It’s the moisture, stupid, not the temperature

(Photo of Capitol Building in last week's snowstorm from Flickr and photographer eped1999)

Heavy snowstorms in the East are causing quite a tizzy. Climate skeptics are loving it and spreading doubt about the validity of global warming. Especially in Washington, D.C.

Sen. Jim DeMint (R-S.C.) tweeted that “It’s going to keep snowing in D.C. until Al Gore cries ‘uncle.’”

And Sen. James Inhofe’s (R-Okla.) daughter and grandchildren built an igloo on the National Mall, calling it “Al Gore’s new home.”

My, my, they certainly have it in for the former vice president.

But the truth is the heavy snowstorms in the mid-Atlantic states are completely consistent with global warming.

1. The temperature is changing SLOWLY, folks. Only 1.4 degrees F in the past 100 years. That’s enough to change weather patterns, but not enough to feel.
2. Precipitation is not the same as temperature. More concentrated precipitation as the Earth warms was predicted by climate scientists. Whether it’s in the form of rain and floods or snow depends on if it’s above or below freezing. And the rain or snow tends to get dumped in some places while others stay too dry.
3. Heavy rains and snows are the result of more moisture in the air, which is caused by warming land and oceans. Water vapor in the air is up 4% since 1970.
4. The East and Upper Midwest were predicted to see see the most precip, while the South and West, which have suffered droughts, get less.

A study in 2004 said there had been a 14% increase in heavy rain or snowstorms in the past 100 years, including a significant increase in the winter in the Northeast. Another study in 2006 found a decline in precipitation in the lower Midwest, South and California, but an increase in the upper Midwest and East between 1901 and 2000.

The 2009 U.S. Climate Impact Report found “Cold season storm tracks are shifting northward and the strongest storms are likely to become stronger and more frequent. There will also be an increase in lake-effect snows. The ice cover on the Great Lakes has decreased 8.4% per decade since 1973, which leads to more evaporation and heavier storms.

So don’t let people get away with saying unusually heavy snows, like those last week and in December, mean there’s no such thing as global warming. More likely they are caused at least in part by global warming and will get worse in the future if Congress sits on its hands and hopes the threat has gone away so they don’t have to stand up to the oil and coal lobbies.

(Special thanks to Climate Progress for its research and commentary on this topic. To read in more detail, go to climateprogress.org. For the U.S. Climate Impact Report see The U.S. Global Change Research Program.)