April 8, 2012

City on Pace for Record Low Snowfall

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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.

Prof. Paul Curtis, natural resources, said that these warmer New York winters have become a trend over the past couple of decades in Ithaca.

“What is important is not the weather in any single year, but the long term trends in weather. Over the last 50 years, there is a definite trend for shorter, milder winters — especially during the last decade,” he said.

Although students and faculty said they were glad that they did not have to trudge through snow to get to classes, Curtis said the warmer winter negatively alters the typical behavior of wildlife. For instance, Curtis pointed out the impact the weather could have on insects, which could start appearing earlier than expected.

“With the very warm weather a couple of weeks ago, ticks and mosquitoes were already active,” he said. “This is about a month earlier than usual.  If warm weather continues during April and early May, this will extend the season for human and pet exposures to biting insects, mosquitoes with West Nile virus and ticks with Lyme disease.”

Because of the warmer winter season, Curtis predicted that there will be more deer on the roads around Ithaca.

“Adult female deer should have survived winter in excellent condition, meaning a higher potential birth rate for fawns this summer,” he said. “Both of these factors could lead to deer population growth and associated impacts … [such as] deer-vehicle accidents, plant damage and Lyme disease.”

Prof. Stephen Colucci, earth and atmospheric sciences, said that although warm winters have occurred in the past, global warming has also caused this winter to be the warmest in Ithaca’s history.

“This combination has occurred before but, superimposed on the general upward trend in air temperatures — global warming — it resulted in unusually warm weather conditions,” he said.  “The official forecast from the National Weather Service’s Climate Prediction Center is for a continuation of this trend, [meaning] above normal temperatures through June 2012.”

In addition to pointing out the immediate effects of the warmer weather, Curtis noted the changes that may be seen if global warming is not reversed.

“If the global climate-change models are correct, we will see very rapid increases in temperature during the next 50 years, especially during the winter months,” he said. “By the end of this century, the weather in Ithaca may be similar to current conditions in North Carolina.”

Original Author: Jonathan Swartz