The decline in Arctic sea ice over the past few decades has doubled the chance of severe winters in Eurasia, suggests a study published online in Nature Geoscience. This trend towards a higher frequency of severe winters is unlikely to continue into the future, however, because climate warming is expected to outweigh the sea-ice effect towards the end of the twenty-first century.
Masato Mori and colleagues performed 200 slightly different computer simulations of the global atmospheric circulation using a model based on two distinct settings for Arctic sea-ice concentrations. These settings were derived from observations in years with high and low ice cover, respectively. They found that the observed sea-ice decline in the Arctic Barents and Kara seas since 2004 has made persistent atmospheric circulation patterns that are termed blocking situations, more than twice as likely. These blocking situations favour the transport of cold air to Eurasia, and hence severe winters in the region. Analysing existing climate model projections of twenty-first century climate they found that this phenomenon is likely to be temporary, although uncertainties remain about the future evolution of Arctic and mid-latitude climates.