Three or four years ago, I heard a talk by Roger Pielke Jr. at an American Meteorological Society meeting that changed the way I think about the relationship between climate and human societies. It was about hurricanes, and he talked about Hurricane Mitch, which killed something in excess of 10,000 people in Central America - perhaps as many, by some counts, as 20,000. Roger's simple point, as I remember it, was that the dominant variable in the equation leading to that death toll was the fact that the people in Central America were sufficiently poor that they lacked the resources to not die.

At the time, I had been rather naively thinking that the threat of more powerful hurricanes as a result of global warming was a good argument in favor of reducing greenhouse emissions. Roger's talk convinced me that reducing societal vulnerability to the storms that will happen, warming or not, is a far more effective approach to helping people not die in hurricanes. I've since come to realize that, while there are good reasons to reduce greenhouse gas emissions, reducing societal vulnerabilities in a range of areas, from droughts to floods, is a far more important issue in coping with climate variability and change, both natural and human-caused.

I can't begin to keep up at this point with the important issues being raised by this discussion, but clearly Katrina offers an opportunity to crystallize this sort of thinking. Roger's got a blog now, and has a lot to say. Go read it.