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How the climate crisis is affecting tornadoes
How the climate crisis is affecting tornadoes
By Rachel Ramirez, CNN
Updated 2:39 PM ET, Sun December 12, 2021
(CNN)The series of tornadoes that ripped through the Midwest and the Southeast United States this weekend adds to another stretch of deadly and potentially unprecedented weather disasters this year, exacerbating the already growing economic toll brought by climate disasters across the country.
And in the wake of this deadly night of extreme weather, which meteorologists and climate scientists say is historic, questions of whether climate change is intensifying tornadoes are beginning to emerge.
In Kentucky, the series of tornadoes uprooted trees, tore down homes and infrastructure, and killed at least 70 people. Gov. Andy Beshear said in a news conference that the tornado event reached a "level of devastation unlike anything I have ever seen," he said.
But unlike other extreme weather events such as drought, floods and hurricanes, scientific research about the connection between the climate crisis and tornadoes has not been as robust, making the link especially challenging.
Scientists say the short-lived scale of tornadoes, coupled with an extremely inconsistent and unreliable historical record, makes connecting outbreaks to long-term, human-caused climate change extremely challenging.
Victor Gensini, a professor at Northern Illinois University and one of the top tornado experts, said last night's outbreak is one of the most remarkable tornado events in US history -- and while climate change may have played a part in its violent behavior, it's not yet clear what that role was.
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"When you start putting a lot of these events together, and you start looking at them in the aggregate sense, the statistics are pretty clear that not only has there sort of been a change -- a shift, if you will -- of where the greatest tornado frequency is happening," Gensini told CNN. "But these events are becoming perhaps stronger, more frequent and also more variable."
Research by Gensini found that over the past four decades, tornado frequency has increased in vast swaths of the Midwest and Southeast, while decreasing in parts of the central and southern Great Plains, a region traditionally known as "tornado alley." Some studies also indicate climate change could be contributing to an eastward shift in tornado alley, for instance, resulting in more tornadoes occurring in the more heavily populated states east of the Mississippi River, such as this tornado outbreak.
"It's also very common when you have La Niña in place to see this eastward shift in highest tornado frequency," Gensini said. "But if you look at the past 40 years, the research I've done ... has shown that places like Nashville, Tennessee, for example -- or Mayfield, Kentucky, that we saw got hit last night -- their frequency of tornadoes, their risk of having a tornado has increased over the last 40 years."
Tornadoes take shape under particularly specific atmospheric conditions, but are primarily fueled by warm, moist air from strong winds that shift direction with altitude. Scientists have warned that the rise in greenhouse gas emissions in the atmosphere is drastically changing the climate system, even causing the jet stream -- fast-flowing air currents in the upper atmosphere that influence day-to-day weather that could trigger a tornado event -- to behave oddly.
Jennifer Marlon, a climate scientist at the Yale School of Environment, told CNN it's too early to say what primed last night's outbreak, but there are "some really important signatures that suggest that this very well may be linked to climate change," and that scientists are "observing changes in the outbreaks, not just the severity of individual outbreaks and tornadoes, but also quiet periods."
For example, if any of last night's tornadoes are rated EF-5 (estimated winds of 260 mph or greater), it would end a streak of 3,126 days since the last EF-5, which is the longest stretch without since records began in 1950. The last EF-5 tornado was the Moore, Oklahoma, tornado on May 20, 2013.
And as climate disasters worsen and expand in scope, Marlon also points to significant factors that increase disaster risks across society during these times including worsening weather disasters, increasing exposure due to growing populations, and more vulnerable infrastructure assets.
That's already taking shape in Mayfield, Kentucky, where officials say the city's main fire station and some of its police assets have become inoperable as a result of last night's devastating tornado system. Now, authorities are looking for alternative ways to address emergency calls.
"All these things are feeding into increase disaster risk, with many more consequences, including the fatalities, of course, but also enormous economic damages," she said.
As the climate crisis accelerates, more people will be vulnerable to the most severe consequences of extreme weather events. Experts say cities shouldn't put off adaptation plans any longer, and instead treat them as a larger emergency response system.
But Gensini said one thing is certain: regardless of climate change, these types of tornado disasters will continue to worsen as humans alter the landscape and build larger, more sprawling cities.
"We have more assets and more targets for the severe storms to hit," he said. "So even if you take climate change out of the equation, which is very likely to make the problem worse, we still have this issue of human and societal vulnerability."
CNN Meteorologist Brandon Miller contributed to t
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