If the planet is getting warmer, why is it so cold this winter?

The seeming contradiction comes up often when talking to Judah Cohen, a research scientist at M.I.T. who has been studying how global warming might also be causing colder winters in the eastern United States.

The idea, explained Dr. Cohen, is that a warming Arctic can cause a high-altitude ribbon of air called the polar vortex to stretch and wobble. That wobble can affect the flow of the jet stream that controls much of the atmospheric conditions over the United States, causing waves of high and low pressure that affect our daily weather.

For weeks, a mass of frigid air over the North Pole has dipped into eastern North America, bringing record cold temperatures for a prolonged period. In the West, a ridge of warm, dry air has stalled for weeks, panicking ski resort operators and prompting concerns for communities that rely on a healthy snowpack for drinking water in the summer months.

The polar vortex stretched and wobbled in February 2021, causing a prolonged deep freeze that killed 248 people in Texas and knocked out power for millions. The same wobble reappeared in the winter of 2024-2025 and again last month, causing blizzard conditions across the East and an icy blast.

Dr. Cohen expects the grip of cold temperatures to continue throughout February.

“It’s weird what’s going on now in the stratosphere,” Dr. Cohen said. “These stretching events happen every winter, but just how the pattern is stuck is really remarkable.”

Climate warming in the Arctic is causing this disruption of the polar vortex, Dr. Cohen said. With more snowfall in Siberia and melting sea ice in the Barents and Kara seas, just north of Norway and Russia, the ocean is feeding more heat into the atmosphere, setting up a weather pattern that leads to a burst of extreme cold in North America.

Dr. Cohen cowrote a study in the journal Science last year that linked the stretching of the polar vortex to more frequent severe winter weather in the United States in the past decade. A new analysis by Dr. Cohen and colleagues finds that a warming Arctic is also making the wobble in the polar vortex last longer.

“This is very consistent with this winter,” he said.

Not all scientists agree.

“These are interesting ideas,” said Russell Blackport, a research scientist at Environment and Climate Change Canada. “But I’m very skeptical. When I look at these papers, they’re often not that convincing.”