A polar blast doesn’t negate climate change

With frigid Arctic weather descending on tens of millions of Americans, states have declared emergencies, mail carriers are staying inside, and there’s a risk of frostbite for exposed skin in Chicago in as little as five minutes.

Little wonder that global warming is the last thing on people’s minds and that from some sectors — most notably (and predictably) the president of the United States — a familiar mocking of climate science has resumed. “What the hell is going on with Global Wa(r)ming?” Donald Trump tweeted Monday. “Please come back fast, we need you!”

Trump’s tweet might have been meant mainly as a tongue-in-cheek way of making liberal heads explode, but the fact is global warming hasn’t gone anywhere.

Much as one day of falling stocks doesn’t portend a recession, 48 hours of record-setting cold doesn’t negate decades of accumulating greenhouse gases in the atmosphere. That buildup, created by the burning of fossil fuels since the dawn of the industrial age, is leading to a steady rise in average global temperatures.

“Winter storms don’t prove that global warming isn’t happening,” the National Oceanic and Atmospheric Administration tweeted Tuesday.

The past four years were the planet’s warmest since modern record-keeping began in 1850. And oceans are heating up even faster.

What is tragically lost on the president and others is that weather (short-term changes in the atmosphere) and climate (average weather over time) are two different things. And a crucial hallmark of man-made climate disruption, scientists agree, is that it can multiply and intensify extreme weather events.

So even as a zone of frigid air known as the polar vortex slips south into the United States this week, Australia endures record heat that has touched off devastating fires on the island of Tasmania.

Extra heat in the oceans and atmosphere can cause hurricanes to grow more intense and raise the frequency of both flooding rains and droughts. The Camp Fire that all but destroyed Paradise, California, last year was the world’s costliest natural disaster of 2018. Wildfires raking the state led California’s largest utility, Pacific Gas & Electric Corp., to file for bankruptcy this week.

It’s too early to say whether this week’s Arctic outbreak had anything to do with climate change, but there’s emerging science that it can trigger extreme temperature shifts. Years of record-keeping show that the Arctic is warming faster than the rest of the planet, as heat-reflecting ice is replaced with heat-absorbing open ocean waters, intensifying this cycle.

One result, according to recent studies, could be changes in the jet stream that otherwise holds the polar vortex over the Arctic, allowing lobes of frigid cold to descend farther south, as happened this week.

The feel of Arctic air against the skin is real and scary. But equally undeniable is the growing accumulation of heat-trapping carbon dioxide in the atmosphere from burning fossil fuels. It has risen from 280 parts per million in the late 1800s to 410 parts per million last year.

This frigid outbreak (to be followed by a rapid weekend warmup) isn’t a refutation of global warming; it’s a harbinger of weather extremes to come.