Climate scientist Patrick T. Brown wrote a thread on Twitter discussing claims in the New York Times that climate change is making hurricanes more intense. Brown is, unusually for climate scientists on Twitter (or anywhere else), a stickler for avoiding unfounded alarmism, and he takes exception to the Times claim because in order to promote their thesis, they have to engage in a bit of statistical sleight of hand, taking evidence that hurricanes are becoming less common and less threatening overall and turning it into evidence that climate change is making them worse. How do they do such a thing? By torturing fractions.
The secret formula, Brown explains, begins by looking past the number of hurricanes happening overall to the proportion that are Category 3 or higher. It’s just the beginning, though, because the overall trend across all categories is down. But the number of Category 1 and 2 hurricanes has declined considerably while the number of “major” (Category 3+) hurricanes held essentially steady. During the 19 years from 1979 to 1997 there were 9,420 storms globally (496 per year), of which 3,202 (34%) were major (169 per year). During the 20 years from 1998 to 2017 there were only 8,700 storms (435 per year), a 12.3% decrease overal, of which 3,242 were major, a decrease of 3.8% to 162 per year but an increase to 37% of all such storms.
In sum, all kinds of hurricanes got rarer. But the chance that if one did happen it would be major rose trivially. The Times’ conclusion? Climate change is making hurricanes worse. Brown says a more accurate conclusion would have been “There is no clear global trend in the occurrences of major hurricanes, but there is a negative global trend in overall hurricane occurrences driven by reduced instances of weaker hurricanes.” But everybody knows that kind of conclusion doesn’t sell papers.
Mind you empty climate hype isn’t exactly a formula for long-term success either given how it damages your credibility.