‘Perfect storm’ caused last winter’s East Coast blizzards

El Niño moisture combined with cold air surging down from the Arctic to bring record snow to big East Coast cities.

Some researchers say big snows were not related to climate change; others claim North Atlantic Oscillation is intensified by warming over the polar region

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By Summit Voice

SUMMIT COUNTY — Last winter’s East Coast blizzards were the result of a “perfect storm” scenario, as El Niño-driven moisture in the Southeast collided with cold air pushing down from the Arctic over the North Atlantic, according to measurements made by the Lamont-Doherty Earth Observatory at Columbia University.

Researchers at the observatory have been measuring snowfall and temperatures for 60 years. They said snowfall in Washington, D.C. Baltimore and Philadelphia reached all-time record levels, with up to six feet of total snowfall in those locations. They said the record-breaking storms were not caused by global warming, but by the collision of the El Niño pattern with another lesser-known cyclical weather event called the North Atlantic Oscillation.

Other researchers are on record as saying that the North Atlantic oscillation has been intensified by climate change, as warmer air over the Arctic displaces colder air southward. The last time the North Atlantic experienced a strong negative phase of the oscillation was in the winter of 1995-1996, when the East Coast was also hammered with above average snowfall. This winter, the North Atlantic Oscillation was even more negative.

In spite of last winter’s snow, the decade 2000-2009 was the warmest on record, with 2009 tying a cluster of other recent years as the second warmest single year. Earth’s climate has warmed 1.5 degrees on average since modern record keeping began, and this past June was the warmest ever recorded.

Using a different dataset, climate scientists at the National Oceanic and Atmospheric Administration came to a similar conclusion in a report released in March.

“Snowy winters will happen regardless of climate change,” said Richard Seager, a climate scientist at Lamont-Doherty and lead author of the study. “A negative North Atlantic Oscillation this particular winter made the air colder over the eastern U.S., causing more precipitation to fall as snow. El Niño brought even more precipitation—which also fell as snow.”

While the heavy snow on the East Coast and northwest Europe dominated headlines this winter, the Great Lakes and western Canada actually saw less snow than usual—typical for an El Niño year, said Seager. Warm and dry weather in the Pacific Northwest forced the organizers of the 2010 Winter Olympic Games in Vancouver to lug in snow by truck and helicopter to use on ski and snowboarding slopes. The arctic also saw warmer weather than usual, but fewer journalists were there to take notes.

“If Fox News had been based in Greenland they might have had a different story,” said Seager.

While El Niño can now be predicted months in advance by monitoring slowly evolving conditions in the tropical Pacific Ocean, the North Atlantic Oscillation— the difference in air pressure between the Icelandic and Azores regions—is a mostly atmospheric phenomenon, very chaotic and difficult to anticipate, said Yochanan Kushnir, a climate scientist at Lamont-Doherty and co-author of the study.

“The events of last winter remind us that the North Atlantic Oscillation, known mostly for its impact on European and Mediterranean winters, is also playing a potent role in its backyard in North America,” he said.

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