IF we don’t get off our current emissions path
Sea levels may rise three times faster than the official predictions of the Intergovernmental Panel on Climate Change (IPCC) and the global average sea level may increase by as much as 1.9 metres (6ft 3in) by 2100, scientists said yesterday.
The new assessment comes just one week after another international scientific body concluded that the IPCC had been too conservative in estimating a maximum of 59 centimetres of sea level rise this century as a result of global warming.
That’s the UK’s Independent reporting on a new study in Proceedings of the National Academy of Sciences, “Global sea level linked to global temperature” (open access), by Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research and Martin Vermeer of Helsinki University of Technology in Finland.
The figure above is from the study, with the caption, “Projection of sea-level rise from 1990 to 2100, based on IPCC temperature projections for three different emission scenarios (labeled on right…). The sea-level range projected in the IPCC AR4 [Fourth Assessment Report, 2007] for these scenarios is shown for comparison in the bars on the bottom right. Also shown is the observations-based annual global sea-level data (red).”
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“), though I am hopeful that the agreement coming out of Copenhagen coupled with the bipartisan U.S. climate bill will take us off that trajectory.
But the bottom line is that if we listen to the anti-scientific ideologues urging inaction, the midrange sea level rise projection is now about 5 feet by century’s end. And that is consistent with many other recent studies –see, for instance, Startling new sea level rise research: “Most likely” 0.8 to 2.0 meters by 2100.
While that 2008 study was quite comprehensive for its time, it projects under 15 cm (6 inches) of SLR from Antarctica in its 0.8 m case and 62 cm (2 feet) in its 2.0 m case. Yet WAIS alone could exceed that, see “Q: How much can West Antarctica plausibly contribute to sea level rise by 2100?” [A: 3 to 5 feet]. See also Satellite data stunner: “Our data suggest that EAST Antarctica is losing mass”¦. Antarctica may soon be contributing significantly more to global sea-level rise.”
The other study referenced in the news article is from the Scientific Committee on Antarctic Research, which endorsed Dr Rahmstorf’s 2007 assessment of future sea level rise. SCAR — a perfect acronymn if ever there was one — explains in their news release here:
Loss of ice from the West Antarctic ice sheet is likely to contribute some tens of centimetres to global sea level by 2100. This will contribute to a projected total sea level rise of up to 1.4 metres (and possibly higher) by 2100.
The Independent article on the new study notes:
Last week the Scientific Committee on Antarctic Research endorsed Dr Rahmstorf’s 2007 assessment of future sea level rise, when it agreed that the IPCC will have to increase its future predictions. Dr Rahmstorf said that if the committee agreed with his earlier assessment, it is also likely to go along with his latest study, predicting a 1.9m rise.
Another 2007 study from Nature Geoscience came to the same conclusion (see “Sea levels may rise 5 feet by 2100“). Leading experts in the field have a similar view (see “Amazing AP article on sea level rise” and “Report from AGU meeting: One meter sea level rise by 2100 “very likely” even if warming stops?“). Even a major report signed off on by the Bush administration itself was forced to concede that the IPCC numbers are 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).
And don’t forget this 2009 study “” Nature sea level rise shocker: Coral fossils suggest “catastrophic increase of more than 5 centimetres per year over a 50-year stretch is possible.” Lead author warns, “This could happen again.” And this one, too “””High Water: Greenland ice sheet melting faster than expected and could raise East Coast sea levels an extra 20 inches by 2100 “” to more than 6 feet.”
The study’s abstract makes clear the projection is based on empirical data
We propose a simple relationship linking global sea-level variations on time scales of decades to centuries to global mean temperature. This relationship is tested on synthetic data from a global climate model for the past millennium and the next century. When applied to observed data of sea level and temperature for 1880-2000, and taking into account known anthropogenic hydrologic contributions to sea level, the correlation is >0.99, explaining 98% of the variance. For future global temperature scenarios of the Intergovernmental Panel on Climate Change’s Fourth Assessment Report, the relationship projects a sea-level rise ranging from 75 to 190 cm for the period 1990-2100.
“Since 1990, sea level has been rising at 3.4 millimetres per year, twice as fast as on average over the 20th century. Even if that rate just remained steady, this would already lead to 34 centimetres rise in the 21st century,” Dr Rahmstorf said.
“But the data show us clearly – the warmer it gets, the faster the sea level rises. If we want to prevent a galloping sea level rise, we should stop global warming as soon as possible,” he said.
The time to act is most definitely right now. The alternative may look something like this: