“Scientists have yet to prove any causal relationship between global warming and the frequency and intensity of Atlantic hurricanes.”

Webster says (in his interview on the AAAS site):

“The variability of hurricane intensity is almost certainly a complex interaction of natural variability superimposed on a longer term warming trend. Natural cycles of variability (such as El Niño, North Atlantic Oscillation, Pacific Decadal Oscillation) individually have signals that are predominant in certain regions.” He didn’t exclude the North Atlantic basin from this assessment.

The two statements are not literally inconsistent, but a certain figurative difference is apparent.

“Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment” by Webster et al.

Here is the concluding paragraph, which I found interesting:

“We conclude that global data indicate a 30-year trend toward more frequent and intense hurricane, corroborated by the results of the recent regional assessment(29). This trend is not inconsistent with recent climate model simulations that a doubling of C0_2 may increase the frequency of most intense cyclones(18,30), although attribution of the 30-year trends to global warming would require a longer global data record and, especially, a deeper understanding of the roles of hurricanes in the general circulation of the atmosphere and ocean even in the present climate state.”

Correlation does not mean causation and the Nature paper indicates that only part of the sharp increase in PDI in recent years can be directly explained by SST (Pg 688). Other factors such as vertical wind shear, temperature distribution are just as important.

I do not work in this field, but would be very interested in knowing if scientists can conclusively say that the same causes that might increase global warming (land-use pattern shift, rainforest reduction, atmospheric pollution etc, etc) are causing more intense hurricanes, thus showing a strong correlation between SST and hurricanes.

thanks,
Joyoni Dey, PhD

Thanks for the question. I do think that Krauthammer’s statement is too strong. I’d be comfortable with something like the following:

“Scientists have yet to prove any causal relationship between global warming and the frequency and intensity of Atlantic hurricanes.”

Whether GW makes hurricanes worse, or reducing emissions is good policy are moot points if our government doesn’t listen to evidence, or the media refuses look seriously at any issue that generates negative e-mails from a small segment of the population. It doesn’t matter what effect GW has on weather because our government will ignore it just the same.

There will be many Katrinas in many different forms. GW is just one of them.

Dylan: We need to protect against a cat 5, but we don’t need to concern ourselves immediately with global warming effects because those impacts are 50 plus years out. Of course, we could get more abrupt global warming than the models call for, but that’s unlikely.

Politician: When is that next cat 4 or 5 likely to hit NO?

Dylan: It could happen soon, but probably it will be at least 30 to 50 years.

Politican: Just to make sure I’m clear on this, let me be more specific: Will it happen during my active political career?

Dylan: Well, probably not.

Politician: OK, then I’ll take your good advice about global warming and apply it across the board. After all, neither are really immediate threats.

Dylan: Yes, but what about the statistics showing all that hurricane damage in the next 30 to 50 years?!

Politician (getting into his SUV): That’s for the entire coast! You just admitted that another hit on NO in that time frame isn’t very likely.

Dylan (desperately): But I only wanted you to discount the 50 to 100 year future!

Politician (driving off): What I needed was something consistent I can tell my voters. Thanks for giving it to me!

—————

I would suggest that a single focus with two aspects would be a better approach.

Also, speaking as one of those accursed environmentalists, I think we’re pretty well surrounded by more than sufficient evidence for global warming. Per current polling, the public is rapidly coming into agreement with that. The seizing of the Katrina issue is motivated not by the desire to convince sceptics (who will ever be with us) of global warming’s reality but by the need to demonstrate that we have to start doing something serious about it now.

Also, Roger should correct me if I’m wrong, but I think his “no regrets” argument very much favors immediate major emissions reductions on the grounds that there are plenty of good environmental, economic and security reasons to do so even if global warming were not happening. I don’t disagree in principle, but would observe that those other good reasons in and of themselves don’t seem to have been enough so far (although the peak oil and national security factors have changed so much recently that they may yet do the job once their implications have a chance to sink into the collective thick noggin of the American body politic).

“It’s easy to use the tragedy of Hurricane Katrina to call attention to human-caused global warming, as Nicholas Kristof did in his New York Times column on Sunday. But the scientific evidence currently is too thin to blame Katrina and other hurricanes on carbon dioxide emissions. And environmentalists may risk embarrassment if they exploit the theoretical link to promote their causes.”

I see no problem with stating that there is evidence to suggest GW effects weather, if that’s true. Considering the fact that GW probably has a small effect on hurricanes, and that reducing emissions won’t do much to stem them for quite some time, it seems to me to be the wrong focus.

The issues more brought into focus are whether the federal government should play a role in natural disasters, and how to get government to listen to science (which, in the end, will help the “cause” of Gore more, since the science is being ignored there, too). What would benefit Gore the most is a return of a respect for science’s role in informing policy makers, and a recognition that federally funded research has a purpose.

I think environmentalists are latching onto this because they want a concrete example of GW. This is due to the fact that although consensus clearly shows a human contribution to climate change, we spend all our time in the media debating about “if”, when it should be about what, if anything, should be done about it. So we never actually get around to discussing the points Pielke raises about whether reducing emissions is the right route to go because accepting consensus would cause CNN get angry e-mails shouting “Why didn’t you show the other side?”

We’ve successfully avoided the policy debate by keeping the focus on whether it’s occurring at all. The lasping onto Katrina by environmentalists seems to be motivated (not justified) by a desire to settle the argument of whether it’s occurring once and for all.

One last point: I do think journalism has a lower bar for bringing up certain topics. There’s no consensus on String Theory, for instance, but you can talk about it. Scientists can voice their opinions, and these are valuable because scientists are experts in their field. (What I ojbect to is pundits offering their uninformed opinions as science). As long as it’s clear where consensus lies, and what the data shows vs. where researchers think it’s heading, I’m okay with it. At least it’s a scientist’s view of these things, which is an improvement. But you’re right, the peer-reviewed research is the bottom-line, so to speak.

Regarding your quote of Emanuel with repect to the next 30-50 years, as you know it is the 50-100 year time frame that is of more concern with regard to global warming impacts. I know you’re not really saying this, but putting it in those terms buys in to the “discounting the future” mentality that’s gotten us into the pickle we’re in now. From the point of view of one of these politicians, when they hear that we don’t have to worry much about global warming impacts until 50 plus years out and combine that with information about the likelihood that another levee-breaching event will hit NO in the next 50 years, they see that as a free pass to make only minor adjustments to present coastal development patterns. And of course it is very likely indeed that they, just like the past politicians who decided to only build the NO levees up to a cat 3 level, will be long gone before it’s time to pay the piper.

This is an example of what we’re up against: I spent much of the day yesterday interviewing candidates for the Sierra Club endorsement for mayor of Oakland, CA (SF Bay area, pop. 400k). Because of Katrina, just now the issue of what will happen in the inevitable maximum earthquake on one or the other of our local faults (the Hayward or the San Andreas) is rather higher on their agenda than would normally be the case. The level of ignorance was still amazing. Not one of them was able to successfully answer the general question of how good our current plan and preparations are for the event. There were even more at sea with respect to the specific question of how much of Oakland’s population will be rendered homeless and how that will be handled (even assuming the situation isn’t compounded by major fires). Again, this was in the SF Bay Area where one would expect the level of information about such things to be rather better than average. Underlying their ignorance (I think) is an unconscious assumption that probably “the big one” won’t happen during their political careers.

Sorry if that turned into a bit of a rant, and of course this discussion is far more complex than I’ve had the time to lay out here. I’ll close by suggesting that it might be that you would make a more effective contribution to the present debate if you focused more on the damage that will result from increasing global warming, and less on it not being a major short-term factor (and this is not to suggest any softening of your stance on current exposure absent any AGW effect). Your present approach may be good science, but the one I suggest is equally good science and has the advantage of not sending an unintended mixed message to the politicians.