Global Warming Paradox in A Killer Freeze

Last April, a late-season deep freeze killed plants and crops across a wide area of the East Coast.

The cause? Global warming.

At least, global warming played a critical role in the destructiveness of the weather episode, according to new research by the Oak Ridge National Laboratory, published in Bioscience.

It's not the freeze that was linked to a warming climate, but the vulnerability of the plants at that time of year.

Spring temperatures came earlier, as they have been doing frequently as the climate has warmed. The growing season in some areas is two weeks longer, or more, than a century ago.

The early warm temperatures trigger vegetation to come out of dormancy. Fruit trees flower early. Trees send out new shoots. And then, the frost killed them. The variability in the climate didn't disappear, but the trend toward an earlier warm-up made plants and crops more susceptible.

"The warm weather was as much a culprit for the damage as the cold," said lead author Lianhong Gu. "We see the paradox in that mild winters and warm, early springs make the plants particularly vulnerable to late-season frosts."

For an apple grower, an ill-timed freeze during bloom can destroy a crop.

Beyond that, the scientists found that plants and trees damaged by the frost didn't regenerate to their former extent following the freeze. That resulted in less carbon absorbed from the atmosphere, an unexpected feedback loop that would result in an even greater greenhouse gas effect, as forests lose their capacity for absorbing carbon.

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