Air flow changes predict weather extremes even if climate change doesn't

"In some places amplified waves increase the chance of unusually hot conditions, and in others the risk of cold, wet or dry conditions," researcher James Screen explained.
By Brooks Hays  |  June 23, 2014 at 11:45 AM
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EXETER, England, June 23 (UPI) -- Arctic amplification -- the warming of the poles at a faster rate than the rest of the globe -- is one of several factors that's been blamed for the extreme cold witnessed in the U.S. and Europe this past winter. But a new study suggests global warming means less temperature variability, not more.

While it's true that arctic amplification and a slower, meandering jet stream helped instigate extreme cold spells and lingering storms over the last year, researcher James Screen says such extremes are likely to be mitigated over time.

"Autumn and winter days are becoming warmer on average, and less variable from day-to-day," explained Screen. "Both factors reduce the chance of extremely cold days."

Screen, a mathematics fellow at the University of Exeter, collaborated with a number of other researchers in analyzing climate and weather patterns of the last quarter century. The result is a study, published in the journal Nature Climate Change, that suggests the future holds fewer and fewer extremely cold days.

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

All that being said, a different study -- also by Screen and also published in Nature -- does suggest certain regions will see more extreme weather than others -- despite a decrease in temperature variability. These changes are predicted by high atmosphere air flows, like the jet stream, which pull cold air from arctic south and warmer weather from the tropics north.

"The impacts of large and slow moving atmospheric waves are different in different places," he explained. "In some places amplified waves increase the chance of unusually hot conditions, and in others the risk of cold, wet or dry conditions."

Screen hopes his study of major air flows and their effects on weather can help government officials better predict and prepare for extreme meteorological conditions.

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