This year, Ithaca is on pace to see the lightest snowfall in its history. Only 21.1 inches of snow have fallen this year, compared to the current record low of 25.1 inches in the winter of 1918-19.
Global warming, though real, may not be the primary reason that this Ithaca winter has been one of the warmest yet, according to Prof. Arthur Degaetano, earth and atmospheric sciences.
“We cannot attribute this winter to global warming,” Degaetano said. “However, this winter is typical of the type of winters we expect to see in the next 50 years due to global warming … global warming likely made this winter a bit warmer than it would have been without global warming. It was one small factor.”
Degaetano said that Ithaca has had warmer temperatures because cold air was trapped in Canada and Alaska and could not move southward into the continental United States.
Because La Niña conditions occurred in the tropical Pacific Ocean this winter, water in the central Pacific Ocean reached colder than normal temperatures, Degaetano said. This phenomenon affected the atmospheric circulation across the northern hemisphere, causing drought conditions in the western Pacific and in the southeastern U.S.
In combination with La Niña conditions, Degaetano said that the positive Arctic Oscillation prevented cold air from reaching New York State.
“Over the North Pole, the Arctic Oscillation was persistently positive,” he said. “A positive Arctic Oscillation means strong low pressure exists over the poles — this prevents cold air from moving southward out of the Arctic.”
Degaetano said that the rare combination of La Niña conditions and the positive Arctic Oscillation caused this winter to be warmer than usual.
“Although they infrequently occur in combination, when they do winters in New York are typically very warm,” he said.