It's Official: People Are Warming the Poles

Oct. 31, 2008 -- The verdict is in. Warming near the poles is caused by human activity, according to new research.

"The polar regions exhibit the largest climatic variability on Earth," said Andrew Monaghan of the National Center for Atmospheric Research, Boulder, Colo., who wrote a commentary accompanying the study, published in Nature Geoscience. "Detecting and attributing climate change has been more difficult than elsewhere, and the issue has been confounded by comparatively short and sparse temperature records in both the Arctic and Antarctic."

Antarctica was the only continent where evidence for human-caused climate change was inconclusive, according to the most recent assessment report from the Intergovernmental Panel on Climate Change, published in 2007.

The new study finally makes the link: "The main message of this paper is that we're able for the first time to directly attribute warming in both the Arctic and the Antarctic to human influences on climate," said lead author Nathan Gillett, who completed the work while at the University of East Anglia in Norwich, U.K.

Greenhouse gases, primarily carbon dioxide, are transported globally and persist in the atmosphere, so they exert a warming effect even in uninhabited polar regions.

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A global team of researchers used climate data collected from the Arctic and the Antarctic over 100 years and 50 years, respectively, and compared the measurements with predictions from four different climate models.

In one test, they used only natural influences on climate, like variations in the sun's intensity and volcanic eruptions, in the simulations. In another, they added human influences, including greenhouse gas emissions and the ozone hole, which tends to have a cooling effect.

"What came out of that is that there was a clear detection in both the Arctic and Antarctic of a human influence on climate. We've shown that we detect the human fingerprint in both...regions," said author Peter Stott of the Met Office Hadley Center in Exeter , U.K.