Global warming could make lightning strikes more common, according to a new study from the University of California Berkeley.
Cloud-to-ground lightning occurs roughly 25 million times each year, a number which researchers believe could increase by 12 percent for each degree Celsius rise in global temperatures.
"With warming, thunderstorms become more explosive. 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," David Romps of Lawrence Berkeley National Laboratory, said.
Hundreds of people are struck by lightning every year, up to 1,000 worldwide. Dozens of these people are killed by these bolts from the sky. Direct hits on people are not the only hazard, as property damage frequently results from the strikes, as well as wildfires ignited by the electrical discharge. Many of the fires started by lightning rage deep in the wilderness, where they are most difficult to battle.
Lightning strikes could become 50 percent more common than today over the next 100 years, according to many modern climate models.
Nitrous oxide formed by extremely high temperatures around lightning bolts can also drive additional global warming. The gas is naturally produced during the nitrogen cycle of living beings, and currently also accounts for six percent of all greenhouse gas emissions from human activities in the United States. Molecules of the gas remain in the atmosphere for an average of 120 years before they are once again absorbed or destroyed by the action of other chemicals.
Lightning is ultimately caused by differences in charges between a pair of clouds, or the cloud and the ground. When the amount of charge in a cloud, generated by the uplift of water vapor and ice in to the system, increases, so does the total potential charge. The strength of the updraft is known as the convective available potential energy, or CAPE. When the resistance of air between the charge and another source, such as a tree, is lowered through atmospheric conditions or distance, lightning flies.
"Cape is a measure of how potentially explosive the atmosphere is, that is, how buoyant a parcel of air would be if you got it convecting, if you got it to punch through overlying air into the free troposphere. We hypothesized that the product of precipitation and CAPE would predict lightning," Romps stated in a university press release.
Computer simulations showed lightning could be predicted from just those two factors.
Rising global temperatures could increase the strength of updrafts, providing clouds with greater charges, leading to more frequent lightning, the research claims.
Study of the effect of rising global temperatures on lightning was profiled in the journal Science.
