What is the connection between winter storms and global warming?

The planet is warming, including winters. However, the United States has experienced severe winter storms in recent years, prompting experts to take a closer look at the link between these extreme cold episodes and climate change. Even if such a comparison seems completely counter-intuitive, certain relationships have been clearly established, while others are still highly debated by the scientific community. Because the link between global warming and heat waves is very direct, the behavior of winter storms is driven by complex atmospheric dynamics that are more difficult to study. Michael Mann, a climatologist at the University of Pennsylvania, told AFP that there are still “some aspects of winter storms (…) the link to climate change is pretty strong.” Warming of bodies of water such as lakes or oceans, for example, affects the amount of snow that falls. In the United States, the mechanism called “lake effect” occurs especially around the Great Lakes region, on the Canadian border. The city of Buffalo, located in this area, is particularly affected by the storm that hits the United States. year, in the middle of the Christmas weekend. The collision of cold air from the north with the warm water of these lakes causes convection, which leads to snowfall. “The warmer the temperature of these lakes, the more moisture in the air, and the more likely lake-effect snow is,” Michael Mann described in a text published in 2018. On the other hand, other mechanisms, such as the effects of climate change on the polar vortex and the Jet Stream, are not a matter of consensus. just above it). It is surrounded by a rotating band of air that acts as a barrier between cold air in the north and milder air in the south. But as the polar vortex weakens, this band of air begins to undulate and become more oval in shape, bringing more cold air south. 2021 According to a study in so that the cold air from the north reaches the lower latitudes, especially in the United States allows access to tlar. states. “Everyone agrees that severe winter storms are more likely when the polar vortex breaks,” study climatologist Judah Cohen, lead author of the study, told AFP. . And this “elongated” polar vortex is what was seen just before the storm that hit the US in December, he noted. This was also the case in February 2021, when freezing cold weather hit Texas and caused massive power outages. But the heart of the argument lies elsewhere. The main question is: what causes the increased disruption of the polar vortex? According to Mr. Cohen, they are due to changes in the Arctic accelerated by climate change. On the one hand, the rapid melting of sea ice, and on the other hand, the increase of snow cover in Siberia. “It’s a subject I’ve been studying for over 15 years and I’m more confident today than I’ve ever been about it,” he told AFP. Michael Mann stressed that this last point, however, remains an “active debate in the scientific community”. “Climate models do not yet capture all the underlying physics that may be involved in how climate change affects the behavior of the jet stream.” Therefore, research will still be needed in the coming years to unravel the mystery of these complex chain reactions.

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