The kerfuffle over my intemperate denunciation of Chris Mooney refers. Check the comments.
As CM observes, “There have now been eight Category 5 Atlantic hurricanes in the past five years (Isabel, Ivan, Emily, Katrina, Rita, Wilma, Dean, Felix); There have been two Atlantic Category 5s so far this year; only three other seasons have had more than one (1960, 1961, 2005); There have been eight Category 5 Atlantic hurricanes so far in the 2000s; no other decade has had so many. The closest runner up is the 1960s with six (Donna, Ethel, Carla, Hattie, Beulah, Camille).”
I dislike the way CM is approaching discussing this, because I consider it misleading. However, I’m struggling to explain what I mean, so the below tries to discuss this more. Its something of a series of random jottings rather than a coherent post, which is my attempt at a caveat, but -cough- see below on that 🙂
[Update: a good place to look for the numbers is Webster et al 2005. They sensibly merge 4+5’s to get more stable numbers. But they don’t go back into the 60’s]
CM properly stuffs in lots of caveats into his post, but he you and I all know that people just blip over those. Putting in caveats is necessary when you’re speculating, but it isn’t a defence against leading writing. And I think his stuff is excessively leading. And vague. CM is clearly trying to talk around the issue of hurricanes and GW, and is pushing the recent numbers as exceptional, but doesn’t seem to have formulated his questions in an answerable form. Or indeed, really formulated any questions at all.
I’m not familiar with the hurricane record, so I’m relying entirely on CM’s data above. Lets try a few questions:
Q: Does having 2 cat 5’s in a season imply a worrying trend towards more cat 5’s? A: clearly not. 1961 disproves this.
Q: well how about 6 cat 5’s in a decade? A: no, the 60’s disprove this.
At which point you might step up and say “well wot about 8 in a decade? the 60’s don’t disprove that!” Which is true but cheating. You’re only using 8 to exclude the 60’s. And what about *landfalling* hurricanes? There are fewer of these so you just get noisier statistics.
Q: does the record of cat 5 hurricane numbers tell you anything useful, statistically? A: I don’t know. But I suspect not, because if it did people would have published it and CM would be referring to it. CM has been in close touch with lots of hurricane folk recently so would be aware of this, if it existed.
Q: OK, so it doesn’t say anything rigourous statistically, but come on look at those numbers! Surely its pretty suggestive A: Careful, you’re sounding like the solar variation causes global warming folk; they can find you any number of “suggestive” correlations that aren’t quite significant.
But… its also true that statistics aren’t everything. In fact a mechanistic explanation is better. Consider, for example, a biased die. Suppose I know that a 6 has a 1/3 chance of showing up, and the others adjusted accordingly. Then I’d be happy to bet, on 1/6th odds, on the 6. But I wouldn’t be very surprised if a 6 didn’t turn up first, second or third go. Conversely, if given two die, one loaded as above and one fair, I wouldn’t be confident of telling them apart by just rolling them and looking at the distribution without a lot of throws (cue JA to tell me how many, at 5%). And since we’re on JA… you can probably do better that simple cat-5-#-counting by some clever Bayesian combining of different sorts of anomalies (that may be what CM is trying to do, in an informal way, by finding records in different aspects. But post-hoc record finding isn’t good).
A mechanistic explanation is better, if you’ve got one. And indeed we do have the beginnings of one.
But what is CM actually saying? However, the more Category 5 storms we get in the 2000s — which are hardly over yet — the more this decade will appear anomalous when compared with previous ones. And at some point, it seems to me that people will simply have to throw up their hands and say: We are in a new place now.
Does this predict *more* cat 5 storms this decade? I can’t tell. Is the current decade anomalous, at the moment? I can’t tell. If yes, in what sense is it anomalous? Are we in a new place now? Presumably not, because the sentence is phrased in the future.
Lets try another approach. Prediction. Often regarded as the hallmark of science, even though observational astronomy still counts as science. Anyway. The assertion seems to be some connection between GW and h#’s, though clearly not a linear one.
Q: does this theory of a connection allow the prediction of h5#’s from SSTs? A: I’m not sure, but I doubt it, because no-one is trumpeting their predictions of 1 or 2 cat 5’s this season (if people did make such predictions, please let me know).
Q: how about prediction h5#’s for the rest of the season? A: well funny you should ask that…
Because CM says In my opinion, we also have a right to be very worried about what else this hurricane season might bring… Felix is only our sixth storm of the year in the Atlantic. The forecasts suggest there will be 13-16. Could that conceivably mean yet another Category 5? Is this a prediction? No, except in the Piers Corbyns sense: if there aren’t any more it will be forgotten; if there are it will be remembered. Yes, I know, thats a bit unfair because of course it wasn’t clearly labelled as a prediction. But its something we need to be worried about. How worried? A bit? Not much?
So… how about a challenge:
Q: how many more cat 5’s will there be this season, and/or in the rest of this decade?
A: (your turn now): 0, 1, 2, .. n? Or: at least 1, 2, ..; Or: at most 0, 1,..; Or: the available data and theory doesn’t allow me to make a confident prediction?