Arctic thaw tied to European, U.S. heatwaves and downpours

http://www.reuters.com/article/2013/12/08/us-climate-arctic-idUSBRE9B709W20131208

By Environment Correspondent Alister Doyle
OSLO Sun Dec 8, 2013

A thaw of Arctic ice and snow is linked to worsening summer heatwaves and downpours thousands of miles south in Europe, the United States and other areas, underlying the scale of the threat posed by global warming, scientists said on Sunday.

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But the science of a warming Arctic is far from settled.

Writing in the journal Nature Climate Change, experts in China and the United States said they could not conclusively say the Arctic thaw caused more extreme weather, or vice versa.

But they said they had found evidence of a relationship between the two. Rising temperatures over thawing snow on land and sea ice in the Arctic were changing atmospheric pressure and winds, the report said.

The changes slowed the eastward movement of vast meandering weather systems and meant more time for extreme weather to develop - such as a heatwave in Russia in 2010, droughts in the United States and China in 2011 and 2012, or heavy summer rains that caused floods in Britain in 2012, the paper added.

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Sea ice in the Arctic shrank to a record low in 2012 and the U.N.'s panel of climate scientists says it could almost vanish in summers by 2050 with rising greenhouse gas emissions.

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In September, the U.N.'s panel of climate scientists raised the probability that most global warming since 1950 has a human cause - mostly gases released by burning fossil fuels - to 95 percent from 90 in a previous assessment in 2007.

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