Less Snow Punctuated by More Blizzards
The 2012-13 winter season in the Northeast turned out to be a warm one. From December 1, 2012 through February 14, 2013, the average temperature at 34 of 35 climate stations ranked in the top 30 warmest seasons ever recorded. Winter temperatures have warmed by 4°F since 1970 in the Northeast, which has caused a marked reduction in winter precipitation falling as snow (more falls as rain). According to the Global Snow Lab at Rutgers University, spring snow cover in the Northern Hemisphere has shrunk by 1 million square miles on average over the last 45 years.
At the same time, however, the Northeast has been hit by some really large snowstorms – like the nor’easter that dumped up to 40″ of snow on parts of the region from February 8-9, 2013. As a result of this one event, the period from February 1-14 was one of the top 30 snowiest periods of all time at 26 climate stations in the Northeast. In fact, the US has been hit by two times as many extreme snowstorms in the past 50 years than in the previous 60 years, according to a new study on extreme weather by Kunkel et al. in the Bulletin of American Meteorological Society.
According to the Northeast Regional Climate Center at Cornell University, the February 8-9 nor’ easter storm is making history. The State Climate Extremes Committee recently approved a new all-time snowfall record for the state of Connecticut. An official Cooperative Observer station in Ansonia, CT received 36 inches of snow in 24-hours from February 8-9, 2013. This breaks the previous record of 30 inches on February 10, 1969 at Falls Village, CT. The committee examined the observation site and methods used before approving the new record.
How can scientists explain this seeming contradiction of warmer winters on the one hand, and record snowfall events, on the other hand? According to the Associated Press, the historic 2013 nor’easter was the result of a perfect set of conditions occurring at one time: arctic air colliding with air warmed by an unusually warm ocean, which produced large amounts of moisture and big temperature contrasts, resulting in more energy, more moisture, and thus more snow (Borenstein, “Climate contradiction: Less snow, more blizzards,” February 18, 2013). While scientists cannot determine if climate change caused one specific event, or even a specific seasonal change, they are able to project how the climate will continue to change in the future. Climate change will continue to cause a decrease in annual snowfall amounts overall, and a shortening of the length of the snow season. But when it finally does snow, there may be added moisture in the air and extra moisture coming from a warmer ocean, potentially generating more intense rates of snowfall.
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