The following are some, perhaps, disjointed items related to the frequency of tornado occurrence and death rate in the United States. They are intended to convey some of the challenges associated with looking at the observed record, particularly for the purpose of conveying anything to do with changing climate. It has been proposed that extreme weather events will increase in frequency in an enhanced greenhouse-gas climate.
Tornadoes seem a natural event to consider in that light.
The nature of the record, however, makes it difficult to do. That does not mean that there will not be a change in tornadoes in a greenhouse-gas climate, but that it may not be possible to see that change, particularly without giving some thought to the statistics to be examined. In particular, we want to look for stable parameters, which perhaps give us some hope of detecting changes. For this beginning effort, I'm going to look at only national numbers. No regionalization has been done and none will be done in the near future.