Arctic sea-ice loss is not responsible for the spate of extreme winters in Eurasia over the last two and a half decades after all, according to fresh research by climate modellers.
Over the past 25 years, unusually cold winters in Europe and Asia have occurred (even as warming has generally been seen elsewhere in the northern hemisphere) alongside record Arctic sea ice losses, which is caused by anthropogenic global warming. As a result, other researchers’ work has suggested that one is causing the other.
In 2014, a widely covered paper appeared in Nature Geoscience, reporting that the chances of severe winters in southern Russia, Mongolia, Kazakhstan, and northern China has doubled over the past decade as a result of Arctic sea-ice loss. Sea-ice loss in the Barents and Kara Seas off the northern coasts of Norway and Russia in particular has been in the frame.
A second paper appearing the following year in the Philosophical Transactions of the Royal Society, also featured prominently in the press, further extended the idea, suggesting that sea-ice loss is affecting the jet stream, causing it to extend further south and remain there for longer. In essence, when the temperature difference between the north pole and mid northern latitudes is lessened due to global warming, the jet stream slows down.
However, in a fresh counterpoint to this hypothesis, a paper out this week also in Nature Geoscience describes an investigation of over 600 years’ worth of global atmospheric climate model simulations and a further collection of models looking at the interactions between the atmosphere and the oceans. The climate scientists affiliated with the School of Earth and Ocean Sciences at the University of Victoria and led by Kelly McCusker, found no evidence in their models of Arctic sea-ice loss in the Barents and Kara Seas or anywhere else in the Arctic having had an impact on cooling in Eurasia.
Instead, the trend toward cool winters in the region are a product of a long-lasting circulation pattern (a large-scale movement of air that works to distribute heat around the Earth’s surface) that persisted from 1979 to about 2012. This pattern combined high pressure over the Barents and Kara Seas and a trough of lower pressure further downstream.
In other words, it has been circulation that is driving temperature changes, rather than temperature changes that are driving circulation. The new research is suggesting that the earlier papers may have had their correlation the wrong way round. Moving forward, if researchers are to improve the long-term predictability about winters in Eurasia, they will have to look further afield than Arctic sea-ice changes.
The new findings bookend research from earlier this year made by two of the same scientists that concluded that the bitterly cold ‘Polar Vortex’ winters in North America are actually within the normal range for central North America, and not a result of atypical warming in the western tropical Pacific ocean, a product of anthropogenic global warming, as had been suggested by earlier investigations.
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