How a wobbly polar vortex brings cold weather
“Judah Cohen, a climatologist at MIT and the director of seasonal forecasting at Atmospheric and Environmental Research, told Newsweek that, as average global temperatures rise, winter temperatures are increasing at a slower rate than expected.”
As the current dramatic winter storm hits Canada and particularly most parts of the US except California, again- as in 2014 – we learn the cause is a ‘wobbly polar vortex’ as it strikes vehemently down on the continent. See the 2014 coverage:
Another useful explanation at:
https://www.treehugger.com/polar-vortex-linked-to-climate-change-5112639
Here are some points from the above article, :
By
Updated February 16, 2021 01:24PM EST
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Normally, the polar vortex swirls from west to east in the stratosphere above the Earth’s poles, keeping cold air over the Arctic and Antarctica.5 At the same time, the jet stream also circulates, keeping warm air to its south and cold air to its north.
Sometimes in the winter, the Arctic stratosphere will heat up through an event known as a Sudden Stratospheric Warming (SSW).6 This causes the winds keeping the polar vortex in place to weaken or even reverse, which in turn weakens the jet stream, making it wavier. The cold Arctic air is then brought down into the mid-latitudes.
The polar vortex itself is not a new phenomenon, and NOAA says the term likely originated in 1853.
………the Arctic has been warming two to three times faster than the rest of the planet on average, and a growing body of observational research links this Arctic warming with extreme winter weather in Eurasia and North America, which has in fact increased in the past two decades7.8
A 2018 paper found that extreme cold and snowfall in the eastern U.S. were more common when the Arctic was warmest.9 ……..
Another 2020 study found that the melting of sea ice in the Barents and Kara Seas was associated with a weaker polar vortex in mid-January to late-February, which was typically displaced over Eurasia.10
At the same time, sea ice melt near Greenland and eastern Canada was associated with a weaker polar vortex from December to early February, that was displaced over Europe.
This trend is a problem for both the U.S. and Europe, and the Arctic itself.
borderslynn 
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