The correlation between sea surface temps and hurricane frequency is not linear, and direct cause-and-effect is not well-supported by computer models. Of particular importance is the activity of upper-atmospheric winds, which can scatter or shear rising columns of air over warm water, preventing organization of a depression into a cyclone. These shearing winds are also part of the ocean-atmosphere linkage that global warming affects. In short, even as more depressions (baby storms) form, more shearing winds also form, and blow them away before they start spinning. There's even some evidence that increasing ocean temperatures will eventually lead to *fewer* organized storms (i.e., hurricanes) as the shearing winds become more stimulated. No one knows for sure.
In short, global warming may, or may not, end up having an impact on hurricane frequency and strength, but right now, it's no more than a small increment above background noise. Instead, the rising intensity and frequency of hurricanes in recent years is part of a natural hurricane cycle that is reaching its peak.
Take a look here if you want to see the pattern yourself in the raw frequency data:
http://www.nhc.noaa.gov/pastdec.shtmlThe biggest driver of this cycle is decadal oscillations in total thermal content of the Atlantic...decadal as in, it takes decades for the cycle to rise and fall. The mechanisms driving decadal oscillations is ancient, and predates industrial activity. It is also poorly understood. Sea surface temps do not follow a simple pattern of general enhancement as the total thermal content of the ocean rises. The factors involved are complex and sometimes counterintuitive; among other things they involve the confluence and re-direction of deep ocean currents, and aberrations in ocean-atmosphere couplings called teleconnections.
Anyone who draws simple conclusions (such as "Global warming has nothing to do with hurricanes," or "Global warming is increasing hurricane strength, and it's going to get a lot worse") is at best overextrapolating from incomplete data or crude models. At worst, they are bending science to meet a political agenda. You can go out on the web right now and find articles and research that draw one or the other conclusion, often adamantly so. Hmm. That kind of says it all, doesn't it? Meanwhile, I notice there are very few articles out there saying the sun won't rise tomorrow or that gravity will be at half-strength in November.
Politics and science are every bit as nightmarish a mix as religion and science.
We all need to stay vigilant about letting our politics select which data drive our science. That goes double for highly-political people, like most of us here.
Peace.
"The essence of the Liberal outlook lies not in what opinions are held but in how they are held: instead of being held dogmatically, they are held tentatively, and with a consciousness that new evidence may at any moment lead to their abandonment."
-- Bertrand Russell