Is Tornado Alley shifting due to climate change? Scientists explain how warming climate affects tornado activity

As the earth’s temperature climbs, so does the threat of extreme weather events such as drought, wildfire, hurricanes and tornadoes — all occurring more frequently at higher strengths, according to climate scientists.

More violent and widespread tornado activity — like the line of severe storms in recent days that killed dozens of people — is expected in the future as global warming persists, experts told ABC News.

At the start of the weekend, a powerful storm system unleashed a line of violent tornadoes across 14 states. At least nine EF3 tornadoes — wind speeds ranging from 136 to 165 mph — were confirmed to have touched down in Arkansas, Illinois, Indiana, Tennessee and Delaware on Friday and Saturday.

While such events have occurred in the past, the evidence points to climate change contributing to the frequency and magnitude of tornado behavior, Walker Ashley, an atmospheric scientist and disaster geographer at Northern Illinois University, told ABC News.

“This is a representation of what we might perhaps expect to happen in a particularly active tornado season as we move forward in a warming climate regime,” said Jana Houser, associate professor of meteorology at Ohio State University, of the recent deadly tornado activity.

A warming planet creates favorable conditions for strong tornadoes to form

Simulations of the atmosphere indicate that, as global temperatures continue to rise, so do the chances that the “fundamental ingredients” for a severe thunderstorm will be present, Ashley said.

With more moisture, atmospheric instability — the “gasoline” for storms — and wind shear, the unique dynamical force that allows the twister to become organized — strong storms, hail and tornadoes are more likely, Ashley said.

“Outbreaks just happen to occur with a lot more of these ingredients coming together,” he said.

Not only do the fundamental ingredients exist at a higher rate, but they are also occurring across large areas, Ashley said. While severe weather has always existed, climate change appears to be the cause of the greater magnitude of impacts when it comes to severe storms, Walker said.

Tornado Alley is expanding, scientists say

The geographic location with the most frequent tornado activity tends to change year over year, Houser told ABC News. One year the Southeast may get slammed with tornadoes, while another year the activity could be concentrated further west, she added.

Overall, the research indicates that an environment supportive of the formation of tornadoes is expanding in the southeast, the experts said.

A 2018 study by the National Oceanic and Atmospheric Administration and Northern Illinois University found that tornadoes are slightly declining in the Great Plains and increasing in the east.

Recent simulations indicate that the area that produces the most significant tornadoes will be east of Interstate 35 — including the mid-South, the Ozark plateau and the lower Ohio Valley, Ashley said. The areas west of I-35, Oklahoma, Kansas, the Dakotas, eastern Colorado and west Texas, will slightly decline, Ashley said, adding that those who live in the mid-South are at 25% greater risk of tornado threats.

It’s not so much that Tornado Alley will no longer apply to a large swath of the Central U.S., but that other regions are beginning to catch up to the tornado production rates that are more typical of the Central Plains, Houser said.

If the frequency of tornadoes were measured purely by touchdown points, the Great Plains would easily clock in the most in the world, Ashley said. But tornadoes are typically measured by landscapes and how much damage they cause.

Another factor driving the cause of increased impacts from tornadoes is the “expanding bullseye effect,” in which rural communities between the large cities in the south — Atlanta, Charlotte, Nashville — have rapidly increased in population over the past 50 years, Ashley said. In past decades when a tornado formed in those areas, it may not have hit anything.

“The odds of something being hit by one of these events is going up substantially,” Ashley said. “It’s projected to continue to increase, just because people continue to build out. It’s just the natural occurrence of development in the United States.”

An unusual aspect of the recent tornado activity is how far north lines of twisters are forming — especially in what is traditionally a cooler season, Houser said. It is not common to see tornadoes in places like Iowa, Illinois and New Jersey in this time of year, she added.

American Meteorological Society expects that with the changing climate tornado season will escalate outside of the traditional peak season, which is March through May, according to a study published earlier this year.

Tornadoes are notoriously hard to predict

Meteorologists can predict favorable tornado conditions further out than ever before — up to 10 days in some cases — which is quite the mathematical feat, Ashley said.

“It is remarkable that we have been able to take what is a fluid atmosphere, which interfaces with a rotating planet, and take mathematical equations, and plug them into a model,” Ashley said.

But, they will probably never get to the point where they can predict with certainty when a tornado will form, namely because scientists “don’t really have all of the full complete picture of what makes a storm produce a tornado,” Houser said.

“It is incredibly difficult to pinpoint when and where a specific ongoing storm is going to make a tornado — even a couple of hours before,” Houser said.

A herculean effort would involve a plentitude of weather balloons and the ability to locate an atmospheric needle in a haystack — a “relatively small scale phenomena,” she added. And because they are so small-scale, tornadoes are “incredibly sensitive” to small nuances in environmental conditions.

“You’re dealing with something that is only, in many cases, tens of yards wide, at most, two and a half miles wide,” Ashley said. “That is tiny, compared to the entire global atmospheric system.”

In order to survive a tornado, the “best thing to do” is to be inside a sturdy structure, in the basement or an interior bathroom or closet, the experts said. The worst place to be is somewhere fully exposed, where flying debris can hit and kill you, or in a manufactured or mobile home.

“These houses are just not built to withstand even minimally strong tornadic winds,” Ashley said.

The leading cause of death in a tornado is blunt force trauma, Houser said — so appropriate attire, such as hard-soled shoes and bicycle helmets, is essential for survival in some cases.

“The truth is that if you prepare and do the right thing, your chances survivability is almost 100%,” Ashley said. “Now if you don’t do the right thing, you can certainly increase your odds of death and injury substantially, though.”