Tornadoes Not Getting Worse
October 21, 2012

Tornadoes Not Getting Worse, Despite 2011 Activity

April Flowers for — Your Universe Online

In 2011, 550 people were killed by tornadoes in the United States. It seems as though the tornadoes are getting worse, along with their deadly and devastating damage. It would be easy to make that assumption, but a new study says no, that is not the case.

The new research investigated historic tornado damage and the detailed analysis finds tornadoes are occurring at about the same rate as they always have.

"There is absolutely no evidence of an increase in damaging tornadoes," the authors state. The study also suggests the number of U.S. tornadoes might actually have decreased since accurate records began in the 1950s.

In the U.S., an average of 1,300 tornadoes form each year. The vast majority of those cause little or no damage. The study has been accepted for publication in the journal Environmental Hazards.

There is no doubt that 2011 was a bad year in terms of tornado damage, but it appears to be an anomaly, not part of a trend. Tornado damage can vary widely from year to year, and 2012 is on track to be the quietest year on record, according to data from the Storm Prediction Center in Norman, Oklahoma.

In addition, the study claims the tornado damage has actually decreased since the 1950s, once the figures are adjusted for inflation, wealth and population. This is the first study to "normalize" historical economic losses from tornado damage, Professor Roger Pielke of the University of Colorado says.

This study attempts to "adjust for the amount of stuff that's in the way," says Harold Brooks of the National Severe Storms Laboratory in Norman, who finds no fault with the study. "It's pretty reasonable," he says, adding that there is no sign tornado incidence has worsened over the decades. "There is no long-term trend in tornadoes," he says.

Mike Smith of AccuWeather Enterprise Solutions, agrees, "His findings do not surprise me. I do not see an upward trend in disasters in general and do not see one for tornadoes in particular." Smith adds, "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."

Smith acknowledges "2011 sticks out like a sore thumb." According to the dataset used for the study, 2011 was in the top three for damage since 1950.

In a controversial stance, Pielke says this study "provides strong counter-evidence to claims found in the scientific literature that the atmospheric environment that spawns tornadoes has intensified."

The Intergovernmental Panel on Climate Change's released a report on weather extremes earlier this year that claimed, while there is a link between global warming and other extreme weather events, the "long-term trends in economic disaster losses adjusted for wealth and population increases" are not the a direct result of climate change.  According to the IPCC's report, the link between climate change and tornadoes, which can be affected by "competing physical processes," is weak.

Earlier this week, Munich Re — the world's largest reinsurance firm — released a report noting climate change as a driving force in the increase in natural disasters, such as the tornados that nailed the U.S. last year.