That said, looking at Emanuel’s next to last paragraph he seems to be saying that if one goes back a little farther in time than his paper did, enough data appears to make the connection for the Atlantic. Am I not reading this correctly?

Finally, I notice that the timing of sunmission of the comments seems to have precluded you and Landsea from commenting on the 2005 season even though Emanuel was able to, and that Landsea described the 2004 season as “extreme.” Any idea what the Atlantic PDI is for 2005? If it looks anything like I suspect it will, Landsea may find himself faced with thesaurus suggestions like “catastrophic,” although I suppose he could just cop out with “even more extreme.”

Thanks for these comments. Yes, I hear the same things from scientists and right now we are in a situation where different people have different expectations about what future research will reveal regarding to role of AGW on hurricane behavior. I haven’t taken a poll but I’d bet that most climate scientists expect that future research will show a clear connection between AGW and trends in (and future behavior of) hurricane intensity. Note that in the recent exchange between Landsea and Emanuel, Emanuel clearly disassociates the PDI trend in the Atlantic from the AGW signal. So I don’t think explaining the 2005 situation in the Gulf is nearly as wide open as you describe. Again scientists may discover a clear linkage but today it remains only speculation.

However, identifying a trend in a physical parameter or index and showing that such a trend is societally relevant are two different things, as you allude to. To date, I am convinced that whatever trends may be found in past hurricane behavior related to whatever cause, they are far less important than patterns of development. Looking to the future I’d advance this as a hypotheses, i.e., with respect to loss of life and property damages, societal change will continue to be the overwhelming factor driving losses. If there is research to suggest otherwise, I am open to it, but it is not there yet.

When I was at the AGU meeting, there seemed to be a growing consensus among those I chatted with that AGW is likely making some contribution to hurricane strength based on the following line of reasoning:

1) based on both thermodynamics and shown during 2005, warmer waters make for stronger storms

2) ocean temps have been increasing

3) greenhouse gases are responsible for some part of the increase in ocean temps

Conclusion: it is likely that hurricanes are having some impact. (and I use “likely” as the IPCC does … 75% chance true)

I think that you’re going to see more and more research supporting these three points as time goes on, as well as a growing agreement among relevent scientists.

It seems that the real question is how much of an impact AGW is making on hurricane strength — e.g., what role did humans play in the warm Gulf of Mexico this year? I think this is a wide open question. It might be that the impact of AGW is negligible compared to other variability.

Regards.