A barrage of tornadoes ripped through parts of the South and the Midwest over the night Friday, taking the lives of dozens. Though the exact link between tornadoes and climate change remains uncertain, climate scientists say there is growing evidence a warming world could make spates of intense tornadoes like Friday’s more common or more intense.
“The specific impact on these specific storms, I can’t say at this point. I’m going to be asking the EPA and others to take a look at that,” President Joe Biden said at a Saturday briefing. “But the fact is that we know everything is more intense when the climate is warming — everything. And obviously it has some impact here.” According to the New York Times, at least 90 people were killed after at least 38 tornadoes swept across six states — Arkansas, Illinois, Missouri, Mississippi, Tennessee, and Kentucky, where 80 of the deaths took place.
Tornadoes are vertical air columns that form when denser, dryer cold air is pushed over warmer, moist air, creating a thunderstorm. As the warm air rises, it creates an updraft with gusts of wind jostling that rising air in various speeds and directions — a condition called wind shear.
The ingredients that fuel more powerful storms — including rising temperatures, moisture, and wind shear — are intensifying as the planet warms. “It’s certainly fair to say that Friday’s disaster should disabuse anyone of the notion that tornado ‘season’ is limited to spring,” Bob Henson wrote for Yale Climate Connections. “Residents of the world’s most tornado-prone nation have to be vigilant year round, especially in a climate where winter warm spells are getting warmer.”
Victor Gensini, a meteorology professor, told ABC News that a warm December air mass in much of the country and La Niña weather conditions created ideal conditions to spawn tornadoes, adding that in aggregate, extreme storms are “becoming more common because we have a lot warmer air masses in the cool season that can support these types of severe weather outbreaks.” (Temperatures in the zone hit by tornadoes rose into the 70s to nearly 80 degrees Friday afternoon; in Memphis, temperatures soared to 79 degrees, breaking a 103-year-old record)
Still, it’s complicated. Less than 10 percent of severe thunderstorms produce tornadoes, which makes finding the climate link — if there is any — tricky. “It’ll be some time before we can say for certain what kind of role climate change played in an event like” Friday’s, Gensini said.
“This is going to be our new normal,” FEMA administrator Deanne Criswell told CNN on Sunday. “ At this magnitude, I don’t think we have ever seen one this late in the year. But it’s also historic. Even the severity and the amount of time this tornado or these tornadoes spent in the ground is unprecedented.”