Tuesday, December 14, 2010

Warming in a Winter Wonderland

It never fails. The first spell of bad winter comes along (we’ve currently got four inches of snow and temps in the teens here in Pittsburgh), and questions start to arise about the validity of global warming. Last year, when two feet got dumped on us in a single night, the naysayers, conservative talk-show hosts, and industry lobbyists had a field day. How, they asked--and expected only one answer--can the planet be warming when it’s so gosh-darned cold outside?

Never mind that there’s nothing in the science of global warming that says anything about cold days vanishing from the globe. Never mind that increased precipitation is one of the expected results of warmer air, which holds more moisture than its colder cousin. The real problem is that most people get all confused--and the skeptics thrive on seeding such confusion--about the difference between weather and climate. The former, since we live with it on a moment-by-moment, day-by-day basis, might seem like the thing to focus our attention on. But it’s not.

Weather--the atmospheric conditions in any given place at any given time--is, as we all know, wildly variable. The proverbial butterfly’s wings can change it, and meteorologists struggle to predict it as little as twenty-four hours in advance. It would be foolhardy to attempt a weather forecast of more than a few days--to predict, say, the weather in Pittsburgh a year from now. Chances are you’d be off by as much as 30 or 40 degrees in either direction--to say nothing of clouds, precipitation, wind, and all the rest.

Climate is different. As the composite of weather averaged over space and time, climate is remarkably stable, and can be forecast with considerable confidence years, even centuries, in advance. In the case of global climate, human beings have enjoyed roughly the same one for thousands of years. The last time the planet’s climate looked significantly different, Cro-Magnons were hunting mastodons and a mile of ice flattened Manhattan. The time before that, when the planet was appreciably warmer, tyrannosaurs roamed North America and crocodiles cruised the poles. The stability and predictability of our present climate is what enabled human civilization to become what it is today.

And that’s the ultimate irony: for the past two centuries, human civilization has tampered with the very climate that, for the past two millennia, made human civilization possible. The planet is warming--and more rapidly than ever before. (Indeed, even with its unseasonably cold December, 2009 is tied for second hottest year on record, and at the end of the day the past winter, on average, was warmer than the one that preceded it.) We’ve made great, and undeniable, advances as a species: advances in technology, in medicine, in science, in human rights, in art. Since the dawn of the Hydrocarbon Era, we’ve made those advances with ever accelerating ease. But in so doing, we’ve degraded the planetary climate (not to mention the planetary soils, waters, and affiliated organisms) perhaps beyond recall.

We have a couple choices here. We can acknowledge the reality of climate change, and respond appropriately. Or we can deny that dire reality and continue to dig ourselves deeper into a hole.

If we choose the first option, our choosing can’t be like the weather, which changes every day. It has to be like the climate, which steadies us and survives deep into the future.

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