Photograph by Jewel Samad, AFP, Getty Images

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Skiing Washington, D.C.'s National Mall on February 7, 2010.

Photograph by Jewel Samad, AFP, Getty Images

More Mega-Snowstorms Coming -- Global Warming to Blame?

Get used to heavy U.S. snowstorms, scientists say. The cause, though, is a subject of hot debate.

As snowstorm-ravaged states on the U.S. East Coast dig out, scientists say the past week's "Snowpocalypse" could be a taste of harsh winters to come—and that, strangely enough, global warming may be to blame. Others aren't so sure.

Meteorologist Joe Bastardi says the recent snowstorms may be the start of a trend of cold, snowy winters similar to those of the 1960s and 1970s.

Bastardi, of the AccuWeather forecasting service in State College, Pennsylvania, believes the February record snowfalls, though, are due more to an El Niño that formed last year than to climate change.

An El Niño occurs when Pacific waters off the northwest coast of South America become unusually warm. The event is erratic and unpredictable, but it occurs roughly every three to seven years.

In a prepared statement, Bastardi noted that the current El Niño has been "very strong, prompting many major blizzards for the mid-Atlantic region."

The El Niño also is altering the normal flow of upper-level winds known as the jet stream, he said. That disruption is pushing cold air from northern Canada into the United States, Bastardi added.

Global Warming Fueling Snowstorms?

Cyclical patterns of heating and cooling—as opposed to long-term global warming—could herald a coming period of harsher U.S. winters, Bastardi told National Geographic News.

"We know that Earth's cycles are changing," he said. "The Pacific is cooling. The Atlantic will join it in several years. When you get an El Niño with a cold Pacific, you get crazy winters in the East."

Still, other scientists say global warming is the main culprit behind this month's eastern-U.S. snowstorms—and it could cause more heavy snowfalls in future winters.

Attributing snowstorms to warmer weather seems contradictory, but climate scientist Amanda Staudt says relatively warmer weather causes more water to be evaporated from the oceans and thus creates more moisture for winter storms, as long as temperatures remain below freezing.

As for Snowpolaclypse, said Staudt of the National Wildlife Federation in Reston, Virginia, "It's hard to determine global warming's effect on any particular storm, but it's highly unusual to have these really large winter storms in one winter."

Washington, D.C., for example, has had two two- to three-foot snowfalls this winter—which should be a once-every-300-to-400-years rarity, according to Staudt.

Waiting ... and Waiting ... for More Global Warming Evidence

Like AccuWeather's Bastardi, Staudt believes the current El Niño is contributing to this winter's harsh U.S. snowstorms, but to a lesser extent than climate change, which she sees as a clear and present danger.

"I think there's overwhelming evidence that global warming is happening and that human activity is responsible for it," Staudt said.

Regarding scientists who believe global warming is under way, Bastardi said, "I respect their argument; they may have a point." But he thinks it'll take many more winters—not to mention springs, summers, and falls—before we know for sure whether global warming is occurring.

"I feel strongly," he said, "that we'll get an answer in the next 20 or 30 years."