Thursday, February 11, 2010

Science - a human endeavor

Science is a creative human activity that it's been my privilege to participate in for the majority of my adult life. I've had to work at the actual process and gain understanding (as well as knowledge of my limitations) in my chosen field - but a bigger challenge has been to understand science as a human activity. This blog is no place to go into this in detail, but I want to comment about one small part of the process, using a particular example.

In order to be a contributor to science, each individual has to have a unique perspective and use that vantage point as a take-off point for exploration of ideas. In the process, the practitioner inevitably comes to ideas that either break entirely new ground (quite rare) or challenge existing concepts. If you do anything at all in science, your ideas will challenge those of other scientists. Confrontation is virtually inevitable so long as the science is alive and active (see here for an extended discussion). And when those whose ideas you're challenging learn of your new ideas, they'll have strong motivation to find fault with what you've done. In other words, they'll be in a defensive mode, fighting your ideas with those of their own, and seeking to discredit your version in order to protect theirs. This amounts to a sort of "marketplace of ideas" in which each of us becomes a salesman for their scientific creations. The market determines the survivor by a process of reaching a consensus about new ideas, although the process can unfold over a long time. The poster child for this process is Wegener's ideas about continental drift, which when introduced were summarily dismissed in that marketplace, only to emerge many decades later when new technologies provided the evidence that Wegener lacked to buttress his hypothesis.

Recently, I've been encouraging the National Hurricane Center (NHC) to review their assessment of the intensification of the tropical storm known as Erin in 2007, which reintensified over land. It's pretty evident that the system by which NHC classifies storms has the usual problems that any taxonomy does - reality often fails to fit into neatly organized categories with arbitrary boundaries. Because this storm had declined in intensity after landfall, as hurricanes usually do, it passed a threshold whereby it fell out of their purview. In effect, NHC had washed their hands of it before it reached Oklahoma, and when it re-intensified over Oklahoma, it must have been something they must have wished would just go away. As discussed below, their assessment seems to reflect this wish.

Of course, most landfalling tropical storms have a life that continues for a time after landfall but they typically don't reinvigorate over land because science has shown that such storms derive their energy from heat flux out of warm ocean waters. How could such a storm intensify over land? If it's intensifying, then that process must be by some mechanism that would disqualify it from tropical storm status. This is essentially the argument cited by the NHC authors in their assessment.

In this case, prior heavy rainfall had transformed most of central Oklahoma into a warm, shallow sea - standing water was everywhere. The process by which tropical cyclones can intensify over land has been described in a recent paper by Prof. Kerry Emanuel and his collaborators* - who gave such events their own unique name: agukabam. The name is derived from the Australian aboriginal language, because they had only been documented in Australia - until Erin in 2007.

Recently, a group of NHC authors published a review of the 2007 Atlantic hurricane season** and concluded that Erin's overland intensification didn't meet their criteria for a tropical storm and so had deemed it simply to be a "low" - which is roughly comparable to calling a tornado a "low" - it's true that the system involved reduced pressure at its core, of course. But the vast majority of the scientific community has agreed that this was not just any old low pressure system. It had once again become a tropical cyclone, with all the earmarks of such a system: a warm core, spiral bands, increased winds (not to hurricane force, though), and even an eye. So why does NHC wish to avoid calling a spade a spade, in opposition to the meteorological consensus? I can't answer that, of course. I wasn't involved in the discussion.

I've recently learned from a source at NHC that if such an event were to happen again, it would likely be considered as a tropical cyclone by NHC. Thus, they seem to have adopted a new policy that amounts to a revision of their concept of what qualifies as a tropical cyclone. So why would they insist on continuing to defend their published assessment of Erin? I can only speculate about their reasons. There's an easy solution to this dilemma: I believe the best and most honorable thing to do is for NHC to publish a retraction of those conclusions from their recently-published paper. This retraction would, in fact, be consistent with their new policies regarding such events and with the scientific consensus about the issue of what constitutes a tropical cyclone. Otherwise, the erroneous assessment will remain in the scientific literature as a very public example of a process gone wrong.

Perhaps someone will publish a 'comment' about that misclassification, of course. Unfortunately, the usual 'comment - reply' process carries with it a sort of adversarial overtone that could result in a defensive response by the NHC authors. Such a reply by NHC would be unfortunate and could convey the impression that the NHC is engaging in defensive rationalization rather than participating in meteorological science. I would hope it wouldn't have to come to someone submitting comments about this mistake - it would be a credit to NHC for them to submit on their own a retraction to the journal (Monthly Weather Review) that published their 2007 storm season summary.

But science is done by humans, with egos and positions to defend, and who often struggle to make public admission of error, as if it's some sort of disgrace in science to have been wrong. In our marketplace of ideas, mistakes are common and easily forgiven if admitted to and repaired when they become known. It seems to me that the time has come for NHC to admit they made a mistake and move on. And tropical storm science will show by this example that it's mature enough to learn from its mistakes.

* Emanuel, K., J. Callaghan, and P. Otto, 2008: A hypothesis for the redevelopment of warm-core cyclones over northern Australia. Mon. Wea. Rev., 136, 3863-3872.
** Brennan, M.J., R.D. Knabb, M. Mainelli, and T.B. Kimberlain, 2009: Atlantic hurricane season of 2007. Mon. Wea. Rev., 135, 4061-4088.