Study: Forecast of more severe tornadoes is all wind

As 2012 shapes up to be the least active year on record for tornadoes, new research suggests climate change is not necessarily driving up the number and force of killer twisters .

The research, accepted for publication in the journal Environmental

Hazards, counters assertions that climate change is fueling this form of severe weather. The findings are limited to tornadoes and don’t delve into whether climate change could be affecting other weather extremes such as heat waves, floods or droughts.

“There is absolutely no evidence of an increase in damaging tornadoes,” the authors write in the study. They add that the number of U.S. tornadoes might actually have decreased since accurate records began in the 1950s.

On average, just over 1,300 tornadoes form each year in the United States, the vast majority of which cause very little or no damage.

Roger Pielke, a professor of environmental studies at the University of Colorado, led the study, working with Kevin Simmons of Austin College in Sherman, Texas, and Daniel Sutter of Troy University in Troy, Ala.

As awful as 2011 was, when 550 Americans died in tornadoes, last year appears to have been an outlier and not part of a trend. Tornadoes and tornado damage can fluctuate wildly

Storms in 2011 don’t appear to be part of trend

from year to year.

The study also finds the damage from tornadoes has decreased since the 1950s, once the figures are “normalized,” or adjusted for inflation and population. This is the first paper to comprehensively “normalize” his- torical economic losses from U.S. tornadoes, Pielke says.

Harold Brooks of the National Severe Storms Laboratory in Norman, Okla., says the study is “pretty reasonable,” adding that there is no sign that tornado incidence has worsened over the decades. “There is no long-term trend in tornadoes,” he says.

Meteorologist Mike Smith of AccuWeather Enterprise Solutions in Wichita, agrees. “I believe there is some evidence ( but not enough to form a robust conclusion) that tornadoes were worse in the first half of the 20th century,” he says.

Even so, Smith acknowledges that “2011 sticks out like a sore thumb.”

When it comes to climate change, Pielke adds that his study “provides strong counter-evidence to claims in the scientific literature that the atmospheric environment that spawns tornadoes has intensified,” leading to more destructive storms.

An Intergovernmental Panel on Climate Change report this year said “there is low confidence” in a link between climate change and tornadoes.

Pielke’s study counters a report this month by Munich Re, the world’s largest reinsurance firm, that said climate change is driving the increase in natural disasters, such as the severe storms and tornadoes that hammered the United States last year.