Science Features

Europe facing colder winters due to climate change

By Simone Humml Feb 9, 2012, 21:23 GMT

Berlin - The death toll from the freezing temperatures currently sweeping much of Europe has already topped 400 - and there is no end in sight to the cold snap.

Some climatologists expect such winters to become increasingly common as Northern Hemisphere warming leads to more severe northern continental winters.

The reason for potentially colder winters is a decrease in the wintertime sea ice concentration in the Eastern Arctic Barents and Kara seas, which scientists believe may cause changes in air circulation, thus allowing cold Arctic air to pour down to the mid-latitudes.

Vladimir Petoukhov of the Potsdam Institute for Climate Impact Research (PIK) in Germany says the phenomenon could starkly increase the probability of extremely cold winter temperatures over large areas of Europe and northern Asia.

An 'anomalous decrease of wintertime sea ice concentration in the Barents-Kara seas could bring about extreme cold events like winter 2005-2006,' Petoukhov wrote in a research paper from 2010, which was co-authored by Vladimir Semenov from the Leibniz Institute of Marine Sciences at the University of Kiel.

Computer simulations indicate that sea ice reduction is the cause of colder winter temperatures in Europe. These results are similar to research carried out by climatologists at the Alfred Wegener Institute (AWI) for Polar and Marine Research in Germany.

'The probability of a cold winter with lots of snow increases in Central Europe when the Arctic has low sea ice cover in summer,' the AWI wrote on January 26, just days before the current cold snap hit the continent.

The retreat of the light-coloured ice surface causes the darker ocean to warm up more in summer from the solar radiation. The reduced ice cover can no longer prevent the heat stored in the ocean being released into the atmosphere.

This leads to increasing air temperatures in the Arctic region, which last into autumn and winter. Last summer, the Arctic sea ice cover was the second lowest since satellite records began in 1979.

According to AWI scientist Ralf Jaiser, the lead author of a global climate analysis published last month, the altered conditions in the Arctic influence air circulation and pressure patterns.

If the conditions lead to a reduction in wind, cold Arctic air can penetrate down through to Europe, although Jaiser admits the research does not provide a watertight explanation of what is happening.

'Many other factors naturally play a role in the complex climate system of our Earth, which overlap in part,' he wrote.

Other mechanisms are also involved, such as the snow cover in Siberia or tropical influences, he said.

The phenomenon of colder European winter temperatures is not seen as questioning the reality of global warming.

Jaiser pointed out that the research only looked at winter temperatures in one region.

'We believe that the Arctic is getting warmer and where we are is getting colder,' he explained.

'Europe is a relatively small region and winter is only one of four seasons. The others will be noticeably warmer.'

This development has already manifested itself in the warmer seasons growing longer.

'Our research is just one piece in the climatic jigsaw puzzle,' wrote Jaiser.