Science | Shepherd 
Recent years have seen a series of unusually cold winters in northern mid-latitudes, including the eastern United States, where they have been accompanied by extremely heavy snowfalls. Some atmospheric scientists have argued that such cold events may be associated with the rapid warming of the Arctic that has been observed over recent decades and that is manifested in the precipitous decline of Arctic sea-ice extent since the early 1990s. Others have argued that the cold events merely reflect the chaotic variability of the climate system and are becoming less likely under climate change. How can different atmospheric scientists come to such different conclusions from the same data?
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