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A record-breaking tornado that hit Kentucky over the weekend is sounding alarm bells about the role of climate change in environmental disasters in land-locked states. While it’s difficult to directly attribute any one disaster to climate change, the type of devastating tornado seen in Kentucky over the weekend is likely to become much more common due to the effects of climate change.
The Kentucky tornado is estimated to be one of the most destructive weather events in the state’s history: The death toll is likely more than 70, Gov. Andy Beshear said in a press release Saturday, after watching the storm touch down and rip across more than 227 miles of ground. And that’s just in Kentucky—per CNN’s live weather coverage, Friday’s was just one of six tornadoes that tore through six states nearby over the weekend as part of the same weather system.
“It looks almost guaranteed at this point that it’s going to go down as the deadliest tornado we’ve had in the U.S. since the Joplin, Missouri tornado in 2011,” Paul Markowski, a professor of meteorology at Penn State University and long-time tornado chaser, told Motherboard. “It’s been a decade since we’ve had something quite as deadly as on Friday.”
There’s no definitive word yet on the precise role that climate change could have played in the conditions that led to Kentucky’s tornado, but the federal government and climate scientists alike are already postulating that distinctly warm temperatures led to instability in the atmosphere that created a cyclone system (tornadoes are pretty rare in December). President Joe Biden, for his part, has asked the Environmental Protection Agency to investigate the role of the climate crisis in the occurrence of U.S. tornadoes, he told reporters Saturday.
“The specific impact on these specific storms, I can’t say at this point,” Biden said. “The fact is that we all know everything is more intense when the climate is warming — everything. And, obviously, it has some impact here, but I can’t give you a quantitative read on that.
Tornadoes typically begin during thunderstorms, which are generally only possible in warm, humid conditions (that’s why thunderstorms take place more frequently during the summer.) This can create instability, or high levels of energy, in the atmosphere. If a body of warm, humid air is buried beneath a body of much colder air, and wind conditions differ in speed and direction at different altitudes (known as ‘wind shear’), it can create a cyclone of wind, forming a tornado.
The warmth and humidity that’s required is most common in the spring and early summer. The typical tornado season runs from May to July, with slight variance by region, so Friday’s tornado was out of the ordinary purely by its timing. But climate change is fueling the frequency of abnormally warm wintertime conditions, and of warm, humid conditions more broadly, so scientists like Markowski are weighing whether this weekend’s catastrophe wouldn’t have been possible without global warming.
One 2014 study by researchers at Florida State University tracked the density of tornado occurrences across the U.S. since the mid-1900s and found that while the number of days with a single tornado has decreased over the decades, the number of days with many tornadoes has surged. They hypothesize that changes in the amount of energy in the atmosphere, driven by increases in moisture and temperature, are driving this surge—evidence that extreme weather events fueled by climate change are not limited to the coasts, which are traditionally thought of as frontlines of sea level rise, wildfires and hurricanes.
“The unusually warm, moist air is a product of an exceptionally warm Gulf of Mexico caused by climate change,” James Elsner, lead author on the 2014 study and professor and chair of Geography at Florida State University told Motherboard in an email. “Big outbreaks (many tornadoes), although still very rare, are becoming more frequent. This is particularly true of outbreaks during the cool season.”
Kentucky also falls outside of ‘tornado alley,’ the region of the U.S. where the majority of the approximately 1,200 violent tornadoes that hit the country each year typically fall. The boundaries are loose, but broadly speaking, this includes the Great Plains (the Dakotas, Kansas, Nebraska, Oklahoma, and Texas), where the conditions Markowski describes are most likely to occur. The National Oceanic and Atmospheric Administration (NOAA) Severe Storms Laboratory stresses in educational materials that it’s not abnormal for tornadoes to occur outside of this region; Markowski says the same, noting that parts of western Kentucky have been hit by violent storms before.
“Are the odds as high as, say, central Kansas? Probably not,” Markowski said. “The laws of physics are agnostic about when and where these conditions arise … They’re not as common in other places, but the probabilities aren’t zero either.”
He notes that winter tornadoes can wreak more havoc than summer ones because of light conditions alone. With more of the day in darkness during December, tornadoes can be difficult for both scientists and residents of tornado-prone regions to track. Couple that with the general lack of what he calls “situational awareness” of the likelihood of tornadoes this time of year—most people have their guard down and aren’t prepared for severe storms—and these weather events become all the more threatening.
“It’s just not really on your radar to even be thinking about, ‘hey, later today, there could be killer storms,’” he said. “You’re kind of thinking about decorating for the holidays. It’s not really in the back of your mind.”
Though Markowski says confirming a link between climate change and Friday’s event would take more precise, devoted research, he believes it would be foolhardy to rule this out as a possibility. Climate change is most certainly “stacking the deck,” in favor of the probability of abnormal weather events, he said.
“It’d be irresponsible to say, ‘Well, climate had nothing to do with this,’” he said. “Friday was a warm day and warm days or more are happening more often now. Especially in December. Climate probably did contribute a bit in the background.”
Environmental groups took to social media over the weekend to express their condolences and stress the connections between Friday’s disaster and the growing threat of climate change.
“This is a climate emergency,” the Sunrise Movement shared on its national Twitter account on Saturday.