'False Springs' May Become Thing of the Past


As if winter hadn’t dragged on long enough, parts of the upper Midwest saw a foot of snow last week. Freeze warnings hastened the end of Washington, D.C.’s Cherry Blossom Festival, dubbed “the nation’s greatest springtime celebration.”

Hard freezes following spring-like blossoming are known as “false springs” and a new study shows that, thanks to rising global temperatures, such chilly interruptions of spring revelry may someday disappear.

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The impacts of false springs go far beyond the annoyance of digging out winter coats and gloves again. Plants in bloom expose sensitive tissue during spring flowering that can be damaged by freezing temperatures. False springs in 2007 and 2012 caused billions of dollars of agricultural damage in the United States.

Researchers from the University of Idaho aimed to track trends in false spring occurrences throughout the years. They used meteorological data to identify both the date of plant green-up and the date of the last hard freeze of each spring nationwide between 1920 and 2013. A false spring, by their definition, occurred whenever the last spring freeze fell a week or more after plant green-up.

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They found that coastal areas of the country, where the ocean moderates air temperatures, saw fewer false springs than the Great Plains, Midwest, and Northeast, which all may experience dramatic temperature swings during spring.

Further, the researchers found that between 1920 and 2013, the date of first green-up shifted, on average, 1.8 days earlier in the year. But the average date of last spring frost shifted, on average, nearly six days earlier in the year.

The shift in timing may be due to climate change, the authors write in Geophysical Research Letters, which published their results.

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If current trends continue, then the date of last spring frost may continue to advance earlier and earlier in the year, eventually diminishing incidents of false spring. Such trends lengthen growing seasons and enhance plants’ ability to sequester carbon dioxide, the authors write.

Photo: Snow dusts cherry blossoms in southern England during an unseasonable snow storm in 2008. Photo by Colin Smith.

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