In spite of global warming, parts of Eurasia have seen a number of unusually harsh winters in the past couple of decades — a puzzling countertrend that is mainly the result of drastic sea-ice retreat in the Arctic Ocean.
Winters in temperate zones can become severe when patterns of atmospheric pressure persist that favour the transport of cold Arctic air to mid-latitudes. Climate scientists have long assumed that Arctic sea-ice cover influences atmospheric circulation in the Northern Hemisphere, but the strength of that long-distance effect has not been clear.
To reconcile differing estimates, Masato Mori and his colleagues at the University of Tokyo combined observations and outputs from repeated runs of seven global climate models. They found that existing models tend to underestimate how strongly mid-latitude winter temperatures are affected by sea-ice loss in the remote Arctic. Over central Eurasia, almost half of the observed winter cooling trend for 1995 to 2014 can be clearly attributed to shrinking sea ice in the Barents and Kara Seas, they conclude.