Date: Sun, 4 Feb 2007 16:37:34 -0500 (EST) To: letters@nytimes.com Subject: Sea Level Rise Regarding Andrew Revkin's article in today's Week In Review: Most popular summaries of the subject of sea level rise in the Fourth Assessment Report of the UN's IPCC misconstrue the predictions presented. In the Third Assessment Report, released in 2001, the scientists attempted to model the flow of ice off of Greenland and Antarctica in order to predict the increased sea level in the year 2100. Between 2001 and 2006, it became clear that our understanding of melting glaciers was inadequate. Accordingly, rather than speculate on the dynamics of melting, the report simply includes the rate of ice flow as observed from 1993-2003, and allows for no additional increase as the temperature warms up. Accordingly, the upper limits on sea level rise was reduced to 20 inches or so, lower than the numbers presented in the 2001 report. Some (especially those disinclined to believe global warming to begin with) are taking this to mean that the scientists have reduced their estimate for the risk of larger sea level rises. The rebuttal to this is found in the text of the report itself, right below the column of numbers so often quoted. There it says, "Larger values cannot be excluded, but understanding of [ice flow] effects is too limited to assess their likelihood or provide a best estimate or an upper bound for sea level rise." Your article seems to indicate that sea level rise is only something to be worried about in the course of thousands of years. Unfortunately, we still don't know if that's true, and, unfortunately, there is no solace to be found in the Fourth Assessment Report. Mitch Golden