likely contributed to recent decreases in Arctic sea ice extent".
Scientists urged more study of ice and temperatures.
The UN Climate Panel projects that sea levels will rise by between 18 and 59 cm (7-23 inches) this century, part of shifts also likely to include more droughts, floods, heatwaves and more destructive storms.
"We really need to pay closer attention to what's going on with these ice sheets," Andrew Monaghan, of the US National Centre for Atmospheric Research, told a telephone news conference with Gillett.
Asked if the findings would affect his view of the likely pace of melting, he said: "I would say that it would lean towards a little bit bleaker side of the picture."
