Rarely a day goes by without publication of a scientific report telling us some bad thing is likely going to get a whole lot worse because of climate change. To that ever-expanding list of woes, you can now add an increased likelihood of being struck by lightning.
In a paper published on Friday in the journalScience, researchers from the University of California, Berkeley say climate change will likely increase the number of lightning strikes by 50 percent in the United States this century.
"With warming, thunderstorms become more explosive," said David Romps, lead author and a scientist at Lawrence Berkeley National Laboratory. "This has to do with water vapor, which is the fuel for explosive deep convection in the atmosphere. Warming causes there to be more water vapor in the atmosphere, and if you have more fuel lying around, when you get ignition, it can go big time."
2011 lightning strikes as observed by the National Lightning Detection Network. This material relates to a paper that appeared in the 14 Nov. 2014 issue of Science, published by AAAS. The paper, by David M. Romps at University of California, Berkeley in Berkeley, CA, and colleagues was titled, "Projected increase in lightning strikes in the United States due to global warming." (Video by David M. Romps, UC Berkeley)
Estimates vary on the number of people struck by lightning in the US each year, but the figure ranges from a few hundred to nearly a thousand. More frequent lightning strikes might also increase the number of wildfires, half of which are ignited by lightning.
This study is the first of its kind. There had been no reliable research of how a warming planet might affect the frequency or intensity of lightning. Romps and his team hypothesized that precipitation and cloud buoyancy were the key predictors for lightning strikes. Indeed, by looking at 2011 data, they found a correlation between the two atmospheric properties.
The amount of water hitting the ground — whether as rain, snow, or hail — proxies for determining how convective the atmosphere is, says Romp, and lightning is generated by convection.
"Lightning is caused by charge separation within clouds, and to maximize charge separation, you have to loft more water vapor and heavy ice particles into the atmosphere," he said. "We already know that the faster the updrafts, the more lightning, and the more precipitation, the more lightning."
This graphic shows the intensity of lightning flashes averaged over the year in the lower 48 states during 2011. (Data from National Lightning Detection Network, UAlbany, and analyzed by David Romps, UC Berkeley)
Romp and his team used 11 different climate models for precipitation and cloud convection. The 50 percent increase in the frequency of lightning strikes assumes greenhouse gas emissions continue to rise at their current rate, and that by the end of the century global average temperatures will increase four degrees Celsius (seven degrees Fahrenheit) compared to pre-industrial levels.
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