OK, time to talk to the weatherman. As in what the freak is going on? As in how do we go from wind-lashed, sub-zero temperatures and then rubber band to mild sunny days with gentle zephyrs bathing us in warmth?
As in why did we spread a month’s worth of sand and salt on icy roads only to have it all wash away the next morning, but not before those caught in the transition zones spun off the black ice into other cars, guard rails and ditches? As in who wants to be in the insurance business these days?
For most of us, a new term entered our lexicon last week — the “polar vortex,” which one radio wit on NPR described as a giant cold monster that lives at the North Pole, got drunk, stumbled into the United States and passed out on us.
If your pipes were not freezing, you could even joke about the fact that it was colder in parts of Maine during the first week in January than on Mars, where it was only 20 below. This must be good news for Richard Branson’s Virgin Galactic tourism-to-the-solar-system enterprise.
Well, weather is weather, which means it is unpredictable at any given time and place across the globe. But within this vast array of unpredictability are permanent features of the climate system. One of these is the polar vortex — a giant mass of swirling cold air normally penned in over the north pole by the jet stream — the upper atmospheric steering current that keeps polar zones polar and temperate zones temperate all across the northern hemisphere.
Every once in a while, a piece of the polar vortex breaks away, pushes the jet stream south and stampedes its way down into the lower 48. That’s when citrus crops freeze in Florida and the price of winter vegetables spikes. Happens from time to time.
But this was different. The jet stream weakened over the entire northern tier of the U.S., and the polar vortex bulged southward all the way to Atlanta, Ga., and across most of the southern tier of the country. And stayed there for a week.
Climate change skeptics — let’s be candid and call them denialists — chortled and twittered away on the Internet that last week’s cold weather proves that climate change is a hoax. Climate, by definition, means the average weather over long periods of time, say a decade or two, whereas weather is what you get from day to day, no matter where you live.
In explaining the very strange lurch of the polar vortex, however, some climate scientists point to a real change in climate over the Arctic observed during the past few decades, where the Arctic climate is now incontrovertibly warmer. Arctic sea ice is thinner in the winter and has melted over vast areas in the summer, warming the ocean underneath in a powerful feedback loop. Ice-free Arctic seawater absorbs more heat than when covered in ice, which leads to greater melting, which warms the sea further and so on. That’s a feedback loop.
No climatologist has yet discovered a physical mechanism linking the rapidly changing climate in the Arctic to the weakening of the jet stream and the appearance of the polar vortex in the U.S. But stay tuned. Global warming does not mean that the globe gets inexorably warmer at every location around the globe all at once.
Climate change, likewise, does not mean the climate changes in predictable, lock-step fashion. During previous natural climate changes — for instance during the Medieval Warm Period when sea ice retreated far enough north so Norse Vikings could inhabit Greenland — climate changed from a warm phase back to a cold phase in fits and starts. These periods were marked by times of great climate instability.
Because climate instability has been the most significant feature of the last few decades, some people, like Amory Lovins and his colleagues at the Rocky Mountain Institute, have proposed substituting the term “global weirding,” for global warming. It hasn’t yet taken hold, but you get the idea.
When I first moved to Washington County during the winter of 1972 and lived in a little cabin I heated with green firewood, I remember an expression I heard for the first time: “It was so cold, I almost got married.” What expression will take hold during the period of global weirding? Be careful with your reply; you might be weirder than you think.