A pocket of arctic air rolled down over Canada and the Midwest this week and brought record cold temperatures, as low as the -50s. Schools were closed, mail delivery was suspended, and several deaths were linked to the cold.
President Donald Trump quipped on Twitter that he wanted global warming to “come back fast,” suggesting, as he has before, that the cold weather proves climate change isn’t happening. But that’s far from the truth.
In fact, the extreme cold may be linked to extreme warming in the Arctic.
“We believe it has a connection to global warming, believe it or not,” said Jennifer Francis, one of the scientists to first connect the two phenomena. Francis is a senior scientist at Woods Hole Research Center.
“The true polar vortex is sitting over the North Pole, way up high in the atmosphere … about 30 miles up,” Francis said. “Occasionally something will cause it to become less circular. It can take on the shape of a dumbbell or even split into two or even three separate circulations.”
Those circulations can drift southward and invade North America and Eurasia, as they did this winter.
Francis is one of the scientists who have connected these invasions of Arctic air to warming ocean waters.
“Because of that extra heat that has come out of the ocean, it can generate extra wave energy in the jet stream,” she said. “In the winter time, that wave energy can transfer upwards into the stratosphere, and if enough of it gets transferred and it goes on for a long enough time, it can actually have this effect on the polar vortex.”
This can happen naturally because of the chaos of the system, Francis said.
“But we are seeing an increase in the frequency,” she said. “It happened last year, as well. Normally would only expect to see them every few years.”
Everyone is relieved that the temperature has finally warmed back up in North America. But don’t get too comfortable, Francis said.
“It does tend to create a very persistent pattern,” she said. “There's another blast coming.”
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