To the ever-growing list of projected effects from global warming, add a curious entry: a potentially huge jump in lightning strikes in the United States.

Researchers reported Thursday that they had discovered a simple physical relationship that seems to predict lightning strikes, and used it to produce a better estimate of the likely change if warming continues unchecked through this century. The forecast: an increase on the order of 50 percent.

That would likely alter the chemistry of the atmosphere in complex ways, not all of them necessarily bad. It might also increase the risk of wildfires, especially in remote areas where most fires tend to be ignited by lightning. And it could kill more people directly, although lightning causes well under a hundred deaths a year in this country.

David M. Romps, an atmospheric physicist at the University of California, Berkeley, who led the work, said the change would come about from a global temperature increase of roughly 7 degrees Fahrenheit. “This increase in lightning is an example of a fairly large change that you can get from what sounds like a relatively small global temperature increase,” Dr. Romps said.