11.12.2008 8:53 AM

Study: Pollution May Trigger Tornadoes

Could Reducing Air Pollution Reduce the Threat of Killer Twisters?

A tornado in Riverside, California, in May 2008.

Photo: AP Photo / Michael Ritter

By Dan Shapley

The 2008 tornado season has been the deadliest in recent years, with 35 killer twisters killing 123 Americans.

Could pollution be, partly, to blame?

That's the implication of a new Colorado State University study, detailed by MSNBC, which suggests that microscopic particulate pollution — dust, soot and chemical droplets — may trigger the formation of twisters when clean air would not. Of course, dust can enter the air from natural sources, as well as from human activity.

Study author David Lerach "thinks the abundance of microscopic particles prevents water from condensing into raindrops big enough to fall to Earth," according to MSNBC. "Rising warm air lofts the miniature droplets high into the cloud, where they freeze instead. This leaves the air currents that are the precursors to tornadoes free to swirl beneath the cloud."

The study is hardly the last word on the subject, but it raises the interesting prospect that reducing air pollution could reduce the risk of killer twisters.

Other recent research has suggested that global warming will trigger more tornadoes and thunderstorms, as warmer air currents increase the likelihood of strong storms.

Incidentally, though 2008 appeared to have started on a course to be a record-breaking year for tornadoes, the initial counts were inflated 43% by duplicate reports. The actual tornado total for the U.S. to date stands at 1,485, more than most recent years, but still significantly fewer than the 2004 total of 1,817.