January saw some major bouts of subfreezing temperatures across much of North America and significant snowfall in places like Pensacola, Florida and New Orleans. This spate of frigid weather undoubtedly prompted many people to question whether global warming is really happening. But such cold spells quite likely are not happening in spite of global warming, but actually as a result of it.
The polar jet stream is a slim band of westerly winds that circles the Arctic. It is formed where cold air from the north meets warmer air to the south. As the planet warms, the Arctic has been heating up nearly four times faster than the rest of the planet, which narrows the difference in temperature between the northern air and southern air. The result is that the jet stream is weaker and more meandering, which allows frigid air to reach further south.
The polar vortex is a whirling mass of cold air that extends across the Arctic. It is stronger in the winter when the Northern Hemisphere leans away from the sun. The polar jet stream normally holds on to the vortex and keeps it far to the north. But when the jet stream gets wobbly, this mass of cold air can break out and travel south, even to places like Florida, Louisiana, and Texas.
The planet as a whole is warming, and the Arctic is warming even faster. But there will still be plenty of ice, snow, and frigid air in the Arctic winter for decades to come. As the behavior of the polar jet stream gets increasingly erratic, there may well be more frequent episodes of plunging temperatures in areas unaccustomed to them.
**********
Web Links
Severe Cold Spells May Persist Because of Warming, Not in Spite of It
Photo, posted January 5, 2025, courtesy of Dermot O’Halloran via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio
