Inconvenient weather fact for Earth Day: the frequency of violent tornadoes fell to a record low in 2017

From Mark Perry.

"Earth Day 2018 will take place this Sunday (April 22) and I’ll put up an updated version of my annual Earth Day post (“18 spectacularly wrong predictions made around the time of the first Earth Day in 1970, expect more this year”) within a few days. For now, in preparation for Earth Day, let me present an “inconvenient weather fact” displayed graphically above of the annual US tornado count from 1954 to 2017 based on data from the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Information.

In 2017, there were only 15 tornadoes in the US that registered in the strong to violent categories of F3, F4 or F5 (there were 13 F3 tornadoes, 2 F4s, and no F5s), which was the fewest annual number of F3+ tornadoes in more than 60 years going back to 1954 when NOAA started collecting annual US tornado data, and below the previous record low count of 17 F3+ tornadoes in 1987. In addition to setting a new record low, last year’s strong/violent tornado count of 15 was slightly less than one-third of the 45.25 average number of annual violent tornadoes since 1954. The trend line in the chart above shows that the frequency of strong/violent tornadoes in the US has been declining consistently since the 1950s. For example, the average number of annual F3+ tornadoes in the first half of the sample above was almost 56 compared to an average annual count of 34.5 tornadoes during the second half of the sample.

As James Taylor wrote in Forbes in 2012 (five years before the record-setting low last year):

Tornadoes are becoming less frequent and less severe as our planet modestly warms. Yet global warming alarmists focus attention on the few tornadoes that still do occur and say that global warming is causing these increasingly rare tornadoes.

For example, here’s what Brad Johnson of the progressive activist organization Center for American Progress wrote in 2012 trying to link global warming to tornadoes (“Poisoned Weather: Global Warming Helped Fuel Killer Tornadoes“):

Carbon pollution from fossil fuels is poisoning the weather, helping drive the conditions that created the killer tornado outbreak last week across the heart of the United States. “It is irresponsible not to mention climate change,” climatologist Kevin Trenberth of the National Center for Atmospheric Research told ThinkProgress Green. “The environment in which all of these storms and the tornadoes are occurring has changed from human influences (global warming). As spring moves up a week or two, tornado season will start in February instead of waiting for April.”
Scientists have not found a measurable trend in tornado intensity and number. However, with greater greenhouse pollution scientists expect changes. “The number of days when conditions exist to form tornadoes is expected to increase” as the world warms, atmospheric scientist Robert Trapp told Reuters. NASA climate scientist Anthony D. Del Genio wrote in 2011: “As the climate warms, we might experience fewer storms overall, but more of the strongest storms.” They have identified the risk of longer tornado seasons with stronger thunderstorms.

Bottom Line: The frequency of strong to violent tornadoes in the US has declined consistently and significantly over time, especially since the peak decade between 1965 to 1974 when there were more than 700 F3+ tornadoes at an average rate of more than 70 per year. It’s also important to note that the decline in violent tornadoes has taken place despite the improved scientific ability over time to find, track, and measure tornadoes. At least based on the evidence to date, I think we can dismiss the connection between “poisoned weather and tornadoes” suggested by Brad Johnson and the earlier predictions of Al Gore (and others) that global warming would cause tornadoes to increase in frequency and intensity. We can add Gore’s prediction to the list of many other spectacularly wrong predictions that have been made about the climate and environment since the time of the first Earth Day in 1970, and I’ll highlight those predictions in a later post closer to Earth Day 2018 on Sunday!"