Report from AGU meeting: One meter sea level rise by 2100 “very likely” even if warming stops?

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"Report from AGU meeting: One meter sea level rise by 2100 “very likely” even if warming stops?"

Why so many geophysics-related posts this week? First, all of the major groups that track temperature and climate put out their news-making annual reports this week — and I don’t think the media is doing a terribly good job of focusing on the important issues.

Second, this week, the American Geophysical Union has its big fall conference where all the leading geophysicists go to report their latest research. ClimateProgress has glommed on to a roving reporter on site, Jeff Goodell, author of the terrific book, Big Coal.

Goodell reports that Dr. Eric Rignot, Principal Scientist for the Radar Science and Engineering Section at NASA’s Jet Propulsion Laboratory, “rocked the house tonight (tues) with his talk on polar ice melt”:

The room was packed, SRO, spilling out into the halls. I only caught the tail end of the talk, unfortunately, but he concluded that one meter sea level rise by 2100 is “very likely” if the rate of ice melt just stays the same, leaving unsaid the fact that it is likely to rise even higher if rate of melt accelerates. Said that the way we are studying ice in the poles today is “like climbing Mt. Everest in tennis shoes,” because our monitoring and measurement is so bad.

Rignot is one of the world’s top ice sheet and sea level rise experts (see “The Antarctic ice sheet hits the fan“), so that’s why he packs them in.

If Rignot is right, then Hansen and Gore are right — our target must be 350 ppm or lower (see “Stabilize at 350 ppm or risk ice-free planet, warn NASA, Yale, Sheffield, Versailles, Boston et al“). That’s because, thanks to lags in the climate system, we are going to warm more than another 0.6°C even if greenhouse gas emissions were zeroed out tomorrow — and that will surely speed up all ice loss processes.

One small critique of the AGU meeting: They should put far more of their talks online. This stuff is incredibly fascinating and important to a great many people.

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15 Responses to Report from AGU meeting: One meter sea level rise by 2100 “very likely” even if warming stops?

  1. Jeff Green says:

    (but he concluded that one meter sea level rise by 2100 is “very likely” if the rate of ice melt just stays the same)

    When I do the math of rate of melt times one hundred years

    4mm/year times 100 gets 400mm which is far short of a meter

    I’m curious what is it that I am missing?

    [JR: I assume Rignot meant that the linear growth rate of increase in melting keeps at its current level.]

  2. David B. Benson says:

    Another sci8entist (or two) from Colorado concluded that 80 cm was the least and ‘most likely’. Up to 2 m was possible, but ‘highly unlikely’. There is a thread about that paper on RealClimate.

    I take this result (if it is not the same author) as confirmatory.

  3. Raven says:

    This comment caught my eye:

    “Said that the way we are studying ice in the poles today is “like climbing Mt. Everest in tennis shoes,” because our monitoring and measurement is so bad”

    Translation: Everything Rignot says is a wild-a** guess and we really have no idea how fast the ice is melting – or for that matter – we have no idea whether the ice is actually melting.

    What Rignot does not mention is he does not use actual measurements to calculate the ice melt. He uses computer models to estimate it. Computer models which cannot be tested to determine if they have any connection to reality.

  4. Jeff Goodell says:

    Jeff:

    Yes, I meant linear increase. Should have been clearer. His point was one meter of SLR was “very likely” even if you do not take into account dynamic changes in ice sheets.

  5. David B. Benson says:

    Raven — So then the actual SLR might even be larger than one meter, yes?

  6. Raven says:

    David,

    As with most climate model outputs the 95% confidence intervals are likely large enough to cover any possible outcome from negative SLR to catastrophic postive SLR. This allows the modellers to claim that any real outcome is “consistent with” their models.

    Of course, they don’t explain this detail to the press who merrily repeats the ‘average’ as if it was a proven fact when it really an arbitrary number that provides no useful information.

  7. Mark Shapiro says:

    Raven –

    More likely he is just calling for more measurement – just like every scientist does when they see something worth measuring. “Arbitrary number”? No.

    If you don’t have any confidence in the models, just sit back and watch it happen. UIC’s cryosphere website shows the ice extent at both poles with daily updates. You can even see the ice melt pools on Greenland from Google Earth.

    Or go to Glacier National Park and watch the glaciers melt.

  8. Raven says:

    Mark,

    We are talking about alleged melting from the Greenland and Antarctic land based ice caps. There may be less sea ice in the arctic or melt pools on Greenland but that does not automatically mean the land based ice caps are experiencing a net loss in volume (i.e. the amount of melt is the greater than the new accumulation from snow fall).

    Rignot has come up with a scheme that estimates numerous parameters with a climate model and claims that we have experienced a net loss ….

    [JR: Rest of comment deleted because there is only so much disinformation any person can be expected to stomach. It isn’t “alleged” — it is actually confirmed by different methods. Again, I assume you self-medicate because modern medicine uses the same method Rignot does.]

  9. John Hollenberg says:

    > [JR: Rest of comment deleted because there is only so much disinformation any person can be expected to stomach. ]

    Best comment in this thread so far. Thanks, Joe.

  10. Jeff Green says:

    (Jeff Goodell Says:

    December 17th, 2008 at 6:42 pm
    Jeff:

    Yes, I meant linear increase. Should have been clearer. His point was one meter of SLR was “very likely” even if you do not take into account dynamic changes in ice sheets)

    That one was bugging me. Thanks for the response.

  11. rp says:

    I noticed that the ice in my freezer is building up, thicker and thicker.

  12. jorleh says:

    Notice one point: up every kilometre the temperature is 5 degrees Celcius lower, in three kilometres 15 C lower than on the sea level. Most of the melting effects lower levels, the ice sheet melts at the root and then the upper part of the region collapses and so on.

    This cancerous degeneration of the ice sheet is something not studied so much?

  13. Raven…

    The computer models aren’t as inaccurate as you may have been lead to believe. For example, let’s say you program all the variables, have the program ready, and want to know how well it might work.

    Well… then you go back to 1800 and run the simulation to see if it gets accurate results about the weather for the last 208 years.

    If it does, then you’re probably on the right track. If it doesn’t, you start over.

    My understanding is that the computer models provide highly accurate results for the last 208 years. Are they likely to go badly wrong going forward…?

    You’ll have to provide something concrete and scientific for me to believe it, and my understanding is that there is no such evidence.

  14. Jeff Green says:

    I emailed Eric and got this reply.

    Jeff,

    4mm/yr would be if melting stops increasing today.

    But melt is increasing with time.

    If it increases at the same rate over the next century, we will
    get 1 m by 2100.

    But it is likely to increase faster …

    Eric

  15. David B. Benson says:

    I haven’t kept up with the latest advances in ice modelling. However, ice modeling is very different than climate models of the AOGCM type. The principal problem appears to be that all the decay mechanisms are not known until actually observed. The older ice models work fine for slow changes, either advance or retreat. But those do not for rapid decay of large ice masses.

    So the researchers are playing catch up. But is does look that the Dutch engineer’s working assumption of 1.3–1.4 m sea level rise in 2100 CE is not so far off the mark.