Global warming likely to bring more "perfect storms"
Rising temperatures will set the stage for more severe storms—doubling the likelihood of such events in some places in the U.S.
Conditions favorable to the development of severe thunderstorms—those that generate destructive winds, hail, flooding, and sometimes tornadoes—will likely become far more frequent in the U.S. by 2100, concludes a study published online December 3 in the Proceedings of the National Academy of Sciences U.S.A. Coastal areas near the Atlantic Ocean and the Gulf of Mexico will be most at risk for such extreme weather, the researchers warn.
Severe thunderstorms exact a painful toll on society in loss of life, injuries, and damage to property and crops. From 2000 to 2004, the annual costs of such storms topped $2.1 billion in the U.S. Previous research has shown that rising temperatures foster higher rates of evaporation, leading to increases in warm, moist air near the ground—a key condition for thunderstorm formation. However, theoretically, global warming should weaken strong, storm-fueling winds at higher altitudes in the atmosphere. To assess which factor might be more influential, a team led by Robert Trapp of Purdue University modeled conditions over the U.S. from about 2050 to 2100. The results were then compared with current and past environmental conditions shown to produce severe thunderstorms. The results revealed an overall increase in the likelihood of severe storms. Although the effect was slight in some locales, in other places—notably, around New York City and Atlanta—the chances for severe thunderstorms more than doubled. The study also showed the storm season likely will be longer in some regions.
"What we are seeing is the strong likelihood of a significant impact on weather due to a relatively small increase in temperature," Trapp says. The future upsurge in warm, humid, surface air apparently will outweigh the expected reduction in strong winds higher in the atmosphere, he explains.
This research is the first to comprehensively examine the potential impact of elevated greenhouse gases on the frequency of severe thunderstorms in the U.S., notes Roger Wakimoto of the National Center for Atmospheric Research. "It also addresses an important question that the public would like to ask atmospheric scientists: what does an increase in greenhouse gases mean for me?" he adds.
