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Why Global Warming Can Make Chicago Cold

When warm temperatures in Alaska push the jet stream north, it can release Arctic air into the U.S. and Canada.

Our nation’s chief climate science expert, Donald J. Trump, Tweeted some encouraging words earlier this week as we prepared for the subzero temperatures of the polar vortex:

Alone among the world’s major political parties, the Republicans deny the existence of global warming. In fact, climate change denial has become a defining issue for Republicans, as central to partisan identity as opposition to abortion or an embrace of tax cuts.

Trump himself has declared global warming a hoax “created by and for the Chinese in order to make U.S. manufacturing non-competitive.” As a result, he pulled the United States out of the Paris Climate Agreement, making us the only industrial nation not to participate.

Republicans have always benefited from campaign contributions by fossil-fuel burning industries such as oil and coal. Beyond that, the bond Trump forged with Midwestern coal miners and factory workers — those threatened by clean energy and foreign competition — was a key to his 2016 victory. Trump has a real motivation to mock the idea that the planet is warming.

The president may believe that this cold snap bolsters his conviction that global warming is fake. In fact, though, the polar vortex currently chilling Chicago could be a direct result of global warming.

The University of Maine’s Climate Change Institute puts together a series of “Climate Reanalyzer” maps that display changes in mean temperature around the world.

Consistently, eastern North America is one of the few places getting colder in the winters. On the map for New Year’s Day, 2018, when the temperature in Chicago hit six below zero, there was a deep blue blotch above the United States, indicating temperatures up to ten degrees below normal.

January 1, 2018.

The reason can be traced to the Arctic, which is warming twice as quickly as the rest of the world. Warmer air weakens the jet stream, which ordinarily traps Arctic air at the top of the world.

Inside Climate News compared the jet stream to a garden hose: an upward bend in one direction will result in a downward bend in another. Last winter, warmer temperatures in Alaska forced the jet stream north, causing it to plunge southward over Canada and the U.S., allowing Arctiv air to rush into those regions.

As science writer Andrew Freedman explained at Mashable:

A massive northward bulge in the jet stream, also known as a ridge, has set up across Alaska, bringing the state record warmth for this time of year. Temperatures have been above freezing in Fairbanks, where they’re typically near or below 0 degrees Fahrenheit at this time of year, so we’re talking some seriously anomalous mild air here.

Alaska and much of the Arctic have been milder than average for this time of year, while Canada and the U.S. are experiencing near-record to record cold.

In fact, North America is currently experiencing the most unusually cold air of any region on Earth right now.

On the east, or downwind, side of this ridge, the jet stream is plunging southward in what is known as a dip or trough in the upper air flow. This is allowing frigid air from a large gyre spinning around Hudson Bay, Canada, to steer cold air toward the U.S. This circulation pattern is distinct from the stratospheric polar vortex, which has actually been displaced across northern Asia.

Trump is a politician. He cherrypicks local situations that suit his narrative.

In truth, we’re experiencing our second polar vortex in five years not in spite of global warming, but because of it. We may as well learn to enjoy the vortices, because they’re becoming regular occurrences. Go outside and throw some boiling water in the air, then watch it evaporate like a baseless claim.

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