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Sealevelgate

Filed under: — stefan @ 11 March 2010 - (Italian)

Imagine this. In its latest report, the IPCC has predicted up to 3 meters of sea level rise by the end of this century. But “climate sceptics” websites were quick to reveal a few problems (or “tricks”, as they called it).

First, although the temperature scenarios of IPCC project a maximum warming of 6.4 ºC (Table SPM3), the upper limit of sea level rise has been computed assuming a warming of 7.6 ºC. Second, the IPCC chose to compute sea level rise up to the year 2105 rather than 2100 – just to add that extra bit of alarmism. Worse, the IPCC report shows that over the past 40 years, sea level has in fact risen 50% less than predicted by its models – yet these same models are used uncorrected to predict the future! And finally, the future projections assume a massive ice sheet decay which is rather at odds with past ice sheet behaviour.

Some scientists within IPCC warned early that all this could lead to a credibility problem, but the IPCC decided to go ahead anyway.

Now, the blogosphere and their great media amplifiers are up in arms. Heads must roll!

Unthinkable? Indeed. I am convinced that IPCC would never have done this.


The North Sea (see Stefan’s photostream on Flickr)

But here is what actually did happen.

In its latest report, the IPCC has predicted up to 59 cm of sea level rise by the end of this century. But realclimate soon revealed a few problems.

First, although the temperature scenarios of IPCC project a maximum warming of 6.4 ºC (Table SPM3), the upper limit of sea level rise has been computed for a warming of only 5.2 ºC – which reduced the estimate by about 15 cm. Second, the IPCC chose to compute sea level rise up to the year 2095 rather than 2100 – just to cut off another 5 cm. Worse, the IPCC report shows that over the past 40 years, sea level has in fact risen 50% more than predicted by its models – yet these same models are used uncorrected to predict the future! And finally, the future projections assume that the Antarctic ice sheet gains mass, thus lowering sea level, rather at odds with past ice sheet behaviour.**

Some scientists within IPCC warned early that all this could lead to a credibility problem, but the IPCC decided to go ahead anyway.

Nobody cared about this.

I mention this because there is a lesson in it. IPCC would never have published an implausibly high 3 meter upper limit like this, but it did not hesitate with the implausibly low 59 cm. That is because within the IPCC culture, being “alarmist” is bad and being “conservative” (i.e. underestimating the potential severity of things) is good.

Note that this culture is the opposite of “erring on the safe side” (assuming it is better to have overestimated the problem and made the transition to a low-carbon society a little earlier than needed, rather than to have underestimated it and sunk coastal cities and entire island nations). Just to avoid any misunderstandings here: I am squarely against exaggerating climate change to “err on the safe side”. I am deeply convinced that scientists must avoid erring on any side, they must always give the most balanced assessment they are capable of (and that is why I have often spoken up against “alarmist” exaggeration of climate science, see e.g. here and here).

Why do I find this IPCC problem far worse than the Himalaya error? Because it is not a slip-up by a Working Group 2 author who failed to properly follow procedures and cited an unreliable source. Rather, this is the result of intensive deliberations by Working Group 1 climate experts. Unlike the Himalaya mistake, this is one of the central predictions of IPCC, prominently discussed in the Summary for Policy Makers. What went wrong in this case needs to be carefully looked at when considering future improvements to the IPCC process.

And let’s see whether we learn another lesson here, this time about society and the media. Will this evidence for an underestimation of the climate problem by IPCC, presented by an IPCC lead author who studies sea level, be just as widely reported and discussed as, say, faulty claims by a blogger about “Amazongate”?

p.s. Recent sea level results. A number of broadly based assessments have appeared since the last IPCC report, which all conclude that global sea level rise by the year 2100 could exceed one meter: The assessment of the Dutch Delta Commission, the Synthesis Report of the Copenhagen Climate Congress, the Copenhagen Diagnosis report as well as the SCAR report on Antarctic Climate Change. This is also the conclusion of a number of recent peer-reviewed papers: Rahmstorf 2007, Horton et al. 2008, Pfeffer et al. 2008, Grinsted et al. 2009, Vermeer and Rahmstorf 2009, Jevrejeva et al. 2010 (in press with GRL). The notable exception – Siddall et al. 2009 – was withdrawn by its authors after we revealed numerical errors on Realclimate. This is a good example of self-correction in science (in stark contrast with the climate sceptics’ practice of endlessly perpetuating false information). Rather bizarrely, Fox News managed to turn this into the headline “More Questions About Validity of Global Warming Theory“.

** About the numbers stated above. Regarding the actual IPCC AR4 numbers, adjust the IPCC upper estimate of 59 cm by adding 15 cm to make it apply to 6.4 ºC warming (not just 5.2 ºC) and 5 cm to make it go up to 2100 (not just 2095). That gives you 79 cm. Add 50% to adjust for the underestimation of past sea level rise and you get 119 cm.
For the hypothetical case at the start of this post, just introduce similar errors in the other direction. Let’s add 31 cm by going up to 7.6 ºC and the year 2105 (in fact that is “conservative” but it gives a nice round number, 150 cm). Now assume you have a model compared to which actual sea level is rising 50% slower (rather 50% faster): now you’re at the 3 meters mentioned above. For details, see The IPCC sea level numbers.


305 Responses to “Sealevelgate”

  1. 101
    Hank Roberts says:

    Gilles, Stefan’s been answering you inline (adding to your response). Are you missing these answers? You keep restating your problem and he’s several times now pointed out the words in the actual paper that answer the question, and suggesting you read the paper.

    Most recently quoting in response to your problem the paper where it says “we can approximate it by assuming a linear increase in the early phase; the long time scales of the relevant processes give us hope that this linear approximation may be valid for a few centuries.”

    Check the right sidebar to see where there’s a recent inline response, but also back up and look at your earlier posts for inline replies. Otherwise you may feel you’re being ignored and repeat yourself unnecessarily.

  2. 102
    Jim Eager says:

    Re FHSIV @97,

    Tectonic changes to the volume of the oceanic basins would alter the potential change in sea level from melting ice sheets, but not the [em]volume[/em] of water resulting from the melt.

    The glacial cycles that dominated the Quaternary were initiated by northern hemisphere summer insolation levels, which were driven by the Milankovitch cycles. Changes in CO2 levels in turn [em]amplified[/em] those glacial cycles.

    Fast forward to present: global mean temp had been declining since the peak of the Holocene Climate Optimum 7000-8000 years ago….until now. The sun didn’t get hotter, the orbital configuration yields [em]less[/em] northern hemisphere summer insolation, yet it is or nearly is as warm as the Holocene Climate Optimum. What changed?

    CO2 increased by ~38%, CH4 by ~150%. Greenhouse gases are no longer acting as an amplifying feedback, they are acting as a direct [em]forcing[/em].

  3. 103
    Gilles says:

    “Which no one has asserted. Never the less, continued paleoclimate research shows that the correlation between atmospheric CO2 and global average temperature continues to get stronger. The miocene is no longer the exception it once was, and now even the ordovician is not looking so anomalous.
    The past can never be an exact analogue for the present and future because not all factors and conditions will be duplicated, but Richard Alley’s assertion that CO2 is the control knob is looking stronger and stronger.”

    sorry, but then what was the point of your question about Miocene? and I can’t see how a correlation between A and B can show that A is the cause of B or B the cause of A ??

  4. 104
    Jean B. says:

    Hi,
    about errors in SRES, you should definitely check out the amount of fossil fuel reserves they are using, which is total nonsense.

    For example all scenarios range between 11ZJ an 50ZJ of oil (with 17ZJ to 30ZJ for median scenarios), when ultimate exploitable reserves are estimated to be at most 14ZJ (best estimate : 11ZJ).
    How can you ever get 50ZJ ?!!

    Same for natural gas : between 15ZJ and 55ZJ in SRES, but only 11ZJ of ultimate reserves.

    And for coal : between 3.3ZJ and 68ZJ in SRES (median scenarios between 13ZJ and 47ZJ) when ultimated reserves are 15ZJ.

    You can see those data graphed for oil, natural gas and coal here starting page 70 against all 40 SRES scenarios here :
    http://www.tsl.uu.se/uhdsg/Publications/Sivertsson_Thesis.pdf

    All datas can be found here:

    IPCC SRES scenarios, column “hydrocarbon use”:
    http://www.grida.no/climate/ipcc/emission/097.htm

    Data for oil (p7):
    http://www.ifp.fr/content/download/69134/1492238/version/2/file/Panorama2010_11-VF_Produits-petroliers.pdf
    or this page for proven reserves :
    http://tonto.eia.doe.gov/cfapps/ipdbproject/iedindex3.cfm?tid=5&pid=57&aid=6&cid=ww,&syid=2008&eyid=2009&unit=BB

    Data for natural gas (last page) :
    http://www.ifp.fr/content/download/69135/1492244/version/2/file/Panorama2010_12-VF_Ressources-gas-naturel.pdf
    or this page for proven reserves:
    http://en.wikipedia.org/wiki/List_of_countries_by_natural_gas_proven_reserves

    Data for coal :
    http://www.ifp.fr/content/download/69133/1492232/version/4/file/Panorama2010_10-VF_Charbon.pdf

    Now you just have to find the conversion rates to Joules to find the numbers cited above.

    By the way, this information is also confirmed by one of the climategate e-mails:
    http://eastangliaemails.com/emails.php?eid=112&filename=926947295.txt
    “We ARE NOT supposed to be working with the assumption that these scenarios are realistic.”

    Cheers,

  5. 105
    Completely Fed Up says:

    “and I can’t see how a correlation between A and B can show that A is the cause of B or B the cause of A ??”

    Because you need causation. If A can cause B but B cannot cause A, then you can tell the difference.

  6. 106
  7. 107
    Hank Roberts says:

    > Gilles
    > the amount of fossil fuels we burn is immaterial … whatever we burn.

    Wrong, if you’d read the 2009 paper you’d probably see where he points out why emission _now_ early in the century causes more sea level rise faster.
    At least read the paper, don’t just state your beliefs without any cite.

  8. 108
    greyfox says:

    What is happening is that because of a couple of errors, the nay-sayers have introduced a new whipping boy, madly spinning this into a credibility issue, blanketing any and all issues connected to climate change. A classic trick of debate…paint your opponent as inept or lying, and then no matter what they say, the audience is finished with listening. And, typically, the people on the right side of the issue are clueless as to how to deal with this. I’m afraid academics and scientists are good at the book-larnin’ and science, but dreadful at hand to hand combat. Someone needs to have a Paladin to come and clean out the bad guys.

  9. 109
    Jim Eager says:

    Re Gilles @102: “I can’t see how a correlation between A and B can show that A is the cause of B or B the cause of A ??”

    Correlation can’t show causation, but the known radiative physics of CO2 can.

  10. 110
    Jan Lindström says:

    #7 exactly what are you referring to as my humble opnion differs 180 degrees from yours?..

  11. 111
    Edward Greisch says:

    6 degrees C of warming is the for-sure extinction point for humans. At 5.2 degrees C of warming, there will be few, if any, humans left. Civilization will have long since collapsed due to famine and other factors. Any people still alive in 2100 will have no competition for space on higher ground. Indeed, they will be lonely and searching for other people. What this article really tells us is that 2100 is the cutoff date. Thanks, RC, for giving us this definitive date.

    [Response: I appreciate your point, but overly definitive statements about the future simply serve as targets for the inactivists. Truly, you cannot know such things and suggesting that RC has told you this will happen is not appropriate. – gavin]

  12. 112
    Geno Canto del Halcon says:

    Reminder: scientists are the “skeptics” – at least the good scientists. Denialists ARE NOT skeptics, and it is wrong to give them that much credit. Anyone who has reached a conclusion such as “global warming is a hoax” is making an untenable, illogical, scientifically unsupportable conclusion.
    Alarmists, on the other hand, can still be skeptics; it is easy to be alarmed by some of the projections that are made by climatologists, even when one still continues to question the data, analyses, models, and projections.

  13. 113
    wilt says:

    Comment from Stefan at #91:
    ‘If you look at short periods, the rate of sea level rise does indeed fluctuate wildly up and down, as you say.’

    Thank you for your response.
    But if you realize that on a short term basis there is so much fluctuation, why then did you write at my previous contribution (#38): “At the beginning of the 20th Century sea level rose at a rate of about 1 mm/yr, and after 0.8 ºC global warming this rate has roughly tripled, now standing at about 3 mm/year. –stefan “
    Such a formulation suggests that from the start of the century till the end there had been a 3-fold increase in the rate of sea level rise. Whereas the data that I have referred to before
    (http://sealevel.colorado.edu/) clearly indicate that there was no consistent increase in trendvalue per decade for the whole period since 1880, in other words the rate has remained almost the same and certainly has not “roughly tripled”.
    The other thing that I would be worried about if I would have to defend your hypothesis, is that the trendvalue was virtually the same in the period 1940-1975 as in the two warm periods before and after those years.

    [Response: Fig. 3 of Rahmstorf (2007). -stefan]

  14. 114
    Septic Matthew says:

    Now, the blogosphere and their great media amplifiers are up in arms. Heads must roll!

    You should drop that style of writing, here at Real Climate, and focus on science. All science, all the time: data, models, estimation, precision and uncertainty. Science is your expertise. Rebut errors, fix your own errors when they are disclosed (checking first, of course, to see if they really are errors.)

    “If a donkey bray at a donkey, who can tell the difference?” Cut out all braying, and leave it to those to whom you feel a superiority. You’ll win in the long run and gain (perhaps regain) the respect of scientists and non-scientists.

  15. 115
    werecow says:

    Sorry if this has been asked before, but:

    “Regarding the actual IPCC AR4 numbers, adjust the IPCC upper estimate of 59 cm by adding 15 cm to make it apply to 6.4 ºC warming (not just 5.2 ºC) and 5 cm to make it go up to 2100 (not just 2095). That gives you 79 cm. Add 50% to adjust for the underestimation of past sea level rise and you get 119 cm.”

    I take it that this does not include the “rapid dynamic changes” in continental glaciers (e.g. due to lubrication by meltwater) that were excluded from the original calculation in AR4, right? Or does some of the 50% fit into that pattern? If not: how much could this add to the rise, based on current best estimates?

    [Response: I gave those numbers just to illustrate that one could have equally plausibly come up with very different values, erring in the other direction. I did not mean to imply that you could simply “correct” the IPCC projections by adding 50% if they’ve been off by 50% in the past – that wouldn’t be sound science for a number of reasons. I do think that other approaches to estimate future sea level rise, like the papers I linked in the p.s., are a valid alternative to the IPCC approach. -stefan]

  16. 116
    sidd says:

    Mr. Gilles writes on the 12th of March, 2010 at 10:45 AM:

    “since the sea will continue to rise at some mm/yr during one millenium, inexorably and whatever we burn. ”

    The last part, ‘whatever we burn,’ is not yet established.

    But do allow me to explore your thought a little further, for you have touched upon a nagging concern of mine.

    There is an instability sometimes called the ‘Weertman instability.’ Consider an iceshelf, grounded submarine. If the seabed below the ice deepens landward, the configuration is not stable, see for example, Schoof,Journal of Geophysical Research,v112,F03S28,2007. The situation we are in is depicted in Panel 3g in the following figure and we are set to proceed to 3h. The time progression goes down the left hand column, across and up the right hand column.

    http://membrane.com/sidd/longthaw/schoof-3.png

    In short, consider the West Antarctic Ice Sheet, 7 meter of sea level rise. How fast can it collapse? Bindschadler commented on the ANDRILL results that a millenium ought to be regarded as an upper limit. You will find a discussion of the ANDRILL results on this site.

    If we have indeed destabilized the WAIS, your sentence above would be literally true, together with the last clause. ‘Inexorable’ is quite apposite, for we shall have begun the long retreat from the coasts. There will be no stable coastline for centuries.

    In another life, I used to indulge in a game of bridge, now and then. I seem to recall that sometimes, a contract could only succeed for a small set of card distributions, and one played the hand assuming that were indeed the case.

    I prefer to imagine that the outcome may yet be in doubt, and although these may be the last throws of a losing hand, I shall play as though I meant to win.

    sidd

  17. 117
    Ric Merritt says:

    Bengt A @ 12 March 2010 at 12:46 AM

    Thank you, that paper is a valuable contribution.

  18. 118
    J Bowers says:

    86 Barton Paul Levenson says:
    “Did anyone see yesterday’s MacPaper? USA Today repeated all the lies about how the CRU hack revealed that scientists had concealed data and conspired to keep out skeptics.”

    BPL, check out physicsworld.com’s story on the IOP sumission to the Parliamentary inquiry.
    http://physicsworld.com/cws/article/news/41965

    The level of knowledge on climate science in the comments makes me feel like a rocket scientist, which is both incredulous and especially alarming given that it’s a website of the IOP itself.

    (cough) it takes a minute to sign up… (cough)

  19. 119
    Gerry Quinn says:

    Stefan claims in his response to the first comment “data of the past century show how the rate of sea level rise increases in proportion with temperature”.

    But the graph of sea-level rise over the past century, as given in Wikipedia based on long-term tide gauge measurements, is almost perfectly linear! You can place a straight-edge along the period from 1910-2010. If the temperature has been rising, and if increased temperature increases the rate of rise, it should curve upwards. But any such upward curvature is negligible to the point of invisibility. How come?

    [Response: Don’t know what Wikipedia shows, but the main two global sea level data sets that I know, those of Church and White (2006) and Jevrejeva et al. (2006), give a similar acceleration of sea level rise, as we discussed in “Ups and downs…”. Full references given there. -stefan ]

  20. 120
    John N-G says:

    I recognize the estimate in the P.S. is a back-of-the-envelope estimate, but is there a particular reason for assuming that the 1.8 mm/yr observed vs. the 1.2 mm/yr modeled represents a multiplicative bias rather than an additive bias or a random error?

    Assuming a multiplicative bias gets you from 79 cm in 2100 to 119 cm in 2100, while assuming an additive bias gets you from 79 cm in 2100 to 85 cm in 2100, and assuming a random error keeps you at 79 cm.

    I suppose sea level rise is sufficiently like a deterministic system that random error can be plausibly discounted, but how do you choose between the other two possibilities?

    [Response: See response to #115]

  21. 121
    Hank Roberts says:

    > Edward G

    Realclimate contributors and other scientists have been trying to get you to stop making this false claim for years now.

    For example, you were told the same thing at RC and at Tamino’s in 2007:

    http://initforthegold.blogspot.com/2007/12/theres-no-ulitmate-tipping-point.html

    “Thursday, December 20, 2007
    There’s No Ultimate Tipping Point
    Ray on a response on RealClimate says nicely something I have been trying to say to the doomsayers: Edward Greisch: …'”

    You don’t actually cite an actual link to an RC source when you’ve made this claim. You can’t — checking it would show you were wrong.

    Google on your own name and a few words you regularly use and you’ll find a
    lot of blogs you might want to revisit to correct this misstatement, either posted by you or by someone using _you_ as the source.

    No wonder people think RC is full of alarmists, with this kind of nonsense being widely posted elsewhere.

    Remember, kids — check the source. Don’t believe some guy on a blog.

  22. 122
    wilt says:

    Regarding my posting #111 on sea level data, I supplied the wrong link, sorry about that. The data on sea level since about 1880 can be found here: http://www.climatedata.info/Impacts/Impacts/sealevels.html
    The Colorado site mentioned earlier only deals with the recent (satellite-based) measurements.

  23. 123
    FHSIV says:

    Completely Fed Up #99

    Sorry to be unclear. I meant what geographic location is your reference point, not what point in time.

  24. 124
    FHSIV says:

    Jim Eager Re #101

    You said “Tectonic changes to the volume of the oceanic basins would alter the potential change in sea level from melting ice sheets, but not the [em]volume[/em] of water resulting from the melt.”

    That’s my point. Have the changes in the volume of the ocean basins over the last 40my been assessed and factored into the comparisons of documented/observed sea level stands over the same period. It seems like an apples and oranges comparison if the ocean basin volume changes are not considered.

    You said “The glacial cycles that dominated the Quaternary were initiated by northern hemisphere summer insolation levels, which were driven by the Milankovitch cycles. Changes in CO2 levels in turn [em]amplified[/em] those glacial cycles.”

    I agree regarding Milankovitch cycles, but I am not convinced regarding CO2 amplification. Can you provide me with a reference so that I can get up to speed on this?

    You said “Fast forward to present: global mean temp had been declining since the peak of the Holocene Climate Optimum 7000-8000 years ago….until now. The sun didn’t get hotter, the orbital configuration yields [em]less[/em] northern hemisphere summer insolation, yet it is or nearly is as warm as the Holocene Climate Optimum. What changed?”

    Well if it is only “nearly is as warm” than nothing needs to have changed!

    You said “CO2 increased by ~38%, CH4 by ~150%. Greenhouse gases are no longer acting as an amplifying feedback, they are acting as a direct [em]forcing[/em].”

    Then I’ll ask what changed? Did we pass a tipping point?

  25. 125
    Completely Fed Up says:

    I would suggest the location is the same location as the one millions of years ago.

    You know.

    Since the only thing you’ve changed is the date and said that the difference between them is 70m.

    It’s only a shot in the dark, but seems fairly clear and reasonable.

    Doesn’t it?

  26. 126

    NASA: Feb 2010 was 2nd hottest ever globally, for land+ocean (http://bit.ly/GISlandoc) as well as for land only (http://bit.ly/GISland)

  27. 127

    Slower feedbacks such as the albedo feedback due to the melting of large ice sheets in Greenland and Antarctica were not considered by the IPCC. (Hanson, et al., 2008) When these feedbacks are included, the sensitivity value increases to approximately 6 oC. Hanson et al. explain:

    Paleoclimate data show that climate sensitivity is ~3°C for doubled CO2, including only fast feedback processes. Equilibrium sensitivity, including slower surface albedo feedbacks, is ~6 oC for doubled CO2 for the range of climate states between glacial conditions and icefree Antarctica. Decreasing CO2 was the main cause of a cooling trend that began 50 million years ago, large scale glaciation occurring when CO2 fell to 425±75 ppm, a level that will be exceeded within decades, barring prompt policy changes. If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm. The largest uncertainty in the target arises from possible changes of non-CO2 forcings. An initial 350 ppm CO2 target may be achievable by phasing out coal use except where CO2 is captured and adopting agricultural and forestry practices that sequester carbon. If the present overshoot of this target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects.

    and

    Humanity today, collectively, must face the uncomfortable fact that industrial civilization itself has become the principal driver of global climate. If we stay our present course, using fossil fuels to feed a growing appetite for energy-intensive life styles, we will soon leave the climate of the Holocene, the world of prior human history. The eventual response to doubling preindustrial atmospheric CO2 likely would be a nearly ice-free planet.

    Humanity’s task of moderating human-caused global climate change is urgent. Ocean and ice sheet inertias provide a buffer delaying full response by centuries, but there is a danger that human-made forcings could drive the climate system beyond tipping points such that change proceeds out of our control. The time available to reduce the human-made forcing is uncertain, because models of the global system and critical components such as ice sheets are inadequate. However, climate response time is surely less than the atmospheric lifetime of the human-caused perturbation of CO2. Thus remaining fossil fuel reserves should not be exploited without a plan for retrieval and disposal of resulting atmospheric CO2.

    Paleoclimate evidence and ongoing global changes imply that today’s CO2, about 385 ppm, is already too high to maintain the climate to which humanity, wildlife, and the rest of the biosphere are adapted. Realization that we must reduce the current CO2 amount has a bright side: effects that had begun to seem inevitable, including impacts of ocean acidification, loss of fresh water supplies, and shifting of climatic zones, may be averted by the necessity of finding an energy course beyond fossil fuels sooner than would otherwise have occurred.

    To summarize, Hanson et al. believe that it is quite possible Earth could end up ice free with CO2 levels of 350 ppm which is well below where we currently are. Because the melting of Antarctic ice takes centuries there is time to lower the “tipping point” level of CO2 before it is too late.

    As Forrest Gump would say, “and that’s all I have to say about that.” :)

  28. 128
    Hank Roberts says:

    > FHSIV
    > what changed? Did we pass a tipping point?

    Yes, in evolution.
    Primates started burning fossil fuels.

    In all previous events, the planet warmed naturally (look up Milankovich for example). With that warming, CO2 started to go up. That’s a feedback.

    This time, the CO2 increase–very fast– started artificially, happening while the planet was otherwise in a long slow cooling period. That’s a forcing.

    Now, as the planet warms up again, due to the forcing from fossil carbon being burned, _that_ warming is causing CO2 to increase; that increase is a feedback.

  29. 129
    FHSIV says:

    Completely Fed Up #123

    Eschew obfuscation!

  30. 130
    RoySV says:

    Re rate of ice sheet melting. These pictures from Discover magazine show researchers kayaking on a river of melt water atop Greenland. I’m no scientist, but seeing a literal river of surface melt water gives me no confidence that future melting will be linear with temperature. Also, I haven’t noticed mention on this thread of the fact that the Western Antarctic ice sheet is grounded many meters below sea level.

    http://blogs.discovery.com/earth/2009/07/a-river-runs-along-the-top-of-it.html

  31. 131
    David B. Benson says:

    FHSIV (122) — Please read “The Discovery of Global Warming” by Spencer Weart, first link in the science section of the sidebar. Then you may care to read the Chareny et al. 1979 NRC report:
    http://books.nap.edu/openbook.php?record_id=12181&page=R1

  32. 132
    caerbannog says:


    These pictures from Discover magazine show researchers kayaking on a river of melt water atop Greenland.

    Given that some of those meltwater rivers disappear down moulins, just the thought of kayaking down one of those gives me the heebee-jeebees!

  33. 133
    Ken Peterson says:

    The temperature has just gone from 31.9999 to 32.0001.

    I’m standing in front of the glacier screaming,”Run, run, run!”

    “These scientests…”, say the deniers. “They get so excited over the littlest things.”

  34. 134
    Mike says:

    125
    Scott A Mandia says
    “To summarize, Hanson et al. believe that it is quite possible Earth could end up ice free with CO2 levels of 350 ppm which is well below where we currently are. Because the melting of Antarctic ice takes centuries there is time to lower the “tipping point” level of CO2 before it is too late.”

    Youve gotta ask what caused the co2 drop? 50million years ago is when the continents came to be where they are, and the gradual decrease in co2 began, 35million years ago is when full blown ice sheets formed over Antarctica(depends who yah source, but generally between 700-900ppm co2) and 20-15 million years ago co2 dropped too around current levels, and glaciations commenced in the northern hemisphere with the continuing decline in co2 til full blown glaciation around 2.5mybp.

    During glaciations co2 levels drop, through increased oceanic absorption and burial. But id put it to you, that when Antarctica came to be where it is, and prevented ocean transport of heat over the pole, and the circumpolar ocean current came into being, it lead to the gradual burial o co2, and the climate we have today(obviously over millions o years) But i just find it very hard to swallow in light of this, that 350ppm could cause Antarctica to be ice free. Change the dynamics for sure, but ice free?

  35. 135
    stevenc says:

    “Paleoclimate data show that climate sensitivity is ~3°C for doubled CO2, including only fast feedback processes. Equilibrium sensitivity, including slower surface albedo feedbacks, is ~6 oC for doubled CO2 for the range of climate states between glacial conditions and icefree Antarctica”

    A large long term climate sensitivity to present forcings indicate that previous forcings should also have a large long term climate sensitivity and that the long term reaction to forcings would have to be attributed for today’s climate. In other words, how much of the warming of the latter part of the 20th century would you attribute to the warming that occurred in the early portion of the 20th century? If little or none then why would today’s forcings behave any differently?

  36. 136
    Gilles says:

    Hank :> Gilles
    > the amount of fossil fuels we burn is immaterial … whatever we burn.
    Wrong, if you’d read the 2009 paper you’d probably see where he points out why emission _now_ early in the century causes more sea level rise faster.
    At least read the paper, don’t just state your beliefs without any cite.”

    No, YOU’re wrong (again, after your stating that stratosphere is warmed by the long wavelength IR radiation from below…). The paper states (correctly within its hypothesis) that all scenarios are more or less the same until the mid 20’s, which contribute most to the sea level rise, so the result in 2100 is rather insensitive to the scenario. Which is quite understandable if the equlibration timescale is about one millenia, the sea level is a very strong low-pass filter and rather insensitive to the last years. If the timescale is really much longer than one century, it means also that the current rise is only a small part of the asymptotic one (which will be neared only after one millenium or so), and so it means that the sea level rise will continue inexorably throughout centuries whatever we do. It’s true that the asymptotic value will depend on the final temperature, but the 3 meter rise is already in the pipe, sorry , guys. Now of course it’s only IF the paper is right. If you’re not convinces, I can write you a more mathematical demonstration.

    That’s a very general statement : if the reaction timescale is much larger than a century , then we can’t do much to avoid it before 2100 since it has already started and will last for a long time, and if not, then the sea level will saturate at rather modest values. Choose your preferred scenario.

  37. 137

    It is my impression that Stefan, author of article here, represents the best of the IPCC thinking and correctly represents that process.

    It is not a criticism of the science, rather it is recognition of how difficult the problem is. But I find it “unsettling” that the IPCC related sea level rise to surface temperature as a linear relationship. ((6.4/5.2) = ((59 + 15)/ 15) shows this linearity based on the numbers from the article above.) By this thinking, the 50% unexpected increase in sea level rise would indicate a 50% unexpected increase in “warming” which really means surface temperature only.

    It sort of looks like the 50% unexpected increase in sea level rise is in lieu of some of the expected temperature increase, thus there would not be a linear relationship between these changes. Correcting the atmospheric temperature model would not necessarily result in an indicated increase in the surface temperature, as it seems that Stefan here seems to be suggesting.

    How the extra heat is apportioned between sea ice “heat of fusion (melting really)” and deeper ocean heat content is not clear in data I have seen. It seems this would be known for the present circumstances if the radiative imbalance were known, and the measured ocean heat content down to 700 meters was the whole story on ocean heat content.

  38. 138
  39. 139
    Jim Eager says:

    Re FHSIV @122: I agree regarding Milankovitch cycles, but I am not convinced regarding CO2 amplification

    Then with respect, you do not understand the Milankovitch cycles and how a relatively small change in insolation over only a relatively small part of Earth’s surface during only part of the year could lead to continent-wide glaciation or deglaciation. The change in watts per square meter is simply not great enough by itself. Only when you add in the amplifying feedbacks is there a large enough change in energy.

    Can you provide me with a reference so that I can get up to speed on this?

    I’ll second Spencer Weart’s The Discover of Global Warming, but it sounds like a basic earth science text would help as well.

    Well if it is only “nearly is as warm” than nothing needs to have changed!

    Yet another indication that you do not understand the Milankovitch cycles. Hint: we should be cooling. We are not. Why not?

    And don’t forget that because of the thermal inertia of the ocean we have not yet seen the full warming that the increase in greenhouse gases will produce.

    Then I’ll ask what changed? Did we pass a tipping point?

    Yes, humans invented agriculture and domesticated rice (methane) and started burning fossil carbon based fuels on an industrial scale (CO2), releasing carbon into the atmosphere and active carbon cycle that had been locked out of that cycle for hundreds of millions of years.

  40. 140
    GlenFergus says:

    Thanks Stefan, really good stuff.

    “Just to avoid any misunderstandings here: I am squarely against exaggerating climate change to ‘err on the safe side’.”

    I’m not so sure. An old collegue runs flood forecasting in this state; has done for decades. He had to do his stuff again last week as a record flood approached a western town. He said 14 m, but I knew what the peak would really be, because I’ve watched him for a long time. It came in at about 13.5. Fact is, he’s always wrong. Not because he can’t run a flood model. Because, unlike most in his scientific organisation, he’s an engineer.

    The object isn’t to be right. It’s to give the most useful answer, especially for those who won’t grasp the uncertainty.

    [Response: There is a difference between doing science (as we do) and running operational flood warnings. I don’t know much about the latter, but probably there is a case here for adding a safety margin to account for the fact that there is uncertainty and the warning should cover the worst case. If that’s so, of course this should be a transparent and previously agreed procedure. -stefan]

  41. 141
    donald moore says:

    Could someone please tell me whether or not carbon sequestration from increase in humus on farms [which is going on worldwide and at the moment unquantifiable]has been taken into account in any of these scenario/climate models.

  42. 142
    Edward Greisch says:

    111 response: Sorry Gavin. Oh! You mean some people will just give up and say: “Since it’s inevitable, there is nothing I can do.”? I have a neighbor like that, but I find that stance impossible to understand. Many other people say: “It won’t happen for centuries”; and “Let the grand kids solve their own problems.” For them, you have to have a hard date and it has to be right now. Neither type of person can be moved by anything I say. They leave me wanting to move to Mars.
    How do you deal with them?

  43. 143
    Gilles says:

    “Then with respect, you do not understand the Milankovitch cycles and how a relatively small change in insolation over only a relatively small part of Earth’s surface during only part of the year could lead to continent-wide glaciation or deglaciation.”
    Sorry, something bothers me (again); I understood that the main feedback that amplifies anthropogenic CO2 action is water vapor, not CO2 it self (the gamma value is rather low, so the retroaction to raise the CO2 concentration can be neglected with regards to the H20 average concentration). But this should be true for any cause of variation of the forcing, including the Milankovitch cycles, so the main amplifier should be the water vapor, and not the CO2 which is only a (almost passive) tracker when it’s not the primary cause of change ?

  44. 144
    JiminMpls says:

    104 Jean B

    The paper is severely flawed. It only deals with proved reserves. Proved reserves are a small fraction of the projected technically and economically recoverable reserves.

    A simple example that everyone should understand: ANWR. There are ZERO proved oil and natural gas reserves in ANWR. NOT ONE DROP or cubic foot has been discovered or proved. Does that mean that if ANWR were opened to production that no oil or natural gas would be produced?

    The thesis also understates the potential for unonventional resources. Another example: US proved reserves – esp of conventional oil – have declined signifantly. Yet, US oil production is projected to INCREASE by 25% by 2027 and continue at a rate 20% higher than current production. The projected increase is due almost exclusively to the production of unconventional reserves. US production from unconventional natural gas reserved is projected to increase by 50% by 2030. NOTE: The unconventional oil reserves considered do NOT include oil sands or shale oil.

    http://www.eia.doe.gov/oiaf/aeo/overview.html#production

  45. 145
    Dave Burton says:

    Actually, the best and longest coastal tide gauge records indicate that:

    1) global average mean sea level has been rising at a rate of less than 1.2 mm/year; and

    2) it was rising at that rate long before there was a major anthropogenic contribution to atmospheric CO2; and

    3) there has been no sign of acceleration in the rate of sea level rise either recently or at any other time in the last 120 years. The graphs of Mean Sea Level are essentially straight lines + noise.

    The fact that the rate of sea level rise now is about the same as it was when anthropogenic CO2 emissions were very low, before there were any automobiles or coal-fired electric power plants, leads to the obvious conclusion that anthropogenic CO2 does NOT appear to cause a significant increase in sea level.

    See:
    http://www.burtonsys.com/climategate/distance_weighted_MSL_avg.html

    Dave Burton
    Cary, NC

  46. 146
    Gilles says:

    Concerning again the estimate of relaxation time, I am also perplex on the accuracy of its determination. In , there are several estimates based on different reconstructions and satellite measurements, and they all differ by more than their error bars ! I prefer not commenting the validity of pre 1900 temperature reconstructions, this has been the subject of a number of discussions here and elsewhere. But I’m puzzled by this kind of result : ” Mediterranean archaeological data (Sivan et al., 2004), and salt-marsh records from New England (Gehrels et al., 2005) suggest variations in sea level have not exceeded ±0.25 m from 2,000 to 100 yr be- fore present.”
    If the relaxation time is really around 1000 yrs, it means that the current 0.3 m for 0.6 °C is actually a 5 m/°C sensitivity, because we have felt still only one tenth or so of the real change. Limiting the past variations to 0.25 m over two millenia would mean that the temperature averaged over one relaxation time (hence close to the equilibrium situation) wouldn’t have changed by more than 0.25/5 = 0.05 °C throughout two millenia …??? strange, I thought there was multisecular warm periods during Roman Empire and Middle age… why was the sea level insensitive to these variations ?

    Satellite and historical estimated do not agree very well, and if the whole “acceleration” story is just due to the difference between two experimentally different ways of measuring sea level, ahemmm… I think one should be VERY cautious before taking that as proven facts. Even the “one relaxation time” or “two relaxation times” can obviously be a very crude approximation : what about possible multidecadal cycles that could have been unnoticed before, for instance ? satellite measurements are much too recent to be really constraining. I don’t have the impression that all this stuff can be considered as solid science at all, it’s only possibilities… and as I said IF the equilibration time is very long, there is nothing much we can do to change the evolution throughout the century anyway. If I lived on a coast , I would wait after all before moving… after acceleration is really confirmed :). But anyway I live at 200 m above sea level.

  47. 147
    Gilles says:

    JiminMpls : I understood peak oil wasn’t the preferred subject here, but the situation is very simple : if you’re right, peak oil is far away. If peak oil is close, you’re wrong (because unconventional resources are simply too expensive to allow a large demand). We’ll know that within 5 or ten years, much before climate models will have been really validated and the climate sensitivity fixed. BTW I maintained on a French forum a thread monitoring short term EIA forecasts for 4 years, which shows they have been constantly wrong and deceiving (they were constantly predicting since 2005 a rise in oil production that never really happened, even before the crisis, and even despite a very high price of the barrel), if you’re interested on the subject.

  48. 148
    Gilles says:

    oops sorry for the misuse of html flags… unfortunately no editing is possible here !

  49. 149
    Completely Fed Up says:

    FHSIV, #139, you can chew what the hell you like.

    Got anything substantive?

  50. 150
    Chris Dudley says:

    As long as we are beating up on the IPCC why not ding them for not including an estimate of how increased erosion owing to stronger precipitation events mentioned elsewhere in the report lead to a faster filling in of the ocean bottom and an increase in sea level as measured from the coasts. A small effect to be sure, but since the report fails to be logically consistent by not including the estimate we can surly conclude that it is trying to cover up climate risks and is in the pay of Saudi Arabia.

    This is kind of fun. There must be a few more things on the silly side in this direction that compensate for silliness in the other direction.


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