Thunderstorms will become more explosive over the coming years as a result of global warming, scientists said.
Lightning strikes across the US will increase by 50% before 2100, according to research published in the journal Science.
David Romps and colleagues from the University of California, Berkeley, used precipitation predictions and cloud buoyancy from 11 different climate models to determine what impact warming temperatures will have on lightning strikes.
"With warming, thunderstorms become more explosive," Romps said. "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.
"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. We already know that the faster the updrafts, the more lightning, and the more precipitation, the more lightning."
Researchers looked to see if precipitation and cloud buoyancy is a predictor of lightning by observing strikes over 2011 to see if there was a correlation. Precipitation serves as a measure of how convective the atmosphere is and convection generates lightning.
The speeds of convective clouds – Cape – are worked out by balloon-borne instruments that are released around the US twice every day. By combining these measurements with data on precipitation and lightning strikes, researchers were able to conclude that 77% of the variations in strikes can be predicted from these two factors.
"We were blown away by how incredibly well that worked to predict lightning strikes," Romps said.
On average, climate models suggest a 11% increase in Cape with ever degree Celsius rise in global average temperature. It also assumes CO<sup>2 emissions rise in line with current levels. This means that by 2100, there will be a 50% increase in lightning strikes if the planet warms by 4C as is expected.
An increase in lightning strikes will result in more human injuries – hundreds of people are killed by strikes every year. It will also increase wildfires and generate more nitrogen oxides, which have a huge impact on the atmosphere.