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The Greenland Ice

Filed under: — rasmus @ 2 March 2006

by Rasmus Benestad, Eric Steig and Gavin Schmidt

In a recent paper in Science, Eric Rignot and Pannir Kanagaratnam present new satellite observations of the speed of glaciers of Greenland, and find that they are sliding towards the sea almost twice as fast as previously thought. Additionally, between 1996 and 2005, they detected a widespread glacier acceleration and consequently an increased rate of ice discharge from the Greenland ice sheet. However, previous papers have recently noted an increase in snow accumulation in the interior (i.e. Johannessen et al., 2005), so how do these different measurements fit into the larger picture of Greenland’s net mass balance?

2004/150 - 05/29 at 14 :25 UTC Southern Greenland Satellite: Terra The measurements by Rignot and Kanagartnam were made with interferometers which measure the movement of the surface horizontally, and so is complimentary to the altimeter data published previously (which measures the absolute height of the ice). Overall, they found widespread increases in glacier speeds, and increases of about 30% in ice discharge rates. (Note that the satellite image shows that the glaciers in the east tend to slide far into the sea whereas on the western coast that happens less).

The higher velocity of the ice is thought to be related to higher temperatures causing increased melt-water which can penetrate to the base of the glacier and hence reduce the ground friction. However, this accelerated movement is not necessarily tied to an increased rate of melting of the Greenland ice, although it can be related. Surges of ice streams from the ice sheet can also occur due to increased accumulation at the head of the glacier. However, when the increased ice velocity is matched to a decreasing thickness that can be sign of net mass loss. These ideas are consistent with observations of surface melting which had a record extent in 2005, and has been increasing steadily (though with significant interannual variability) since 1993. Using the analysis of Hanna et al (2005) (based on the reanalysis datasets) for the surface mass balance, Rignot & Kanagartnam estimate that Greenland is on balance losing mass, and over the period of their study the ice sheet mass deficit (the amount of ice lost to the sea) has doubled increasing from 90 to 220 km3/year (an increase of 0.23 to 0.57 mm/yr sea level equivalent – SLE).

In the earlier Science paper, Johanessen et al. found increased snow accumulation on the top of the interior Greenland ice sheet between 1992 and 2003. Above 1500m a.s.l in much of the interior Greenland they estimated an increase of 6.4 ± 0.2 cm/year and below 1500m they observed a decreasing trend of -2.0 ± 0.9 cm/year. Hence, growth in the interior parts and a thinning of the ice nearer the edges. However, Johanessen et al. were not able to measure all of the coastal ranges. Indeed, the thinning of the margins and growth in the interior Greenland is an expected response to increased temperatures and more precipitation in a warmer climate. These results present no contradiction to the accelerated sliding near the coasts, but both will affect the ice/snow (fresh water) mass estimate. Whereas the finding of Rignot and Kanagaratnam suggests a larger sink of the frozen Greenland fresh water budget (the ice is dumped into the sea), the snow deposition in Greenland interiors is a source term (increases the amount of frozen fresh water). It does not matter for the general sea level in which form the water exists (liguid or solid/frozen) when it is discharged into the sea: The same mass of liquid water and immersed ice affect the water level equally (Archimede’s principle).

A third relevant study is a recent paper in the Journal of Glaciology by Zwally et al. (2005) on the ice mass changes on Greenland and Antarctica. They use the same satellite obsevations (ERS 1 and 2) as Johanessen et al. and again find that the Greenland ice sheet is thinning at the margins (-42 ± 2 Gt/year = -46 ± 2 km3/year below the equilibrium-line altitude – ELA), but growing in the inland (+53 ± 2 Gt/year = 58 ± 2 km3/year). The mass estimates have been converted to volume estimates here, assuming the density of ice is 0.917 g/cm3 at 0°C, so that the mass of one Gt of ice is roughly equivalent to 1.1km3 ice*. This means that the Greenland ice has an overall mass gain by +11 ± 3 Gt/year (=10 ± 2.7 km3/year) which they estimated implied a -0.03 mm/year SLE over the period 1992-2002.

The critical point for Greenland is whether the increased rate of glacier motion more than compensates for the greater accumulation on the surface. While the broad picture of what is happening is consistent between these papers, the bottom-line value for Greenland’s mass balance is different in all three cases. Looking just at the dynamical changes observed by Rignot & Kanagaratnam, there is an increased discharge of about 0.28 mm/year SLE from 1996 to 2005, well outside the range of error bars. This is substantially more than the opposing changes in accumulation estimated by Johannessen et al and Zwally et al, and is unlikely to have been included in their assessments. Thus, the probability is that Greenland has been losing ice in the last decade. We should be careful to point out though that this is only for one decade, and doesn’t prove anything about the longer term. As many of the studies make clear, there is a significant degree of interannual variability (related to the North Atlantic Oscillation, or the response to the cooling associated with Mt. Pinatubo) such that discerning longer term trends is hard.

The largest contributions to sea level rise so far are estimated to have come from thermal expansion, with the melting of mountain glaciers and icecaps being of second order. Looking forward, the current (small) imbalance (whether positive or negative) of the Greenland ice sheet is not terribly important. What matters is if the melting were to increase significantly. Ongoing observations (most promisingly from the GRACE gravity measurements, Velicogna et al, 2005) will be useful in monitoring trends, but in order to have reasonable projections into the future, we would like to be able to rely on ice sheet models. Unfortunately, the physics of basal lubrication and the importance of ice dynamics highlighted in the Rignot & Kanagaratnam results are very poorly understood and not fully accounted for in current ice sheet models. Until those models include these effects, there is a danger that we may be under-appreciating the dynamic nature of the ice sheets.


Hanna, E; Huybrechts, P; Janssens, I; Cappelen, J; Steffen, K; Stephens, A (2005) J. Geophys. Res.Vo. 110, D13108, doi:10.1029/2004JD005641

Johanessen, O.M; Khvorostovsky, K; Miles, M.W; Bobylev, L.P. (2005) ScienceVo. 310 no. 5750, pp 1013-1016

Ringnot, E; Kanagaratnam, P (2006) ScienceVo. 311 no. 5763, pp 986-990

Velicogna, I; Wahr, J; Hanna, E; Huybrechts, P. (2005) Geophys. Res. Lett.Vo. 32, L05501, doi:10.1029/2004GL021948

Zwally, H. Jay; Giovinetto, Mario B.; Li, Jun; Cornejo, Helen G.; Beckley, Matthew A.; Brenner, Anita C.; Saba, Jack L.; Yi, Donghui (2005), Journal of Glaciology, Volume 51, Number 175, December, pp. 509-527(19)

*Update: Correction for arithmetic error in orginal post in converting Gt to km3, see comments.

175 Responses to “The Greenland Ice”

  1. 51
    Hank Roberts says:

    John, until killfiles* are implemented for web comments, without burdening the moderators grievously, it helps if we all ignore trolling no matter how tempting the bait. Do not bite. See the history, Usenet was just getting fairly good at this, then the web came along. So it goes.

  2. 52
    pete best says:

    These warmer winters, are they down to human induced climate change or natural climate variation. A series of warm winters is often the case is it not ?

    Can we show it is down to human induced climate change ?

  3. 53
    Coby says:

    I don’t just trust the IPCC sanctioned experts, because I read the sceptics sites and they bring up really good points

    Firstly, it is not just IPCC santioned experts, the list of reputable scientific organizations that have done the hard work of verification and found the arguments sound is very long, as presented in the link I provided:

    Secondly, the sceptic sites do not bring up really good points. They only sound plausible to people, like most people, who do not have the time or the desire or the ability to verify them. When you do start to verify them you will find they do not hold up. You will also discover quite a few out right falsehoods and this may make you feel like you have been duped and taken for a ride.

    You are also seriously misled to believe that the sceptics are publishing in the reputable scientific journals.

    Don’t give up, keep learning and you will come to the only supportable conclusion.

    “How much warming will occur?” is a legitimate area of debate, but the doubt is between “alot” and “a hell of a lot”, not between “a bit” and “nothing worth worrying about”.

    “Can we do anything about it?” is a socio-political issue, not a scientific one, though there is surely alot of good science needed to make sure we know the best choices.

  4. 54
    David B. Benson says:

    Ian —

    I found the following two books of considerable value in understanding modern climatology (and being able to follow RealClimate posts):

    W.F. Ruddiman
    “Earth’s Climate: Past and Future”

    F. Oldfield
    “Environmental Change: key issues and alternative approaches”

  5. 55
    grundt says:

    Re #49
    I feel that no serious scientist could disagree with your post.
    You are right. “….the most important theory that should be applied to the global climate changes we are seeing is Chaos theory and though a few are looking at it from that perspective, most are still applying old models in trying to predict what effects we’re going to see as our planet warms rapidly…..”
    Most of us are worried due to our ignorance. Models are extraordinarily useful, but are empirical tools no matter how complex they are.
    The more we know greater is our concern about our ignorance.

  6. 56
    Ian says:

    Thank you to those who have posted further references. I guess I won’t give up trying to understand the situation quite yet and will do some further reading, but I will also read Patrick Michaels books for a balancing perspective. Keeping objective is hard, but I want to seriously attempt to do so. I have a further question (one of the minutiae from the infinite minutiae that seeme to arise in this area). Looking at the rising CO2 it most definitely seems to have a strong linear trend. However, I would expect the trend to be exponential (exponential GDP, exponential population growth …). Does anyone know of a mechanism to explain why CO2 growth has been linear instead of exponential? Maybe it is as simple as increased absorption by the oceans (but don’t warmed oceans release CO2?), or perhaps it is in additional biomass growth (fertilization effect of CO2). Again … ugh. It seems to me ironic that only a decade ago or so I remember articles talking about “the end of science” as if we were close to knowing everything, but obviously those authors had not looked very closely into climate science ;-)

    [Response: What time period are you thinking of? See – William ]

  7. 57
    Ian says:

    Just a note to moderators. It is admirable to try to keep the conversation high-level and to reduce the amount of spam, unnecessary flaming, etc. Unfortunately there seems to be quite a large delay between posting and that posting showing up on the site. This seems to really drag out threaded conversations. Perhaps this is just an unavoidable trade-off.

    P.S. To those that posted book references, I am heading to the store right now to take a look ;-) but also as I mentioned I will browse through Patrick Michaels and the “other side” books as well.


  8. 58
    Ian says:

    #49 While the chaos approach is interesting I don’t know if it really adds very much. The thing about chaos is that you do not know the effect of a perturbation, and “stuff” will happen even without any obvious perturbations. In fact, skeptics could easily latched on to chaos theory as an example of why not to worry about global warming (if random inputs, or indeed no inputs results in random outcomes, then outcomes are outside of our control — so why worry about it).

  9. 59
    Blair Dowden says:

    Ian, get a copy of the Patrick Michaels book “Meltdown”, and read chapter two very carefully. A lot of common skeptic myths are dismissed in this brief but reasonable overview of climate science. But note while he is critical of the results of climate models, he confidently predicts the next 100 years based on simple extrapolation, which is a rather simple-minded model.

  10. 60
    Ian says:

    #56 William — Specifically I am thinking of this graph — and those like it i.e. the actually measured increase of CO2 in the atmosphere.

  11. 61
    Ian says:

    Sorry my last post was not very clear. Yes of course there is absorption by oceans and other natural processes to absorb CO2. I guess if the absorption functions were logarithmic then that would transform an exponential growth of CO2 production into a linear growth of CO2 concentration in the atmosphere. Anyways it was just a curiosity. Totally getting off track. Time to go read some books.

  12. 62
    Don Baccus says:


    If you’re going to read Patrick Michaels, I do hope you keep in mind that he’s been caught blatantly lying about Jim Hansen’s 1989 predictions. He was caught doing it in testimony to Congress. Despite his lie being pointed out, he continues to repeat it.

    Personally, I don’t pay much attention to proven liars …

  13. 63
    Mikel Marinelarena says:

    Re #14, #21, #25,… At the risk of annoying Ray P. again, on the “X started in 1850” argument I find myself closer to Ferdinand and John Finn than to him or Dano. If we observe an X event occurring around 1850 and then again around 1910 and 1978 it is reasonable to ask ourselves “did the same cause Y necessarily provoke X in all 3 cases?” But much more pertinent in the context of this debate is to ask ourselves “how can we be so sure that it is Z what caused X in 1978 if we still don’t know what exactly caused X in the 2 previous occasions?”

    I think that the burden of proof clearly lies on the side advocating that Z provoked X in the 3rd case but (obviously) not in the 1st or the 2nd one. Assuming that the same kind of force Y must have been behind all three X events seems in principle the logical thing to do and one need not justify it further until all 3 events and their causes are well understood.

    Besides, the corollary Ray P. imposes on Ferdinand’s argument is unreasonable. Very long before the whole Greenland ice-sheet melted away (!) we would all conclude that it was not quite X what we were observing this time but something of a different nature and causation.

  14. 64
    Steve Bloom says:

    Re #62: I haven’t read any of Michaels’ books, but do bear in mind that he has also been caught out a fair number of times fabricating claims on his World Clinate Report site, the latest instance being just last month as described in the last paragraph of my comment 7 above. As someone else noted, many skeptics engage in this sort of tactic because most of their readers lack either the necessary journal subscriptions or the time to check the facts themselves.

  15. 65
    Gerald Machnee says:

    Re #40 **I suggest starting with the narrative discussions here**
    – Rather a slanted discussion. No further comment.
    Re #41 **the warming is primarily driven by human actions**
    – I do not know of any study which has measured the percentage of the warming due to human activities. All I see is statements.

  16. 66
    Steve Bloom says:

    Re #63: It’s an interesting dilemma you pose, Mikel. Do we have any means of knowing the exact degree of insolation in 1850? No? So really you’re saying that we can never draw any conclusions with regard to the present glacial retreat even though modern measurements techniques allow us to exclude insolation changes as a major factor. Or are you arguing that there is some other cause entirely for the 1850 retreat that we don’t know about and/or can’t measure? I would suggest that a better approach would be to take our modern knowledge and measurements of all of the possible forcings and engage in a detection and attribution analysis to figure out the cause(s) of the retreat. It’s useful to look at historical glacier records to see if the results of our D+A exercise makes sense given what we do know about the history of the various forcings, but that can never be an exact exercise. I suggest you carefully read comment 36 and the responses to 43, plus look at the linked material.

  17. 67
    Matt says:

    RE: 49,55,58 and mathematical methods.

    The obvious method, must have already been done.

    Take the glacial function over as many periods as we have acccuracy for. Deconvolve the known solar forcing function, perform a least squared frequency analysis on the rest, and of the frequency response, retain only the moments you know are related to ocean/ice timescales. The rest would be the biomass forcing functions, short term ocean circulation, and geologic changes.

    This approach gives us very important information if we can go back to a particular cycle, remove the solar and ocean/ice driver, then look at the result as possibly changes in biomass feedback from cycle to cycle.

    But, this is what everyone is doing, I presume.

  18. 68
    Steve Bloom says:

    Re #64: Gerald, just as it’s hard to figure out the right gift for the person who already has everything they need, it’s hard to know what to say to someone who questions the entirety of climate science while believing that it’s all based on some sort of International Climatological Conspiracy involving the IPCC, the national academies of science, most climate scientists and all the major environmental organizations. All I can think of is to suggest that you read the History of Global Warming and the TAR, both of which are linked from this site. To get the answer to your attribution question I’m afraid you’ll have to read the hard bit of the TAR, which unfortunately will take a bit more time and concentration than “Climate of Fear” did. Sorry to be so brief, but the weekend is short and my tsunami generator is in desperate need of a wash and wax. :)

  19. 69
    Randall Simpson says:

    To #55:

    That certainly could be one argument made to do nothing…but in fact, Chaos Theory is quite scientific and of course quite mathematical too. Going in line with even the uncertainty of quantum events themselves. But what scientists can begin to say to policy makers and others is this: We can’t tell you exactly what will happen, but we can tell you that it will not be pleasant. In this sense Lovelock is exactly right…he senses the tipping point is already passed and that something quite nasty is ahead. this is Chaos Theory applied to Gaia and global systems. Just like when you stick your hand under a smooth running stream of water, and the spray is Chaotic by nature, you know that you’re going to get splashed, but no theory in the world can tell you exactly where any individual drop will fall. This is the message that scientists, in all good conscience must begin to get across to policy makers. We don’t know exactly where the next mega-hurricanes will occur, but we do know they will occur because of global warming and we do know that people in their path will get hurt.

    Chaos Theory is quite precise is telling us how systems reach tipping points and then go chaotic. This is the most important message and one that Lovelock is once more ahead of the pack on. For him, he’s convinced some major tipping point is already past and we’re headed for extremely chaotic and species threatening events. His message seems radical now…just like Gaia did 20 years ago, but I wonder how it will sound 20 years from now after we’ve experienced whatever Chaotic climate events are just ahead.

    One final note in my long winded reply: One of the greatest unknowns right now is the methane clathrates. With Siberia and other northern hemisphere permafrost melting…this positive feedback loop with methane being so much more potent a greenhouse gas and being released now from these regions is something that only increases the Chaotic nature of what lies ahead.

  20. 70
    Matt says:

    I read and reread the post on Lovelock, and the thing that strikes me his his choice to stabilize at the glacial maximum. In the background, some mute voices make a similiar plea, that if we are to be stuck, then is the glacial minimum the right spot? A quick glance would suggest one choice for best spot is the glacial midpoint, for that spot is mid-range in the ice/water interface, the most linear region, the spot where we can have the most control.

    I am assuming the majority will prevail, and we will be stuck at these temps for some time, with some blips along the way. It often bothers me that the global warming alarmists seemed so intent on defending the glacial minimum, for the ice data tells me that is the most unstable.

    But this seems strange, because if it was so unstable, then how are we stuck here? That question is the most haunting, for to have such a stable point, just a degree celsius from a very unstable point, indicates an extreme non-linearity.

  21. 71
    Ian says:

    #68 Stick ourselves at glacial maximum in a chaotic system … Interesting idea, but I doubt we have the necessary understanding or control. Can anyone flap their arms in just the right way to stop the next hurricane yet?

  22. 72
    Pat Neuman says:

    re 40 41 64

    In 64, Gerald Machnee wrote … “I do not know of any study which has measured the percentage of the warming due to human activities. All I see is statements.”

    During the last 50 years, polar ice, glaciers, ice sheets and permafrost have been thawing much too rapidly to be from anything other than human activity. In thawing episodes in Earth’s past, given similar starting conditions as 50 years ago, how quickly were polar ice, glaciers, ice sheets and permafrost areas reduced within a 50 year period? I think we all should know the answer to that question… minimally. Thus, the percentage of global warming due to non human activities now is minimal, i.e essentially all global warming since the 1960s is due to human activity, mainly from our greenhouse gas emissions. There is no need to attempt to extract a minimal effect on global warming from non human activity, it’s too small to measure or estimate.

  23. 73
    Alex says:

    I usually work on the assumption that the phrase “chaos theory” is an HTML tag meaning “insert handwaving here”. Is there really any other intellectual concept that is the basis for as much ill-thought-out bollocks?

  24. 74
    Gerald Machnee says:

    Re #72 – You illustrate exactly what I have been pointing out – NO DATA or CALCULATION. You then pick an abstract number – 50. You then make a statement “Thus, the percentage of global warming since the 1960s is due to human activity, mainly from greenhouse gas emmissions. There is no need to attempt to extract a minimal effect on global warming from non human activity, it’s too small to measure or estimate.” – with no backing.
    It does not look like you have been following to discussion of the Greenland Ice Cap or you would have seen some discussion of measurements of flow and thickness. Summarizing the points, it indicates that the ice cap has been advancing and retreating over the last 150 years of records. However the records are not perfect so a definite conclusion cannot be made even though some scientists have tried to say that based on the last 10 years or so, the ice cap is retreating and the oceans will rise significantly. Some have made this their whipping boy for rising sea levels. You are treating AGW like a religion.

  25. 75
    Pat Neuman says:

    re 74 Actually,

    In 72. I wrote … During the last 50 years, polar ice, glaciers, ice sheets and permafrost have been thawing much too rapidly to be from anything other than human activity. … i.e essentially all global warming since the 1960s is due to human activity, mainly from our greenhouse gas emissions. There is no need to attempt to extract a minimal effect on global warming from non human activity, it’s too small to measure or estimate.


    I’ve seen the recent data, calculations, and photography, including video presented at the Minnesota state capitol in 2005, by polar explorer and dog-sledder Will Steger from Ely, MN.

    I’ve studied the Cretaceous and Paleocene/Eocene evidence, and subsequent. There is nothing remotely close to the high thaw rate with similar starting conditions. GHG emissions are now at rates determined to be 30 times larger than the rate of GHG emissions which contributed to the Paleocene Eocene Thermal Maximum, about 55 myrs ago, according to a presentation given last month in St. Louis by Dr. Zanchos. We’ve spent way too much time looking back for things that aren’t there or don’t matter much. It’s beyond the time to focus on the future of the planet. Forward!

  26. 76
    Blair Dowden says:

    Re #75 – Pat, your last paragraph does not entirely make sense. There was no thaw rate in the Cretaceous or Paleocene/Eocene because there was no ice. There have been rapid melting rates in the past, eg. at the end of the Younger Dryas. Present GHG emissions may be higher than during the PETM, but those lasted for thousands of years. If we are smart we will stop long before that, hopefully as soon as possible.

    But there is no credible explanation for the warming of the last 40 years that does not involve anthropogenic greenhouse gases. One study claimed it might be 10% to 30% solar, a) that is disputed, and b) so what?

    A relevent observation from paleoclimate data is that the previous interglacial period (the Eemian) was one or two degrees warmer than the current one, and sea levels were 6 meters higher. The question is how long did it take for this sea level rise to occur?

  27. 77
    Pat Neuman says:

    In 75. Blair wrote … “There was no thaw rate in the Cretaceous or Paleocene/Eocene because there was no ice.”

    Blair, I’ve seen studies and articles that refer to ice during the Paleocene Epoch. I posted this excerpt and link to RC in Oct or Nov of 2005. There are other studies (in Science, which mention sea level changes from rapid ice thaw in the ancient past, some as rapid as over thousands of years, but none as rapid as over hundreds of years.

    Large (“rapid”) climate changes preceded the PETM, 65-55 mya, as shown
    in work by Robert Speijer. “A relative sea-level fall (~30 m)
    immediately preceded the late Paleocene thermal maximum, during which
    sea-level rose again by ~20 m. This rise may have been eustatically
    controlled, possibly through a combination of thermal expansion of the
    oceanic water column and melting of unknown sources of high-altitude or
    polar ice caps in response to global warming.”

  28. 78
    Hank Roberts says:

    Today’s Doonesbury cartoon:

  29. 79
    Pat Neuman says:

    re 77 … “Based on sea-level history, we have proposed that ice sheets existed for geologically short intervals (i.e., lasting ~ 100 ky) in the previously assumed ice-free Late Cretaceous-Eocene Greenhouse world (36).” … These ice sheets existed only during “cold snaps,” leaving Antarctic ice-free during much of the Greenhouse Late Cretaceous-Eocene.” …

    25 Nov 2005 article in Science, The Phanerozoic Record of Global Sea-Level Change (Miller, K.G. et. al.).

  30. 80
    Armand MacMurray says:

    Re: #43
    Those wishing an independent evaluation of the science of past temperature reconstruction may wish to follow the progress of the National Academies’ project “Surface Temperature Reconstructions for the Past 1,000-2,000 Years: Synthesis of Current Understanding and Challenges for the Future,” which had its first meeting and heard testimony last week. Reporters were in attendance, so accounts of the meeting may become available to the general public.

    [Response:. The most significant development here is the paper that has just gone to press by Wahl and Ammann]

  31. 81
    Pat Neuman says:

    re 75. Correction to spelling of name: James Zachos, professor of Earth sciences at the University of California, Santa Cruz

    Ancient Climate Studies Suggest Earth On Fast Track To Global Warming

    by Staff Writers
    Santa Cruz CA (SPX) Feb 16, 2006
    Human activities are releasing greenhouse gases more than 30 times faster than the rate of emissions that triggered a period of extreme global warming in the Earth’s past, according to an expert on ancient climates.
    “The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we are likely to emit the same amount over the next three centuries,” said James Zachos, professor of Earth sciences at the University of California, Santa Cruz. …

  32. 82
    Blair Dowden says:

    The climate of the Cretaceous is still not well understood. We are unable to explain why warmth was so evenly distributed between the equator and poles. Now we have evidence of rapid sea level changes (how often these occur is not said) that can be best explained by short (100 ky) glaciations, but no evidence of such events. If true, the interesting question is what kind of cooling event triggered them? I have not seen an explanation of the 30 m sea level fall preceeding the Paleocene Eocene Thermal Maximum (PETM).

    As for the article on the Zachos study, they claim 4.5 trillon tons (4,500 gigatonnes, or Gt) of carbon entered the atmosphere in 10,000 years, ie. at a rate of 0.45 Gt / year. Present emissions are around 7 Gt/yr, which I make to be about 14 times higher, rather than 30. 5,000 Gt is the estimated coal reserves, and it is very pessimistic to assume we will burn it all in 300 years. Surely we will invent better technology before then.

  33. 83
    Eli Rabett says:

    WRT “Surface Temperature Reconstructions for the Past 1,000-2,000 Years: Synthesis of Current Understanding and Challenges for the Future,” the schedule of the first meeting is at

    It looks like something I am sorry I missed, but still I think “taking testimony” is the wrong description. They use the term “invited speaker” which is more in keeping with NAS processes I am familiar with.

  34. 84
    Matt says:

    The comments on the Cretaceous period and that other thermal maximum sent me off looking things up only to discover man is planning to mine methane hydrates and convert coal to portable carbon fuels.

    There will be a continual need for 2-3 Gigaton/year of portable fuel emissions for another 300 years. It doesn’t matter where you get it, the only solution is to have photosynthetic carbon be more competative than the alternatives, either by collective wisdom or dynamic markets. We need economic incentives to extract atmospheric carbon, even if we need 75 year planning cycles.

    Back to climate. How is the climate going to be for large scale carbon sequestering during the warm period?

  35. 85
    Andrew Dodds says:

    Matt – I would say it is a bit unwise to try to project human fuel usage 300 years into the future. Photosynthetic carbon is not really a long term alterative in any case; farming is by definition very destructive of the environment.

    Methane hydrates are a very unlikely fuel source indeed; they are far too distributed in nature.

  36. 86
    PHEaston says:

    Re: Response to No. 80. Where is the Wahl & Ammann paper to be published?

  37. 87

    Re: Steve Bloom’s Comment #64 and #7


    I don’t see where you are going with these comments. According to my copy of Rignot and Kanagaratnam (R+K) the date of submission of this article was October 14, 2005. According to my copy of Johannessen et al. (J et al.) it was published on-line on October 20, 2005. Although your timeline (re:#7) is wrong, the point I guess you are trying to make is that R+K did not reference J. et al. because J et al. was published a week AFTER R+K was submitted. However, this seems to neglect that period between October 20, 2005 and January 17, 2006 (the date R+K was accepted) during which time any of the reviewers and, in fact, R+K themselves could have modified their text to include at the very least a reference to J. et al. Reviewers suggesting that references should be added happens all the time. In fact, in a new paper that we have under review examining the relationship (or lack thereof) between SSTs and hurricane strength (which we hope will appear in the peer-reviewed mainstream scientific literature belive it or not), we added references (to our original submission) at the insistence of reviewers and, in fact, added an additional reference ourselves to a brand new paper that was published AFTER our original submission. There was plenty of opportunity for R+K to have done the same in regards to J. et al.

    Further, as the RC article mentions, in addition to the interior Greenland mass gains reported by J. et al., the study by Zwally also reported mass gains. Therefore, it would seem appropriate to ask, as Pat Michaels did, why then did R+K only decide to incorporate the interior mass loss modelled (rather than observed) by Hanna et al.

    Heck, even RC doesn’t suggest that using Hanna et al was the correct thing to do. Instead, they point out simply that the losses reported by R+K were larger than to gains reported by J. et al. and Zwally et al. And this is what R+K probably should have done–recognize the results of J. et al. and Zwally et al. and then put them into context–not simply ignore them and use Hanna et al. instead. This gives the impression that they were attempting to make their results more extreme and thus noteworthy.

    As always, we invite everyone to fact check our stories and we make every attempt to provide the references to do so.

    And further (re: #64) it is not a valid criticism that we make reference to articles in journals that no one else has access to. A trip to the nearest University library should remedy that situation. That’s what we do!


    [Response: You’re missing the point of the criticism. The criticism isn’t that professionals with time to delve into the literature fail to check your facts. The remark only says that World Climate Report can count on getting away with misquoting or distorting the scientific literature because most of your readers don’t bother to do so, still less the newspaper reporters who used to quote WCR for the sake of “balance.” If more people checked your spin on the issues (and that is one of our jobs here at RealClimate) WCR would probably lose what little credibility it has left. –raypierre]

  38. 88
    Matt says:

    Dodds –

    I am going to have to challenge you a little on this fuel use projection.

    The steam engine is 300 years old. For 100 years the four cilinder carbon combustion has been the transportation of choice. The peak oil projections from: have us using oil 50 years from now at 1960 levels, and extending their graph beyond has us using at 1950 levels in 75 years. I have not seen serious projections of a commercial fusion reactor for 50 years. Carbon and hydrogen are the only real energy carriers in contention. The population will still be in the billions at 2300. Automotive manufacturing has a depreciation life of nearly 75 years. Rail transportation still occupies a second place to the automobile.

    If we are not using mainly carbon as a portable fuel in 300 years, then give me the alternative.

  39. 89
    Dano says:

    I find it fascinating that, reading raypierre’s reply to checking source material (current 87), the comment immediately above asks where a paper is to be published. The journal name is both in the HTML page properties (the joys of tabbed browsing) and in the abstract immediately below the affiliations.

    I guess that is a good example to make Steve Bloom’s point (and my often-stated point, just not here). The skeptics get away with some of their standard tactics because no one “audits” their work.



  40. 90
    Steve Bloom says:

    Re #87: Thanks, Raypierre. Chip, there might have been something to what you say except for the fact that the editors of Science, recognizing the need for all of these results to be synthesized, commissioned Dowdeswell to do just that (and in the same issue as R+K). You then proceeded to attack the editors and R+K for their failure to address the material Dowdeswell covered, and never told your readers that Dowdeswell even existed. But of course if you’d done so, the whole premise of your article would have evaporated.

  41. 91
    David B. Benson says:

    Gerald, Re #74 —

    I’ll do a rough-and-ready calculation of the proportion of GW which is AGW, and obtain vastly more than 100%! The argument depends upon probability and some work on Ruddiman, specifically
    the figure on page 83 of F. Oldfield’s book cited previously in comment #52. First the probabilities, given via a standard marble-in-box argument.

    There is a line of eight boxes, the first seven of wood and the last carved from jade. Each box contains a marble, either black or white. Before opening the first box, you need to have some a priori probability that the marble is black. Suppose you choose 50%. So after opening the first seven boxes and discovering all the marbles are black, you are now in a position to assign a probability to the hypothesis that all marbles are black, 99% and a little more. But upon opening the last box, the one of jade, the marble is white. So either you were terribly unlucky or else you require a more refined hypothesis in which the nature of the box, wood or jade, is taken into account. At this point, the hypothesis that all wooden boxes have black marbles is well supported, 99%. About jade boxes there is only the one observation on a white marble. The hypothesis that jade boxes are different from wooden boxes, regarding the color of the marble inside, is also highly confirmed.

    The climate hypothesis, corresponding to all boxes, is that after every time in the Vostok ice core record that methane concentration rose above 550ppb, it then declined subsequently
    following orbital forcing. Looking at the figure cited just above, the first seven times support the hypothesis. Using the wooden box analogy, this hypothesis is now highly confirmed. However, the eighth is the Holocene and like the jade box we discover something very different: not only did methane concentration fail to decline, it rose dramatically, in complete disaccord with the previous 400,000 years of methane concentration records. Clearly the Holocene is a jade box.

    Thus my claim of more than 100% of GW is AGW. Methane etc should be declining, not rising.

    Ruddiman’s book “Plows, Plagues and Petroleum” makes the case in a different manner, and for a non-technical audience.

  42. 92

    Dr. Pierrehumbert (re: #87 response),

    The funny thing is, I always thought that we (World Climate Report et al.) existed to counter the alarmist spin on this issue and do the work for the man-on-the-street who doesn’t have the time and resources to fact check everything he reads or hears in the media. And now RC exists to counter us.

    My this is a cozy little self-perpetuating existence that we have created for ourselves isn’t it!


  43. 93
    Hank Roberts says:

    Please respond to the criticism of your description of the Science Magazine contents; if you made a mistake, correcting it is appropriate.

  44. 94
    Dano says:

    Chip (92), you can go on sci.env to see a rich history of folk pointing out stuff that ‘counters’ ‘you et al.’, so I don’t see that particular niche being filled in quite the way you say.

    Unless you mean that the folk that write the source material are addressing ‘you et al.’ now, instead of people who read the articles and regurgitate the scientific literature…



  45. 95
    Steve Sadlov says:

    #47. 20 years ago I was a borderline Earth Firstoid, hard core Gaia worshipping worst case scenario promoter. I subscribed to the world views espoused by Amory Lovins, Malthus and James (“Greenhouse: It WILL Happen in 1997.”). Now I am not so sure. I don’t work for big oil. I *do* work for big “we are going to get rich if people take Kyoto seriously.” Sorry that I don’t fit into your pigeonhole. I am a skeptic even in the face of my own financial conflict of interest (which would make me, in terms of raw interest, a natural “warmer”). I am therefore a pure skeptic, with absolutely no conflict of interest pushing me in that direction. Only my own sense of ethics pushes me in that direction.

  46. 96
    Steve Sadlov says:

    #48. At some point, it will have to come to resemble the precious metals economy albeit with a much more intensive recyling component “fueled” by photosynthesis. That is, unless we colonize space and find a new home that is as good as or better than Earth.

  47. 97
    Armand MacMurray says:

    Eli, “taking testimony” was purely my own phrasing, intended to describe the speakers giving 45-minute presentations, answering questions from the panel, and participating in the open discussion. I’m sure there’s a better phrase for that process… :)
    Also, there are some initial reports of the events there at climateaudit (for those who don’t know, the site is what many here would call a “skeptic” site).

  48. 98
    Peter wright says:

    I am yet another concerned layman who has been following the climate change debate for 20 years or so,
    and I am left with a feeling that a very major aspect is been neglected by those most able to address it, namely professional climate scientists. That is the way that one aspect of the changes brought about by elevated co2 affects another and so on that often changes the base assumptions of The rate of melting of say the Greenland ice cap is based on an assumption about likley global temperature rise which in turn is based on expected levels of atmospheric co2.
    Projected rates of rise of co2 (for given anthropogenic emissions scenarios) assume (?) that current natural carbon sinks remain basically unchanged but melt water from say Greenland may reduce the thermohaline circulation which would reduce the rate of absorbtion of co2 by the oceans (various mechanisums such as reduced displacment of co2 rich surface water by co2 poor deep water, reduced activity of photosynthetic plankton because of reduced nutrient levels, loss of shell forming plankton due to acidification, all of which resulting in higher than projected atmospheric co2 for a given anthropogenic emmissions scenario. This would then lead to higher than projected air temperatures (also as a result of higher sea surface temperatures due to reduced mixing) with consiquent increase in the rate of melting of Greenland ice and so on. Do you see the point.
    I know that there are enormouse uncertainties in maney of these effects but I think someone ought to do a best guess calculation because I think that in these ,as yet, unquantifiable feedback loops the potential for more rapid and extreme climate change than is currently been predicted is present.

    A quick personal response to this comment would be much appreciated if it dosen’t merit posting on the blog

    [Response: This is indeed a plausible postive feedback on CO2 concentrations, as are melting permafrost releasing carbon, changes in soil respiration as a function of temperature etc. When they are quantified (though they are still uncertain) they add up to about a 10% increased effect (if memory serves me – you might want to look up some relevant literature – Friedlingstein et al, and Cox et al have published on this). However, the postulated increases in CO2 from fossil fuel sources completely dominate what is likely to happen. -gavin]

  49. 99
    Gerald Machnee says:

    Re #91 – you have also illustrated my point. So if you come up with more than 100 percent you are exagerating and also making errors in math. I would sometimes get 100 percent in math and science(before multiple choice), but, damn, I could never get more than 100. I have heard of hockey players putting out at 110 percent, but I did not play hockey.
    To measure the percent of AGW contribution, you have to get right into it, marbles may illustrate a point, but they have not measured it. So, it remains – we may have increased the temperatures in the last several decades – but what caused it?

  50. 100
    Dano says:


    Speaking of recycling and comics in another thread, I’m reminded of a comic that highlighted a similar tactic a couplea years ago, that approached the anecdote assuming about the same level of credulity.