Over the past couple of decades, there have been two observable and measurable trends in tornado climatology across the United States.
The average total number of tornadoes has dropped while the frequency of days with large numbers of tornadoes (outbreaks) has increased. So far, climate scientists have found no link between these trends and the global climate change.
At first glance, one would think the observed increase in summer temperature and humidity across the United States would lead to more severe weather and tornadoes. But severe weather also requires wind shear; differences in wind speed and velocity over different levels of the atmosphere. It is possible that our changing climate is offering fewer of these wind shear days, but a link between this and the changing climate has not been found, yet. It may be due to something else or it could be a temporary trend. As always, climate and climate change is complicated.
