Huge swaths of North America are facing subfreezing temperatures this week as cold Arctic air pushes southward. Paradoxically, such cold spells may persist or even become more common as the planet warms, scientists say.
The polar jet stream, a slim band of westerly winds circling the Arctic, is formed where cold, northerly air meets warmer air to the south. But the Arctic is heating up nearly four times faster than the rest of the planet, narrowing this difference in temperature. The result, according to a recent review of scientific research, is a weaker, more meandering jet stream that allows frigid air to reach further south.
Even as the planet is warming as a whole, “we are still seeing surprisingly severe cold spells that sometimes last for many days and invade regions unaccustomed to severe cold,” said coauthor Jennifer Francis, of the Woodwell Climate Research Center.
She added, “It seems really counterintuitive, but there will be plenty of ice, snow, and frigid air in the Arctic winter for decades to come, and that cold can be displaced southward into heavily populated regions by Arctic heat waves.”
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