Prompted by the proofs of my review of AIT for Met Apps (oh, the fame!) I looked at the site again and found The Science. What they list there is very thin and with no useful links. I would have hoped for something better.
Anyway, their first point is “The number of Category 4 and 5 hurricanes has almost doubled in the last 30 years.” and they source this to Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 436: 686-688. Now E does say This combined PDI has nearly doubled over the past 30 yr, but never uses the word “category”. And this is not surprising, because it starts Theory and modelling predict that hurricane intensity should increase with increasing global mean temperatures, but work on the detection of trends in hurricane activity has focused mostly on their frequency and shows no trend. The paper is about the destructiveness index, not the number of storms. Has Gore… simply misinterpreted the paper? Found something in it my quick skim missed? Or wot?
So… anyone know a good source for hurricane numbers, and how they have changed?
[Update: OK… I think I have to largely forgive them this. Their reference is wrong (it should be Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment, P. J. Webster, G. J. Holland, J. A. Curry, H.-R. Chang but it does say: “hurricanes in the strongest categories (4 + 5) have almost doubled in number (50 per pentad in the 1970s to near 90 per pentad during the past decade) and in proportion (from around 20% to around 35% during the same period). These changes occur in all of the ocean basins”. Thanks to SB for pointing this out -W]