What is the relationship between severe snowstorms and global warming?

Our world has been getting warmer for many years, including in winter. However, we see severe winter storms, for example, in the United States.

The links between climate change and extreme weather are becoming increasingly clear. On a warmer planet, heatwaves are hotter, droughts are longer, and summer rains are more intense.

But when it comes to extreme winter weather, such as the recent storm that devastated parts of the US and Canada, the connection between the two is less clear and often the subject of heated scientific debate.

Experts are closely examining the link between extreme cold events and climate change.

It may seem counterintuitive, but more snowfall during blizzards is an expected effect of climate change.

“There are certain aspects of winter storms where the link to climate change is quite strong and robust,” Michael Mann, a climate scientist at the University of Pennsylvania, told AFP.

For example, the warming of water bodies (lakes or oceans) affects the amount of snowfall.

In the United States, a mechanism called “lake-effect snow” occurs in the Great Lakes region on the border with Canada.

What is the relationship between winter storms and global warming? @LucieAubourg for @AFP/@RawStory: https://t.co/Qw1ijJXqaL

— Professor Michael E. Mann (@MichaelEMann) December 29, 2022

The city of Buffalo, located on the shores of one of the Great Lakes, was hit by a very heavy snowfall during the Christmas holidays.

The collision of cold air from the north with warmer water in these lakes causes convection, resulting in snowfall.

Mann previously reported in a research paper published in 2018: “The higher the lake temperature, the more moisture in the air and the more likely lake effect snow is to form. It is not surprising to observe a long-term increase in the amount of snowfall effect as temperatures rise over the past century.”

polar vortex

There is no consensus on other mechanisms, such as the impact of climate change on the polar vortex and jet streams.

The polar vortex is an air mass over the Arctic, which is located in the upper stratosphere. Humans live in the troposphere, and the stratosphere is right above it.

It is surrounded by a band of swirling air that acts as a buffer between colder air in the north and warmer air in the south. As the polar vortex weakens, this band of air begins to ripple and take on a more elliptical shape, bringing colder air southward.

According to a 2021 study, this type of disturbance occurs very frequently and is reflected over the next two weeks in the lowest layer of the atmosphere where the jet stream resides.

This air current, which blows from west to east, again delineating the boundary between cold and warm air, meanders in such a way that it allows colder air from the north to penetrate into low latitudes, especially over the eastern United States.

“Everyone agrees that when the polar vortex becomes turbulent, there is an increased likelihood of severe winter weather,” Judah Cohen, lead author of the study and climate scientist at Atmospheric and Environmental Research (AER), told AFP.

He pointed out that this “stretched” polar vortex is exactly what was observed before the storm that hit the United States in December of this year.

The same phenomenon was observed in February 2021, when a severe cold wave hit Texas, causing widespread power outages.

What causes this growing disturbance in the polar vortex?

According to Cohen, the unrest is due to changes in the Arctic, which have accelerated due to climate change. There is, on the one hand, a rapid melting of sea ice, and on the other hand, an increase in snow cover in Siberia.

“This is a topic that I have been studying for over 15 years and I am more confident about this connection today than in the past,” he told AFP.

“Climate models have not yet captured all of the underlying physics that may be relevant to how climate change affects the behavior of the jet stream,” Mann added.

Further research will be required in the coming years to unravel the mystery of these complex chain reactions.

Source: phys.org.

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