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article imageExtreme cold weather — blame climate change effects on jet stream

By Karen Graham     Oct 28, 2016 in Environment
Scientists from both sides of the aisle now agree for the first time that climate change may be intensifying the effects of the jet stream, bringing extremes of cold winter weather to the U.S. and U.K.
There have previously been two schools of thought on the atmospheric dynamics that influence the position of the jet stream. One group believed natural variability in the jet stream was the cause of the recent extreme cold spells seen in both the UK and U.S.
The second group includes scientists who are finding a possible connection with the warming of the Arctic and the emergence of severe cold weather patterns. Both camps have been in agreement that the unusual nature of the atmospheric circulations provided no clues leading to easy answers, reports Science Daily.
But research carried out by a team of international scientists has found that warming in the Arctic may be playing a bigger role in the jet stream's position than previously thought, causing such extremes as the winter of 2014-2015 that brought record snowfall levels to New York.
Professor Edward Hanna and Dr. Richard Hall from the Department of Geography at the University of Sheffield in the UK, together with Professor. James E. Overland from the US Oceanographic and Atmospheric Administration (NOAA) brought together a diverse group of scientists from both sides of the aisle to seek some answers.
The researcher's findings were published in the online journal Nature Climate Change on October 26, 2016, and entitled "Nonlinear response of mid-latitude weather to the changing Arctic."
The research team found that the recent patterns of extreme cold weather was mainly caused by natural changes in the jet stream's position. Phys.Org also reports they also agreed that warming in the Arctic is also playing a key role in influencing the cold spells, although the locations of the cold spells in the northern mid-latitudes can vary from year to year.
In the past, studies have shown that when the jet stream is wavy, there are more cold spells in the mid-latitudes, with the cold air from the Arctic plunging down and sometimes lasting for weeks. We also know that when the jet stream is flowing strongly from the west to the east with no waves, countries in the mid-latitudes have a normal winter.
"We've always had years with wavy and not so wavy jet stream winds, but in the last one to two decades the warming Arctic could well have been amplifying the effects of the wavy patterns," Professor Hanna said.
He added: "This may have contributed to some recent extreme cold winter spells along the eastern seaboard of the United States, in eastern Asia, and at times over the UK, (such as was seen in 2009-2010 and 2010-2011)."
The biggest takeaway from the study is that with a better understanding of the dynamics of the jet stream in a warming Arctic, we can better predict winter weather in some of the world's most populous regions. "This would be hugely beneficial for communities, businesses, and entire economies in the northern hemisphere," says Professor Hanna.
More about Climate change, Jet stream, warming arctic, northern midlatitudes, atmospheric dynamics
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