Winters are becoming warmer as the world warms. However, the United States has seen severe winter storms in recent years, and academics are investigating the relationship between these extreme cold occurrences and climate change.

While there is a direct link between global warming and heat waves, the behavior of winter storms is regulated by complicated atmospheric dynamics that are more difficult to understand.

Even so, "there are certain aspects of winter storms (...) where the climate change linkages are fairly strong and robust," Michael Mann, a climatologist at the University of Pennsylvania, said, as quoted by AFP.

The warming of bodies of water, such as lakes or oceans, influences the amount of snowfall.

Explainer: "Lake-effect snow"

In the United States, a phenomenon known as "lake-effect snow" occurs near the Canadian border in the Great Lakes region. A deadly snowstorm rocked Buffalo, which is located on the shores of one of the Great Lakes, over Christmas weekend.

Convection occurs when cold air from the north collides with the warmer water of these lakes, resulting in snowfall.

"The warmer those lake temperatures, the more moisture (is) in the air, and the greater potential for lake-effect snows," Michael Mann wrote in a 2018 paper.

"Not surprisingly, we see a long-term increase in lake effect snowfalls as temperatures have warmed during the last century."

However, there is no agreement on other factors, such as the effect of climate change on polar vortices and jet stream air currents.

The polar vortex is an air mass located high in the stratosphere above the North Pole. The troposphere is where humans live, and the stratosphere is slightly above it.

It is encircled by a band of rotating air that serves as a barrier between the chilly air to the north and the milder air to the south. This band of air begins to undulate and take on a more oval shape as the polar vortex weakens, delivering more frigid air southward.

This form of disturbance is becoming more often, according to a 2021 study, and is reflected in the next two weeks lower in the atmosphere, where the jet stream is located.

This air current, which blows from west to east, again following the boundary between cold and warm air, then meanders, allowing cold air from the north to infiltrate at lower latitudes, particularly over the eastern United States.

This increase in snow cover in Siberia, however, remains "an active debate within the scientific community," said Mann.

"Climate models are not yet capturing all of the underlying physics that may be relevant to how climate change is impacting the behavior of the jet stream."

In the future years, further research will be required to solve the riddle of these intricate chain reactions.

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