Does Global Warming Influence Tornado Activity?

Tornadoes and other severe thunderstorm phenomena frequently cause as much annual property damage in the United States as do hurricanes, and often cause more fatalities (see http://www.nws.noaa.gov/om/hazstats.shtml). In 2008, there were 2176 preliminary tornado reports logged through mid-December, with 1600 “actual counts” (duplicate reports removed) through September, the highest total in the past half century (Figure 1). The mass media have covered these events extensively, and experts have been deluged with requests for explanations, including possible links to anthropogenic global warming. Although recent research has yielded insight into the connections between global warming and tornado and severe thunderstorm forcing, these relationships remain mostly unexplored, largely because of the challenges in observing and numerically simulating tornadoes.