What is the connection between winter storms and global warming?
The planet is warming, yet the United States has experienced severe winter storms for years. Experts are increasingly looking at the phenomenon.
The city of Buffalo was particularly affected by the storm that hit the US over the Christmas weekend this year.
Keystone/AP Photo/Craig Ruttle
Although such a comparison may seem completely counter-intuitive, some connections can be clearly identified. Others, on the other hand, are still debated by the scientific community.
If the link between global warming and heat waves is more straightforward, the behavior of winter storms is governed by complex atmospheric dynamics that are more difficult to study. Even so, “winter storms have certain characteristics […] The link to climate change is very strong,” Michael Mann, a climatologist at the University of Pennsylvania, told AFP.
Warming of bodies of water, such as lakes or oceans, for example, affects the amount of snow that falls. In the United States, a mechanism known as the “lake effect” occurs particularly around the Great Lakes region along the Canadian border. It is also in this area that the city of Buffalo was particularly affected by the storm that hit the United States over the Christmas weekend this year.
polar vortex
Cold air from the north collides with the warm water of these lakes, causing convection that leads to snowfall.
“The higher the temperature of these lakes, the higher the humidity in the air and the higher the humidity and the potential for snow from the lake effect,” Michael Mann described in a paper published in 2018. Lake-effect snowfall as temperatures have warmed over the past century.”
On the other hand, other mechanisms such as the effect of climate change on the polar vortex and jet stream are not subject to consensus. The polar vortex is a mass of air above the North Pole, located high in the stratosphere (we live in the troposphere and the stratosphere lies above it).
It is surrounded by a rotating gyre, which acts as a barrier between the cold northerly winds and the milder southerly winds. But as the polar vortex weakens, this air wave begins to waver and take on a more oval shape, bringing colder air further south.
And more and more often
According to a 2021 study, these types of disturbances are frequent and reverberate over the next two weeks in the atmosphere where the jet stream is located.
This west-to-east flow of air, again following the boundary between cold and warm air, then bends to allow cold air from the north to penetrate lower latitudes, particularly in the eastern United States.
Disturbances of this type occur frequently, and are reflected in the atmosphere where the jet stream is located during the following two weeks.
Keystone/AP Photo/Jeffrey D. Barnes
“Everybody agrees that severe winter storms are more likely if the polar vortex is disrupted,” study lead author and study climatologist Juda Cohen told AFP. Atmospheric and Environmental Research (AER).
This “stretched” polar vortex was observed just before the storm that hit the US this December, he pointed out. In February 2021, when freezing cold weather hit Texas, a massive power outage occurred.
“Active Discussion”
But the heart of the debate lies elsewhere. The key question is what accounts for these increased polar vortex perturbations?
According to Judah Cohen, they are linked to changes in the Arctic accelerated by climate change: on the one hand, the rapid melting of sea ice and, on the other, the increase in snow cover in Siberia. “It’s a subject I’ve been studying for more than 15 years, and I’m more convinced today by this link than I’ve ever been,” he told AFP.
However, this last point remains “an intense debate within the scientific community,” Michael Mann underscored. “Climate models still do not capture all the fundamental physics relevant to how climate change affects jet stream behavior.”
Future studies are still needed in the coming years to unravel the mystery of these complex chain reactions.
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