You might find it hard to keep up on this topic. Every time a major hurricane hits the US or a Pacific island the usual suspects come forward to tell everyone this is exactly what they expected due to anthropogenic warming of the climate. Warming means more storms and hurricanes. Except the data don’t show an increasing trend. No problem, experts say, climate models actually predict that global warming will mean fewer hurricanes. Wait a sec. Are the trends supposed to be up or down? Down, say the modelers. So can we finally attribute something beneficial to greenhouse gases? Don’t bet on it.
The title of the article we linked to (h/t Judith Curry) is “Declining tropical cyclone frequency under global warming”. They start by noting that we only have reliable data on annual tropical cyclone (TC) frequency back to the 1970s, and “this relatively short period of high-quality data does not provide consensus on the detection of trends or on the attribution of trends to anthropogenic influences. On the basis of the few decades of reliable historical data, there is no clear evidence of an observed trend in global TC numbers.” But, the authors argue, if they did have data farther back, it would probably show TCs becoming less frequent. They list several conditions in the tropical atmosphere that are hostile to their formation, including wind shear and dryness in the mid-troposphere. Climate models suggest that those conditions will become a bit more common under greenhouse warming. To check if that has happened, the authors used a model to reconstruct past hurricane formation counts. And then they showed that those estimates are pretty consistent with what other models said should happen under greenhouse warming.
So... one kind of model agrees with another. But where the observations exist (namely over the past 50 years) the data don’t support a declining trend, they just don’t say anything one way or the other.
What they do say, both models and data, is that greenhouse gases are not expected to, nor have they thus far, caused an increase in TC formation. And if the models are right, there will be fewer deadly storms in the future. Which is the exact opposite of the alarmist message. So the alarmists will carry on declaring global warming means more tropical cyclones, and if you point out that the numbers are actually declining, they will say aha! just as we predicted. And before long they will have a reason why having fewer deadly tropical cyclones each year is actually a bad thing. Because science.
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