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First in an occasional series. Read more >>
The Claim
"It's the most severe winter storm in years, which would seem to contradict Al Gore's hysterical global warming theories." -- Sean Hannity, Fox News host
"Historic snow storm in Washington -- third this year -- where is Al Gore to explain it snows this heavily as a sign global warming is imminent." -- Newt Gingrich, former Republican Speaker of the U.S. House of Representatives
The Context
A harsh winter in Washington, D.C., has, predictably, been the source of plenty of Al Gore jokes. Many climate skeptics have held up recent snow storms as evidence that climate change is not actually happening.
The Evidence
First things first -- weather is not climate. But the likelihood of certain weather patterns is determined by climate. What we've seen in the snow-covered middle Atlantic this winter isn't just possible in a warming world, but it was actually anticipated.
Let's go straight to the U.S. Global Change Research Program's very useful synthesis report, Global Climate Change Impacts in the United States. On the subject of winter storms, it says: "There is also evidence of an increase in the intensity of storms in both the mid- and high-latitude areas of the Northern Hemisphere, with greater confidence in the increases occurring in high latitudes. The northward shift is projected to continue, and strong cold season storms are likely to become stronger and more frequent, with greater wind speeds and more extreme wave heights. " (Emphasis ours.)
This report, it's worth mentioning, is no partisan affair. It was commissioned by the second Bush administration, and the U.S. Global Change Research Program itself was established under the first President Bush in 1990. The results were presented last year after President Obama took office.
Why would winter storms "become stronger and more frequent" in a warming world? Weather Underground meteorologist Jeff Masters points us to a few key studies. According to the 2007 IPCC report, "water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970." More moisture means heavier snowstorms, so long as it's cold enough to snow. Which it still is in winter, even in Washington D.C. A couple of recent studies of snowstorm history over the past century bear this out.
The Verdict
Massive snowstorms can coincide with climate change. In fact, scientists specifically predicted that they would, and -- most importantly -- we say again, weather is not climate!
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