2011: the Mississippi flooding, the U.S. tornado season, and climate change.

Recently I was graciously invited to contribute to an online forum on possible links between the increasing frequency and severity of extreme weather events and climate change. The forum organizers asked a dozen climate experts (experts? Hmm. make that eleven plus one camp follower!) to write 250 words in response to the following two-part question:

Do you think there is growing evidence that human-caused global warming is contributing to more extreme weather events worldwide, and on what do you base your conclusion? Please cite an example or two of recent extreme weather events that you think either affirm, or refute, the contention that anthropogenic global warming is increasing the frequency and intensity of extreme events.

How kind of them to ask me to comment! Unless you’ve been vacationing on another planet, you’ve probably been following, as I have, the news of the past month, which has alternated between a focus on the Mississippi River flooding and the rather remarkable tornado season we’ve been having. Furthermore, most blog readers are probably also well aware that the IPCC has indicated that global warming should be accompanied by a rise in the extent and severity of extreme events. Quite natural, then, that these questions would be in the air. They should be! And all of us – whether so-called experts, or policy makers, or business leaders, or educators and journalists – should be entering the discussion.

So…a chance to weigh in? Heaven-sent!

But…limit the answer to 250 words? That was daunting. Fortunately, I had to reply in a hurry. Sometimes, instead of fostering sloppy work, such urgency helps us pare down our thoughts to a few essentials. Here, verbatim, is my response:

We live on a planet that does much if not most of its business through extreme events. What we call “climate” reflects the summing-up of these extremes to find averages. And what we call climate “variability” or “change” will therefore be reflected in variability or change in the locations, timing, patterns, intensity, and duration of these extremes.

 That said, the statistics of the extremes are inherently noisy. Teasing out long-term changes in the relationships linking the extremes and the averages merits concerted and sustained scientific attention, but will remain a multi-year aspiration as opposed to an easily achieved goal. Scientists – let alone non-experts – will be debating any findings for some time to come. [The most likely place to be convincing earliest may prove to be the statistics for heat waves and cold snaps.]

In the meantime, society has to deal with extremes. The truth is that we’re not proving very adept at coping with the extremes and hazards we’re facing today. Furthermore, the biggest change in our experience with hazards in coming decades is most likely going to prove the result of social change and technology advance: population growth, urbanization, and movements to hazard-prone areas such as coasts; dependence on critical infrastructure; the tendency toward zero-margin societies, in both the developed and developing world; and so on. Land-use and building codes; no-adverse-impact policies for levees and other hazard measures; learning from experience; and public-private collaborations for building community resilience are going to be urgently needed in parallel with the natural science.

There’s so much more that could be said. First, with regard to the science: I could have, and probably should have, referred to an extensive literature on this subject. Tom Karl and the folks at NCDC – and many others – have looked at precipitation events from this light. Judith Curry, Peter Webster, Kevin Trenberth, Kerry Emanuel, Chris Landsea, Max Mayfield, Tom Knutson, Gabe Vecchi, and an army of folks have analyzed the link to hurricane intensity, landfall, etc., upside down and sideways. The IPCC itself has considered this question of sufficient import to develop a Special Report on “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation,” with the policymakers’ summary scheduled for release in November 2011.

Second, you’ll note (and I freely confess) that I strayed from the question asked, which focused solely on the science, to talk about options for action.

Why do that? For two reasons. First, nature is going to yield its secrets to scientists only grudgingly.  Take tornadoes, for example. In a recent post, Judith Curry collected some of the relevant information, got a little discussion going. I particularly liked what she said in her summary:

Cumulative catastrophic weather events are being used to support the case for global warming action.  Sorry Bill and Joe, but we need to look at each type of extreme event, in different regional locations, and then interpret them in the context of the local historical records, and then cumulatively in context with the teleconnection weather regimes and multi-decadal oscillations.   Once we’ve done that and then find an upward trend in frequency and/or intensity that cannot be explained by problems with the data record or natural climate variability or weather roulette, THEN lets talk about the potential impact of global warming.

Get the point? Nailing down each piece of this extensive puzzle is going to take a lot of work.

The second reason? Extreme events are eating from our rice bowl, causing us pain and suffering, compromising our prospects – now. We need a policy effort that parallels the science to start stemming the losses. The key elements? No-adverse-impact policies, learning from experience, keeping score, and building private-public collaborations to build community disaster resilience. [LivingontheRealWorld has been choc-a-block full of posts on these issues.]

In any event, I, for one, am really looking forward to the broader dialog of the forum, and the conclusions to follow. I promise to share as soon as more information is available.