The world is getting warmer, including the winters. However, the United States has experienced severe winter storms in recent years, and experts are taking a closer look at the link between these bouts of extreme cold and climate change.
Unlike the relationship between global warming and heat waveswhich is very direct the behavior of winter storms is governed by complex atmospheric dynamics which are more difficult to study.
Even so, “there are certain aspects of winter storms (…) where the links to climate change are quite clear“he told AFP. Michael Mann, a climatologist at the University of Pennsylvania.
For example, warming of water bodiessuch as lakes or oceans, influences the amount of snow that falls.
In the United States, “lake effect snowfall” occur around the Great Lakes region, bordering Canada. The city of Buffalowhich is found on the shores of one of the Great Lakes, was hit hard by a deadly snow storm during the Christmas weekend.
The clash between cold air coming from the north with warmer water of these lakes cause convectionwhich causes a Nevada.
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“The warmer the lake temperatures, the more moisture (there is) in the air and increased potential for lake effect snowfall,” Mann wrote in a 2018 article.
“As expected, we see a long-term increase in lake-effect snowfall as the temperature has been rising over the last century,” he explained.
There is, however, no consensus on other mechanismsAs the effect of climate change on the polar vortex and jet air currents.
The polar vortex is an air mass over the North Polelocated high in the stratosphere. Humans inhabit the troposphere and the stratosphere lies just above it.
this vortex is surrounded by a rotating band of airwhich acts as a barrier between cold air from the north and warmer air from the south. As the polar vortex it gets weakthis band of air begins to wavy and becomes more oval in shapebringing more cold air to the south.
According to a 2021 studythis type of disturbance is occurring more frequently and, when it occurs, rimpacts in the following two weeks lower in the atmosphere, Where is the jet stream?
This air current, which blows from west to east, again following the border between cold and warm airthen meanders in such a way that allows cold air from the north to descend to lower latitudes, particularly about the eastern United States.
“Everyone agrees that when the polar vortex is disturbed, the probability of severe winter weather increases”he told AFP Judah Cohen, lead study author and climatologist at the Atmospheric and Environmental Research (AER) analysis center.
And this “stretched” polar vortex is exactly what was observed just before the storm that hit the United States this December, he noted.
the same phenomenon was observed in February 2021when a strong cold snap hit Texas and caused massive power outages.
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But center of debate is in a key question: What is causing these increasing disturbances in the polar vortex?
According to Cohen, these disturbances are linked to changes in the Arctic, accelerated by climate change. On one hand, the rapid melting of sea ice and, on the other, the increased snow cover in Siberia.
“This is a subject that I have been studying for more than 15 years and Today I am more sure than ever of that bond“, he told AFP.
However, this last point is still an “ongoing debate” within the scientific community.
“Climate models do not yet capture all the underlying physics that may be relevant about how climate change is affecting the jet stream behavior“, accurate.
Therefore, further studies will be needed in the coming years to unravel the mystery of these complex chain reactions.