'Significant' warming in both polar regions

31.10.08 09:56

Humans have already caused "significant" warming in both the polar regions, scientists said today.

The new study published in Nature Geosciences journal showed for the first time that man-made climate change is occurring on every continent on Earth - including Antarctica.

The research showed human activities were responsible for warming at the poles - with impacts on wildlife, humans, the size of ice-sheets and global sea levels.

Natural variations alone were unable to account for temperature rises in the Arctic and Antarctic, the study which used decades of records and climate models found.

Research led by scientists from the University of East Anglia (UEA) and the Met Office Hadley Centre also confirmed there had been rapid warming in the Arctic.

Previous studies had not formally attributed rising temperatures at the poles in recent decades to human activities, because of poor data and large natural variability in weather conditions.

The Intergovernmental Panel on Climate Change (IPCC) last year said Antarctica was the only continent where temperature rises driven by humans had not yet been detected.

But Peter Stott, head of climate monitoring and attribution at the Met Office, today said: "In both polar regions the observed warming can only be reproduced in our models by including human influences - natural forcings 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 researchers took more than 100 years of temperature observations from the Arctic and 50 years in the Antarctic, and compared them to climate models which included or discounted human influence on the climate.

Only models which incorporated human activities produced the changes in the climate witnessed at the poles.

Dr Alexey Karpechko, of UEA's Climatic Research Unit, said: "Especially in the Arctic, warming has been observed for a while. Many people were thinking it was to do with human activity, but nobody formally attributed it to that before."

He said temperature rises in the Arctic were more pronounced, largely because of "feedback" in which warming was melting the sea ice, reducing the white area which reflected the sun's heat and leading in turn to more warming.

The situation in the Antarctic was more complicated, he said, because the hole in the ozone layer had an opposing effect to the warming influences in some regions of the continent.

But he said: "Since the ozone layer is expected to recover in the future, we may expect amplifying Antarctic warming in the coming years."

Last year, the Arctic witnessed record levels of sea ice melt during the summer melting season, prompting scientists at the US National Snow and Ice Data Centre to announce that the effects of climate change were "coming through loud and clear".