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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 year1,2. 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 tornadoes3,4. 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 be2,5. Currently, the best that radar and satellite detection systems can do is a 12-minute early warning6,7. 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 techniques2,8,9. 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 formation7,11,12,13,14. 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 fall3,15. 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 research3,17.

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

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References

  1. Gensini, V. A., and H. E. Brooks. 2018. Spatial trends in United States tornado frequency. NPJ climate and atmospheric science 1. Nature Publishing Group: 1–5.
  2. Nielsen-Gammon, J., S. Holman, A. Buley, S. Jorgensen, J. Escobedo, C. Ott, J. Dedrick, and A. Van Fleet. 2021. Assessment of Historic and Future Trends of Extreme Weather in Texas, 1900-2036. OSC-202101. Texas A&M University.
  3. Brooks, H. E., G. W. Carbin, and P. T. Marsh. 2014. Increased variability of tornado occurrence in the United States. Science 346. American Association for the Advancement of Science: 349–352.
  4. IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press. In Press.
  5. Kloesel, K., B. Bartush, J. Banner, D. Brown, J. Lemery, X. Lin, C. Loeffler, G. McManus, and others 2018. Chapter 23: Southern great plains. Impacts, risks, and adaptation in the United States: The fourth national climate assessment, volume II. U.S. Global Change Research Program.
  6. NSSL. 2022. NSSL Research: Tornadoes. Text. NOAA National Severe Storms Laboratory. https://www.nssl.noaa.gov/research/tornadoes. Accessed February 9.
  7. Runkle, J., K. E. Kunkel, J. Nielson-Gammon, R. Frankson, S. M. Champion, B. C. Stewart, L. Romolo, and W. Sweet. 2022. Texas State Climate Summary 2022. Vol. 5. Silver Spring, MD.
  8. Anderson, C. J., C. K. Wikle, Q. Zhou, and J. A. Royle. 2007. Population influences on tornado reports in the United States. Weather and Forecasting 22. American Meteorological Society: 571–579.
  9. Elsner, J. B., L. E. Michaels, K. N. Scheitlin, and I. J. Elsner. 2013. The decreasing population bias in tornado reports across the central Plains. Weather, Climate, and Society 5: 221–232.
  10. Glazer, R. H., J. A. Torres-Alavez, E. Coppola, F. Giorgi, S. Das, M. Ashfaq, and T. Sines. 2021. Projected changes to severe thunderstorm environments as a result of twenty-first century warming from RegCM CORDEX-CORE simulations. Climate Dynamics 57. Springer: 1595–1613.
  11. Van Klooster, S. L., and P. J. Roebber. 2009. Surface-based convective potential in the contiguous United States in a business-as-usual future climate. Journal of Climate 22: 3317–3330.
  12. Tang, B. H., V. A. Gensini, and C. R. Homeyer. 2019. Trends in United States large hail environments and observations. NPJ climate and atmospheric science 2. Nature Publishing Group: 1–7.
  13. Koch, E., J. Koh, A. C. Davison, C. Lepore, and M. K. Tippett. 2021. Trends in the extremes of environments associated with severe US thunderstorms. Journal of Climate 34: 1259–1272.
  14. Taszarek, M., J. T. Allen, H. E. Brooks, N. Pilguj, and B. Czernecki. 2021. Differing trends in United States and European severe thunderstorm environments in a warming climate. Bulletin of the American Meteorological society 102: E296–E322.
  15. Diffenbaugh, N. S., M. Scherer, and R. J. Trapp. 2013. Robust increases in severe thunderstorm environments in response to greenhouse forcing. Proceedings of the National Academy of Sciences 110. National Acad Sciences: 16361–16366.
  16. Tippett, M. K., C. Lepore, and J. E. Cohen. 2016. More tornadoes in the most extreme US tornado outbreaks. Science 354. American Association for the Advancement of Science: 1419–1423.
  17. Brimelow, J. C., W. R. Burrows, and J. M. Hanesiak. 2017. The changing hail threat over North America in response to anthropogenic climate change. Nature Climate Change 7. Nature Publishing Group: 516–522.