I have only read the first few paragraphs, but know the rest of "Scientific reticence and sea level rise" will be fascinating. Jim Hansen bemoans the conservatism of science. Hmmm. I shall offer my thoughts this weekend, but wanted to point it out now so everyone can chime in as soon as possible.
Interesting article. A couple of questions - first, when Hansen says the current melting of ice sheets is close to 1 mm of sea level rise annually, I don't see how he got this. Using his 150 cubic km/year, I get something closer to 0.4 mm/year (yes, I took landmass into account). And more importantly, while I agree that the ice melting will probably be nonlinear, doesn't it seem like a stretch to immediately propose an exponential model? It seemed to me like he was just pulling that scenario straight out of thin air.
Tim, I thought it was pretty well written. The difference between his 1mm/year and your .4mm/year was that he used 300km2/year (150 greenland and 150 West Antarctic) (ok .8 isn't 1). His exponential model he admits is very ad-hoc, and not supported only by extrapolation of very short time-series data. The case that the rates will very likely increase non-linearly is pretty strong, although what form it will take clearly is not yet apparent.
If the extrapolation is, by Hansen's own reckoning, _ad hoc_, isn't reticence appropriate?