Monday, March 4, 2013

Snowquestration: How D.C. Fits In With The 'Less Snow, More Blizzards' Pattern

Washington, D.C. is abuzz with the news that a new storm is sweeping down towards the mid-Atlantic seaboard, already dubbed "snowquester" (or "snowquestration" if you're a grammar stickler) in honor of the nation's latest budget debacle.

There's a 50 percent chance the snowquester will dump over 5 inches of snow within the Beltway, and a 20 to 25 percent chance it will immobilize the city entirely. Given Washington, D.C.'s meager snowfall in recent winters, the snowquester's impending arrival is understandably grabbing everyone's attention.

It's a "teachable moment" for diving into how Washington, D.C.'s weather specifically fits what we know about climate change.

One paradox that's emerged from climate science in recent years is the "less snow, but worse blizzards" pattern. The Associated Press recently summed up the logic behind this: "A warmer world is likely to decrease the overall amount of snow falling each year and shrink the snow season. But when it is cold enough for a snowstorm to hit, the slightly warmer air is often carrying more moisture, producing potentially historic blizzards."

Global warming is bringing us closer to the sweet spot where moisture in the air is maximized while temperatures remain low enough to cause snow. And recent studies have confirmed that snowfalls over the last 100 years in the United States, as well as those projected for the next 100, fit this pattern.

Jason Samenow over at the Washington Post decided to dig into whether D.C.'s weather specifically has lined up with the "less snow, more blizzards" pattern. Sure enough, it does:

In the 30 winters since 1984 (including this year, assuming we don't miraculously get 14 inches of snow in the coming weeks), only 5 winters have had above average snowfall in D.C. - compared to 25 winters with average to below average amounts (15.4 inches or less). In 4 of the 5 winters with above average snowfall, the total was 2 to more than 3 times normal - or 30.1 to 56.1 inches (in 1987, 1996, 2003, and 2010). Or, put another away, the 25 snow-deprived winters averaged 9 inches of snow, the 5 snowy winters averaged 40 inches.

At the same time, D.C. has not seen accumulating snow in November for the last 16 years, the longest stretch on record. And the 30-year average for snowfall has dropped from 24 inches in 1918, to 18 inches in 1984, to 14 to 15 inches this year.

"Shorter snow season, less snow overall, but the occasional knockout punch," Princeton University climate scientist Michael Oppenheimer told the AP. "That's the new world we live in."

It should be noted that it's the wrong question to ask whether climate change "caused" this or any particular snow storm. The effects of global warming feed into and intensify a range of factors that contribute to more extreme weather. As with a baseball player on steroids, no one hit is "caused" by the steroids - but the use of steroids (a.k.a. global warming) causes the player (a.k.a. the climate) to break records at an unnatural pace. And the rate and severity of snow storms, floods, downpours, droughts, and forest fires have all been on the uptick in recent decades.

Admittedly, even if snowquester does its worst, the 2012-2013 winter season will remain in the "less snow" half of the pattern, given how little snowfall D.C. has already seen. But the above remains an important lesson that the effects of climate change are comprehendible, measurable, at least somewhat predictable - and, most importantly, they're here.

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