More severe storms to come with global warming, NASA says

WASHINGTON -- As the world warms, the United States will face more severe thunderstorms with deadly lightning, damaging hail and the potential for tornadoes, a trailblazing study by NASA scientists suggests.

While other research has warned of broad weather changes on a large scale, such as more extreme hurricanes and droughts, the new study predicts even smaller events such as thunderstorms will be more dangerous.

The basic ingredients for whopper U.S. inland storms are likely to be more plentiful in a warmer, moister world, said lead author Tony Del Genio, a NASA research scientist.

And when that happens, watch out.

"The strongest thunderstorms, the strongest severe storms and tornadoes are likely to happen more often and be stronger," Del Genio said in an interview Thursday from his office at the Goddard Institute for Space Studies in New York. The paper he co-authored was published online this month in the journal Geophysical Research Letters.

Other scientists caution that this area of climate research is too difficult and new for this study to be definitive. But some upcoming studies also point in the same direction.

With a computer model, Del Genio explores an area that most climate scientists have avoided. Simple thunderstorms are too small for their massive models of the world's climate. So Del Genio looked at the forces that combine to make thunderstorms.

A unique combination of geography and weather patterns already makes the United States the world's hottest spot for tornadoes and severe storms in spring and summer. The large land mass that warms on hot days, the contours of the atmosphere's jet stream, the wind coming off the Rocky Mountains and warm moist air coming up from the Gulf of Mexico all combine.

The Southeast and Midwest lie in the path of most of the most dangerous of these storms. However, the new study also forecasts danger for the western United States. It predicts lightning will increase about 6 percent as the amount of carbon dioxide -- the chief global warming gas -- doubles.