The Number of Killer Thunderstorms Could Jump 40 Percent by 2070
Todd WoodySep 24, 2013 Comments Associated Press
That spate of destructive thunderstorms that struck the U.S. last year, killing scores of people and racking up billions of dollars in damages? Get ready for more. A lot more.
In a first-of-its-kind study published yesterday, scientists at Stanford University have linked climate change to the increasing frequency of such super storms. By 2070, the number of severe thunderstorms, which often spawn deadly tornadoes, could increase by 40 percent in the eastern U.S., according to the computer model developed by the Stanford scientists.
Such storms typically are strongest in the spring, but as the planet warms, those storms will also increasingly strike in the autumn and the winter between 2070 and 2099, states the report published in the Proceedings of the National Academy of Sciences. The study found that severe thunderstorms will also hit the Midwest and Great Plains regions of the US with greater frequency.
And don’t take solace in the idea that you’ll be long gone or in your golden years when the big ones hit. Even if the world gets its act together and cuts carbon emissions now, there’s enough heat baked into the atmosphere from centuries of industrial spew to spawn super storms for decades, according to Noah Diffenbaugh, an associate professor of environmental Earth system science at Stanford and the study’s lead author.
But there’s hope for future generations if temperatures are kept in check. "Curbing the increase in emissions would affect the magnitude of the increase of storms in the late 21st century," Diffenbaugh says.
Linking particular weather events to global warming is tricky. That is particularly true of severe thunderstorms, given sparse historical data and the fact that previous computer models indicated that the two atmospheric conditions necessary for their formation tend to cancel each other out.
One of those conditions is warming air in the lower atmosphere that carries moisture to higher altitudes, a phenomenon known as convective available potential energy or CAPE. There it interacts with wind currents—what scientists call vertical wind shear—to create a storm. Earlier computer models seemed to show that as global temperatures rise due to climate change, CAPE would increase while wind shear would decrease, making unclear the impact of global warming on storm formation.
Diffenbaugh and co-authors Martin Scherer of Stanford and Robert Trapp of Purdue University developed a new computer model that confirmed those conditions. But they found that wind shear would decrease mostly on days of low CAPE, meaning that there would be a net increase in severe thunderstorms.
The study did not attempt to quantify the impact of global warming on tornadoes, given the complex atmospheric conditions associated with their formation and the limitations of current computer models. But Diffenbaugh noted that the same atmospheric conditions can produce the type of destructive tornadoes that have devastated parts of the US in recent years.
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