(WFLA) – Recent devastating tornado outbreaks in the Southeast and Midwest have been life-changing — and sometimes fatal — for those caught in the path of the storms. Scientists are concerned this is just the beginning of a trend in stronger outbreaks in the future due to a warming climate.
But how does climate change impact the frequency of tornadoes? And what is projected for the future?
It could be more likely that the increasing trend in tornado occurrences is due to better observations and better Doppler radar. In other words, more people either seeing them or detecting them with technology.
In fact, when you eliminate the weaker tornadoes from the record, the upward trend flattens out, signaling that the weaker tornadoes were simply being missed or underreported in the past, but now are being detected.
It also should be noted that there is not likely a trend in tornado intensity, either. If you look at the record, it may seem like tornadoes are actually getting slightly weaker. But that’s more likely due to changes in the techniques of rating tornadoes over the years, and methods which overrepresented the strength of tornadoes in the past.
The overarching theme, when looking at past tornadoes, is that the record is questionable and subjective, thus it is hard to glean certainty on trends on tornado number and intensity.
But there is more certainty on a few aspects of the connection between climate change and tornadoes — namely changes in geography and outbreaks.
A 2018 study found that the frequency of tornadoes is increasing east of the Mississippi River in places like the Mid South, Deep South and Southeast. At the same time, tornado numbers are decreasing west of the Mississippi River in the more traditional “Tornado Alley” of the Plains States.
This eastward trend in tornadoes is consistent with climate change in that the Southwest U.S. is heating and drying, and the Southeast is becoming more moist due to a rapidly warming Gulf of Mexico.
A 2018 research paper substantiated this concept. The authors found that the 100th Meridian — the statistical divide between arid and humid in the central Plain States — has moved 140 miles in just the last four decades.
As the Southwest U.S. dries out due to increased heating and evaporation, the dry air is intruding further east into the Plains. In addition, the Gulf of Mexico is warming twice as fast as the global average of the oceans, and that is supplying extra energy and moisture to severe weather outbreaks.
Research has also found that tornado outbreaks are becoming larger. Put simply, on days when the atmosphere is favorable for outbreaks, there are more tornadoes in those outbreaks. Conversely, there are less days with tornadoes overall. In other words tornadoes are becoming more clustered on fewer days.
Looking into the future, it appears as though these trends will continue. A new research paper published in January of this year finds that supercells will become more frequent and intense as the climate continues to warm. And the trend of increasing supercells is likely to continue in the Eastern U.S., while decreasing in the Great Plains.