It’s spring here in Ontario and that means we are heading into the warm season (yay!) which sometimes brings thunderstorms (yay! unless you’re stuck outdoors) and once in a while a severe storm with a possible tornado (boo!). These kinds of events are called “severe convective storms” by people observing and studying them from a safe distance. Up close they may get different names because they bring high winds, black clouds, dramatic downpours and occasionally funnel clouds that can do a lot of damage. And reflexive warnings that climate change is now responsible and is making them worse. So when people claim that climate change means more severe weather, these are the storms they want you to think of. By contrast, what we want you to think of is the fact that the UN’s Intergovernmental Panel on Climate Change, which alarmists often wave vaguely at as the ultimate authority on “the science” without actually reading its stuff, says there is no evidence they are getting more frequent in the U.S. or elsewhere, and that indeed the frequency of intense tornado activity in the U.S. is trending down, not up as the alarmists claim without checking.

Specifically the IPCC’s latest “Assessment Report”, called AR6 for short, said:

“Observed trends in severe convective storms are highly regionally dependent. In the United States, it is indicated that there is no significant increase in convective storms, and hail and severe thunderstorms.”

They also said there isn’t enough data outside the US to identify trends:

“Studies on trends in severe convective storms and their ingredients outside of the United States are limited... In summary, because the definition of severe convective storms varies depending on the literature and the region, it is not straightforward to make a synthesizing view of observed trends in severe convective storms in different regions. In particular, observational trends in tornadoes, hail, and lightning associated with severe convective storms are not robustly detected due to insufficient coverage of the long-term observations.”

Note that they are not saying there are no trends. They are saying nobody knows because of lack of adequate information, which is not a problem for some people but ought to be.

In fact, on the subject of information, the IPCC reported some evidence of an increase in severe storms in Europe. But, they said, it may be due to having better data and observations now than in the past, so storms that went unrecorded in days of yore are now measured and catalogued. Elsewhere, incidentally, they noted that in Canada “there is a lack of detectable trends in observed annual maximum daily (or shorter duration) precipitation” a point we also made in our video on Urban Flooding.

Turning to U.S. tornadoes, we discussed those in our series on the Alimonti et al. paper that was retracted by a journal despite no one being able to find a flaw in it because you’re not supposed to know that things aren’t getting worse and worse. And here the data show that the number of large tornadoes is going down over time. Not up, down.

Again there’s an important evidentiary aspect to this evidence. The total number of tornadoes in the United States does appear to be going up at first glance. But that apparent trend is very likely due to the fact that with Doppler radar and smartphones everywhere we now count small tornadoes that in past decades would have been missed except, perhaps, by those in the immediate vicinity who would not then have reported them.

Roger Pielke Jr. has blogged about this issue, showing the fairly dramatic declining trend in large tornadoes:

and the downward trend in normalized tornado damages in the US:

So here’s a question for the alarmists. If the trend was upward you’d blame climate change and say it was further proof of the need to take costly action to reduce emissions. No unpleasant development on the weather front is ever brushed off as coincidence. Instead, a carping chorus claims there’s a direct cause and effect relationship.

OK, then. If there are no coincidences, and no significant natural variability, then when a trend in nasty weather is going down, do we get to say this outcome is also due to climate change and undermines the case for cutting emissions? Do we get to say some effects of climate change are benign, possibly many?

Or does the automatic cause-and-effect rule apply only when you find something getting worse?