In 2021, a cold wave swept across the U.S., bringing freezing temperatures as far south as Texas. Millions of people lost power, and hundreds died.

Yale Climate Connections meteorologist Bob Henson says this cold wave was caused by disruptions to the polar vortex in the stratosphere, a few miles above Earth.

“The polar vortex is a loop of winds that encircles the North Pole. This loop of winds can stretch. It can break into two pieces across the course of a winter,” he says. “So the polar vortex stretched pretty dramatically, and that allowed cold air to be funneled from the Arctic down into the United States well into Texas.”

Some scientists suggest this stretching is happening more often as the climate warms. And data gathered over two decades initially supported that theory.

“One school of research has found that warming in the Arctic may be causing weather weirding or torquing of the jet stream to pull cold air down more often and perhaps intensify cold and snow,” Henson says.

But he says over longer time scales, the connections are a little less solid.

“So that tends to argue for what we call natural variability,” he says.

So scientists are still debating the role of climate change in polar vortex disruptions. But Henson says no matter what, people should expect occasional extreme cold waves.

Go deeper: What on Earth is a polar vortex? And what’s global warming got to do with it?

Reporting credit: ChavoBart Digital Media