Over at Real Climate, my necessarily cautious words about the relationship between hurricanes and global warming were being taken in the comments section as a suggestion that there's no "evidence" that anything is happening. I had to chime in with a longish comment setting things straight, which I'll reproduce here:
There is certainly evidence of global warming's impact on the intensity of the average hurricane. However, it is evidence that some contest based upon questions about the quality of the data. It would be fair to say there is no "consensus" about the evidence, but not at all fair to say there is no evidence period. An important distinction. Second, I make the point that theoretical considerations--modeling and hurricane maximum potential intensity theory--lead to an expectation that the average hurricane *will* intensify even if it has not already. You seem to be ignoring this. Storm regions of formation and numbers are murkier issues. Was the appearance of 2004's Cyclone Catarina in the South Atlantic an anomaly representative of a truly changing planet, or the kind of event that we would see to have recurred in the past if we had better records? Nobody really knows for sure. As for storm number changes: There's an argument going on right now between scientists over whether the Atlantic is seeing a growing number of total storms because of global warming. Meanwhile, modeling results in this area don't lead to definitive conclusions; as the recent WMO statement puts it, "Although recent climate model simulations project a decrease or no change in global tropical cyclone numbers in a warmer climate there is low confidence in this projection. In addition, it is unknown how tropical cyclone tracks or areas of impact will change in the future." The WMO statement is available here. The statement also says that "If the projected rise in sea level due to global warming occurs, then the vulnerability to tropical cyclone storm surge flooding would increase." All in all: The science isn't settled on this subject (what else is new), but that hardly means that what we know isn't grounds for being concerned.