Credit: © ISTOCKPHOTO / NAJIN

The icy conditions of winter 2009/2010 in Europe caused some public confusion over the extent to which the climate is changing. A study shows that, in fact, it would have been cooler but for an overall warming trend.

Julien Cattiaux at the Laboratory of Climate Sciences and the Environment in Gif-sur-Yvette, France, and colleagues compared the daily temperatures of winter 2009/10, which were about 1.3 degrees Celsius below average, with those recorded in Europe since 1948 (ref. 1). Stagnant seasonal circulation patterns leading to an extremely persistent negative phase of the North Atlantic Oscillation, the climatic phenomenon that dominates weather patterns over Europe, made winter 2009/10 particularly cold. But at about 84 percent of Europe's weather stations, those temperatures were significantly warmer than they had been on days with similar weather patterns during previous winters.

The researchers say that historic weather patterns suggest the winter of 2009/10 could have rivalled the record cold winter of 1962/63, which tallied 4 degrees Celsius below average, if not for the temperature boost caused by climate change in recent decades.