Tornado Outbreaks Could Have a Climate Change Assist

A study released Wednesday posits that changes in heat and moisture content in the atmosphere, brought on by a warming world, could be playing a role in making tornado outbreaks more common and severe in the U.S.

Part of the challenge in examining the climate-tornado link is because individual tornadoes occur on such a small scale.  There’s also just a lot of year-to-year variability that adds noise for researchers trying to look at the big picture.  Tornado records can also seem deceiving as population growth and weather technology like radar have improved to help researchers identify more tornadoes.  While that’s largely good, it has the potential to skew numbers.

The new research, published in Climate Dynamics, finds a way to circumnavigate those challenges to a degree.  Helping refine the number of tornadoes, researchers only counted twisters that ranked as EF1 or higher on the Enhanced Fujita scale, which is used to measure tornado damage and wind speed.  And rather than trying to analyze the connection between climate change and individual tornadoes, they looked at clustered outbreaks of tornadoes.

“It occurred to us that even though the annual number of tornadoes may be stationary, it’s possible there are other metrics that could be analyzed.  When you start looking at the number of days in which a lot of tornadoes occur, you see change,” said James Elsner, a tornado researcher at Florida State and lead author of the study.

Specifically, Elsner and his colleagues found that the number of days with large outbreaks have been increasing since the 1950s and that a greater proportion of tornadoes are occurring in those outbreaks compared to the whole.

Tornado Outbreaks Could Have a Climate Change Assist