Science

It might seem counterintuitive, but global warming plays a role in blasts of bitter cold weather. The reason: It influences the jet stream. Here’s how.

By Bob Berwyn

The jet stream wind speeds over North America. Credit: NASA

The polar jet stream can be several miles deep and more than 100 miles wide, with the strongest winds typically 5 to 10 miles above the ground. In this NASA visualization, the fastest winds are in red; slower winds are in blue. Credit: NASA

The jet stream—a powerful river of wind high in the atmosphere—shapes the Northern Hemisphere’s weather, including bitter cold snaps. Because it plays a key role in weather extremes, climate scientists are striving to understand its changing dynamics.

Here’s a closer look at what the jet stream is, what’s influencing its wobbly behavior and why it matters.

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