NOAA announced last year that the snow had no human fingerprint, but two weeks ago James Overland at NOAA said just the opposite.
Is severe winter weather related to global warming?
Monday, February 7, 2011; 2:56 PM
Over the past two years, the polar vortex has been strikingly unstable, according to meteorological data. James Overland of the National Oceanic and Atmospheric Administration cites a couple of measures in particular: One, called the Arctic oscillation, tracks air pressure and related atmospheric variables over the North Pole. The other, the North Atlantic oscillation, takes into account similar variables in the neighborhood of Iceland. Both indexes are reliable indicators of the strength of the polar vortex.
Last winter, both indexes reflected higher air pressures and therefore less vortex stability than scientists have ever recorded. This year, both were again seriously off-kilter.
Any number of meteorological factors contributed to those anomalies. Some were undoubtedly random, Overland says. But he and other experts suspect climate change is contributing to the unusual pattern, and if they’re right, things could get a whole lot worse in the years ahead.
The root of the problem, Overland says, is melting sea ice. Sea ice forms in the Arctic Ocean during the cold, dark days of fall and winter and hangs around, melting slowly but not completely vanishing, throughout the summer. In recent years, more sea ice has melted during the warm months than can be replenished during the chillier ones.
In 2004, Overland blamed the lack of snow on global warming:
When scientists trained their analytical tools on the North Pole and its environs, they quantified the local knowledge: The polar ice cap is 40 percent thinner and millions of acres smaller than it was in the 1970s.
What happens at the North Pole can affect the rest of the planet, potentially altering the course of the Gulf Stream, which moderates climate from the East Coast of the United States to the British Isles. Closer to home, the jet stream that dictates much of Seattle’s weather can be diverted when the polar vortex speeds up.
“It’s probably contributing to the fact that it’s warmer and we’ve been getting less snow,” Overland said.