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Determining the role of climate change in a single tornado is difficult, but climate change did play a role in the tornado system that hit Kentucky over the weekend, and extreme weather events like it will become more common as the planet warms. 

The science is complicated, but the trends are clear: 

  • Climate change is making winter warmer. The unusually warm conditions this December put more energy in the atmosphere, charging the system that contributed to the tornado outbreak in Kentucky.   
  • The number of tornadoes touching ground during severe storm events has increased over the last 50 years.
  • “Tornado Alley” is shifting north and east, putting western Kentucky in its cross hairs.

At least five tornadoes raked across western Kentucky over the weekend, the longest of which traveled some 227 miles, said Kentucky Emergency Management Director Michael Dossett. At least 74 people have died and some 500 homes “no longer exist,” he said.  

The National Weather Service storm survey teams are on the ground assessing tornado tracks across the state. They have not yet determined the exact number of tornadoes, but the preliminary surveys completed thus far indicate multiple tornadoes with at least an EF-3 rating, and at least one with an EF-4 rating with winds estimated at nearly 200 miles per hour. 

Hot weather meets a cold front

Kentucky doesn’t typically see severe thunderstorms in December. Last Friday’s weather pattern was driven by warm moist air from the Gulf of Mexico meeting cold air from the north and high wind speeds in the upper atmosphere. 

The Gulf of Mexico is near-record hot right now, said Michael Mann, professor of atmospheric science at Penn State University and author of “The New Climate War.” Those warmer temperatures increase evaporation, which adds more moisture to the atmosphere, which fuels thunderstorms. 

The United States is experiencing a warmer than typical winter with the National Oceanic and Atmospheric Administration recording more than 5,000 record high temperatures over the last 30 days. 

National Weather Ser

And there is a direct link between warming temperatures and human-caused climate change.

The largest consortium of climate scientists on the planet say humans have unequivocally warmed the planet through burning fossil fuels, according to the U.N. Intergovernmental Panel on Climate Change.   

By their estimate, humans have already induced about 1.07 degrees Celsius of increased temperatures since pre-industrial levels. Just one degree Celsius of warming of the ocean increases moisture content in the atmosphere by about 7%, Mann said.

“That’s very basic physics. That’s basic thermodynamics,” Mann said. “And so we know there is that much more moisture in these air masses and the moisture is available to help power these storms.”

Severe weather feeds off that energy. Humans have shifted the baseline for the planet, and that increases the likelihood of severe weather. 

Larger tornado outbreaks

Tornadoes, by their nature, are difficult to study. They’re localized, short-lived and there is less data available for them than other extreme weather events. Most of the data that does exist is gathered for the purpose of emergency warnings, not climate science, so it can be inconsistent. All of that together makes it difficult to attribute individual events to human-caused climate change.  

However, climate scientists say the type of tornado system that hit Kentucky over the weekend has become more common since the 1950s. 

Climate Central

The average annual number of tornadoes has remained relatively constant since the 1970s, according to the world’s foremost body on climate, the United Nations’ Intergovernmental Panel on Climate Change. 

However, a clear trend has emerged, showing a decrease in the number of days per year with tornadoes, but an increase in the number of tornadoes present on those days, according to the IPCC. Or said another way, storms like the one Kentucky experienced —  with multiple tornadoes ravaging the state at the same time —  are becoming more frequent. 

“We’re seeing larger outbreaks,” Mann said. “So when you do get tornadoes, you get more of them, and again this was a huge one, nearly 60 storms.”

Tornado alley shifting

For decades, meteorologists and storm chasers have recognized the Central Plains region of the U.S. as Tornado Alley, but that’s changing

Since 1979, fewer tornadoes have been recorded in the Plains and Upper Midwest and more have been recorded in the Mid-South. Kentucky has seen among the largest increases in the frequency of tornadoes, according to Climate Central. 

Climate Central

“We’ve seen the shift between the Tornado Alley in the plains and Dixie Alley to the south. It’s kind of shifting and merging a bit more north and east and it is coming closer to Kentucky over time,” said Interim State Climatologist Megan Schargorodski.

The shift coincides with an eastward shift in the drier climate zone of the western U.S. and with a greater number of severe storms occurring in the eastern part of the country, according to Climate Central.  

As a result, the mid-South has the greatest potential for increased tornado disasters by the end of the century, according to a 2018 study

Kentucky and Climate Change

Scientists warn mankind has a limited time to act to avoid the worst impacts of climate change. 

Decarbonizing the economy is the only way to prevent things from getting worse. In Kentucky, that means eliminating our dependence on coal, Mann said. 

Coal is the dirtiest fossil fuel and Kentucky has among the highest number of remaining coal-fired generating units in the country — fourth behind Indiana, Illinois and Texas, according to a WFPL News analysis. 

Mann said the country should be thankful for the coal industry and all it has done to power the country, but it’s time to change.  

“The whaling industry came to an end in the 1800s because we came up with something better, a better way to produce fuel, and that was fossil fuels. Now it’s time for that next transition,” Mann said. 

Kentucky politicians appear reluctant to make that transition. 

Much of Kentucky’s Congressional delegation doesn’t believe in human-caused climate change, including Sen. Rand Paul, Rep. Thomas Massie, Rep. Brett Gutherie and Rep. James Comer, though Sen. Minority Leader Mitch McConnell does

Gov. Andy Beshear unveiled a new energy strategy in October without a single mention of climate change. Beshear has said that climate change is real, but his plan is energy neutral, meaning it will focus on promoting “all of Kentucky’s energy resources,” according to the strategy document

In the state legislature, Republican Rep. Jim Gooch of Providence, Kentucky, has long been the chair of the House Natural Resources & Energy Committee, and he’s spent more than a decade denying the existence of human-caused climate change. 

The world’s largest consortium of climate scientists say humankind has warmed the planet since the dawn of the industrial era and extreme weather will only get worse in the coming decades if we don’t act swiftly to eliminate our reliance on fossil fuels. 

“Politicians, policymakers, you’re there to represent the people and the people are suffering, the people are hurting. We saw this tragic loss of life because of this heightened risk we now face,” Mann said. “We can connect the dots to climate change.” 

Ryan Van Velzer is WFPL's Energy and Environment Reporter.