WUWT has previously covered a press release from The OAS on the paper, now, Mike Smith, a CCM at WeatherData Inc. writes at Meteorological Musings:
The paper, Tornado Activity is Occurring Earlier in the Heart of “Tornado Alley” brings up some interesting points about the peak of tornado season occurring earlier in the spring in the conventional “tornado alley” of the Great Plains. The paper is an attempt to link global warming to a change in tornado season between 1954 and 2009. Its primary conclusions appear sound. That result is not surprising given the rise in global temperatures during that period of time (see graph).
My objections are not with the primary thrust of the paper. It appears to be a useful addition to the literature.
My objection is the paper’s attempt to make the change in the time of the peak tornado season into something sinister. For example, the first sentence in the paper (it appears in the Abstract) is,
“Tornado frequency may increase as the factors that contribute to severe convection are altered by a changing climate.”
It also says,
“The lack of evidence is due in part to sampling effort: the number of reported tornadoes has increased over time [Dixon et al., 2011].”
The reference to Dixon has to do with Dixie tornado alley, not the one in the Great Plains.
So, let’s go through this yet again. Let’s begin with all tornadoes of F-1 intensity or greater:
Even though world temperatures have risen, there is absolutely no upward trend in tornadoes. This is especially surprising given the storm chase program that started in 1972 and Doppler radar installations beginning in 1991. There are many small tornadoes that now get into the books that never would have been recorded a half-century ago.
Mike has further graphs and analysis here: Another Shabby Attempt to Tie Increased Tornadoes to Global Warming
I suggest you bookmark his website, and may I recommend his book Warnings: The true story of how science tamed the weather.
I’ve read it, and I’ve lived and experienced much of what he’s written about in the quest to make forecasting, especially severe weather forecasting, more accurate, timely, and specific. For those of us that prefer practical approaches over the rampant speculation on mere wisps of connections to climate, this book is for you.