Geophys. Res. Lett. (2018)

Observations reveal an increase in the number of days with multiple tornadoes in the United States, potentially exacerbating their economic impacts. However, quantifying the effects of anthropogenic climate change on severe storm hazards has been constrained by inadequate data and natural variability in tornado occurrence. James Elsner and colleagues from Florida State University, United States, use a hierarchical regression model — which controls for tornado variability over various timescales — to examine changes in US tornado power (or energy dissipated) from 1994 to 2016.

Credit: Cultura RM / Alamy Stock Photo

In addition to the recent increase in tornado days, tornado power is found to have risen by 5.5% per year, highlighting a possible relationship between these two attributes. A proportion of this upward power trend is believed to be linked to regional changes in the storm environment, particularly a concurrent increase in convective available potential energy and vertical wind shear, alongside enhanced convective stability; the authors, however, emphasize that these changes explain only a minor component of the trends in tornado power. Further work is therefore required to more fully understand tornado variability and projections under anthropogenic warming.