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Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100

By Joe Romm on December 9, 2009 at 10:15 pm

"Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100"


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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 endAnd 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.

Rahmstorf explains:

“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:


Automakers: Reduce Emissions By Letting The Market Dictate Which Technologies Can Succeed

China in Copenhagen Day 3: Tuvalu raises the bar, China reacts

18 Responses to Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100

  1. Leif says:

    Joe: I sure hope that you can find some uplifting news to report while you are over there. I don’t know how much more this old bag of bones is going to be able to take.

  2. Wes Rolley says:

    Actually, this makes great political theater. CA Governor Schwarzenegger announced California’s Climate Adaptation Strategy Report on Treasure Island in San Francisco Bay… emphasizing that the land he was standing on may be under water. It is also the location for a major Mayor Gavin Newsome project for low income housing.

  3. Tranche Demerde says:

    Hansen says there was a global sea level rise of 15 feet per century for four centuries in a row when the last great ice sheet disintegrated. This was the Laurentide, which covered Hudson’s Bay and parts of the rest of Canada.

    I don’t understand these guys who are studying ice now who say they can’t figure out how something like that could happen enough to put it into a model, therefore it is unlikely.

  4. Joe Bftsplk says:

    The recent OECD study “Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates”

    ranked Miami as the number one city in the world, for the sheer scale of damage it is going to be hit with, calculated in US dollars, for a scenario set in 2070 which assumes 0.5 meters of sea level rise (1.6 feet).

    The current city, if that’s all that was there in 2070 would have $416 billion in assets “exposed” which means they’d have to protect them from the sea or lose them. The projected growth of the city by that date would result in $3.5 trillion exposed.

    And if the sea level rose by more than that….

  5. jorleh says:

    Joe: in Denmark? Have a look of the Baltic Sea. Ask somebody there of the winter ice of the BS. No more winter ice, I can tell.

  6. Jim Bouldin says:

    Martin Vermeer is the lead author on the paper, not Stefan Rahmstorf.

  7. From Peru says:

    Emissions should be stopped now.

    And one degree warming is already “in the pipeline”
    Probably too late for Polinesia and the Arctic.

    But do you thik cap-and-trade will be the answer?
    That can reduce 30% our emissions. That is like running a car at 100km/h towards a hard wall and then reduce the velocity to 80km/h.

    We still die in the impact(maybe some millisecond later…)

    What is needed is a WWII-type-planned-economy transition. The market is simply too slow to do the trick.

    Probably DAI treshold is ALREADY PASSED… and we are still below 1ºC warmer….. imagine +2ºC….(the target “safe” warming)

  8. Leland Palmer says:

    Hi Joe-

    I ran across this paper recently, which seems to indicate substantial releases of methane from methane hydrates within the past one sixty thousand years. The isotope signatures seem to indicate about 17 separate apparent methane releases from the methane hydrates, in the period from Sixty thousand to about fifteen thousand years ago:


    Carbon Isotopic Evidence for Methane Hydrate Instability During Quaternary Interstadials

    James P. Kennett,1* Kevin G. Cannariato,1 Ingrid L. Hendy,1 Richard J. Behl2

    Large (about 5 per mil) millennial-scale benthic foraminiferal carbon isotopic oscillations in the Santa Barbara Basin during the last 60,000 years reflect widespread shoaling of sedimentary methane gradients and increased outgassing from gas hydrate dissociation during interstadials.

    Furthermore, several large, brief, negative excursions (up to -6 per mil) coinciding with smaller shifts(up to -3 per mil) in depth-stratifed planktonic foraminiferal species indicate massive releases of methane from basin sediments. Gas hydrate stability was modulated by intermediate-water temperature changes induced by switches in thermohaline circulation. These oscillations were likely widespread along the California margin and elsewhere, affecting gas hydrate instability and contributing to millennial-scale atmospheric methane oscillations.

    Joe, with the dynamic thinning of the ice sheets that is going on, and with any large release of methane from hydrates, well, trying to estimate what is going to happen in such a situation seems inherently difficult. I hope that 180 cm is the upper limit, but really, I don’t believe it. Likely it’s more. All the estimates seem to be getting bigger, these days.

    Past releases of CO2 that triggered methane releases from the hydrates had more randomness to them, and did not have the relentless, unceasing one way forcing that our fossil fuel use has, I think, nor did they generally occur as rapidly, nor was there so much interference with the biosphere’s ability to adapt to the changes.

  9. Will says:

    Joe, you have to see this if you haven’t already. 50 youth storming an AFP denier event. http://www.youtube.com/watch?v=ZZw8yF5alkM

  10. ken levenson says:

    does it make anyone else terribly nervous that we seem to be doubling the projected rise every few years?

    A Moore’s Law for Ice Melt seems in the offing. (bonus points for finding the pun! ;) )

    Or maybe that’s doubling every few, couple, single years….more like the Fibonacci series of progression…now that’s scary!

  11. mauri pelto says:

    Ken what does not make sense is the IPCC low estimate in 2007. They had clearly been very conservative in using any of the acceleration data or thinning data from Greenland or Pine Island Glacier. Tranche the models can replicate the rapid ice losses projected at the termination of the last ice age, they could 20 years ago. The problem is not replicating what you know happened, but forecasting what will happen.

  12. Mike#22 says:

    (from page 6 of the study)

    “In addition, highly nonlinear responses of ice flow may become increasingly important during the 21st century. These are likely to make our linear approach an underestimate. Therefore, we have to entertain the possibility that sea level could rise faster still than suggested by the simple projection based on Eq. 2.”

    I wonder if they ran the projection ahead to 2200 Anno Domini?

  13. WAG says:

    Joe – there’s a banner ad to the right hand side with protesters saying “Say no to Joe!”

    They’re talking about Lieberman, but I thought it was kind of funny.

    [JR: Saw it, yes. Funny.]

  14. Here is an interesting, interactive Web site that shows the impact of sea-level rise on major US cities:


  15. Joe Bftsplk says:

    According to Hansen, the IPCC in 2007 simply left out all consideration of what contribution to sea level rise disintegration of the ice sheets over Greenland and Antarctica could cause.

    The IPCC “quantified the thermal expansion of the ocean and the melting alpine glaciers and they have simply not dealt with this Greenland/Antarctic problem because it’s difficult”

    And as for how much any particular prediction at this point is worth:
    “this is a very nonlinear problem and maybe there’s going to be big response even in a hundred years but we just can’t evaluate it” although scientists are taking a crack at it.

    And it isn’t so much what happens by a certain date – the reason Hansen started calling for 325 – 350 ppm is his studies of paleoclimate indicate Earth is ice-free if GHG levels rise to much more than that. There will be “no stable shoreline on any time-frame relevant to human beings”, he says.

    Paul Ehrlich says as bad as that sounds, there might be worse things in the cards for us. We all might wake up one day and find out we can’t reproduce because of one or some combo of the hundreds of thousands of untested chemicals we are mixing into the biosphere. “You’ll be able to outwalk it”, Paul says, of sea level rise.

  16. ken levenson says:

    Mauri, agreed! And it is the future nonlinearity pointed out by Mike#22, that makes it almost futile – I think. While I’m an optimist on almost everything, I’m a pessimist here and sense that the ice melt is going to be more radical than anyone imagines.

  17. Wit's End says:

    “The current scientific discussion on possible anthropogenic interference with the Arctic sea ice and the Greenland and the West Antarctic ice sheet is evaluated in the article by Notz (12). He speculates about the so-called ‘‘small ice-cap instability,’’ which could cause a sea-ice-free Arctic ocean during the entire year under extreme warming conditions. Compared with sea ice, inland ice seems much more vulnerable to regional warming owing to the lack of large internal stabilizing feedbacks. This cryosphere component is likely to reveal TE behavior that could lead to rapid mulitimeter rise in mean sea level.”

    from http://www.pnas.org/content/early/2009/12/03/0911106106.full.pdf

  18. Joe Bftsplk says:

    re: Wit’s End: That article your quote from is entitled: “Tipping Elements in the Earth System”. “TE” means “Tipping Element”, i.e. “those characteristic features that will be switched (out) first and (possibly) irreversibly as the planet warms”.

    The Notz evaluation of the current scientific discussion referred to in your quote is entitled: “The future of ice sheets and sea ice: Between reversible retreat and unstoppable loss”.

    Exerpts from the abstract:

    “…Once these ice masses have shrunk below
    an anticipated critical extent, the ice–albedo feedback might lead
    to the irreversible and unstoppable loss of the remaining ice”.

    “…such a tipping point probably does not exist for the
    loss of Arctic summer sea ice…”

    “…a tipping point is more likely to exist for the loss of the Greenland ice sheet and the West Antarctic ice sheet.”