The unusually cold temperatures and string of heavy blizzards along the U.S. Eastern Seaboard last winter had nothing to do with global warming, scientists at the Earth Institute of Columbia University report in the peer-reviewed Geophysical Research Letters. The snow anomalies were in fact typical of winters with the cyclical world-climate conditions that were in force last year, the report noted.
Media Claim Warming Connection
Although global warming would logically seem to produce fewer rather than more extreme cold weather events, environmental activist groups and the media have frequently asserted the blizzards were another sign humans are creating a global warming crisis.
For example, Time magazine reported on February 10, in the wake of two East Coast blizzards, “There is some evidence that climate change could in fact make such massive snowstorms more common, even as the world continues to warm. As the meteorologist Jeff Masters points out in his excellent blog at Weather Underground, the two major storms that hit Philadelphia, Baltimore and Washington, D.C., this winter … are already among the 10 heaviest snowfalls those cities have ever recorded. The chance of that happening in the same winter is incredibly unlikely.”
On the same day, the New York Times added, “Most climate scientists respond that the ferocious storms are consistent with forecasts that a heating planet will produce more frequent and more intense weather events.”
Ocean Cycles the Cause
Columbia University scientists, however, report in the July 24 Geophysical Research Letters that El Niño—a cyclical warming of surface water in the eastern South Pacific—and colder than usual temperatures in the North Atlantic caused the unusually severe Eastern Seaboard winter.
“An El Niño state is associated with positive snowfall anomalies in the southern and central United States and along the eastern seaboard and negative anomalies to the north. A negative NAO [North Atlantic Oscillation] causes positive snow anomalies across eastern North America and in northern Europe. It is argued that increased snowfall in the southern U.S. is contributed to by a southward displaced storm track but further north, in the eastern U.S. and northern Europe, positive snow anomalies arise from the cold temperature anomalies of a negative NAO. These relations are used with observed values of NINO3 and the NAO to conclude that the negative NAO and El Niño event were responsible for the northern hemisphere snow anomalies of winter 2009/10,” the scientists wrote.
“[S]now anomalies across the northern hemisphere this past winter are typical of winters with a negative North Atlantic Oscillation (NAO) and an El Niño and are related to mean temperature and storm track anomalies,” the scientists added.
“Snowy winters will happen regardless of climate change,” Richard Seager, a climate scientist at Lamont-Doherty and lead author of the study, noted in a Columbia University press release.
James M. Taylor ([email protected]) is managing editor of Environment & Climate News.
