In 2010, Germany has recorded the coldest winter for 40 years. But at the same time – globally seen – 2010 has belonged to the hottest years since 1860. In the USA, Europe and Asia, last December was far colder than average and at the same time, in the southern hemisphere, it was much hotter than average. What are the causes?

US climatologist, Judah Cohen, recommends us to turn our attention to the snow in Siberia to understand the weather extremes. Neither El Nino nor solar variability could be held responsible for the surprising cold in the winter of 2010 and the previous ones. One phenomenon was that the seasonal snow cover was permanently increasing although the earth’s frozen areas were in retreat. And exactly this phenomenon was a result of climate change.

According to Cohen, the global temperatures have increased in the past two and a half decades and thus melted the Arctic sea ice. So, more moisture has become available to fall as snow in winter over the northern parts of the globe. This is why there is so much snow in Europe, North Asia and the USA. The sun’s energy reflects off the bright white snow and escapes back out to space with the result that the temperature drops. It’s getting regionally colder.

When snow cover is more abundant in Siberia, it creates an unusually large dome of cold air. That’s why we have had colder air and exceptionally snow-rich and cold winters in the northern hemisphere since the turn of the century. Most forecasts have failed to predict these connections, however, because the primary drivers in their models are the oceans. They have ignored the snow in Siberia. Long-term climate predictions are far more difficult than short-term weather forecasts.

And so climatologist Cohen recommends viewing toward the east to gain a better understanding of the future weather extremes. Also the Potsdam Institute for Climate Impact Research (PIK) assumes that global warming could cause colder winters. The ice melting in the Arctic was causing a cooling of the northern continents. Vladimir Petoukhov from PIK: “these disturbances could triple the probability of the occurrence of extremely cold winters in Europe and North Asia.” The researchers of PIK also estimate the influence of reduced solar activity as low. The connection between the retreat of permafrost and the increasing snow masses as well as the cold winter was more likely, they say.

In the “Journal of Geophysical Research” Petoukhov writes: “hard winters like the one last year or in 2005/2006 are not contradictory to the picture of global warming; they rather complete it. ” The current extreme weather conditions on our globe could lead to the following understanding – at least in Europe: bundle up – it’s global warming!

© Franz Alt 2011

Übersetzung Andrea Polak 2011