Today’s Tornado Outlook: High Risk of Global Warming Hype

May 24th, 2011 by Roy W. Spencer, Ph. D.

After the catastrophic death toll from the Joplin, MO tornado, which now stands at 117, we are no doubt in for more claims — dutifully amplified by the news media — that ‘climate change’ must somehow be at least partly responsible for this Spring’s wild weather.

And, to some extent, I’m inclined to agree. That is, if they are talking about the natural cooling effects of La Nina and the tendency for tornado outbreaks to be associated with cooler (not warmer) climate conditions.

But I suspect that’s just the opposite of the message they will be preaching.

So, let’s look at 2 statistics: 1) the number of strong to violent tornadoes, and 2) the deadliest tornadoes in U.S. history

The bottom panel of following graphic shows what most meteorologists already know: there has been a downward trend in strong (F3) to violent (F5) tornadoes in the U.S. since statistics began in the 1950s. As seen in the top panel, this has also been a period of general warming. For those statistics buffs, the correlation coefficient is -0.31. Obviously, the conclusion should be that warming causes fewer strong tornadoes, not more. (Or, maybe a lack of tornadoes causes global warming!)

Even when I de-trend the data, the remaining year-to-year variability still has a negative correlation: -0.17, so the conclusion is the same for the long-term trend AND the year-to-year variations in strong tornado activity.

So how does anyone get away with claiming that global warming is contributing to more tornadoes?

Well, maybe because there has indeed been an UPward trend in total reported tornado sightings in the U.S. during the same period of time. But this is only because (as I mention in my first book, Climate Confusion) there are so many more people now spread across the fruited plain, with so many video cameras, and now so many Doppler radars are measuring the wind rotation associated with tornadoes, that it is difficult for any to go unnoticed by at least someone.

Also, if you hear any news reports that more deaths due to tornadoes are due to global warming, this is also a bogus claim. Here’s a little quiz for you:

QUESTION: Out of the 25 deadliest tornadoes in U.S history, how many would you guess have occurred in the last 50 years (since 1960)?

…wait for it….

ANSWER: Up until a month ago, NONE of them.

On April 27, one of the Alabama tornadoes made the bottom of the list at #25, but now has been knocked back off the list because Sunday’s tornado in Joplin will be ranked #8.

So, to the extent that you hear reports of ANYONE connecting tornadoes to global warming, I think it proves only one thing: The belief that global warming is causing most of the world’s ills is so pervasive that the facts simply do not matter anymore.

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