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Wednesday July 6th 2011

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Scientists withdraw low-ball estimate of sea level rise — media are confused and anti-science crowd pounces

Projected sea level rise

The 2007 IPCC Fourth Assessment Report (AR4) report ignored dynamic ice-sheet disintegration, which was already happening (see Nature: “Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized”).  The IPCC therefore low-balled sea level rise estimates, suggesting seas might rise “only” a foot or two this century, greatly delighting the anti-science crowd (see “Debunking Bjørn Lomborg:  Misrepresenting Sea Level Rise“).

Within a year, even a major report signed off on by the Bush administration itself was forced to concede that the IPCC numbers were simply too out of date to be quoted anymore (see US Geological Survey stunner: Sea-level rise in 2100 will likely “substantially exceed” IPCC projections).  About half a dozen major studies since the IPCC report concluded that we face much higher sea level rise this century (see “PNAS Study:  Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100” and links therein).

The figure above from the PNAS study is especially alarming since we are currently on the A1F1 emissions trajectory (see “U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” — 1000 ppm“).  In short, we appear to be on track for 1.4 meters (56 inches) of sea level rise.

So the anti-science crowd was delighted when a Nature Geoscience study suggested that the IPCC estimates might not be so far off.  The top anti-science website, WattsUpWithThat, cheered, “Sea level rise by 2100, “nailed”! Between 7 and 82 centimeters” (3 to 32 inches).  At the time RealClimate scientists explained why the study was flawed.

Well, it turns out that the RC scientists were right — but the anti-science crowd is now cheering the withdrawal of the paper!  Brad Johnson explains how that could be:

What follows is a Wonk Room repost.

Scientists who challenged the possibility of catastrophic sea level rise in coming decades have retracted their argument. Mark Siddall, whose paper claimed sea level rise from global warming could not be more than 82 centimeters (32 inches) by 2100 — despite other estimates of up to 1.9 meters — asked for the conclusions published in 2009 in Nature Geoscience to be retracted, accepting corrections from researchers who had made the higher estimates. The Guardian misleadingly presented the news with the headline, “Climate scientists withdraw journal claims of rising sea levels“:

Study claimed in 2009 that sea levels would rise by up to 82cm by the end of century – but the report’s author now says true estimate is still unknown.

If all one read was the introduction, a reader might get the false impression that sea level rise from global warming is in doubt. The misleading Guardian headline was picked up — as per usual — by the Drudge Report and Marc Morano’s conspiracy site Climate Depot. Right-wing bloggers, unsurprisingly, latched on to the headline without any comprehension of the story:

Betsy Newmark: Another global warming claim that has had to be retracted because of problems with the data.

Sammy Benoit: OOPS Never-mind! Climate scientists withdraw IPCC-related article claiming sea is rising.

JammieWearingFool: Another global warming myth comes crashing down. No warming since at least 1995, no melting glaciers and now no rising sea levels.

Jules Crittenden: Warmal scientists are compelled to admit (again) that they don’t know what they’re talking about, retract study that predicted up to a nearly three-foot sea level rise by 2100.

Law professor William A. Jacobson: But now the seas are not going to rise? My dream of a waterfront home is melting away faster than the glaciers.

Caleb Howe: Yet another card removed from the geodesic dome of cards that is AGW hysteria.

However, the retraction instead admits that the paper’s calculations for an upper bound to future sea level rise were incorrect, and sea level rise could be much worse. Siddall’s study, “Constraints on future sea-level rise from past sea-level change,” used paleoclimate reconstructions to predict that sea level rise from global warming would be constrained to between 7 cm and 82 cm (3 to 32 in) by the end of the century, in line with the estimated sea level rise in the 2007 Intergovernmental Panel on Climate Change (IPCC) report, which excluded possible effects from ice sheets.

Unfortunately for the future of human civilization, the best scientific estimates of future sea level rise continue to worsen, as it becomes evident that the Greenland and Antarctic ice sheets are losing mass much more rapidly than estimated before 2007. December’s “Global sea level linked to global temperature,” published by Martin Vermeer of the Helsinki University of Technology, Finland and Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany in Proceedings of the National Academy of Sciences projects a catastrophic rise of 0.75 to 1.9 m (2.5 to 6 feet) by 2100 (see figure above).

Over the past twenty years, actual sea level rise has been at the top of estimated limits since the first IPCC report in 1990. By 2200, scientists warn, the oceans could rise by more than three meters, submerging cities like Los Angeles, Amsterdam, St. Petersburg, and lower Manhattan.

JR:  Another dreadful media headline, another round of anti-science confusion.  WhiskeyFire exclaims, “This is getting monotonous.”

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This article was originally posted on Climate Progress