Guest essay by Alberto Z. Comendador
Temperatures in the USA have generally increased since the 1950s. Of course, anything that mostly increases over time will have a positive correlation with everything else that also increases; in the USA this includes tornado counts. And of course most correlations are utterly meaningless and devoid of causation. For a hilarious take on the issue, see spurious correlations.
The problem , as NOAA itself says, is that there is a bias: just because we observe more tornadoes than before, doesn’t mean their number has actually increased.
‘With increased National Doppler radar coverage, increasing population, and greater attention to tornado reporting, there has been an increase in the number of tornado reports over the past several decades. This can create a misleading appearance of an increasing trend in tornado frequency.’
They illustrate this by excluding the weakest tornadoes (the F-0 category), which is…
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