Timed for the Katrina anniversary, the Competitive Enterprise Institute has put out a short report on the hurricane-climate issue (PDF). Without taking a premature stand on who is or isn't winning the scientific debate at the present moment, I'd like to point out how CEI misrepresents the state of that debate. The chief technique seems to be to debunk strawman arguments that no one is actually making. Consider the following:
Claims of a definite link between hurricanes and global warming rely on the simple hypothesis that, as waters warm, storms get stronger. In fact, some storms may get stronger, but others may get weaker. There are two main types of storms: hurricanes (tropical cyclones) and winter (frontal) storms. Global warming is likely to affect each type differently.... Winter storms draw their energy from the collision between cold and warm air fronts. If, as climate models predict, higher northern latitudes warm more than do lower tropical latitudes, the temperature differential between colliding air masses should decrease, reducing the intensity of some winter storms.
Voila: Strawman number one. The central debate that CEI presumably wants to address, and which was greatly amplified by Hurricane Katrina, involves hurricanes and climate, not extratropical cyclones (winter storms) and climate. So CEI"s above comment is completely off topic, especially in a report tied to Katrina. Katrina wasn't directly caused by global warming, but it also wasn't a snowstorm. [Moreover, whence this idea that there are "two main types of storms"? Where do ordinary thunderstorms fit into this dichotomy? And what about tornadoes? CEI is practicing pretty bad meteorology here, it seems to me.] Pretty soon CEI finds another strawman to attack:
Alarmists often claim that Japan has seen an increase in typhoon activity due to global warming. Figure 4 shows the number of tropical storms and typhoons (Tropical Cyclones) over the Western North Pacific, from 1950 through 2005. The data simply do not reveal a linear trend corresponding to the gradual increase in atmospheric CO2 levels. Further, whether a particular storm "hits" Japan--its trajectory--depends on local meteorological factors, not on average global temperatures.
There are multiple ploys here. First, the hurricane-climate debate of the present moment centrally turns on whether storms are intensifying, not on whether they are increasing in number. Yet here CEI is talking about numbers rather than intensity. Let's call it strawman number two. Second, who is arguing that global warming affects the "trajectory" of "particular" storms? No one that I'm aware of, because that would be ridiculous. Yet by debunking this silly concept, CEI implies that some unspecified group of "alarmists" actually hold the position. Call it strawman number three. Finally, although such individuals may exist, I am not myself aware of anyone who has explicitly stated that Japan's really bad 2004 typhoon season was a direct result of global warming. Sure, the season broke records with 10 typhoon strikes on the islands of Japan. So it naturally gets pulled into the discussion by Al Gore and others who are highlighting weird weather phenomena. But I suspect that if you asked him, Gore would admit that he was not implying a direct causal connection. (Granted, anyone discussing the 2004 typhoon season in a climate change context ought to be sure to draw distinctions about what he/she is or is not saying.) Meanwhile, here's CEI again:
Another alarmist rhetorical gambit is to point out that during the 2005 hurricane season, there were so many storms that NOAA ran out of assigned names for them.
Well, there were so many storms that NOAA ran out of assigned names for them. Does this directly prove the hand of global warming? Of course it doesn't--but who said it did? Once again, tropical cyclones Alpha through Zeta inevitably come up when hurricane anomalies are being discussed. But I'd be surprised if we could find an academic scientist who thinks these storms directly prove a climate influence. Let's call it strawman number four. Granted, it's not beyond the realm of possibility that CEI may be able to dredge up a few bloggers or pundits who, not really understanding the issues, have erroneously made statements of the sort that the CEI report endeavors to debunk. But I'm confident that no one seriously engaged in, or seriously following, the hurricane-climate debate embraces these positions. And as for people like Al Gore--presumably one of the central targets of the CEI report--I have seen his movie, and he does not explicitly make these arguments. (Again, Gore could have been more clear about what he was and wasn't saying.) Finally, I'd like to add that I am very tired of the use of this word "alarmists," which appears throughout the CEI report with a frequency that appears deliberate. The hurricane-climate debate is a serious one with serious people on both sides of it. The scientists who detect a hurricane-climate influence today are not "alarmists," and those who question it are not "deniers." CEI's report could have used a lot more nuance--and a lot fewer attacks on positions that nobody actually holds.