This piece of AFP news from Straits Times came into my attention through Google News: Estimated icecap loss halved . In it, it was said that new published research showed that glacial ice melting in Antarctica and Greenland is only half as much as previously thought because the older estimates "fail to correct for a phenomenon known as glacial isostatic adjustment".
Having scanned through the mentioned research article a couple of days ago and knowing something about this subject, I must say that the article is quite wrong in its summary of the results. First, glacial isostatic adjustment (GIA) is a very well-known but poorly-constrained problem in such estimates. All previous estimates do take into account GIA, but how they take it into account is another matter. Different ways of modelling GIA yields different results. There is currently no best method of doing so.
Some are simple: a direct linear elastic rebound with a constant upward velocity; some are more complicated. Of course, if we have observations -- which can be achieved through GPS stations -- that will be ideal, but planting a station in the middle of Antarctica isn't quite cheap or easy.
What the new article has to offer is a semi-empirical method of modelling GIA. It is certainly insightful and novel, but this does not mean that its estimates are necessarily more accurate than previous numbers. Certainly, as the authors have suggested, more GPS stations will better constrain the uncertainties and eliminate poor models.
From my perspective, the AFP journalist is either poorly equipped to interpret scientific research, or has an opinion which skewed his writing. Regardless, it is a very lousy piece of news.
If you're interested, the original research article is here. If that's too tough, there's an analysis by Nature as well.
07 September 2010
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