A study released this week finds that higher surface temperatures probably means more frequent severe thunderstorms — which may sound like a fairly unremarkable addition to what many consider the consensus around climate change, but it’s actually not. It’s the first major study that’s examined this question to find such a result, that global warming will create more meteorological environments conducive to severe thunderstorms. The study, published in the Proceedings of the National Academy of the Sciences, relies on a model different from what’s been used in previous work (which was also run, apparently, in a much more comprehensive way).
This is revealing not because that there are any particular flaws with the study itself, or its new model (I have no idea), but because most people advocating action against global warming would tell you it’s eminently obvious that higher temperatures will mean more frequent and stronger storms, “more extreme weather,” or whatever (in some sense, the “more extreme weather” arguemnt is a truism — compared to the past couple centuries, yes, higher temperatures will mean more extreme events that involve high temperatures, such as deadly heat waves). But in reality, the scientific evidence on this is remarkably weak — the theses may not be wrong, but it’s not nearly as well-supported as, say, evidence of rising CO2 concentrations, their effect on temperature, and higher average global temperatures (though there may be increasing problems with those consensuses, too). Specifically, this new paper notes that, before its release, the correlation between higher temperatures and the number of severe thunderstorms “has remained highly uncertain.”
It’s pretty obvious why. The study explains that there are two main factors at play here, and they’re countervailing: ”convective available potential energy,” or CAPE, when warm air at lower altitudes carries moisture upward; and vertical wind shear, meaning the difference between wind at higher altitudes and wind at lower altitudes. Warmer overall temperatures means more CAPE but less wind shear, so global warming’s effect on thunderstorms has generally been considered inconclusive.
The authors of this new paper, though, found with their model that wind shear is not substantially lower due to temperature on days where there’s a lot of CAPE, so the wind-shear effect doesn’t cancel out the other issue on days when big storms are more likely. Voila, a greater number of environments conducive to severe storms.
So more storms, right? For one, even if the scientists’ model is entirely right, the result doesn’t tell us much: A meteorologist with the National Weather Service told the Washington Post it was “good work,” but cautioned, ”environments are not severe thunderstorms. And, while an increase in daily environments supportive of severe storms will more than likely relate to an increase in actual severe thunderstorm formation in the mean, predicting the number and variability of actual severe thunderstorms remains elusive.”
And obviously, it is. The scientists at work here are predicting a 25 percent increase in severe thunderstorms at the end of the 21st century. The point isn’t that scientists can’t effectively model the climate, but that we should always be skeptical of such work — especially when only one paper has found a model, so far, that produces a given prediction. Global warming might well cause more thunderstorms, but one study, after years of inconclusive findings, could be a big deal to the scientific community but doesn’t begin to represent a conclusion that can be relied on, or actionable information for us.