ARCTIC WARMING --> MEANDERING JET STREAM --> MISERABLE WINTERS IN US AND UK

If you live in the eastern US or in the UK, you've suffered through some of the coldest winters in recent history during the last decade.

North American cold wave November 4-23, 2014

Credit: Wikipedia

An international team of climate researchers from a variety of disciplines has now concluded that those extremely cold winters were the product of natural variability made worse by Arctic warming and ice melt.

Writing in the prestigious journal Nature Climate Change, the authors conclude that a reduced temperature gradient caused by more rapid warming at high latitudes has contributed to a slowed jet stream that meanders farther north and south, and takes longer to shift from one location to another. 

Global air temperature anomalies, January 2016
from Overland, et al., "Nonlinear response of mid-latitude weather to the changing Arctic"

When an extreme dip to the south stalls over a particular region--most recently the UK and the eastern US--arctic air can pour down and stay.

"We've always had years with wavy and not so wavy jet stream winds," says Edward Hanna, a professor of climate change at the University of Sheffield, in the UK, "but in the last one to two decades the warming Arctic could well have  been amplifying the effects of the wavy patterns."

That extra-wobbly jet stream is likely to continue or even grow worse as still-increasing levels of atmospheric CO2 warm the far north and melt more ice. However, the unlucky regions that serve as parking garages for prolonged blasts of Arctic air can vary from year to year. Hanna and his colleagues hope to use what they've learned to sharpen up forecasts of future extra-bitter winters.

“This would be hugely beneficial for communities, businesses, and entire economies in the northern hemisphere," says Hanna. "The public could better prepare for severe winter weather and have access to extra crucial information that could help make live-saving and cost-saving decisions.”