More severe tornado outbreaks may be linked to climate change

Michael Roppolo in CBS News: Climate change may be playing a role in the strength and frequency of tornadoes, a new study suggests. Research published in the journal Climate Dynamics finds that although tornadoes are occurring fewer days per year than they used to, they are forming at greater density and strength. This means that on days when tornadoes do form, there tend to be more of them and they're often more powerful.

...In the past, many scientists dismissed the impact of climate change on tornadoes because tornado occurrences vary so greatly from year to year. The number of tornado days in a year -- days in which at least one tornado occurred -- have declined since the 1970s, with a high of 187 in 1971 and a low of 79 tornado days in 2013. But at the same time, the number of days with multiple tornadoes has risen sharply.

Using data from the Storm Prediction Center, Florida State University geography professor James Elsner and his colleagues studied tornadoes with EF-1 intensity and stronger. Elsner told CBS News that when he first looked at tornado days with at least four tornadoes, he noted no change. However, when he looked at instances with larger numbers of tornadoes in a single day, he found a significant increase.

..."The bottom line is that the risk of big tornado days featuring densely concentrated tornado outbreaks is on the rise," the study states.

The researchers say their findings suggest climate change may be a factor. "These trends represent observational evidence of changes in severe deep moist convection possibly related to our changing climate," they write....

A tornado in Quail, Texas