WASHINGTON -- With scant snowfall and barren ski slopes in the Midwest and Northeast the past couple of years, some scientists have pointed to global warming as the culprit.
Then, when a whopper of a blizzard smacked the Northeast this month with more than 2 feet of snow in some places, some of the same people again blamed global warming.
How can that be? Among skeptics, it's been a joke, pointing to what seems to be a brazen contradiction.
Well, the answer lies in atmospheric physics. A warmer atmosphere can hold, and dump, more moisture, snow experts say. Two soon-to-be-published studies demonstrate how there can be more giant blizzards, yet less snow overall each year. Consider:
The United States has been walloped by twice as many of the most extreme snowstorms in the past 50 years as in the previous 60 years, according to an upcoming study on extreme weather by leading federal and university climate scientists. This fits with a dramatic upward trend in extreme winter precipitation, both rain and snow, in the Northeastern U.S. charted by the National Climatic Data Center.
Yet the Global Snow Lab at Rutgers University says spring snow cover in the Northern Hemisphere has shrunk on average by 1 million square miles in the last 45 years.
An upcoming study in the Journal of Climate says computer models predict annual global snowfall to shrink by more than a foot in 50 years. The study's author said most people live in parts of the United States that are likely to see annual snowfall drop between 30 and 70 percent by the end of the century.
"Shorter snow season, less snow overall, but the occasional knockout punch," Princeton University climate scientist Michael Oppenheimer said. "That's the new world we live in."
Ten climate scientists say the idea of less snow and more blizzards makes sense: A warmer world is likely to decrease the overall amount of snow falling and to shrink snow seasons. But when it is cold enough for a snowstorm to hit, the slightly warmer air is often carrying more moisture, producing potentially historic blizzards.
"Strong snowstorms thrive on the ragged edge of temperature -- warm enough for the air to hold lots of moisture, meaning lots of precipitation, but just cold enough for it to fall as snow," said Mark Serreze, director of the National Snow and Ice Data Center.
Look at the last few years in the Northeast. And Chicago, until late January, had 335 days without more than an inch of snow. Historic storms have hit both in recent years. Scientists say they are just now getting a better picture of the complex intersection of man-made warming and extreme snowfall.