Climate change will likely make extreme weather events more common. Some types of weather are easy to attribute to climate change. But with tornadoes, things are a bit more complicated.
While tornadoes have been recorded all over the world, the United States experiences around a thousand of them each year, which is far more than anywhere else on the planet, according to National Geographic.
Most tornadoes occur in an area of the country called “tornado alley,” which is defined as giving the highest incidence of tornadoes. Although the official boundaries of Tornado Alley are not clearly defined, its core extends from northern Texas, Louisiana, Oklahoma, Kansas, Nebraska, Iowa along with South Dakota.
A study of 1921–1995 tornadoes concluded almost one-fourth of all significant tornadoes occur in this area.
This extensive area of the Great Plains region is where the atmospheric conditions are just right for massive, tornado-spawning thunderstorms. The resulting tornadoes leave a trail of destruction in their wake, often with deadly consequences.
A changing climate and extreme weather events
Climate change is on just about everyone’s minds today, and the resulting extreme weather events linked to global warming are often “right in your face” events that wreak devastation and hardship around the planet.
However, according to Yale Climate Connections, tornadoes are in a class of their own. They contend that human-warmed climate isn’t making violent U.S. tornadoes any more frequent.
However, they also point out that climate change may be involved in some noteworthy recent shifts in the location and seasonal timing of the tornado threat.
First, though, let’s look at what is so special about the high number of tornadoes in the U.S. Simply put, it has a lot to do with our unique geography that allows hot, dry air from the Southwest to flow atop moist, warm, unstable surface air east of the Rockies, with cold air at the jet-stream level overtopping it all.
This unique combination of air masses creates a “layer-cake” of winds and air masses, varying with height, that supports the development of rotating supercell thunderstorms, the kind that produces the most long-lived and intense tornadoes.
The total number of U.S. tornadoes observed each year has roughly doubled from the 1950s to the 1990s. This is probably due to better forecasting as well as more tornado spotters being on the ground. (Remember the movie, “Twister?”).
How does climate change influence tornadoes?
Climate change, while a broad threat to all of us, actually plays out in localized events, such as river flooding, the intensity of storm damage from hurricanes, and the like. Tornadoes are unique, localized weather events, so linking them to climate change can be difficult.
Tornadoes and their parent thunderstorms are brief and episodic, and they normally vary a great deal over time and space, so it’s tougher to distill long-term trends in their behavior and distinguish those from normal ups and downs.
However, a few interesting signals have shown up over the past few years that scientists are looking at closely. Some may be the result of year-to-year or decade-to-decade variability; while others could be related to longer-term, human-caused climate change.
The facts, based on scientific studies
A 2014 study found that the monthly variability of EF1+ tornadoes has increased since the 1970s, with a growing occurrence of both record-busy and record-calm months.
In other words, there has been a decrease in the number of days per year with tornadoes but an increase in the number of days with multiple tornadoes. Why this clustering effect has occurred is not clear.
Another study published in 2014 examined the belt traditionally known as Tornado Alley, from northern Texas to southeast Nebraska, and it found that the region’s yearly springtime peak of tornado activity had shifted from around May 25 to May 14.
A 2016 study found that an increasing number of each year’s tornadoes are occurring in outbreaks (periods of one to several days with at least six closely spaced EF1+ tornadoes), and the outbreaks themselves are becoming more frequent.
A more recent study, published in the journal of the American Meteorological Society in 2021, found that tornado-favorable environments during wintertime have increased across the Southern Plains and Southeast.
But, these, as well as other studies have not proven conclusively that climate change is directly responsible for tornado activity.
Predicting tornadoes based on weather ingredients
Scientists must figure out how to predict how climate change might affect the individual weather “ingredients” that support the development of supercell thunderstorms (the type that produces tornadoes). These weather ingredients are:
- warm, moist air;
- an unstable atmosphere; and
- wind at different levels moving in different directions at different speeds, a phenomenon known as wind shear.
Climate simulations can help scientists predict what effect climate change might have in the future. They can also examine official records to see if there have been any changes in the frequency and strength of tornadoes over time.
Unfortunately, in the United States, tornado records only date back to the 1950s. It was not until the early to mid-1990s that an extensive Doppler radar network was established in the United States for the detection of tornadoes.
In remarks on Saturday addressing the devastation, President Joe Biden said he wanted to know to what degree climate change might have been a contributory factor, reports The Guardian.
“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,” the president said in an afternoon briefing in his hometown of Wilmington, Delaware.
“But the fact is that we know everything is more intense when the climate is warming. And obviously, it has some impact here.”
All in all, it is something to think about, yes?
