Saturday, February 04, 2012

Europe's Extreme Frost Gives Climate Deniers False Hope

By Theodora Filis

Until this week, Europeans had been enjoying an unusually mild winter with spring-like temperatures in many cities. Scientists say a string of freezing European winters, scattered over the last decade, has been driven in large part by global warming.

The recent week-long cold wave, with temperatures plunging as low as minus 32 degrees Celsius, has claimed hundreds of lives so far. Snow has stranded travelers across the continent with roads blocked, airplanes grounded, and trains unable to move. The snow is forecast to intensify before easing on Saturday, February 4, 2012.

Big freeze tightens its grip on Europe

Meteorologists blame the weather on a strong high pressure system that has pushed cold Siberian air across the continent. According to a new study Arctic's receding surface ice, which at current rates of decline, could disappear entirely during summer months by century's end – tripling the chances that future winters in Europe and north Asia will be just as bad as this year.

Bitterly cold weather across Europe in the winter months of 2005-2006, dumped snow in southern Spain and plunged eastern Europe and Russia into an unusually, and deadly, deep freeze.

Another long cold streak in 2009-2010, gave Britain its coldest winter in 14 years, and caused transportation delays across the continent – much like this week.

Climate deniers who question the gravity of global warming say these bitter winters are at odds with the standard climate change scenarios in which Earth's temperature steadily rises, possibly by as much as five or six degrees Celsius (9.0 to 10.8 degrees Fahrenheit) by 2100.

However, scientists caution that these extreme winters mistakenly bring together the long-term patterns of climate with the short-term vagaries of weather, and ignore regional variation in climate change impacts.

New research shows that global warming has actually contributed to Europe's winter frost.

Scientists explain that the rising Arctic temperatures that have reduced floating ice cover by 20 percent over the last three decades, and the sun's rays that are now absorbed by dark-blue sea rather than being bounced back into space by reflective ice and snow, together with extreme heat, has created a strong high-pressure system that has brought the cold polar air into Europe this week.

Stefan Rahmstorf, a climate scientist at the Potsdam Institute for Climate Impact Research in Gremany said, "Say the ocean is at zero degrees Celsius (32 degrees Fahrenheit), that is a lot warmer than the overlying air in the polar area in winter, so you get a major heat flow heating up the atmosphere from below which you don't have when it is covered by ice. That's a massive change."

The result, according to a modeling study published earlier this month in the Journal of Geophysical Research, is a strong high-pressure system over the newly exposed sea which brings cold polar air, swirling counter-clockwise, into Europe.

"Recent severe winters like last year's or the one of 2005-2006 do not conflict with the global warming picture, but rather supplement it," explained Vladimir Petoukhov, lead author of the study and a physicist at the Potsdam Institute.

"These anomalies could triple the probability of cold winter extremes in Europe and north Asia," he said.

Colder European winters do not indicate a slowing of global warming trends, only an uneven distribution, researchers say.