appeared yesterday in the Dot Earth blog by Andrew Revkin at the New York Times, while a briefer, quite lucid (and more sympathetic) account was posted this morning by Elizabeth Kolbert at the New Yorker website. Hardcore readers can hear Hansen offer 'context' in this audio of a conference call with reporters linked by Revkin. All in all it's an important event, though I'm not sure how clear the moral is.
A few key facts: first, Hansen et al. published the paper as a 'discussion paper,' not yet peer reviewed, and intended for critical comment. Such publications are not meant to be definitive, but at the same time the authors used a publicist to highlight the importance of the findings--which are in fact quite alarming. In very brief, the paper--which Hansen distilled over the past 8 years by his account with 300 citations from reputable sources--suggests that with the impending collapse of the West Antarctic ice sheet, sea levels might well rise much faster and higher than previously estimated, to the point of 'swamping' coastal cities within several decades.The draft goes on to suggest the dire humanitarian and civil breakdowns that would be expected from such a disaster.
A pressing question is posed by Revkin: is it responsible to publicize such a preliminary 'discussion paper,' as Hansen clearly set out to do? He himself cites the urgency of the Paris conference as justification for getting the material into view--and he's right in a sense: the tone of complacency in much of the discussion leading up to Paris--and the near-total acceptance in mainstream articles of the 2C measure as a threshold for 'safety'--does indeed call for strident language, especially from scientists like Hansen who command a large audience. I agree with Hansen that putting forward this dismal scenario--which has considerable support in the scientific community, even as other scholars rush to challenge it--is a useful addition to the discussion leading up to Paris.
But the more pressing question is the substantial one: should we all be looking more closely at the range of scenarios, including disastrous feedback accelerators like the melting ice sheet (and there are others), rather than clinging to more optimistic, slower estimates, and dubious markers like the 2C benchmark? Is the problem with Hansen et al.'s work not that it is premature, or debatable, but that it is demoralizing, disempowering, ultimately counter-productive? In point of fact, from my non-scientist's angle, we will never quite know where we are with climate change, what's coming, or at what rate: climate just isn't knowable to that degree. So the question as we sift all this scientific data, hypothesis, and debate, is really not 'what's true' but what is useful: i.e., where do we draw that fine line between complacency and apocalypticism? How do we maintain an appropriate urgency in the tone of the discussion without scaring the world's leaders and its electorates into running away from it? Hansen may not appreciate this dilemma--it's not his role--but his work can usefully drive the discussion toward a more focused attentiveness. At this pivotal moment I don't see how that can hurt.