Is Climate Change Causing Devastating Tornadoes?
At least 291 people died in the storms that ripped across the South this week, with 204 fatalities occurring in Alabama. This month, there have been nearly 300 confirmed tornadoes, breaking a 36-year-old record. Now, Mississippi and Louisiana are bracing for flooding as the Mississippi River swells with rain from the fierce storms.
While scientists have a good idea of how tornadoes—violently rotating column of air that extends from the base of a thunderstorm to the ground—form, predicting them is a still a guessing game, as is how climate change might affect them.
 Supercell thunderstorm. Photo courtesy NOAA |
What’s certain is that tornadoes require warm, moist air meeting fast-moving cold air. Yet scientists can’t accurately predict when and where they’ll strike. They do know that the most destructive and deadliest tornadoes occur from supercells (rotating thunderstorms with a well-defined radar circulation called a mesocyclone). Yet the exact conditions that produce a tornadic thunderstorm aren’t known, and even under seemingly ideal conditions the twisters don’t always form. Also up for debate is what causes tornadoes to dissipate. (NOAA has more on tornado basics here, including fun facts like most rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.)
“There’s a large crapshoot aspect,” Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, told the New York Times. “A little quirky thing can set one off at one time, and another time not.”
 A tornadic thunderstorm. Click here for larger image, courtesy National Severe Storm Laboratory |
Scientists, including those at the National Severe Storms Laboratory, use a variety of technology to track storms and conditions and forecast tornadoes, like Doppler radar, satellite images, and computer models. Currently, the average lead-time for tornado warnings is 13 minutes, according to NOAA.
A major tornado outbreak of historic proportions impacted portions of Mississippi, Alabama, and Georgia on Wednesday. More than 150 reports of tornadoes were received on Wednesday, with the majority across northern Mississippi and Alabama. This movie, from NOAA, shows the rapid scan infrared imagery from the GOES-East weather satellite from April 26-28.
The government is still tallying up the tornadoes, but it looks like this April is poised to break the record for the most tornadoes in April (currently, the record goes to April 1954, which saw 407 hit). The cause is an unusually powerful jet stream.
The extreme tornado activity has many people wondering if global warming is the cause, or at least a contributing factor. Scientists don’t really know. The number of April tornadoes has been on the rise—increasing from 74 a year in the 1950s to 163 a year in the 2000s—but “nearly all of the increase is of the least powerful tornadoes that may touch down briefly without causing much damage. That suggests better reporting is largely responsible for the increase,” explains A.G. Sulzberger.
In fact, while models show that climate change will contribute to increasingly severe weather phenomena—including floods, droughts, and hurricanes—there’s little scientific consensus about how it may affect tornadoes. “It remains unclear, partly because of the lack of historical data and partly because of their unpredictable nature, whether they will increase in number or strength or geographic range,” The New York Times reports.
In an article in today’s paper, Kirk Johnson explains:
| Many climate models, for example, predict a weakening upper atmosphere jet stream over time on a warming planet, Dr. [Jeff] Masters [director of meteorology at Weather Underground, an Internet-based weather service] said, which would presumably create less energy for tornado formation. But some of those same models also suggest wetter conditions in tornado country, which is the other key ingredient in storm formation. |
For a more detailed explanation, check out Andrew Freedman’s Washington Post blog post on the topic.
In short, there’s not enough research to predict how global warming will affect tornadoes.
Still, as the planet warms, we’re going to see changes in weather events. Instead of cutting funding for climate-related programs at agencies like NOAA, we should be investing in them.
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