Arctic warming taking the edge off extreme winters, Study

Cold winter temperatures have become less extreme through large swathes of Europe and North America as global warming has taken hold, according to new research.

The study, published in Nature Climate Change, says this trend is likely to continue. It means that punishing winters, like the deep freeze which struck the US in early 2014, could be less frequent in years to come.

Dr Screen, a Mathematics Research Fellow at the University of Exeter, said: “Autumn and winter days are becoming warmer on average, and less variable from day-to-day. Both factors reduce the chance of extremely cold days.”

The idea that there was a link between Arctic amplification and extreme weather conditions became prevalent during the severe winter weather that plagued large areas of the United States in January 2014, leading to major transport disruption, power cuts and crop damage.

In his study, Dr Screen examined detailed climate records to show that autumn and winter temperature variability has significantly decreased over the mid-to-high latitude Northern Hemisphere in recent decades.

He found that this has occurred mainly because northerly winds and associated cold days are warming more rapidly than southerly winds and warm days.

Dr Screen said: “Cold days tend to occur when the wind is blowing from the north, bringing Arctic air south into the mid-latitudes. Because the Arctic air is warming so rapidly these cold days are now less cold than they were in the past.”

Using the latest mathematical climate modelling, Dr Screen has also been able to show that these changes will continue in to the future, with projected future decreases in temperature variability in all seasons, except summer.

‘Arctic amplification decreases temperature variance in northern mid-to-high-latitudes’, by James Screen, is published in Nature Climate Change online, on Sunday, June 15.

Agencies/Canadajournal