Tornadoes

The majority of the world’s tornados happen in the United States’ Tornado Alley in the spring, totaling an average of 1,200 per year^1,2. In Texas, warm moist air from the Gulf of Mexico converges with cool and dry air masses descending from the Rocky Mountains. The warm air overlaps underneath the cold air and rises, forming supercells and generating tornadoes^3,4. While researchers understand how tornadoes develop, there are still many unknowns in trying to predict where exactly they’ll occur, how often they form, how long they last, or how intense they will be^2,5. Currently, the best that radar and satellite detection systems can do is a 12-minute early warning^6,7. In comparison, extreme weather events like hurricanes give days or weeks of advance notice, or in the case of droughts, they are slow-moving but easily detectable.

In recent years there appears to be an increase in the number of observed tornados, but scientists are unsure whether this is a definitive increase or a result of better tornado-spotting instruments and techniques^2,8,9. As such, research into climate change’s influence on tornadoes is relatively uncertain, especially when compared to larger-scale trends like drought, hurricanes, wildfires, floods, and rainstorms that have clear links to higher temperatures and trends in precipitation⁴. In comparison, tornadoes happen in smaller concentrated areas for much shorter—but intense—bursts of time and are not currently able to be captured by climate models¹⁰. This inability to predict tornado events precludes directly connecting tornado behavior to current and future climate changes.

Researchers know that the conditions that lead to the formation of tornados are changing with rising temperatures and shifting humidity patterns but cannot yet directly connect them with strong mathematical certainty⁵. Greater atmospheric greenhouse gas concentrations are projected to increase regional humidity and the conditions leading to thunderstorm and tornado formation, but wind shear can also decrease under changing conditions, which lowers the likelihood of tornado formation^{7,11,12,13,14}. This decrease in wind shear could be outweighed by enhanced atmospheric instability that increases the length of the tornado season¹⁵.

The records since the 1950s show that tornados are being recorded more often and in places where they haven’t been before, suggesting a future eastward shift in the boundaries of Tornado Alley¹. Other studies propose an increase in tornado variability in the United States³ and that outbreaks, that being the total number of tornadoes happening in one day, are becoming more frequent and of greater magnitude¹⁶.

While the direct attribution between climate change and tornado frequency and magnitude is still being studied, there is a link between climate and tornadoes. Modeling studies are confident that there will be an increase in the conditions that foster severe storms that produce tornadoes, especially in the winter and fall^3,15. This would likely mean more winter and fewer summer tornadoes, with more intense outbreaks in the mid-South and Southeast United States¹⁰. These connections remain difficult to quantify as future increases of the conditions favorable to thunderstorms and tornados would not be spatially uniform and require further research^3,17.

Explore the graphics and resources below to learn more about the ongoing study of tornadoes and climate change.