Greenland Glaciers — not so fast!

Our study does not include many of the measurements that are a part of determining total mass balance, and thus total sea level rise. In another paper that we highlight in our study, Pfeffer et al. [2008] used a specifically prescribed velocity scaling to examine potential worst-case values for sea level rise. The Pfeffer et al. paper did not produce “projections” of sea level rise so much as a look at the limits that ice sheet dynamics might place on sea level rise. It is reasonable to comment on how our observations compare to the prescribed velocity values that Pfeffer et al. used. They lay out two scenarios for Greenland dynamics. The first scenario was a thought experiment to consider sea level rise by 2100 if all glaciers double their speed between 2000 and 2010, which is plausible given the observed doubling of speed by some glacier. The second experiment laid out a worst-case scenario in which all glacier speeds increased by an order of magnitude from 2000 to 2010, based on the assumption that greater than tenfold increases were implausible. The first scenario results in 9.3 cm sea level rise from Greenland dynamics (this does not include surface mass balance) by 2100 and the second scenario produces 46.7 cm sea level rise by 2100. The observational data now in hand for 2000-2010 show speedup during this period was ~30% for fast-flowing glaciers. While velocities did not double during the decade, a continued speedup might push average velocities over the doubling mark well before 2100, suggesting that the lower number for sea level rise from Greenland dynamics is well within reason. Our results also show wide variability and individual glaciers with marked speedup and slowdown. In our survey of more than 200 glaciers, some glaciers do double in speed but they do not approach a tenfold increase. Considering these results, our data suggest that sea level rise by 2100 from Greenland dynamics is likely to remain below the worst-case laid out by Pfeffer et al.

By adding our observational data to the theoretical results laid out by Pfeffer et al., we are ignoring uncertainties of the other assumptions of their experiment, but refining their velocity estimates. The result is not a new estimate of sea level rise but, rather, an improved detail for increasing accuracy. Indeed, a primary value of our study is not in providing an estimate of sea level rise, but in offering the sort of spatial and temporal details that will be needed to improve others’ modeling and statistical extrapolation studies. With just ten years of observations, our work is the tip of the iceberg for developing an understanding of long-term ice sheet behavior. Fortunately, our study provides a wide range of spatial and temporal coverage that is important for continued efforts aimed at understanding the processes controlling fast glacier flow. The record is still relatively short, however, so continued observation to extend the record is of critical importance.

In the same Science issue as our study, two perspective pieces comment on the challenges of ice sheet modeling [Alley and Joughin, 2012] and improving predictions of regional sea level rise [Willis and Church, 2012]. Clearly, all three of the papers are connected, as much as in pointing out where we need to learn more as in indicating where we have already made important strides.

Alley, R. B., and I. Joughin (2012), Modeling Ice-Sheet Flow, Science, 336(6081), 551-552.

IPCC (2007), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, S. Solomon et al., Eds., Cambridge University Press, ppp 996.

Moon, T., I. Joughin, B. Smith, and I. Howat (2012), 21st-Century Evolution of Greenland Outlet Glacier Velocities, Science, 336(6081), 576-578.

Pfeffer, W. T., J. T. Harper, and S. O’Neel (2008), Kinematic constraints on glacier contributions to 21st-century sea-level rise, Science, 321(000258914300046), 1340-1343.

Straneo, F., G. S. Hamilton, D. A. Sutherland, L. A. Stearns, F. Davidson, M. O. Hammill, G. B. Stenson, and A. Rosing-Asvid (2010), Rapid circulation of warm subtropical waters in a major glacial fjord in East Greenland, Nature Geoscience, 3(3), 1-5.

van den Broeke, M., J. Bamber, J. Ettema, E. Rignot, E. Schrama, W. Van De Berg, E. Van Meijgaard, I. Velicogna, and B. Wouters (2009), Partitioning Recent Greenland Mass Loss, Science, 326(5955), 984-986.

Willis, J. K., and J. A. Church (2012), Regional Sea-Level Projection, Science, 336(6081), 550-551.

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269 comments on this post.
  1. Phil Mattheis:

    I’ll apologize for re-posting this link just sent to the unforced variations thread – I had linked directly to the jpeg, which does not include the accompanying narrative from NASA that explains the image:

    As I said, Greenland ice is not just a drop in the ocean, but water is just a drop on Earth…spread thin and vulnerable.

    [Response:That’s a very compelling image. I would love to see the same but for a) a water drop that represents the glaciers and b) a water drop representing all the unfrozen fresh water on earth. You’d have to zoom in a lot more! –eric]

  2. jaykimball:


    I thought the same thing when I saw that image. I would love to see a water sphere for fresh water – surface and aquifer.

    Jay Kimball
    8020 Vision

  3. Rick Brown:

    Eric – an image including a representation of your b) [all fresh water] is available at (From a link in the explanatory text for the image Phil provided.)

  4. BillS:

    ” On a local scale, there is notable variability in glacier speeds, with even neighboring glaciers exhibiting different annual velocity patterns.”

    Here is a wonderful photo demonstrating entirely different behavior of three neighboring glaciers:

  5. Doug Proctor:

    The 30% rise as measured for Greenland:
    A 2X rate increase by 2010, staying that way to 2100, results in 9.3 cm of ocean rise. Even if it rose to 2X by 2100, the average would be much less than 2X, and the resultant rise would be less than 9 cm.

    The concluding statements are nicely put. While saying 10X is implausible, and 2X might occur, the reader is still left with the idea that a crisis of ocean rise is possible or probable. The number these researchers are speaking of is considerably less than “crisis”, but by not giving a number, they cannot be criticized – by either side.

    [Response: Which is precisely right of course, because the reality is that this new paper provides no real guide here. It simply says “here are the data” and if we MUST say something about sea level, here’s what we can say. It may be boring, but it’s right. By the way, a crisis of ocean rise is actually CERTAIN already if you live in particular places. The question is how many places that will wind up being, and over what timescale.–eric]

  6. MMM:

    Doug Proctor: The question is whether a 30% increase over a decade is a 30% increase to a maximum speed, or whether it heralds continuing 30% increases. If the former, then we’re looking at 1.3 over 2 time 9.3 or 6 cm of sea level rise by 2100 from Greenland. On the other hand, 30% increase every decade means about a 5x average speed over the century, or about 25 cm of sea level rise from Greenland alone. Not as bad as the 10x future, but solidly in the middle of the original range.

    (remember also that Greenland is not the only source of sea level rise: thermal expansion and land-glacial melt are fairly certain to contribute tens of centimeters, and Antarctica is a dark horse)

    [Response: Yes, all correct –eric]

  7. John Mashey:

    Thanks for this useful summary …
    and for the single most appropriate use I’ve seen of a common phrase:

    “…our work is the tip of the iceberg…”

  8. TimD:

    The ice mass loss in the Greenland region as measured by the GRACE satellite system clearly shows an accelerating rate of loss with a doubling time of less that ten years. If the arbitrary and unsupported “assumption” that a 10X speedup in mass loss turns out to be wrong, it seems we will know it pretty soon. The discussion in the article does not adequately cover the nonlinear behavior of ice and partially melted ice as it rapidly warms to near the melting point. As the ice slides away on the edges of the sheet, the slope increases, flow rates increase, viscous heating increases with flow rate, viscosity decreases, flow rates increase, partial melting occurs in the high flow rate areas, viscosity drops precipitously… RAPID COLLAPSE.

  9. Tenney Naumer:

    The question I’ve had for the last few years is:

    What proportion of the mass balance loss is due to glacial outflow and what proportion to melt runoff and how are these proportions changing over time?

  10. jaykimball:

    For those that are wondering what size sphere would be required to hold the fresh water accessible to humans, I updated the USGA image and posted it here:

    Rick, the image you link to doesn’t look right. The sphere is too small. Perhaps they are not including ground water. They link to their definition of freshwater, but it is a dead link. So hard to know what their assumptions are.

    The USGS says that about .75% of the earths water is freshwater. That yields a sphere with about 20% of the diameter of an “All Water” sphere.

    Jay Kimball
    8020 Vision

  11. Martin Vermeer:

    Great story, thanks Eric.


    s/Jakoshaven Isbrae/Jakobshavn Isbræ/

    (If that’s too difficult to pronounce, try ‘Sermeq Kujalleq’ :-)

    [Response:Will correct! –eric]

  12. Kevin McKinney:

    The link in #1 has now ‘moved on’ a day, and so no longer reflects the topic. The correct image can be found in the archives, here:

    It is indeed striking.

  13. Dan H.:

    I am not sure where you are getting your GRACE data, but a recent study does not comfirm your statements.

  14. Susan Anderson:

    Thanks to Tenney and particularly TimD @~8:

    The ice mass loss in the Greenland region as measured by the GRACE satellite system clearly shows an accelerating rate of loss with a doubling time of less that ten years.

    Typical: 3 guesses and the first 2 don’t count: Hal( is an outfit that either allows self-publishing or uses an internal biased so-called peer review in favor of an agenda. Distracting from what should be a real conversation again, and I’m one of the first sinners there …

  15. Hank Roberts:

    Susan, look at the linked page, that’s a copy at a repository for open access docs. The source is identified at the top of the linked PDF:
    Bergmann et al.: Global and Planetary Change 82-83 (2012) 1-11
    DOI : 10.1016/j.gloplacha.2011.11.005

    It’s on the list of GRACE-related publications here:

    Full cite from that list:
    Bergmann, I., Ramillien, G., and Frappart, F., 2012. Climate-driven interannual ice mass evolution in Greenland. Global and Planetary Change, 82:1–11, doi:10.1016/j.gloplacha.2011.11.005.

    As GavinEric wrote earlier:

    “… the reality is that this new paper provides no real guide here …”

    That would apply for “TimD” who cited nothing and Dan H. who cited an irrelevant paper.

    If there are papers out on ice sheet collapse, and our hosts want to go into it, it’d be interesting — the ANDRILL work might give some paleo data as it’s beginning to be published, for the Antarctic. But that’s not the topic.

  16. BillS:

    Tenney at #9

    It may be the case that more mass is lost via basal melting than through calving or surface runoff for marine terminating glaciers north of about 74-75 deg. North latitude on both the east and west coasts. In Fig. 1 above that melting would occur in the area between where the base of the glacier rests on the bed (the grounding line) and the front of the glacier.

    A search at on “runoff, greenland” will lead you to any number of accessible papers. I think you will find that the proportions vary with regions.

  17. Kevin McKinney:

    #14, 15 and previous–

    I scanned the Bergmann et al paper and it seemed reasonable to these amateur eyes. It found a slowing of mass loss rates in 2009-10, which seems entirely reasonable in conjunction with the low 2009 SSTs which we already knew about.

    That slowing is the basis of Dan H’s comment that acceleration was not supported by GRACE data in recent years. True enough, I suppose, but then with study pretty much limited to 2002-2010, it’s pretty early innings for *any* firm conclusion about the evolution of loss rates.

    The *fact* of ice mass loss, though, seems a pretty darn firm conclusion; the present study has the lowest rate found so far (which would account for why Dan likes the study), but that’s still 32 GT/year, over the full span from 2002 to 2010. (Their highest number was 92 GT/year.)

    Velicogna (2009) had the highest number so far–230 GT, for the span 2002-(Feb)2009.

  18. TimD:

    DanH,Kevin M, The most recent Grace data I had seen (, which doesn’t discuss methodology for data reduction, but which is consistent with the earlier results doesn’t show a slowdown as the Bergmann paper does. Honestly, I will need a bit more time to digest that paper, but it clearly is a review of the data using different reduction methods and seems to be an outlier. But even if it isn’t, it’s results are clearly highly smoothed and show a slowdown over an insignificant amount of time. The result I showed clearly illustrates seasonal variation, so it is resolving the mass changes well, and this is not decelerating. It would be interesting to look at the GRACE data in conjunction with ENSO and the North Atlantic cycles. If the slowdown suggested in the Bergmann paper are supported by further work, it would be coincident with the La Nina phase we have experienced for the last couple years and may not be significant in the long term. The point of my previous post was that there are plenty of nonlinearities in ice physics near the melting point that are generally poorly represented in ice sheet models, explaining the current and, no doubt, future surprising behavior of ice sheets.

  19. Aaron Lewis:

    At the heart of of this model is a glacier sliding down hill from a colder environment into a warmer environment (see Fig, 1 above). In this model, the rate of downhill movement is faster than the conduction of heat into the core of the glacier and the core of the glacier remains cold enough to provide some structural strength to the ice. Where the ice warms to the core, a “calving face” forms.

    However, much of the Greenland ice is not sliding down hill, rather the environment around it is warming, and heat is being advected down into the ice. Thus, it is not just the calving face that is warming and losing structural strength, it is the the entire volume of ice affected by moulins carrying melt water from the surface.

    This is not something we have seen (on this scale) before. Icesheet breakup is a non-linear process. Extrapolation of recent trends tell us nothing. GRACE data gives the mass of the structure, not structural strength of the ice. We have to calculate the mechanical and structural stresses, sources of heat, the Gibb’s energy, the structural strength of ice, and trust the result. It is not pretty.

    The result is that the massive core of Greenland’s ice is supported by gently sloping ice bulwark or buttress. When the top surface of this is “bulwark” ice is above the melting point, pools of melt water and condensate form on the surface, then form moulins, and the melt water drains through the moulins. Large volumes of ice are warmed and weakened simultaneously. (When one gram of water condenses, it releases enough heat to melt 7.5 grams of ice resulting in 8.5 grams of “runoff”. Thus, water vapor from an ice free Arctic sea, will dramatically affect Greenland.) Then, the cumulative weight of the ice structure blows the weakened bulwarks outward, followed by the progressive collapse of the ice core (as it is no longer supported by the bulwarks).

    With the loss of Arctic sea ice, more latent heat is available to melt the surface, cold dry air is less common around the shores of Greenland, and warm moist air is more common around Greenland. Loss of Arctic sea ice will dramatically accelerate the decay of the GIS.

    After a lengthy period of warming and weakening, the progressive collapse happens rather fast. This does not often happen in glaciers moving down slope because the uphill ice is colder and structurally stronger, and there is less potential energy involved. The glacier model does not work for ice sheets.

    Published? Naw, this is just basic undergrad physics. As such it is very crude. However, it has other implications. For example, the wave benches on Lake Missoula were the result of super-glacial ponds, and Missoula Floods were the result of the progressive structural collapse of an ice structure. Likewise, some of the Lake Agassiz floods were the result of the rapid progressive collapse of ice structures rather than the failure of ice dams holding lakes of liquid water. The truth is that no ice dam can support a head of more than ~6 meters of liquid fresh water. Ice in contact with sea water can be colder and withstand higher pressures.

  20. Hank Roberts:

    Ice sheet system model links:

    and ‘Google Scholar’ comes through with
    Sell Me Your Beach House, Please!
    PJ Michaels – The Tea, 2012

  21. TimD:

    Aaron L, I like your analysis. In the near term,I think the big question is; “Is this recent acceleration in ice mass loss in Greenland a short term thing due to sub-sea melting affecting the grounding of ice streams, or is this likely to continue over several doublings because the acceleration is reflecting deeper non-linear fluid effects?” Things can change rapidly in this environment because loss of sea ice is rapidly warming surface waters, which, being saline, can slip below fresh meltwaters and very quickly transfer heat by mass tranfer of heat deep beneath the ice sheet. And, of course surface melt waters, which have increased quickly during the summers, have reduced the albedo of the melt water lakes and when they frack their way through the sheet, the heat from that water is transferred quickly through the sheet, reducing its strength. If a number of melt water lakes were to hook up, a very large calving surface could form, and lead to a propagating collapse front. But I can pretty well guarantee that these sorts of effects are not included in the ice sheet dynamic models. In paleo data we lots of indications of rapid sea level rise due to ice sheet collapse, but the time resolution of that data isn’t sufficient to tell if the changes occurred in months or centuries, which is a pertinent uncertainty in the context of the current situation. A good review of pleoclimatology related to current global warming is Hansen, et. al.: Hansen has done some modeling that suggests that ice mass loss could continue to double until so much ice is unleashed to the north Atlantic that there would be an end to sea ice melt in the summers and the climate could jerk back into cooling, but throwing the climate into a chaotic mess.

  22. Tom Scharf:

    It should probably be mentioned that instead of all these complex studies and inaccurate methods to attempt to determine the exact melting rate of a particular glacier, it is seemingly simpler and more accurate to measure sea level via satellite measurements.

    Although total SLR has other factors than just this, my understanding is these ice sheet melts are seen as the primary driver for any future high level SLR.

    The pundits in the denial-sphere have a point when they speculate on the possibility of confirmation bias when some studies (not these specifically) conclude the melting rate of an ice sheet / glacier is “worse than we thought”, accelerating, doubling, etc.

    The obvious question is where is all this melt going, because it doesn’t appear to be going into the sea according to satellite measurements.

    I don’t think this conflict with observations is a minor point, but is a bit too easily dismissed as somehow unimportant. I think many would trust the reliability of satellite measurements over these type of models or estimates, and the alarm-o-sphere inevitably picks up on any whiff of speculation that things are “worse than we thought”, and pretending that universities don’t engage in throwing out some red meat for the MSM with their press releases is a fantasy in my view.

    For the record, I thought this piece was balanced overall.

  23. TimD:

    Tom S – Just for the record, I wouldn’t worry about your post being balanced as much as well supported scientifically. We don’t try to balance discussions of geology with flat earthers, we shouldn’t do the same with politically motivated denialists either. But to your points, I believe that total ice mass due to losses from glaciers world-wide is about .5 mm/yr SL equivalent, while annual variability due to precipitation is on the order of 20 mm/yr. So the problem is seeing the signal through a lot of noise. This ref has recent data and a good discussion of SL change factors. Over the last few decades it seems that higher global precipitation due to warmer sea surface temperatures and increased water sequestration in large dams has pretty well balanced the small ice melt contributions. The long term trend is pretty linear:

  24. wili:

    Tom, why do you think a measure of sea level would autmatically tell us more about Greenland melt than direct measures of that melt itself? You do know that sea level has its own dynamics, it can temporarily be (and has recently been) affected by increased evaporation from increased global temperatures, don’t you?

    Back to the issue at hand–How much of a factor will the rebounding land beneath the ice (as the mass above it decreases) have on the rate of glacier movement over the next hundred years or so?

    It seems to me that even a slight change in slope as the interior bedrock rebounds could cause dramatic changes in rate of movement. After all, if you tip a table only slightly, a marble on it will start to move even though it had been stationary before. I have not read all of the recent studies. Has anyone seen this calculation included? Is it too minor to mention? Or too uncertain to predict?

    (reCaptcha: John, bettcom)

  25. Hank Roberts:

    Just as a reminder how little we knew two years ago, which may suggest how little we still knew: do you know how fast drumlins form? Used to be thought they were a slow process, til about 2010:

    —-excerpt follows—-

    Drumlin Field Provides Answers About Glaciation And Climate

    This is a drumlin by the Mulajokull glacier on Iceland. The ravines cutting into the drumlin have given researchers an opportunity to study its structure. Credit: Mark Johnson
    by Staff Writers
    Gothenburg, Sweden (SPX) Nov 18, 2010
    The landform known as a drumlin, created when the ice advanced during the Ice Age, can also be produced by today’s glaciers. This discovery, made by researchers from the University of Gothenburg, Sweden, has just been published in the scientific journal Geology.

    Drumlins generally consist of an accumulation of glacial debris – till – and are found in areas that were covered by ice sheet. As the ice advanced, it moved rocks, gravel and sand and created tear-shaped raised ridges running parallel with the movement of the ice.

    “Until now, scientists have been divided on how drumlins were created,” says Mark Johnson from the Department of Earth Sciences at the University of Gothenburg.

    “Because they are formed under the ice, it’s not an observable process. Drumlins are common almost everywhere the Ice Age ice sheets existed, but they’re almost unknown with modern-day glaciers. Now, though, we’ve found a new drumlin field by the Mulajokull glacier on Iceland. It’s quite unique.”

    The melting of glaciers reveals drumlins
    The melting of glaciers as a result of climate change has helped the researchers to study this geological phenomenon. The drumlin discovery on Iceland has presented unique opportunities to study their structure.

    “One of the drumlins we found was sliced through by erosion. This gave us an opportunity to study it layer by layer, and it was clear that it had been built up only recently. In other words, the glacier has not just retreated to reveal old drumlins, but is continuing to create new ones.”

    There are currently multiple theories about the origins of drumlins. The Gothenburg researchers’ discovery shows that they can form within two kilometres of the edge of the ice.

    “A surging glacier can move 100 metres a day, as opposed to the more normal 100 metres a year. If we can link drumlins to fast-moving glaciers, this would mean that the ice sheet advanced much more quickly than scientists currently believe.”

    Can effect climate research
    The link between drumlins and rapid ice movements is important for climate research. When modelling climate change, we need to know how high and how cold a glacier was in order to understand the last Ice Age. A glacier that moves quickly will not be as thick. This discovery could therefore affect how scientists approach climate modelling.

    Solving the riddle of the drumlin is a longstanding dream for Mark Johnson:

    “We discovered the drumlin field while flying in towards the edge of the glacier to do a completely different study. It was the most exciting thing I’ve been involved in during my research.

    “All geologists know about drumlins, and when I began to study geology in Wisconsin in the 1980s, many people would come there to study the drumlins in the area. Coming up with a theory for how they formed was a big question even then.”

  26. Edward Greisch:

    20 Hank Roberts: Thanks.

  27. Dan H.:


    Here is a paper showing a longer term correlation between Greenland (albeit, only one glacier) and North Atlantic SST. The most recent results correlate reasonable well with the GRACE measurements. The study found that short term measurements correlate with NAO.

    Other studies found similar comparison:

    Also compare the much larger ice mass loss in 2010 with the much lower in 2011. Many of the analyses showing accelerated ice mass loss were performed before the inclusion of the more recent data. All in all, this shows the difficulty in projecting long term trends based on short term data.

  28. Susan Anderson:

    Hank Roberts, thanks for all, and my apologies to anyone paying attention. Given my lack of expertise, I should never butt in here unless I have checked things, particularly when exhausted. I promise to read carefully through now.

    That said, I am heartsick at the way Dan H. is now using these comment sections to feed his fans and getting better all the time, thanks to your tolerance, at appearing plausibly scientific. His arrogant tone and the occasional conversation across comments with those who approve his work are IMO a reason to stop giving him a platform. I do not have standing to say this but cannot in good conscience not do so.

  29. Ray Ladbury:

    Susan Anderson,
    I would note that while Dan H. continues to improve his “scientist” imitation, we also learn how to deal with the likes of Dan H. It is rather like the first battle Grant fought against Robert E. Lee. Upon overhearing some of his staff speculating as to what Lee had in store for them, Grant said sternly, “Don’t tell me what he’s going to do to you. Tell me what you are going to do to him.”

    Dan H. is not the only anti-science type who has started trying to imitate science. You see is not just in climate science, but evolution, the anti-vaxxers and so on. The imitation is flattering, but we have to find a way of distinguishing science from anti-science in the mind of the public.

  30. SecularAnimist:

    Ray Ladbury wrote: “… we also learn how to deal with the likes of Dan H. …”

    Hmmm, I don’t really see that “learning” going on.

    On the contrary, I see people continuing to engage with Dan H. as though he were a legitimate commenter, posting in good faith — rather than treating him as the deliberately, repetitively and blatantly dishonest time-wasting troll that he is.

  31. TimD:

    Dan H. – Thanks for the refs. Will check them out. Sounds like you have made some enemies here. I am a newbie, so I am unaware of the issues, but as long as you support your arguments with good refs, I’m good.

    Back to the issues, if ice loss responds strongly to SST warming, then that is useful in that it indicates that heat transfer by sea water flow under the ice streams is important as a mechanism, and I think that is where things are going. Given SST warming is a strong feedback effect of global warming associated with sea ice loss, it is still fundamentally an anthropogenic effect. The Hansen paper I cited shows clearly how polar ice strongly amplifies small forcings and that human contributions to GHG growth in the atmosphere is orders of magnitude larger than natural sources over the long term.

    I sure don’t see any sign of a slowdown in ice mass loss from the Grace data from John Wahr at Boulder – is the latest I have found and it clearly shows continuing loss acceleration through ’11. I tend to be suspicious of amazing new methods of data reduction as is the case of the Bergmann paper. His results looks more like a filtering edge effect to me. I have recently had an email conversation with Dr. Wahr and I find his data reduction methods to be widely accepted and robust. Since Grace can see the entire change in mass over the region with good spatial and temporal resolution, it is a far superior method than those dependent on observing individual ice streams.

    Wili, isostatic rebound after glacial unloading is an important effect that is taken into account in some detail in the analysis of the Grace data set. While that effect is significant in that regard, since it is due to flow in the upper mantle and the viscosity of the upper mantle is pretty high, it is a slow process in human terms. The Hudson Bay, which lost its thick ice sheet suddenly around 10,000 years ago, is still rebounding strongly. Some have suggested that the mantle flow associated with rebound could go strongly non-linear and produce volcanic activity, but I don’t see any volcanoes around the Hudson Bay.

  32. TimD:

    Dan H. – Maybe I am seeing what those folks are talking about. A quick review of one of your refs ( clearly states that ’11 was a high melt/mass loss year for Greenland, opposite of your statement “compare the much larger ice mass loss in 2010 with the much lower in 2011.” Note the “Highlights” of that article:

    “A persistent and strong negative North Atlantic Oscillation (NAO) index was responsible for southerly air flow along the west of Greenland, which caused anomalously warm weather in winter 2010-11 and summer 2011.

    The area and duration of melting at the surface of the ice sheet in summer 2011 were the third highest since 1979.
    The lowest surface albedo observed in 12 years of satellite observations (2000-2011) was a consequence of enhanced surface melting and below normal summer snowfall.
    The area of marine-terminating glaciers continued to decrease, though at less than half the rate of the previous 10 years.

    In situ measurements revealed near record-setting mass losses concentrated at higher elevations on the western slope of the ice sheet, and at an isolated glacier in southeastern Greenland.

    Total ice sheet mass loss in 2011 was 70% larger than the 2003-09 average annual loss rate of -250 Gt y-1. According to satellite gravity data obtained since 2002, ice sheet mass loss is accelerating.”

    You need to read your own refs…

  33. simon abingdon:

    #28 Susan Anderson “His arrogant tone and the occasional conversation across comments with those who approve his work are IMO a reason to stop giving him a platform”. Quite so Susan, can’t abide skeptics meself.

  34. Susan Anderson:

    Thanks Ray.

    However, my point is that he is talking past you to his fans at this point and likely planning to reference his acceptance here elsewhere, hence the condescending tones. I am well aware of the sciencey imitations which have been around for a while; the cosmetics get better all the time. I’m glad you guys are addressing the actual issues, but the way this particular conversation is morphing is something different. I got my training in anti-science elsewhere, and when the blog starts to be used by its non-audience to talk past the blog owner, it is no longer serving the function you are talking about.

  35. Hank Roberts:

    I do wonder what the four or five real scientists here think, as Dan. H. takes over another topic, pretends to answer questions, his new friends gathering ’round, and he takes on the host role.

    I imagine the scientists think, oh, well, it’s a chatroom, why bother.


    For myself, I’d sure rather be hearing what the scientists who came here to write about their work have to say — without the clutter.

  36. Hank Roberts:

    Anyone invited the biologists here recently?
    Nöthig, E. M. , Bauerfeind, E. , Haas, A. , Boetius, A. , Bracher, A. , Cherkasheva, A. , Kraft, A. , Metfies, K. , Peeken, I. and Schwarz, J. N. (2012): Variability of chlorophyll a distribution in the Fram Strait, Greenland Sea and Central Arctic Ocean , IPY 2012 Conference: From Knowledge to Action , Montreal, Canada, 23 April 2012 – 27 April 2012 .
    Cite this page as:

    “The Arctic Ocean is changing severely since one decade. Extremely low ice coverage in late summer has been recorded since 2007 with a new minimum in 2011. The zone of the receding ice edge is known for its high primary productivity in polar waters, but depending on light and nutrient availability productivity in the ice can also be high.

    We don’t know yet what the influence of less ice will be for the future Arctic Ocean ecosystem. Several scenarios are under discussion.

    Chlorophyll a is a measure of biomass standing stock of phytoplankton and can give information on surface as well as depth distribution of autotrophic biomass in the ocean. Chlorophyll a measurements also serve as ground truth data used to validate productivity estimates by remote sensing from space.

    Here we present a data set obtained since 1991 during several cruises carried out on RVs Polarstern, Lance & Maria S Merian to the Fram Strait, Greenland Sea and to the central Arctic Ocean including Laptev and Kara Seas. Almost every year samples have been taken from at least six different depth horizons …”

    [paragraph breaks added for online readability –hr]

  37. Hank Roberts:

    > primary productivity in polar waters

    Just to make that clear; “primary productivity” is what we eat and breathe.

    What we breathe, and what we eat, starts with photosynthesis — chlorophyll — and mostly comes from polar waters around the edge of the ice.

    The ice that forms in winter, melting from the springtime on, supplies all the fallout from the winter months (good stuff, bad stuff, whatever is carried in and dropped) — in a short interval as the ice melts, mostly. Lots of stuff around the edge of the ice blooms and reproduces.

    Increasing sunlight, fresh water, minerals –> primary production
    The source where life is being made in excess — food and oxygen.

    It’d be a shame if anybody were to damage that.

    But on the other hand, of course right, now it’s not worth anything, economically.

    In fact, as there’s an excess of it in places getting in the way of a lot of petroleum and stuff on the seabed — it’s kind of a nuisance, isn’t it?

  38. Thomas:

    Aaron. I thought I’d estimate a few numbers to put some context on your musings. Surface area of the GIS is roughly 1.7e6 km**2. Net mass loss of circa 200km**3, means an average thinning rate of 12cm/year. I would think changes in surface mass balance of 12cm/year is not so great. The average thickness is 2KM. Stress heating ultimately comes from gravity, so 2KM height loss translates to roughly 4.7 degrees C of heating. I think the surface temp in the interior is on the order of -20C, and this cold ice is advected downwards, and outwards (upwards in abalation areas), so the bulk of the ice should be at least -10C or colder, so without concentration of heating, flow shouldn’t cause melting of the bulk of the ice.
    How those surface ponds/lakes that drain affect ice temps. Once they get started, I think it is assumed they drill through to the bottom pretty quickly. The difference in hydrostatic pressure of a column of water versus ice is great enough that once the depth of the water column gets beyond a critical size, it can easily drill on down. If you assume these drainage pipes only have significant influence on ice temp within say ten meters of the conduit, conduits should be widely spaced, say kilometers apart, so the volume of ice heated by this mechanism should be very small compared to the mass of the ice. I don’t think the meltwater can heat the bulk of the deep ice by anything significant.

    I am far more concerned about how the ice sheet albedo will evolve. It can go from dry-snow, to wet snow, to wet-dirty snow, to wet clean ice, to wet dirty ice. How much dirt can accumulate year to year on the ablation surface? Do we have any way to estimate this effect?

  39. Kevin Hood:

    I have two questions:
    1) I live in Juneau, Alaska near some of the southernmost tidewater glaciers in North America. The longterm rise in temperature here has been accompanied by an increase in precipitation. Is there any significance to the difference between glaciers melting more solely due to higher temps and those melting more due to higher temps combined with exposure to more rain for longer periods? For example, is there a negative feedback that has to be accounted for when accumulating snow converts to wasting rain? Or is all melt the same?

    2) I have been wondering if the cold temperature of the meltwater coming off of the ice sheets and glaciers could be adding to the oceans’ mass but not the volume – at least, until the melt water has mixed in with the sea water and heated up a bit. If this is true, wouldn’t this mean that there is some lag time between melting ice and observing the consequent contribution to sea level rise? I ask this mindful of how our bays/fjords with glaciers or glacial rivers are notably colder than bays/fjords without glacial run-off.

    Thanks for any enlightenment!

  40. TimD:

    Thomas, the problem with your little diatribe is that in non-linear thixotrophic fluids (fluids with viscosities inversely related to strain rate) strain heating is concentrated, and strongly along slip surfaces that can and do develop in large ice bodies. In high strain rate zones, meltwater fracking through from the surface will tend to penetrate into the structure of the ice along sliding crystal interfaces and so better transmit heat from the surface to large volumes of ice with great efficiency, thereby reducing its viscosity and focusing strain heating. These effects are very difficult to model, so they typically are ignored even in some of the latest models, although things are improving all the time. Your back-of-the-envelope calculations show some talent, but don’t really cut it when considering the complexities of large, non-linear, mixed phase fluid bodies. You really need a super-computer to make any reasonable predictions.

  41. Dan H.:

    Read the reference more carefully. The “area and duration” were the third highest. These were lower than 2007 and 2010, but higher than 2008 and 2009; neither accelerating, nor decelerating. Part of the reason that the ice mass loss was 70% higher than the 7-year average (2003-2009), is that Greenland experienced some very low ice mass losses during several of those years, and the average does not include the high ice loss year of 2010. Compared to the first four years, the ice mass is accelerating, compared to the last four, it is not. These are the trials of a short-term data base. These were based on the GRACE calculations.

    Additionally, visible imagery (MODIS) showed a decrease in area loss of marine-terminating glaciers. This was largely due to increases in some larger glaciers (Granted the gain in the Petermann glacier was expected after the rather large calving in 2010).

    Much of this is perspective. Since 2002, the ice mass loss has accelerated, but much of that is based on the large jump that occurred between 2006 and 2007. A more appropriate statement would be that ice mass loss accelerated (past tense) from 2006 to 2007. This coincides with the large decrease in Arctic sea ice measured at the same time, which reinforces the theory that warm North Atlantic waters have enhanced melt.

  42. Dan H.:


    This is the only paper that I know that shows Arctic volcanoes.

    I have been around long enough to know that we scientists tend to overstate the importance of our own theories and findings, and minimizes others that contradict us. Consequently, tempers flare – we are human, afterall. Science thrives when people push the envelope into new horizons. Scientific research will then determine the validity of these new theories. Oftentimes, these new theories are quickly disproven, but other times, we get scientific breakthroughs. Neils Bohr and Albert Einstein argued fervently for years over quantum mechanics (not that any of use can be compared to either great physicist).

    [Response: How on earth did we get onto the subject of volcanoes? I very much hope no one is suggesting changes in Greenland are driven by volcanism?! I’m not bothering to read all the comments, but I will just remind people there is a difference between watts and milliwatts. -eric]

  43. wili:

    eric, by not consigning Dan H and his ilk to the bore hole, you are colluding in destroying this site. When every thread becomes a troll-feeding session, this very promising site can quickly become worse than useless. Everyone but the die-hards will just stop coming here. What exactly is the bore hole for, anyway?

  44. Dan H.:

    Your first question would need to be answer on a case-by-case basis. Oftentimes, higher precipitation will result in an increase in snowfall in the higher elevations, compensating for the losses in the lower elevation due to higher temperatures/rainfall. Mt Shasta in California is an extreme example, where all 7 glaciers have been growing due to increased snowfall overcoming increasing temperatures. I do not know of a study comparing the glacial loss in the ablation zone due to solar insolation compared to rainfall.

    Your second question is basically no. The volume increase would be slightly less due to the lower density of fresh water compared to seawater. The equivalent volume of fresh will decrease by 2.8% once salinity increases to the levels found in the oceans (nutrient-rich runoff would experience less of a volumetric change). Consequently, a liter of pure fresh water from glacial runoff would result in an oceanic volumetric increase of 973 ml. This change in density is at least an order of magnitude higher than changes due to temperature.

  45. Dan H.:


    See response #31. I do not think anyone is suggestion that volcanoes are influencing the Greenland glaciers.

  46. Ray Ladbury:

    Dan H. “I have been around long enough to know that we scientists tend to overstate the importance of our own theories and findings, and minimizes others that contradict us.”

    Bullshit. Pure, irremediable, unadulterated bullshit. Remember those Bohr-Einstein debated, do you?

    Dan, I’d be willing to bet you couldn’t even competently sketch out the positions taken by Bohr and Einstein and why they took those positions. You’ve been around enough to be a wannabe…a pudknocker. That’s all.

  47. Hank Roberts:

    > I have been around long enough to know that we scientists ….

    “we scientists” is it now?

    Do the RealClimate hosts know who Dan H. is, and have some reason to respect him despite the errors he posts?

    If y’all vouch for the guy being real, and the posts coming from a real person, fine — you’ve got your reasons, you needn’t tell us who a pseudonymous person is.

    Dan H. makes claims often implied, not stated explicitly.
    And often enough wrong when checked.

    Is he a scientist? Can anyone we have reason to trust confirm his “we scientists” claim?

    Or …

  48. SecularAnimist:

    Dan H wrote: “we scientists”

    Has Dan H ever, even once, provided the slightest evidence to support his prima facie laughable claim to be a “scientist”?

    Because each time he says that, I get the feeling that it’s his little way of sneering and thumbing his nose at the real scientists who run this site.

    I agree with wili. The RealClimate comment pages have basically become “The Dan H Show”.

    I appreciate that the moderators likely delete and/or send to the Bore Hole a whole host of garbage that gets thrown at this site, with the result that there is a “better class of trolls” here — e.g. those who are more or less polite and able to write more or less “sciencey-sounding” stuff.

    But they are still trolls. And they are still out to dominate the discussion with propaganda, and they are all too often succeeding.

  49. tamino:

    Dan H. is a persistent annoyance to the regulars here, and decreases the value of the site. But far more important than annoying us, is his turning every discussion thread into what wili (#43) aptly describes as “a troll-feeding session.” If the moderators allow him to continue, then the regulars here won’t like it — but we can take it.

    But I urge the mods to consider, very seriously, the non-regulars, especially first-time visitors and uncertain fence-sitters. Seriously guys, what influence do you think the trolls have on them? Aren’t they more in need of your protection from misinformation than those of us who actively seek to refute it for ourselves?

  50. Walter Pearce:

    From the peanut gallery…The RC team’s posts are must-reads, but threads quickly devolve once the current tribe of trolls start posting. Dan H.’s garbage in particular makes me yearn for the Rod B. era.

  51. TimD:

    Seems pretty clear that a bunch of folks have a beef against Dan H. Don’t get the history, but it seems like the most reasonable thing to do is to refute his positions with real data and peer reviewed papers. Like this…

    Dan H., I think I read the paper more carefully than you. We were talking about ice mass loss in Greenland and YOUR ref clearly stated that ice mass loss in Greenland continued to accelerate in ’11, and it is clear by looking at normal sources of the data. The Bergmann paper is a clear outlier. “Area and extent” refers to surface melting, which is probably small compared to warm seawater infiltration eating away at the ice from the base, but it was still large. In general, both the Greenland and Antarctic ice mass loss from normal analysis of GRACE data fits nicely with an exponential curve that has a doubling time of less than ten years

    The big questions we have left here, in my opinion, is how long will Greenland and Antarctica mass loss continue to fit exponential curves and if most of this phenomenon is due to seawater infiltration from below (which I think is the likely case) what does this mean when most of the continental ice sheets are grounded below sea level? In this regard, I don’t think Eric’s statement that ” the results put speculation of monotonic or exponential increases in Greenland’s ice discharge to rest, an idea that some had raised after a doubling over a few years was reported in 2004 for Jakobshavn Isbræ (Greenland’s largest outlet glacier)” was useful or anywhere near true. It is well known that all glaciers individually move in fits and starts, but the overall Greenland ice mass loss is consistently accelerating, nicely fitting an exponential curve. Ice discharge directly by calving of outlet glaciers may be the smaller effect relative to seawater infiltration or non-linear behavior as basal ice is warmed by infiltration of surface melt water. Over the period of the GRACE data measurements, ice mass loss was clearly both increasing monotonically (ignoring seasonal effects) and exponentially, right up to 2011. Gee, I hope Eric reads this…

  52. Susan Anderson:

    What Tamino said @~48

    As a lowly hanger-on, I have the luck to know a bit about how these people operate, but with only a little less history with scientists and scientific integrity and a lot less hard work in the mid-oughts following these intruders to their sources, I might have been taken in.

  53. Susan Anderson:

    Simon Abingdon, clever but not good. They are not true skeptics, as they treat most science as suspicious to a fault, and the very small minority, some of whom are either funded or supplied by wealthy interests, and their hangers-on, as gospel bearers.

    I’m for the skeptics who started this blog to answer real questions, and not for those who wish to cause doubt and delay regardless of the validity of the issues they raise and the answers provided – often hundreds of times.

  54. Steve Fish:

    Re- Comment by tamino — 18 May 2012 @ 11:01 AM, currently at #49:

    I strongly support Tamino in that I agree that obvious troll posts, such as those by Dan H, should go to the Bore Hole. I also caution that this is different than new posters who ask naive questions, regardless of the perceived motivation (e.g. talking points). I am seeing some recent questions/challenges in the Bore Hole that would provide excellent teaching moments. The emphasis should be to reduce distraction and improve education, especially for those just beginning to learn about climate. Steve

  55. wili:

    Thanks for reinforcing my point, tamino.

    Only slightly off topic–I highly recommend tamino’s recent post on GW and denialists:

    “Why I Must Speak Out about Climate Change”

    “Over thirty years ago, James Hansen was lead author of a scientific paper titled Climate Impact of Increasing Atmospheric Carbon Dioxide. They estimated that doubling the amount of CO2 in the air would raise global temperature about 2.8 degrees (C, equal to about 5 degrees F). They projected that from 1980 to 2010, earth would warm a little more than 0.4 degrees C. High northern latitudes, however, would warm at a much faster rate. We would likely see the start of melting of the great ice sheets in Antarctica and Greenland. They further suggested that we could start to lose much of the sea ice in the Arctic, which might even open the Northwest and Northeast passages.

    That was over thirty years ago. What has happened since then?

    From 1980 to 2010, earth warmed about 0.5 degrees C. High northern latitudes, however, warmed at a much faster rate. We’ve seen rapid melting of the great ice sheets in Antarctica and Greenland. We’ve already lost much of the sea ice in the Arctic, which has opened the Northwest and Northeast passages.

    The science is clear…

    Yet there’s a powerful movement to deny it. Some stems from political ideology, some from mistrust of government, and yes, a heckuva lot of it is spread by the fossil fuel industry — because it’s their product that is the cause of the problem. They make immense profits, and they see any interference or accountability — any at all — as a threat to their already bloated wealth. So, rather than accept that something has to change, rather than adapt to the situation, they deny reality and fight tooth-and-nail to preserve the status quo.

    Wake up! We can’t afford to let them build their wealth on our misery. The science really is clear. Stop letting PR pundits and politicians in denial send our future down the toilet. Stop letting them sucker you.”

    It is long past time for all of us with half a heart and half a brain to stand with Tamino, Hansen and the many other brave and intelligent voices calling for a responsible approach to the globe’s future, and to stand against the forces of ignorance, greed and destruction–the Koch’s, Heartland, and denialists of all stripes.

  56. Hank Roberts:

    > excellent teaching moments
    Depends on who’s offering to do the teaching; once people have noticed the Start Here button, and clicked it, the quality of their questions gets either much clearer, or else much more suspicious and political.

    That’s really the first teaching moment, right there.

    Those who can find and follow the Start Here link on the main and every other page — have already taught themselves something, and the teaching moments available can be more useful.

    Those who never find the Start Here button and persist asking the Frequently Answered Questions already answered for them in the Start Here section — are less teachable, probably.

    It’s a lot easier to mislead people who haven’t read the stuff in the Start Here section at least once.

    That’s why the misleading posters get commented on. It’s unfair tactics to mislead those who can’t even find the Start Here button to begin with.

    Or that’s what I think today, anyhow.

  57. Steve Fish:

    Hank, you are getting too jaded. Naive posters who get rebuffed will never learn anything because they will be pissed off. I agree that RTFM is a truism, but in reality most folks don’t. I say, give them a few chances with direction before giving up. Steve

  58. Jim Larsen:

    Dan H says, “I have been around long enough to know that we scientists”

    OMG!! Dan H probably has a high school diploma (they give ’em out for attendance mostly), but I can’t fathom much more. (feel free to correct my unsubstantiated estimate Dan H)

    Dan H does add to the mix – BUT ONLY IN SMALL DOSES. Perhaps RC would profit from a “limited commenter” policy. Let Dan H and other prolific but barely useful folks (oops, does that include me?) post maybe 3 comments to each thread, or perhaps five comments per week for all threads combined, then the rest go to borehole regardless of value. He’d learn efficiency and provide some value without smearing “stuff” all over each and every thread.

    I think the moderators would be wise to pay attention to the dismal hit count RC gets as compared to sites like WUWT. If we subtract the hits from regular users, then RC’s hit count probably goes down to irrelevant. The moderators can either accept irrelevance or improve the experience for the typical user. Previously I suggested a type of ranking of commenters. Nobody even bothered to comment on the idea, good or bad.

    RC could use fewer but better and more responded to comments, and RC’s moderators could save themselves time and effort while improving the site by working on issues such as Dan H with the thrust being to allow Dan H et al to contribute to the RC experience without soiling the nest. After all, Dan H is nearly the perfect example of the person who needs to be debated to carry the day. Simply banning or boreholing him would just make RC more irrelevant. Perhaps the moderators could place “lines in the sand”, where a commenter could be asked to substantiate an outrageous claim or publicly retract it, with their commenting privileges suspended until they do so. “Put up or shut up permanently” so to speak.

    Perhaps there should be two levels of comments for each thread. Extremely constructive comments could be placed first, and often responded to, while those which aren’t so constructive could be placed at the end. Then, visitors could read the posts and the constructive comments and get a good, efficient conversation, yet everyone is treated fairly by being posted on the thread. The truly dismal could still go to the borehole. (Note: boreholed comments should probably have a note placed in the original less-constructive comment thread pointing to the boreholed comment, similar to but more informative than the way edited out text is noted by [edited]. Then, folks who want to read what Dan H said could click the link and see the boreholed comment.)

    In any case, I think a discussion amongst the moderators and the regulars should take place on how to improve the effectiveness of RC, as currently WUWT et al are eating RC’s lunch. There are a lot of talented folks who spend a lot of time on RC. Their time and talents could probably be utilized far more efficiently. For example, a cadre of vetted regulars could moderate and respond to most comments, leaving the principals to do higher level work, including their day jobs. Another possibility is that comments which raise interesting and important questions could be flagged, inviting further discussion. Most important, the whole experience needs to be streamlined. 300 comments later, a thread is useless other than as pseudo-entertainment for regulars. Not a single “normal” user will ever read down a 300 comment thread. Much better would be 30 highly productive comments in a discussion format, with 270 also-rans listed afterwards. Bandwidth gets ever cheaper, but human reading time will always remain expensive. And if I knew my comment had to compete to get in the “top 30”, I’d put a lot more care and consideration into it than I do now.

    Another improvement would be to get rid of the Start Here button. Instead, a Start Here thread should remain at the top of the threads list. First thread seen, first thread clicked. Solves the problem and everyone who has already seen it just clicks on the subsequent threads instead.

    One last thing while I’m on my soapbox. Some of the regulars have been getting rather abusive. I see the same couple of folks (one especially) ridiculing new and old commenters and their thoughts. I’m sure that behaviour has reduced RC’s hit count. The behaviour is poisonous and catching. I’ve even seen it cropping up amongst the moderators. The wide-open 300+ comment format surely has at least partially led to this unfortunate situation.

  59. Brian Dodge:

    “Greenland glacial history, borehole constraints, and Eemian extent.”, L. Tarasov and W. Richard Peltier shows graphs of temperature versus depth of the GIS(Figs 7 & 8.) There is a positive gradient below ~ 1.5 km to the base, and Figure 10 of the following article shows that large basal areas of the northern GIS are at the pressure corrected melting point.

    “The effect of the north-east ice stream on the Greenland ice sheet in changing climates” – “Simulations into the future showed clearly a strong susceptibility of the Greenland ice sheet to global warming on time-scales of centuries. However, the enhanced basal sliding in the NEGIS area calibrated by the paleoclimatic simulations does not speed up the decay of the ice sheet significantly. By contrast, surface-meltwater-induced acceleration of basal sliding for the entire ice sheet can lead to a dynamic speed-up of its disintegration if the surface meltwater coecient is an order of magnitude larger than the estimate of Appendix A. While this process was found to be enhanced moderately in the NEGIS area, the presence of the NEGIS is not crucial for it. So we finally conclude that the NEGIS, unless it behaves in an unexpected way[e.g. like the Larsen Ice shelf – BD] by dramatically increasing its area or speeding up beyond our reasoning, can increase the decay of the Greenland ice sheet to a limited extent, but does not have the potential to dynamically destabilize the ice sheet as a whole.”

    I note that the surface slope of the GIS is low (0.01 – Parizek and Alley 2004), and the basal slope is negative(much of the base is below sea level due to isostatic depression) except at the edges. An X km increase in snow line/surface melt elevation moves the line inland 100X km; at some point, this will result in moulins draining toward the middle of the ice sheet, and accumulation of subGIS lakes – which have very low basal friction – instead of drainage to the sea. I wonder if this would cause exponential, or catastrophic changes in ice export versus temperature, e.g., if the km3(i)/T curve would be analogous to the i/v curve of a junction diode or an SCR.

    See “Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods”, STEARNS et al “Our findings provide direct evidence that an active lake drainage system can cause large and rapid changes in glacier dynamics. The causes of rapid changes in outlet glacier flow speed are not fully understood.”

    Some no doubt will say that since we don’t fully understand the GIS dynamics and associated risks, we shouldn’t disturb our highly profitable BAU.

  60. mark kneubuhl:

    Recent baseline date for glacial melt-rate is problematic in that we’ll get the “really bad news when its too late.

  61. Dan H.:


    This paper presents a nice synopsis of the GRACE analyses, partially explaining some of the many differences in results:

    The authors state that this study is “in agreement with other recent GRACE studies,” and shows 2007 as having the highest net ice loss. The authors also decided to represent the GRACE observations by a linear trend, and “cannot observe a significant acceleration term over whole data series.” Adding the 2010 and 2011 values to their time series does not change this conclusion.

  62. Hank Roberts:

    > Dan H.

    That’s a link to a paywalled site, not to the paper.
    There’s not even a summary there.

    Have you read it?
    If so, where?

  63. Dan H.:


    Sorry, I did not realize that when I accessed the paper. The paper is entitles, “Mass loss of the Greenland ice sheet from GRACE time-variable gravity measurements,” by Joodaki and Nahavandchi. I will see if it is available elsewhere.

  64. dbostrom:

    Depriving the locally famous annoyance of the positive feedback derived from constantly reading its own name as repeated by other people might help as well as prove intriguing.

    Reply, even quote, but don’t repeat the annoyance’s name, don’t attribute. The annoyance’s behavior in the face of failure to successfully manipulate will be information in itself, even if there’s no obviously perceptible response at all.

    Volunteer anonymous experimental subject is at hand, so why not turn the knobs and see what happens?

  65. Hank Roberts:

    How did you “access” the paper?
    First hand at the paid site?
    Second hand from someone else?

  66. Ric Merritt:

    Walter Pearce, #50: Dan H “makes me yearn for the Rod B. era”.

    Hey, has anyone seen Rod and Dan in the same room?

  67. Dan H.:


    Cannot find a freebie. The best I can do is link to the most relevant graphic here (results from JPL):

    While these numbers cannot be directly compared to the noaa values, if one assumes that the most recent melt was also 70% higher than the 2003-2009 average, then the value would be ~-135. This correlates well with the noaa statement where 2005 had almost as much mass loss as 2010.

  68. Aaron Lewis:

    Re: 38
    What scares me is loss of albedo across the Arctic and transport of heat via water vapor to the GIS. It does not matter if the heat comes from the ice free Arctic Ocean, the North Atlantic, or direct light on the GIS.

    Water flow rates during draining of surface lakes from GIS exceed water flow rates over Niagara Falls. However, since the fall through the GIS is greater than the head at Niagara Falls, more energy is released – all inside the ice. The problem is that large volumes of ice do not have to melt, only warm enough that they have less structural strength. And, not all the ice must warm, only small volumes that create structural weaknesses.

    While it certainly takes super computers to get all the detail correct, one can do engineering estimates with a slide rule in the back of your day planner. You will not like the results, but you will not like the results of a super computer program any better. And there lies the rub. Nobody in the organization will like those results, so everybody will fudge them down a bit and the final output of the super computer will be a fairy tail where everybody lives happily every after.

  69. Kevin McKinney:

    “…shows 2007 as having the highest net ice loss…”

    Again, the location of the highest outlier in a series by itself says little about the trend, its acceleration–or really, much of anything.

    As always when I encounter this line of rhetoric, I’m driven to wish that 1998 and 2007 records would be firmly obliterated, just to eliminate those particular ‘cherries’–for a moment.

    Then I recall that it’ll just be “Warming stopped in 201-/Sea ice has been recovering since 201-.”

  70. dhogaza:


    Seems pretty clear that a bunch of folks have a beef against Dan H. Don’t get the history, but it seems like the most reasonable thing to do is to refute his positions with real data and peer reviewed papers. Like this…

    The history is that many people, as you suggest, have treated DanH seriously, only to find that after correcting his misreading of papers, etc, he just waits a bit then reposts the same mistaken conclusion, as though he was never corrected.

    Over and over again, with a persistent pattern spanning many sources that do not say what he claims they say.

    I shall sit back and see if you’re as patient with his modus operandi a few months from now as you are today …

  71. Hank Roberts:

    How did you “access” the paper?
    First hand at the paid site?
    Second hand from someone else?

  72. TimD:

    Dhogaza, please don’t worry much about me getting excessively cozy with Dan H. I don’t think I in any way cut him any breaks in our interactions, other than being polite that he referred to some papers. I just don’t have any emotional investment in this guy, as so many of you seem to. Why that should be is clear to me – I just haven’t beat my head against the wall with this guy as long as you have. But when he said the opposite of what the paper he referred to actually said, I just corrected him. But you folks were going “Here he goes again!” I am sorry you good people have been afflicted with the nonsense that comes with someone clinging desperately to untruths that the deluded person finds painfully challenging his/her deeply held beliefs. You have to imagine just how difficult for a free-market, small government conservative to consider the existence of a huge, global problem that can only be effectively addressed by some form of global enforcement of rules. Everyone deserves some sympathy, even Dan H. I recall a Rolling Stones song about that.

    [Response: Can everyone please not clutter up threads with comments about other commenters? It is extremely tedious. This is a post about glaciers in Greenland. – gavin]

  73. Susan Anderson:

    Very interesting material from those sticking to the topic. I’m especially grateful to Aaron Lewis and Brian Dodge. I hope more will do so (stick to topic, that is).

  74. TimD:

    Well, gavin, since your remark was clearly directed at my remark, I feel it reasonable to respond. A plethora of posts containing nothing but attacks on a commenter occurred from #28. Where were your oh-so-wise, peacemaking comments at that time? Or do you only comment about certain “other commenters”? I was doing my best to return the discussion to the topic of Greenland Ice sheets when this chorus of attacks sprang up, and that is a problem on a site like this. These things should be nipped in the bud and when they aren’t it becomes a reasonable topic of discussion, although I would rather discuss climate change. This is a moderation problem.

    [Response:I agree it is a moderation problem – but we have day jobs and this task is not always our highest priority. My comment was not really directed at you, rather you were a trigger for a general comment. Discussion of the character of other commenters, their motives, moderation, tone etc. are boring, and we try and discourage it (albeit imperfectly). And on this thread, this comment is the last word on that. – gavin]

  75. TimD:

    Bravo, and thanks Gavin. I also have a day job but happen to believe that rapid climate change is perhaps the most significant threat to humans in modern history. The issue of exponential growth of ice mass loss is a critically important sub topic and that is clearly related to the topic at hand. In #51 I directly challenged a key assertion in the main article by Eric that the study he cited ”put speculation of monotonic or exponential increases in Greenland’s ice discharge to rest”. I strongly suggested he respond, but in the entire thread he has only had time to do a little misguided sniping about the mention of volcanoes. The question of exponential ice loss is probably more important than whatever else Eric might be doing at the moment, I would think.

    [Response:One thing I know is LESS important than what I am doing at the moment: responding to people that tell me what I AM doing is not as important as what they think I’m doing. But to respond to your criticism: I am not saying exponential change cannot happen. I was saying that speculation on the basis of a few years of data (which was done) has not (yet) been borne out by the facts.–eric]

  76. Mauri Pelto:

    The recent Moon et al (2012) paper is an excellent paper. Having reviewed at least six papers this year on this topic area, the conclusions fit the results of the other more regional based papers. A 25-30% acceleration in marine terminating outlet glaciers is nothing to ignore. More importantly is that this mean increase lumps all of the marine terminating glaciers into one pool. I suggest that going forward we will need to separate the marine terminating glaciers into two categories. Those that end in deeper water and those ending in shallow water. This was the focus of the categorization of Greenland glaciers in Skeptical Science. There are two key reasons. 1)If enhanced basal melting from seawater is key, this mechanism is typically not a shallow water mechanism. Secondly thinning of a glacier tongue that is at least partially afloat, more likely in deep water, reduces backforces and enhances velocity and calving. This is a mechanism that is more pronounced in deeper water terminating glaciers. In a recent paper, final draft due out soon by Mernild et al (2012), the fastest five glaciers are the largest, and these have experienced the most losses too. Epiq Sermia is an example of a glacier where detailed data provides much food for thought.

  77. Dan H.:

    To reinforce Eric’s statements, see the following article about regional variations in Greenland.

    The estimated ice mass loss from NW Greenland glaciers increased from 30 to 130 Gt/yr, while SE glaciers decreased from 110 to 0 Gt/yr over the periods 2002-05 to 2007-09.

    All told, we have less than 10 years of GRACE measurements, such that making long term predictions based on these estimates are still precarious. None of these studies precludes the idea that ice mass loss could accelerate exponentially. However, there is no evidence that it has been recently.

    Another study found large variations in the changes in the three largest Greenland glaciers.

    An attempt has been made to compare recent satellite data with other, earlier calculations.

  78. TimD:

    Eric, if the work you are doing is less important than the question of exponential ice sheet mass loss, you still could be doing Nobel Prize level work, so it isn’t much of a dig, if you think about it. For the record, I haven’t checked your CV and I have no idea what you are doing. I would love to hear about your work. But you did say ”put speculation of monotonic or exponential increases in Greenland’s ice discharge to rest”, which sounds like plain English for “negated that possibility”. Clearly that is not the case, and in general, extrapolating trends is a lot of what scientific prediction is about. Hansen’s work, which I cited, pointed out that answering the question of how long that trend of rapid acceleration in mass loss persists (we all appreciate that exponential growth is a temporary condition) is critically important. Your suggestion that the exponential growth has stopped is certainly not supported by the latest and highest quality data (Grace) and in human terms, the title of your little review was misleading and, in effect, fuel for the skeptics. Whatever you believe to be true, I think that in this environment, you need to take better care with your use of language. In any case, the paper you cited only considered mass loss from ice stream discharge, which many believe is small compared to the effect of basal melting in response to rapid warming of arctic sea water. An exponential function plus a linear function is still an exponential function.

  79. Mauri Pelto:

    Tim: Ice stream discharge is not small compared to melting in Greenland. There just is a very small area of the ice sheet available to be melted by seawater unlike Antarctica. It is true the increase in surface melting is not considered in the paper, nor it should it be. This is a dynamics paper. Petermann Glacier is one of the few with a large floating ice tongue available for melting. Nearby Humboldt Glacier even though larger does not.

  80. wili:

    Two topics I would like to see discussed further–effect of isostatic rebound (if that’s the right term), and methane and CO2 release from soils newly emerging from the icesheet as it melts.

  81. TimD:

    Mauri, I think there may be some semantic problems here. I took Eric’s use of ice discharge to mean total ice mass loss. I used the more specific “ice stream discharge”. But I definitely didn’t mean “surface melting”. I was talking about basal melting. I think that there is considerable uncertainty as to how efficient the salinity/density convection mechanism is at melting basal ice, but if you are looking for energy sources to melt Greenland ice, the very rapid increase in SST is a reasonable place to look. I suspect that the advent of the recent phenomenon of large moulin floods could have opened paths through the ice to the ocean that then reversed and began to rapidly melt ice at the base of the ice. But whatever the mechanism of exponential ice mass loss seen by Grace measurements, we need to understand it pretty soon.

  82. David B. Benson:

    wili @80 — I’m unsure what about isostatic rebound puzzles you. However, under the ice in Greenland and Antarctica is surely nothing but bedrock.

  83. Hank Roberts:

    > how efficient the salinity/density convection mechanism is …

    One indicator I know the biologists are looking at that probably correlates (somehow) with both basal melt (pure fresh water) and surface melt (nice fix of heavy metals, nitrates, etc. deposited by the wind over the winter) — which probably give different kinds of plankton a boost at the ice edge.

  84. wili:

    Thanks, David. But even bedrock rebounds when millions of tons of overlaying weight starts to be removed from above it. My understanding is that the center of the island is slightly below sea level now because of all the pressure from above. As the ice starts to melt, presumably that will start to bow upward, going from concave to flattish to convex. I would think that this change would accelerate the rate at which ice slips into the sea. I know that this is a long-term thing. But is there anything basically wrong with that basic picture that anyone cans see? Is this rebound figured into the major models for what is going to happen with the Greenland icesheet at what rate?

    And by bedrock, do you mean that there is probably no or not much methane under the ice? Wasn’t there vegetation there before it was covered with ice? Did that all just disappear over the ages?

  85. wili:

    Hank posted this over at the open thread (#135) and it seemed to me to be relevant here:

    —excerpt follows—
    researchers on the new Arctic project, led by Katey Walter Anthony from the University of Alaska at Fairbanks (UAF), were able to identify long-stored gas by the ratio of different isotopes of carbon in the methane molecules.

    Using aerial and ground-based surveys, the team identified about 150,000 methane seeps in Alaska and Greenland in lakes along the margins of ice cover.

    Local sampling showed that some of these are releasing the ancient methane, perhaps from natural gas or coal deposits underneath the lakes, whereas others are emitting much younger gas, presumably formed through decay of plant material in the lakes.

    “We observed most of these cryosphere-cap seeps in lakes along the boundaries of permafrost thaw and in moraines and fjords of retreating glaciers,” they write, emphasising the point that warming in the Arctic is releasing this long-stored carbon.

    “If this relationship holds true for other regions where sedimentary basins are at present capped by permafrost, glaciers and ice sheets, such as northern West Siberia, rich in natural gas and partially underlain by thin permafrost predicted to degrade substantially by 2100, a very strong increase in methane carbon cycling will result, with potential implications for climate warming feedbacks.”

    The story is also covered nicely in the NYT:

    (Sorry, Hank–It may be that I’m just a bit desperate to get this thread back to something at least marginally connected to its stated topic :-/)

  86. Hank Roberts:

    Wili, maybe you know different — I think that the glaciers pretty much rest on bedrock — they grind everything down to the bedrock! — so it doesn’t seem likely that any moving glacier is going to have permafrost melting under it. Now in the central parts of Greenland (and Antarctica) it might be different –would the weight of the ice push all the softer stuff out to the edges over geological time? Or would there be masses of organic material under the icecaps?

  87. David B. Benson:

    wili @84 & Hank Roberts @86 — All the ice eventually moves to the sea over geologic time and so has surely removed every trace of organic matter. Recall that the longest ice cores go back ‘only’ less than 800,000 years and Antarctica has be covered with ice for far longer than that

    wilw @84 — Yes, rebound will occur over a long enough time. In my amateur opinion it is a minor effect with regard to the ice melting.

  88. TimD:

    Wili, I think that isostatic rebound is relevant to the current topic, not so sure about methane emissions from permafrost melting. The methane issue is very important in terms of it being a huge potential positive feedback mechanism, since it is a very potent GHG and there is lots of organic matter locked in permafrost that is doomed to thaw. Also, there is lots of methane stored as methane ice (clathrate) in shallow offshore sediments that could be catastrophically released as the sea surface temps increase rapidly. In general,there are lots of positive climate feedbacks in the arctic and very few negative feedbacks, which tend to only kick in after the climate has been hugely altered.

    But post-glacial isostatic rebound is a concept near and dear to geophysicists since it opens a window to learn about the rheology of the upper mantle, a key issue in plate tectonics. You can read a decent review of it at Because mantle mass is moving around, there is an easily measurable effect on a sequence of gravity measurements, so it is quite relevant to the analysis of the Grace data. But at the same time, because the mantle viscosity is so high, the mantle flow patterns are very stable and not that hard to separate from changes in ice mass when looking at gravity data. The extremely accurate gravity field information from the Grace satellites is very important to ice mass change in places like Greenland since it sees the entire picture, seeing changes through the entire crust and into the mantle. It is so sensitive that it can see the change in mass from a single big rain storm and in the case of Greenland, the Grace data can see ice mass changes at the base of the ice sheet that is very difficult to measure in other ways. That is a critical issue given that it appears that rapidly warming SST is providing a mechanism to melt perhaps the majority of the ice lost from below. (Full disclosure; I am a geophysicist with a long-standing interest in climate issues).

  89. wili:

    Thanks Hank and David. I, also, had always assumed it was pretty much bed rock under the ice, but that line from Hank’s article gave me pause:

    “Using aerial and ground-based surveys, the team identified about 150,000 methane seeps in Alaska and Greenland in lakes along the margins of ice cover.”

    Why would there be so much methane coming out of lakes at the margin of ice cover if it’s just bedrock? Since the Greenland sheet has started to shrink (not radically yet, and mostly at its southern end so far), I would assume that many of these ‘lakes’ are in areas that had been covered with the ice sheet up to fairly recently.

    But perhaps I’m jumping to conclusions. Perhaps it’s time to see if I can get to the original study. Has anyone found an accessible copy?

  90. wili:

    OK, I tracked it down. Here is the relevant section from the abstract of the article:

    “Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-induced open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap.”

    So it is specifically from the boundary of “receding glaciers” in Greenland where they found these methane leakages.

    How much of the “1,200 Pg” (=~ a trillion tons?) of methane they mention are under which of these formations? How fast a feedback should we expect from this source? When we add it to the other carbon feedbacks, and consider that all of these will be feeding back on each other…shouldn’t we be starting to get a bit…worried?

    (reCaptcha: tibugee unusual)

  91. Hank Roberts:

    Thanks David, that fits my recollection — both for Greenland and for Antarctica; I do recall some imagery from deep ice drilling in Antarctica that reached the bottom of the ice and found only a meter or so of water then rock, and mention that the pressure was enough to make water and rock flour flow uphill from the low spots and squeeze out toward the edges.

  92. Jim Larsen:

    wili, rebound in Greenland is 1.4-10mm/yr, depending on location. It’s expected to double by 2025 for exactly the reasons you proposed.

    Compare that rate to the thinning of the ice sheet. Page 2 shows thinning at the margins of ~50cm/yr over much of the island. They conclude, “Even if the large mass loss at the margins stopped, the interior ice sheet would continue thinning for 300 years.”

  93. MARodger:

    Re:- old vegetation under ice caps.
    The Baffin Island ice caps are sat on old vegetation (& so presumably frozen soils). This is possibly because the ice is not thick enough to ‘unstick’ itself & start flowing.
    Antarctic & Greenland ice is thick.

  94. Kevin McKinney:

    “Or would there be masses of organic material under the icecaps?”

    Interesting question–I’ll opine that if there were, you’d find extremophile bacteria munching happily away at it.

  95. wili:

    Thanks, Jim. So up to 2 cm/year by 2025.

    That might seem slight. But consider that a marble on a level table top will stay in place for ever. But tip the table even a mm, and it is likely to start rolling toward the edge of the table. So ice that might not otherwise moved toward the sea, may start doing so with even a slight shift in the tilt of the land.

    Interesting point about Baffin Island. It sounds like they may be talking about deep methane associated with coal seams in this article, so it may be beneath bedrock, but still be able to be liberated through cracks in the rock once the overlying ice is gone.

    In any case, this paper seems to present another very large quantity of free, gaseous methane (1,200 Pt vs 5 Pt in all the atmosphere now), ready to go directly into the atmosphere once the ice keeping it capped in is gone or weakened–another potentially enormous feedback that can drive a runaway GW scenario. It sounds as though it is a very small source right now, but once that camel’s nose gets under the tent, the whole thing is likely to come down, especially when this is added to all the other sea and terrestrial feedback ready to kick in (if not started already).

  96. MS:

    Re organic material in ice cores:
    It seems the NGRIP project in Greenland (2003) found a little organic material in a deep ice core.
    Ref North Greenland Ice Core Project

  97. Hank Roberts:

    > a little organic material

    Very tiny fragment, photographed:
    They said in 2003 they might be able to confirm what it was.
    did they?

  98. Hank Roberts:

    > a little organic material

    Very tiny fragment, photographed:
    Their press release is promising; has anyone seen a conclusion about their speculation from 2004 when they’d just recovered this material?

    It does suggest there’s organic material and dissolved gas — but that’s a press release and we know about those being consistently wrong.

  99. TimD:

    I’m new to this insular little group, so I don’t know your customs. Clearly welcoming new people isn’t one of them. But since there is interest in methane releases, even if marginally related to the topic at hand, it is an interest of mine and I think I can contribute usefully to the discussion.

    Methane ice occur at shallow levels in sediments all around the world and they are particularly easy to see on reflection seismic sections. Methane ice is stable in the deep waters of the Gulf of Mexico and played a part in the BP disaster. A professor/friend from SMU who works on methane ice sent me this link about Russian scientists discovering rapid increases in methane release Since, in the arctic, methane ice is stable at the surface, it can be rapidly warmed beyond its stability zone and disassociate to methane gas and water. It is pretty clear that this is what is going on in arctic oceans. It is not at all unreasonable to suspect that we are seeing the beginning of an exponential increase in clathrate gas releases as losses of sea ice, huge changes of albedo and resultant SST increases hit this very fast feedback mechanism. I proposed to my friend that once the gas disassociation gets started in permeable sediments, the rising bubble column will reduce the hydrostatic pressure and effectively pump warm water from the surface through the sediments, leading to rapid heat transfer through the sediments by mass transfer rather than conduction. If that is what is going on here, very rapid and very large increases in methane release from the arctic seems pretty likely. Clearly, this could be a huge wild card in terms of climate change modeling. Just another example of arctic fast feedback surprises that leave vaunted arctic scientists with mouths agape.

  100. dbostrom:

    Hubris along the lines of “just another example of arctic fast feedback surprises that leave vaunted arctic scientists with mouths agape” tends to find a chilly reception no matter where it’s found.

    Social calibration is key; before assuming that mouths will be left gaping by a “new” thought, raise the periscope out of the cranium and scan the horizon. There are 7 billion thinking people on the planet; the risk of conceptual aliasing due to imaginary originality is fairly large.

  101. Kevin McKinney:

    “..conceptual aliasing due to imaginary originality is fairly large..”

    Apt, given that aliasing often arises from undersampling.

  102. MS:

    >Hank #98
    Looking for newer results I only found this
    Ancient Biomolecules from Deep Ice Cores Reveal a Forested Southern Greenland .
    NGRIP is not mentioned, but material from other ice cores is used.

  103. TimD:

    Dbostrom, A fair snipe, I suppose. But if you read the article I referenced, you would find quotes of arctic scientists expressing shock at the ACTUAL PHENOMENON of rapidly increasing methane emissions in the shallow Arctic Ocean. I am not claiming authorship of the phenomenon, and it was that I was referring to, not a “new thought”. My apologies if it was new to you. I don’t think social calibration is required to make the true statement I made, except perhaps in your mind. And so nice to meet you.

  104. dbostrom:

    Tim, for which phenomenon are you not claiming authorship? Clearly it was not that of the release of methane in Arctic seas either in observation or commission, as you duly note. Meanwhile I was not a party to your conversation with your friend wherein you proposed your hypothesis about bulk methane liberation and transport, so I must bow to the narrative of that exchange as you related it and your own conclusion about its significance.

    Anyway, it does seem you’ve a thick skin and need no help. :-)

  105. flxible:

    But if you read the article I referenced, you would find quotes of arctic scientists expressing shock at the ACTUAL PHENOMENON of rapidly increasing methane emissions in the shallow Arctic Ocean.

    I believe most here read that article some months ago. If you read the realclimate post here and the following comments, you might see that “vaunted scientists” aren’t too agape while awaiting further actual data publications by those “shocked” scientists investigating the situation.

  106. Susan Anderson:


    I was so happy to find real science being discussed, but I cannot in good conscience not say what I think about your “insular little group” comment – NOT! For a good perspective, you might check out this interview, and then read the comments, which are characteristic of the unending attacks on unwelcome but honest science prevalent in even the rarefied reaches of a New York Times blog:

    I enjoyed the presentation by Gavin of the genesis of this group there.

    My contributions there were treated far less politely and relevantly than yours have here, for example:
    I was also instructed to have my eyes checked, typical misdirection. I could go on, but best not.

    One of the problems with science is that it is a meritocracy. It is not easy to qualify for a good high-level education, and years must be spent by the best of the best to get to the level you find here. The pay is not comparable to that offered by the fossil fuel industry to the anyone willing to cater to the PR doubt and delay industry. This has been going on for decades: you could do good work, where have you been? Why are you joining the circular firing squad instead of working to get real knowledge publicly acknowledged outside these rarefied circles?

    On the other hand, I have not seen anyone censoring your comments. In fact, I read them with interest because you clearly know more about science that I do; once you went down the same path your hosts did you came to the same conclusion. But once you’ve seen the same tired old arguments repeated a few hundreds of times, it does get a bit old; why blame the victims? It is depressing that people facing this situation and trying to do something about it have to deal with political arguments that have nothing to do with the facts.

    This is the situation they are doing their best to ameliorate:

  107. David B. Benson:

    wili @90 — Rather amazingly some methane comes out of bedrock almost everywhere. Where is is cold enough and with enough pressure it forms methane cathrates, methane ice. Once the pressure is lessened or the temperature rises the cathrates disassociate to express the methane. In my amatuer opinion there isn’t enough of it to be concerned about although some climatologists will certainly like to have good estimates of methane expression.

  108. TimD:

    dbostrom, of course, not being a god I cannot claim any authorship of any natural phenomena. My little joke. Perhaps, being of Nordic descent, you missed it. But we are cool and I can understand your mis-perception of my comment. Honestly, I really would prefer to discuss the science, its implications to policy and to future research, and that is what I have been trying to discuss, but not so successfully given the many slings and arrows that seem to be flying around everywhere. But I guess that is the nature of public fora on climate change. For the record, I would favor more aggressive moderation to eliminate the bickering, but I also understand that it is difficult to walk that “free speech” tightrope in a hurricane of skeptic hot air.

    flxible, given that the author of the subject article here claims to have no time to read even these responses, I hope you will forgive me for not having digested the months of archived comments here. If many or most of the folks in this thread had read the article or a similar one, I hadn’t seen much evidence of that in the thread given the amount of time spent on discussing organic matter trapped in the ice sheet, which certainly will not become a significant source of methane. I thought it useful to try to re-direct to topic to a similar but much more pertinent topic to the issue of climate change.

    Susan Anderson, I really do appreciate your comments and I will take them as a belated welcome to the group. I have no problem with you taking exception to my little barb about this being an “insular group”, but I hope you can see from the history of this discussion that I was really trying to discuss science and then was instantly caught in a barrage of floggings of a commenter. That was my perspective, and I acknowledge that it came from a small sample of experience here. I appreciate your advice about this being a possible “circular firing squad” and you should know, especially given that I am new here, that I really do work on projects that put my money where my mouth is. I am presently working to set up a solar thermal/algae biofuel hybrid system and just today was talking to a Chinese scientist about using super-critical CO2 from power plant exhaust as a fracking and hydrocarbon solvent for tertiary recovery and carbon sequestration. So don’t worry about me getting lost in conversation here. I have a day job. But these are things that I don’t discuss much in public at this point, so don’t bother trying to find those projects on the web, at least at this point.

    And if this website has been discussed in detail before, please forgive, but these folks seem to be trying to do something about the arctic methane fast feedback issue. I will readily admit that this link is the only substantive part of this post.

    Peace, y’all!

  109. tamino:

    Re: #108 (TimD)

    Methane release in the Arctic was indeed a topic of some discussion here not too long ago. I’m certainly no expert on the subject, but the general consensus seemed to be that although the recent observations are troubling, the observed increase in methane concentration — both worldwide and in the Arctic — doesn’t yet justify declaring an emergency. I posted about the issue recently, here:

  110. TimD:

    Tamino, I understand your perspective. It would be very costly to actually do something about methane release, and rapid increases in release seems to be a very recent phenomenon, given that we recently went through a period where atmospheric methane stabalized. But, again, when you are at the beginning of what looks like exponential change, you had better figure out the mechanism before very many doublings so you can make a better decision as to how big the emergency is, if at all. It would appear very reasonable that the rapid increase in methane release that the Guardian article discussed is driven by SST increases, which would, in turn, suggest that it is a big deal in the Joe Biden sense. So I would strongly argue that arctic shelfal methane release from clathrates is really an emergency, at least in the sense that we desperately need to throw some real, hard science at it, and fast, to better understand the mechanism so that prediction becomes something more than curve fitting.

  111. flxible:

    TimD@108 – No, I won’t forgive you for interpreting the responses of 2 of the principals here as being they “have no time to read even these responses”, when you in turn state the same as they did, which was actually that they have day jobs too, and feel that what they decide to do with their time is more relevant than what you think they should be doing. Not to mention that they in fact as moderators here likely read every comment.
    The link I provided you is not “months of archived comments”, but a previous article on the subject you allowed the comments of this article to sidetrack you into, methane emissions in the Arctic. If you’re going to jump into a comment thread with opinions about things that the original blog post didn’t concern, I’d think you would attend to previous posts that did deal with that off-topic subject. To lift your phrases, I “thought it useful to try to re-direct [you] to a similar but much more pertinent topic on [your] issue“, about Arctic methane

  112. dbostrom:

    Tim: Honestly, I really would prefer to discuss the science…

    Good on you, and as you say the air is rather heated regarding this topic, radiating brightly at various wavelengths illuminating and otherwise. My fault for swerving the conversation.

  113. TimD:

    flxible, your forgiveness, in truth, means very little to me, but the truth means a lot. When Eric said in response to #42 ” I’m not bothering to read all the comments, but I will just remind people there is a difference between watts and milliwatts” I think that it is clear that my interpretation of that was wholly correct, and I could add that his remark was dismissive and snooty, especially since the origin of the topic mentioned was only a few comments above. Eric may be a god in these parts, but in my opinion he could well learn some manners so that he doesn’t contribute to the unnecessarily belligerent tone of many of the posts. And your first reference in your #105 comment was to an RC archive from January, so it could only have been found by me by searching “months of archived comments”. You should try to tell the truth, especially about things that are so easily refuted. Now anybody want to talk about the science of climatology? I sure do!

    [Response: I can assure you that no one thinks of me as a god, nor would I want them too. And I apologize for the appearance of snootiness. Problem is a) too busy and b) the “it’s not CO2, it’s volcanoes” comes up so often that I thought that that’s what it was. My apologies. –eric]

  114. Susan Anderson:


    Without entering into much discussion about your recent kerfuffle, you should know that you and I are exactly equal in our participation here – that is, we are posters on somebody else’s website. My humility about the subject matter comes from not being a scientist. My irritation at people’s assumptions about their “rights” to say anything and everything about and to their hosts – especially given the subject matter and the consequences of promoting conflict in this particular arena – is not humble. Once again I have to wonder where you’ve been if you don’t know things are already so rife with conflict that a little irritability is hardly out of place. You might enjoy this as a sterling example of unrestrained language and his characterization of many scientists is spot on:

    You can find plenty of courtesy at some denier sites (though they are rude to those promoting reality) but not much good information. I prefer the truth.

    As for methane, I’d suggest you all move that to the open thread linked below; in January there were a couple of posts about that as well which I found through a simple search on realclimate methane. There was a lively to and fro there about AMEG and a read through might give you some background. Now the Brits have postponed even the geoengineering experiment due to politics, it looks like its going nowhere fast.

    [Please do NOT reply here about this as the topic is Greenland glaciers; I’ll take a look there for any replies since I brought it up.]

    I had to hunt around to find the aforementioned comments, which was here, not in the January methane articles:

  115. Hank Roberts:

    > it could only have been found by me by
    > searching “months of archived comments”

    That’s no burden.

    Did you try?

    Put the words:

    methane emergency
    in the search box.
    Upper right corner of the page.

    You find too much?
    That’s because it’s
    much discussed for
    many years here.

    Too much to read?
    Use more search terms.

    Narrow it down.

    ameg release depressurize

    The “emergency” is to
    capture and burn the methane
    as fuel for sale

    Before people realize
    that either it’s
    a) escaped,
    b) not likely to escape

    Odds favor the latter in
    the short term during which
    most of us will be alive.

    It’s not the most urgent

    What is?
    Stopping burning carbon.

  116. Susan Anderson:

    Hank Roberts, right you are. In my case I was advantaged because I knew to add John Nissen to the search so it showed up immediately. But the RC methane articles in January were very easy to find. I still think this discussion should be moved to Unforced Variations, as the discussion about Greenland’s ice had gotten more like what I enjoy on RealClimate, expertise from people who know what they’re talking about, not conflict promotion ad nauseam.

    Also, this is an educational site for those like me who are interested but lack knowledge and skills. Being too lazy to read through means one should not comment.

    Here, that is:

  117. Susan Anderson:

    My emphasis was wrong. I was talking about its usefulness to people like me, not the purpose of RC which is none of my business.

  118. TimD:

    Eric, I do so much appreciate your apology and it wasn’t that big a deal. I am both happy and sorry that you are so busy. It is a bit hard to imagine putting the considerable work you did into the root article and not being very curious about what people are saying, even if you have to read the posts as you fall asleep at night. You have my apology for being a bit demanding and rude to get you to respond to my points. Let us all strive for professional civility and focus on the pertinent scientific questions.

    Along those lines, I am curious as to how you reconcile the ice stream info, which doesn’t look particularly exponential, with the Grace data which REALLY does: (fig HTC19). The mass loss has been consistently accelerating in a weirdly smooth fashion for ten years now and the data is exquisitely accurate and well sampled. What is your favorite mechanism? To me it has to be basal melting driven by SST increases and when you are talking about basal melting, the slickest analogy is cold butter on a hot flat griddle. It doesn’t require very high degrees of melting to make the slab of butter slide off the edge of the griddle.

    I thank you in advance for your response and for your efforts to educate the public about this, perhaps the greatest threat to humanity since Toba.

  119. TimD:

    Susan and Hank, please note that Eric has graciously apologized and I did so in return, then I returned to the subject at hand. Also note that your effort toward my education in your posts were utterly, and rather rudely, off topic. Hank, I know how to search the internet, but you should ask yourself, what was my incentive to do so? Why should I care what self-absorbed blatherers were saying five months ago? I wanted to discuss the Greenland ice sheet with real scientists here, and instead I am treated rudely and dragged into old battles that I have already said I have no interest in. Susan, you claim to dislike “conflict promotion ad nauseam” but on this thread, you were the one who instigated the flogging of the roundly hated commenter that devolved the discussion into a communal beat down. Note also, that I did not bring up the methane issue and before I joined the extensive discussion on that topic, I noted it was off topic, but that, being new, I did not know the customs in that regard on this site. Again, I would, if I intended to continue posting on this site, strongly argue for better moderation of the egotistical nonsense that seems to make up the bulk of the comments. You folks have most effectively convinced me that I have better things to do. I would hope that the moderator would allow this admittedly off-topic post for 24 hours or so then remove it and the posts it was responding to and similar off-topic nonsense. Hasta luego… P.S. reCapcha totally sucks.

  120. wili:

    And to add to TimD’s analogy, even a slight tilt of the griddle will greatly accelerate how quickly the melting butter slides off the edge. Hence my interest in isostatic rebound.

    Thanks to all for checking on references to organic matter beneath the icesheet. David at 107, while your “amatuer opinion” may lead you to the conclusion that there is not enough methane to worry about, the scientists in the article came up with the figure 1,200 Pg, nothing to sneeze at, given that all atmospheric methane comes to 5Pg. But they didn’t break out what part of that was specifically under the Greenland ice sheet, so that figure could be smaller. Hanks article about forests that once covered southern Greenland is suggestive.

  121. Susan Anderson:

    TimD, I’d best apologize and retire, though you do, now, after thanking me for the “welcome” earlier (@108 re 106), put the blame on me, and seem overready to find fault. The order of comments supports your takedown so I’ll try to take it to heart and try to do better in future. I was interested in the work you do* and wished to point you at discussions that were relevant to that, but phrased it poorly. I have always felt I am only here on sufferance as I cannot contribute to the scientific discussions, only observe and learn. I meant to point out that I do not in any way speak for “the management” nor do many others in comment sections anywhere.

    The discussion about AMEG went on for days and was at the link I provided, and the January methane articles are easy to find.

    * I really do work on projects that put my money where my mouth is. I am presently working to set up a solar thermal/algae biofuel hybrid system and just today was talking to a Chinese scientist about using super-critical CO2 from power plant exhaust as a fracking and hydrocarbon solvent for tertiary recovery and carbon sequestration. So don’t worry about me getting lost in conversation here. I have a day job. But these are things that I don’t discuss much in public at this point, so don’t bother trying to find those projects on the web, at least at this point.

    And if this website has been discussed in detail before, please forgive, but these folks seem to be trying to do something about the arctic methane fast feedback issue. I will readily admit that this link is the only substantive part of this post.

  122. Dan H.:


    I think you argument for exponentially increased Greenland ice mass loss is not well supported? Box, et. al. writing in State of the Climate in 2010, noted that “Glacier ice area elsewhere in 2010 (i.e. excluding Petermann Glacier) remained near the average loss rate of 121 km2/yr observed since 2002.”

    While the GRACE measurements support an increase in annual ice mass loss in its first half of its operation, no such increase can be detected since (which includes the Petermann calving). Again, this is still very short-term results from GRACE, but compared to other long-term measurements, there does not appear to be an exponential increase.

    [Response: You can’t have it both ways. Either the record is too short to tell, or it isn’t too short to tell and it either does or does not show an exponential increase. Logic dictates that you need to decide on one, not two, of these options. Of course, rhetoric dictates that one mangle these things up to ensure the minimum of informational transfer, but I’m hope that’s not the goal. – gavin]

  123. Dan H.:

    I have no idea what you are talking about. My contention is that the GRACE data does not support claims of exponential increase in Greenland ice mass loss.

    [Response: piece of data X may not provide support for proposition A, because X => not(A), or X implies neither A nor not(A). But it can’t do both at once. Having said that, GRACE estimates of Greenland mass loss do show an acceleration. – gavin]

  124. Dan H.:


    Looking at the actual numbers from GRACE (and I am fully aware that there are several different estimates), one cannot conclude that mass loss is accelerating. From the following, the ice mass loss increased from 84 GT in 2003 to 201 GT in 2005, but there is no significant trend since: 2006 – 177 GT, 2007 – 244 GT, 2008 – 287 GT, 2009 – 190 GT, and 2010 – 266 GT. A better analysis would be that ice mass loss has held constant at ~230GT / yr as Rene Forsberg concluded. There is simply too much scatter in the data to conclude that ice mass loss is accelerating.

    [Response: Are you even looking at the same graph? page 9 on that presentation – it is clear that a linear trend through the first half is shallower than a linear trend through the second half, and although I don’t have the exact numbers, I would guess that the trends are significantly different. You could also fit a quadratic and show that the quadratic term is significantly non-zero. Comparing one year to another is not a statistically robust procedure.- gavin]

  125. tamino:

    Re: #124

    In which Dan H. says

    A better analysis would be that ice mass loss has held constant at ~230GT / yr as Rene Forsberg concluded.

    and links to a presentation by Rene Forsberg. In that presentation, Forsberg himself states on the final (“conclusions”) slide:

    Current changes of Greenland ~ 230 GT/yr … accelerating, but slowly

    Dan, how did you get from Forsberg saying “accelerating” to your claim “held constant … as Rene Forsberg concluded.”

    Do tell.

  126. David B. Benson:

    wili @120 — This is the wrong thread to go further. Use the Unforced Variations thread after reading the thread devoted to Arctic methane here on RealClimate and my comment over at Tamino’s. The links to both have been given previously on this thread.

    Vaguely related to the topic here are the buried forests in southern Greenland. Those grew during the Eemian (interglacial 2) and 100,000 years hasn’t been long enough to scrape all of that off.

  127. Hank Roberts:

    > “held constant”

    Are those words a quote?

    Sounds like a modeling study, describing
    something held constant for a run.

  128. Unsettled Scientist:

    Hank, “held constant” was not at all in the link provided by Dan H. He grabs the 230 number out of a link he provides, and then claims it shows something it doesn’t injecting his own “held constant” idea (or maybe he was mislead by a denialist blog and the idea wasn’t even his). My guess is that Dan H. didn’t read the whole thing (and it’s all pictures) and grabbed the 230 number off page 3 instead of page 15 where Forsberg put the conclusions including the point that the rate is accelerating as tamino pointed out. It could be a copy pasta mistake, or it could be him injecting his bias. Either way it’s just another example of a misrepresentation by this commenter.

  129. John E Pearson:

    127 Hank asked was “held constant” a quote. No. Tamino quoted in 125:

    “Current changes of Greenland ~ 230 GT/yr … accelerating, but slowly”

    In other words the kindest way to interpret “held constant” is that it was due to a careless reading of Forsberg on the part of the poster. Given the poster’s past behavior I personally find it easier to believe that it was deliberate misinformation .

  130. MARodger:

    Re Ice burden on Greenland.

    Using the word “acceleration” to describe variations in changing levels of something is fraught with ambiguity unless a pause is taken to define the term. Best to use a less ambiguous term.
    The word orignially bandied about here was “exponential increase” (and previously there has been talk of “doublings” of Greenland’s ice loss) These terms obviously refer to an increase (or in this case ‘decrease’) in level that is faster than linear.
    I have in the past found arguments that GRACE shows the loss of Greenland’s ice mass as increasing exponentially, that the rate is doubling per decade or quicker – such argument I have found entirely unconvincing in the past and have been happy saying so, even when I then am refuting statements from the likes of Jim Hansen.

    I would argue that the GRACE measurements presently suggest no more than that Greenland’s net ice mass loss is increasing linearly, at a rate of 50-60 Gt pa.

    Regarding the past few years annual GRACE data that shows a reduction in this rate of increase of net ice mass loss (eg – 3 year rolling average trends dropping from 60 Gt pa to 6 Gt pa), such assertions requires more supporting analysis & evidence rather than blindly serving up the numbers as some sort of difinitive proof. Indeed, the last couple of melt seasons had record areas of melt & other such extremes (For instance, 2010 see ), yet GRACE shows no spectacular net mass loss (although the quantity ‘max annual ice mass – min annual ice mass’ is starting to look interesting).

  131. Hank Roberts:

    You know that slippery film that forms on, well, anything and everything — rocks in streams for example, or bathtubs and showers, or in distilled water lines in medical and science labs, or inside crude oil pipes, or lungs? It’s generically called a ‘biofilm’ — often a multilayered structure in which a variety of microbes participate, that excels in picking small amounts of nutrients out of flowing water.

    We used to have them so extensively in watersheds that the water in many streams and rivers was cleaned up enough to drink, tho’ we’ve rather overwhelmed that process in recent decades; biofilm ‘reactors’ are being built to replicate the way they clean dirty water: .
    Turns out biofilms grow underneath glaciers.

    One paper here on one glacier finds the stuff is nitrogen-limited.

    What difference will feeding that stuff make, if any? Nitrogen compounds are a significant pollutant falling out in rain — and running off in meltwater that would feed whatever’s living under the ice.

    Pure speculation from here on — is a change in the microbial population underneath glacial ice going to affect movement of the ice?

  132. wili:

    Hank, that is really interesting. Not something I ever would have thought of.

    This is the kind of info and insight that keeps me coming back here, in spite of the DH’s and his feeders.

    David–Thanks. Will do.

  133. TimD:

    MARodger; While I have pretty much sworn off this site, it is the weekend and I have some time to waste. But your statement that GRACE data doesn’t support the argument that Greenland ice mass loss is exponential is COMPLETELY OUTRAGEOUS NONSENSE! (I hope that is sufficient emphasis) How can you look at the figure in the latest available data ( fig. HTC19) and not see a continuously accelerating function? [edit – polite please]
    And please, good Tamino, fit a curve to that data and then tell us what the doubling time is of the best exponential fit. I know, Tamino, that you have the talent to do that fit before or after removing the seasonal (annual) component of the function. [edit]

  134. TimD:

    P.S. This is what that curve fit will look like, but the article unfortunately does not give the parameters of that fitting equation. But, marodger, is that a continuously accelerating function or not?!!!! Jesu Christo.

  135. Unsettled Scientist:

    Is anyone who is competent and honest looking at the GRACE data or Forsberg and concluding that it shows ice mass loss has held constant? It appears not.

    “These data records [more than just Forsberg] suggest that the rate of mass loss is increasing, indeed nearly doubling over the period of record, but the record is too short to provide a meaningful evaluation of a doubling time. Also there is substantial variation among alternative analyses of the gravity field data (Sorensen and Forsberg, 2010), although all analyses have the rate of mass loss increasing over the period of record.

    “Together the two satellite systems show a consistent picture of ice mass loss in marginal zones of the ice shees, and increasing trends in some central regions. …in Greenland chares are largest in SE Greenland, with mass loss trends currently increasing along the NW margin, consistent with the observed increase in flow speeds of major outlet glaciers.”

  136. Dan H.:

    I have to agree with MA on this. The slight increase in the annual ice mass loss cannot be seperated from random noise. The first few years of GRACE data did show a greater annual increase, but the more recent years, have not. This does not preclude that ice mass loss could be increasing exponentially, just that the GRACE data we have to date, is too sparce to show such a trend.

    We seem to have a spilt here between those who would argue for an exponential acceleration of the annual rate of ice mass loss, and those arguing that ice mass loss is increasing only slightly or not at all.

    [Response: #logicalfail. You cannot argue both that the data are too uncertain AND that there is no increase in the loss. Only if the data were clear and unambiguously showing no acceleration or negative acceleration (which they do not), could you make your second point. Please at least try to remain consistent in a single comment. – gavin]

  137. MARodger:

    TimD @133 & 134
    I do admit to some sloppy (potentially ambiguous) writing @130, a problem I was myself warning of as I am not alone in doing this.
    So here let the ‘Quantity In Question’ (QIQ) be defined. Greenland has ice cover. The mass of that ice cover is reducing annually. Let the rate of that reduction be defined for discussion here as QIQ.

    All the evidence (bar Forsberg’s numbers discussed below) shows that QIQ is increasing.

    The GRACE data graphed in Hansen & Sato 2010 ( This version of the paper presents graphs of our QIQ in fig 8c.) extends to 2009 & which is used to support the proposal that QIQ is increasing exponentially.
    I find their argument less than convincing & TimD @133 adds nothing extra except his link to Box et al 2011 provides a graph of data up to 2011. I contend that Hansen & Sato 2010 Fig 8c could as easily be fitted showing a linear trend in QIQ.

    The data presented on Page 9 of Forsberg (linked to by Dan H @124) does present numbers for annual ice loss based on GRACE data to end 2010. These numbers point to a reduction in QIQ over the last 2 years.
    The data presented by Forsberg is however of unknown calculation. Scaling measurements from Box et al fig HCT19, I see no sign of such a reduction in QIQ for the last 2 years from either changes in annual minimums or in changes in the annual max-minus-min values.

    While linearity in QIQ may prove simplistic, given the data available, I remain unconvinced of anything as dramatic as proposed by Hansen & Sato 2010.

  138. tamino:

    Re: #136

    In which Dan H. says

    We seem to have a spilt here between those who would argue for an exponential acceleration of the annual rate of ice mass loss, and those arguing that ice mass loss is increasing only slightly or not at all.

    No, Dan. We have a split between you, who said “ice mass loss has held constant at ~230GT / yr as Rene Forsberg concluded,” and Rene Forsberg, who said “accelerating.”

    YOU are the one who brought this up. Are you now hoping it will go away? Either own up to your distortion of Forsberg’s conclusion, or you have no place in the discussion.

  139. Gene Goldring:

    In debating for AGW an interesting topic came up. Groundwater pumping creating 0.05mmper year sea level rise. Yoshihide Wada, with Utrecht University in the Netherlands has commented on the study at Live Science’s article, “Groundwater Pumping Is Causing Seas to Rise”

    He also claims this has not been addressed in the IPCC reports.

    Any comment?

    [Response: Well, the issue of human water management – both from reservoir construction and groundwater depletion – affecting sea level is indeed discussed in IPCC (section and was taken into account in many recent estimates of future rise (see Rahmstorf and Vermeer for instance). These new estimates are higher than previous ones and so that is interesting to look into. I don’t have any particular insight into the methodology though – perhaps some others might? – gavin]

  140. Unsettled Scientist:

    Dan H.

    We’re not interested in your analysis anymore. You have too many times clearly stated the opposite conclusions of the references you provide. Now you are saying there is a split of people between those who think the ice mass loss rate is increasing and those how think it is not. That may be true among laymen, but we are concerned with the scientific understanding, not the laymen understanding.

    The link you provided shows accelertation of ice mass loss. I provided a link that shows that “all analyses have the rate of mass loss increasing over the period of record.” We don’t care what your opinion is, and nobody should care what my opinion is. This a blog about science. Please provide scientific references for your points because we know how bad you are at analysis after this, the PDSI, and beyond.

  141. Gene Goldring:

    Thanks Gavin for the quick response. I’m a lay person that reads the articles here at RC frequently trying to understand climate science. RC has been a big help in this regard over the years.

    Thank you for all the hard work you folks put in explaining this rather complicated topic.


  142. Paul S:

    Gene Goldring – Looking at the link, it specifically refers to the IPCC not including groundwater depletion in its sea level rise projections, which I think is correct. As Gavin says, AR4 did briefly cover it in terms of past changes but with huge uncertainties. Given that the IPCC reports are about climate change and its effects, it’s not immediately obvious that groundwater depletion should be included in forecasts.

    Wada et al. published a previous paper on this topic in 2010. Konikow 2011 found that there were significant problems with their approach. Presumably those criticisms have been addressed in this latest paper, but I don’t have access to the full text. It looks like they’ve compared their initial results against GRACE gravity data at least.

  143. Paul S:

    Hmm.. looking closer at the numbers in the article it forecasts contributions of 0.8mm/yr by 2050, whereas the 2010 Wada et al. paper suggested a ~0.8mm/yr current contribution, so clearly the methods have changed somewhat.

  144. TimD:

    MARodger, The quantity in question (QIQ, how clever) is not the rate of ice loss, since that is a single value defining a quantity of change withing a specific time period. These discussions have been about the rate of change of ice loss, which describes how the loss rate changes over time and in this case, is a simple mathematical function that best fits the observations. Your statement that the data in Sato and Hansen, and the more recent data I provided, “could as easily be fitted showing a linear trend” is absolutely factually untrue, if the quality of the fit is defined as the RMS error between the data and the fitted curve. Your opinion is of no concern or import, and you might as well keep it to yourself. The value of such curve fitting exercises is predictive, and curve fits found in the paper by Sato and Hansen predicted the continuing accelerating trend seen in the later data. But the important result of understanding the form of the mass loss function is that it has ramifications as to how to understand the underlying mechanisms of that loss. The root article pointed out that outlet glacier velocity may only account for some 30% of the mass loss increase over the decade of GRACE measurements, which shows an increase on the order of 100%. Increases in surface ice melt is significant, but not high enough to account for the losses. The only reasonable mechanism remaining to explain the accelerating ice mass loss is basal melt driven by increasing penetration of the ice that is exposed below sea level to the rapidly increasing sea temperatures, driven in turn by large and fast albedo reductions due to very rapid sea ice loss. Gravity measurements see this phenomenon very well, which is not nearly so apparent using surface measurements of velocity and melt. I strongly criticize the misleading title of the root article, which suggests that ice loss in Greenland is not accelerating when it clearly is, and especially the statement in the article that the results of a cited paper “put speculation of monotonic or exponential increases in Greenland’s ice discharge to rest”, when that is factually in error. I strongly believe that the author should correct that misstatement and the misleading title, which is already being utilized by denialists in their big energy business propaganda campaigns. The article by he guest researchers is also misleading in that they state flatly “The Greenland ice sheet changes mass through two primary methods: 1) loss or gain of ice through melt or precipitation (surface mass balance) and 2) loss of ice through calving of icebergs.” I would maintain that that statement is seriously in question based on the GRACE data and several other studies that show rapid increases in basal melting due to sea water infiltration. These statements contained in the root article are very irresponsible and, potentially, a huge disservice to the task of educating the public about the risks of rapid climate change. They should be changed in a prominent fashion as clear errata and by changing the title of the article.

  145. David B. Benson:

    What Gene Goldring said.

  146. MARodger:

    Further to my whitterings @137 about GRACE data & ice loss from Greenland:-

    Curious about what looked like discrepancies, I plotted Forsberg’s data of increasing Greenland mass loss along side Hansen & Sayo 2010’s data I had hiding on a spreadsheet. Then I scaled the recent Box et al data & grafted it on top (which is not the best of fits but for plotting the trend is likely adequate).

    The resulting graph pretty much reconciles Forsberg’s numbers with the rest. Link to graph here (usually requiring two clicks to get “your attachment”.)

    Concerning comment @136. It is strange that the comment begins “I have to agree with MA on this.” but then goes on to present statements I almost wholly disagree with.

  147. TimD:

    MARodger, a nice graph, but your linear fit is mis-labeled. The linear fit line should be labeled “33 GT pa^2, since the quantity plotted is the annual rate of change in the mass anomaly, and the curve fit to that data is the rate of change of that quantity, otherwise known as acceleration. So your linear fit is consistent with a constant acceleration of the ice mass anomaly, which in turn is an exponential increase of the mass loss. Are we clear now?

    Please also note that the rate of loss has doubled from 150 to 300 gt/a between 2003 to 2010, which gives us a doubling time in annual mass loss rate of some 7 years. As I previously stated, the really pertinent question here is for how long will that acceleration remain high and nearly constant, and therefore, how many doublings of the loss rate will we see before negative feedbacks kick in? To begin to answer that question, we need to understand the mechanism of the increase. If the acceleration stays constant only until mid century, the loss rate will be some 60 times greater than today. That is something we need to understand, with great urgency. The root article severely downplays that urgency and is highly irresponsible as it stands.

  148. MARodger:

    TimD @147

    It is nice that you like the “nice graph”. The trend line indeed should be in Gt pa^2. The trend line is more illustrative than predictive and, yes, presents roughly a 7 year doubling (170 Gt to 350Gt in 7.25 years). As you note, it is achieved with a constant ‘acceleration’. In my speak, as defined @137, dQIQ/dt = constant.

    Given this situation dQIQ/dt = constant, in the next 7.25 years, the annual ice loss will increase by another 180 Gt pa, yielding QIQ = 530 Gt pa. This is not, as you suggested, a further doubling of QIQ over even the 7.25 year period and without such a periodicity for doublings in QIQ, I fail to see how this represents an “exponential” increase.
    Hansen & Sato 2010 do propose an “exponential” increase which is why their figure 8c that graphs my QIQ (in this version of the paper) has a cirving trend.

    You do in your comment @147 address the major problem I have with Hansen & Sato 2010 as you see the process as limited by feedbacks.. In my view, any ‘doubling’ mechanism will quickly begin to impact on the climate system inducing the strongly negative feedbacks that you mention..

  149. john byatt:


    Church et al 2011 is a relevant paper.

    Revisiting the earth’s sea-level and energy budget from 1961 – 2008


  150. Hank Roberts:

    > the comment begins “I have to agree with MA on this.”
    > but then goes on to present statements I almost wholly disagree with

    Debate coaches have a name for that, it’s a tactic.

    > 33 GT per annum

    Out of what total?
    What would that be as a percentage per annum?
    Got a snowfall accumulation in the total?

  151. Dan H.:

    Let me clarify my previous statement concerning MA’s post. I agree with his statement that arguments showing the loss of Greenland’s ice mass as increasing exponentially are entirely unconvincing. Statements from links presented here seem to agree with that. For example: Forsberg, “Current changes of Greenland accelerating, but slowly.” Joodaki, “Although the mass loss of the ice sheet is not constant, we decided to represent the GRACE observations by a linear trend. We cannot observe a significant acceleration term over whole data series.” Bergman, “The decrease of Greenland Ice Sheet ice mass is clearly not constant in time, but contains interannual variability suggesting that the ice mass melting is a transitional complex phenomenon.” Box (estimates from MODIS), “The cumulative pattern of area change from the 39 glaciers surveyed indicates a linear and geographically widespread retreat pattern.” Many papers choose to describe the ice mass loss as linear, not because it was the best fit to the data, but as a general descriptor. None of the data presented show a statistically significant trend.

    Bergman also stated that, “the mass balance of the Greenland Ice Sheet is dominated by snowfall in regions of high elevation and by glacier discharge in regions of lower elevation.” The higher rates of ice mass loss were dominated by large losses in the SE glaciers corresponding to higher North Atlantic SST. This agrees with Tim’s assertion of basal melting due to higher SST (hope he’s still here). The recent large drop in N. Atlantic SST may shed some light on this.

  152. Mertonian Norm:

    “The value of such curve fitting exercises is predictive, and curve fits found in the paper by Sato and Hansen predicted the continuing accelerating trend seen in the later data.”

    A non-rhetorical question for TimD from a non-scientist: How do you determine when or if an accelerating [fit to a] curve has ceased to accelerate and thereby lose its predictive value? Otherwise stated, how much data is required before one suspects a point of inflection is coming up? (A poor example, no doubt, but logistic curves are exponential up until they aren’t.) I am not suggesting that is happening here but curious to know how scientists determine future acceleration.

  153. john byatt:

    Timing and origin of regional ice-mass loss in Greenland
    Last ten years unusually high compared to last fifty years

    Sasgen et al 2012


  154. Unsettled Scientist:

    Dan H.

    Thank you for finally agreeing that the rate of mass loss is increasing. All of those quotes clearly state that rate is increasing. It is not held constant and it certainly can be separated from noise (your previous two analyses of the literature being incorrect).

    It is important to note that what is increasing is the rate of mass loss, not just total mass lost. As a very simple example, if I have 100 apples, on day 1 I remove 1 apple and am left 99. Then to have a linearly increasing rate of loss the next day I remove 2 apples, and have 97, then day 3 apples, then 4. So after 4 days I have removed 10% of the apples am left with 90, instead of the 96 I would have if “apples lost” (total mass loss) itself was linear. So you can see, even a linear increase the rate of Greenland’s ice mass loss is more of a concern than if mass loss was a constant linear rate.

  155. Hank Roberts:

    > Many papers choose to describe the ice mass loss as linear
    > not because it was the best fit to the data,
    > but as a general descriptor.
    > None of the data presented show a statistically significant trend.

    What? ‘many papers’ — which specific papers fit the above description?
    It’s rather damning, if true, isn’t it?

  156. Steve Bloom:

    MAR #148: “In my view, any ‘doubling’ mechanism will quickly begin to impact on the climate system inducing the strongly negative feedbacks that you mention.”

    Thank goodness we can exclude the possibility of cascading positive feedbacks along with any paleo evidence of rapid ice sheet collapse.

  157. TimD:

    Mertonian Norm; I appreciate the excellent question and I would hope that a principal/scientist from this site would also comment on it, since it is an important concept. I am a geophysicist, not a climate scientist, but I think I pretty well understand the science in a closely related discipline that I have closely followed for over 30 years.

    I believe that in the current environment of rapidly rising temperatures in a climate system clearly dominated by positive feedback mechanisms, it is of utmost importance to search carefully for indications of non-linear effects, since that is a hallmark of positive feedback. The rapid loss of ice mass over the last decade, best measured by the GRACE global gravity system, clearly shows a consistent acceleration. If it continues along that trajectory, as it has for at least a decade, then we become increasingly certain that the underlying mechanism is a positive feedback effect. But the important thing is to understand that it is, in effect, a siren, screaming that we need to understand that underlying mechanism as soon as possible. This point is even more significant when one considers that many eminent glaciologists have said over and over, that the “fundamental response time of continental ice sheets is thousands of years”. This effect (ice mass loss) is clearly responding to warming in a matter of a few years, so it is very obvious that the science is seriously lacking in the current environment, which in turn points to areas where significant resources and effort needs to be directed.

    In terms of predictive value, it is a certainty that the exponential character we observe in natural systems will eventually, and usually quickly, cease to continue accellerating, since this behavior rapidly leads to absurdly high values of whatever parameter is being measured. But that also means that due to rapid growth, that parameter will very quickly become a significant or dominant element in the overall system. In the case of polar ice sheet mass loss, Hansen has already studied the effects of the rapid release of cold, fresh meltwater into the oceans and found that high rates of polar warming are likely to suddenly cease, with severe, but hard to predict effects on the stability of the global climate system. I very strongly recommend the Sato-Hansen paper, since it discusses these issues, and puts the current extremely rapid climate system forcing due to increases in GHGs, into the context of what we know about paleoclimatology. That paper direclty illustrates the degree to which the advent of large polar ice sheets has amplified the very subtle forcings of earths orbital cycles which gave rise to the series of ice ages in the Pleistocene. The GHG forcings are large and they are likely more rapid than anything the earth has experienced since the Chicxulub asteroid killed the dinosaurs 65 million years ago. There absolutely has to be a strong, global effort to comprehensively understand the mechanism behind the accellerating mass loss observed with certainty in both Greenland and Antarctica, as well as the numerous other interacting positive feedback mechanisms that are popping up everywhere. This is a serious global emergency, and anything that downplays the seriousness of the situation must be aggressively countered. That is why I am more than a bit strident about this issue.

  158. Unsettled Scientist:

    Ah, Hank, thank you for being a more careful reader than I was. I see Dan H. is still confusing the issue. He is seeing the handful of papers that would describe the increase in the rate of loss as linear, and then confounding that with actual ice mass loss. Shame on me for not reading it more carefully. Obviously if the rate of loss increasing linearly, then the total ice mass lost is faster than that. I find this much easy to describe in math than words, so I hope my apple analogy was decent enough. A linear increase in the rate (1,2,3,4…) would lead to a mass loss increasing faster (1,3,6,10…). So even if the low estimates of a linear increase in the rate are correct, I don’t find that comforting.

  159. TimD:

    Unsettled Scientist @154, Thank-you, Thank-you, Thank-you,… for the superb layman’s explanation for most of the confusion on this topic thread. You must be a very good teacher in real life.

  160. Dan H.:

    How have you determined that the linear trend can be seperated from noise, especially since the cited papers cannot? As stated in post #130, the rate of increase in mass ice loss decreased from 60 Gt/yr^2 to 6 Gt/yr^2. Considering that the uncertainty in the most recent ice mass loss is ~30 Gt, this can certaintly not be seperated from noise.

  161. Hank Roberts:

    > this can certaintly not be seperated from noise.

    That’s weather: a few years’ worth.
    No trend detectable in that few data points.

  162. Unsettled Scientist:

    Dan H.,

    Your question highlights a bit of your confusion. I didn’t say that the linear trend can be separated from noise. That the trend is positive (increasing) has been separated from the noise, the rate of ice mass loss is unquestionably increasing. Whether that is a linear increase or something much more complex (my suspicion) is the question. Whether it be 60 or 6, both are positive numbers and show an increasing rate of mass loss, not being held constant or hidden in noise.

    Simplified math for an example. I start with 500 units of ice and the rate of loss is 60. Then next year I start with 440 and the rate of loss increases 60 (=120 units/yr). Then next year I have 320 units of ice left and the rate increases just 6 units (=126 units/yr). So then next year I start with 194 units of ice. The trend is a faster rate of loss. It might not be a linear increase in the rate (or exponential or other fit), but we are still losing ice more quickly than before.

  163. Unsettled Scientist:

    Dan H.

    Also, I’m not sure if you were able to see my 5:59pm reply when you posted. What you wrote, that Hank was diligent enough to read carefully, is clearly incorrect. I think the two roots of your confusion are conflating the of ice mass loss with net ice mass loss. This is evidenced in what Hank quoted of yours 4:58pm (#155). The second root of your confusion is conflating the shape of the trend, with the sign of trend. I explained that above: the trend for the rate of ice mass loss is increasing, but we don’t know its shape yet be it linear, exponential or something different. Obviously, if the rate of ice mass loss is increasing (no matter its shape) then there is clearly significant trend in ice mass loss itself.

  164. Unsettled Scientist:

    Ugh, typo at 10:14. Should be: “… conflating the *rate of ice mass loss with net ice mass loss.”

    I think I messed up an html bold tag and removed the word.

  165. Lawrence Coleman:

    Very interesting article in Science Daily about Knud Rasmussen the danish explorer who took many photos of SE greenland in the early 1930s. What it shows is that the rate of melt of glaciers then was comparable to that of today and in some cases even faster. These glaciers photographed were land terminating so did not cause any consequent sea level rise. Then in the 1940s to the 1970 a period of relative cooling caused by high levels of sulphur dioxide in the atmosphere stabilised the glacial melt and even partially restored any loss of mass in from the 1930’s back. What is fascinating to me is that the clean air act took effect in 1963 I believe and a return to glacier retreat in greenland began in earnest at about 1972 up to today. That to me shows that for suphur dioxide at least the inertia when it comes to the atmosphere is about 10 years or less since factories wouldn’t suddenly have cleaned up ther act overnight. So I could be naive in thinking but that indicates to me that atmospheric seeding with certain chemicals would cause quite dramatic and rapid results and the sooner this is done the better for only the sake of buying us invaluable time as we do not want to warm the oceans one jot more than what they are at present..that is the unstoppable juggernaut in the entire system. What do you guys think?

  166. Dan H.:

    No confusion on my part, although I mentioned both ice mass loss and the rate of ice mass loss. I understand that a linear (or otherwise) increasing trend in the rate of ice mass loss results in acceleration in total ice mass loss. Visually, the data shows an increase. Statistically, the increase in not significantly different from zero. In other words, we can say with any reasonable certainty that the trend is increasing. Part of this is due to the short time period of the GRACE data, part to the large uncertainty in the estimations themselves. The Joodaki paper (cited previously) agrees quite well with the Forsberg paper except for 2003. Its 8-year trend show an increase of slightly more than 3 Gt/yr^2. Again positive, but not significantly different from zero.

    Reading the Bergman paper, the citation from Lawrence above, and Allen’s ice core measurements, the Greenland ice sheet has shown anything but a linear trend. I agree that the rate of ice mass loss in the previous decade was higher than in the 1980s and 1990s. Glaciers are dynamic. However, claims of significant continued acceleration are unfounded. Putting forth theories, like Hansen and Sayo are fine, and may help to understand the future changes. But until they are support with data, we should treat them as such. Tim, I am curious as to your thoughts on how the recent SST will affect basal melting.

  167. Unsettled Scientist:

    Dan H.

    Clearly you are still confused. Immediately after I say don’t worry about the shape of the trend but the sign of the trend you are back to talking about whether or not we can see a linear shape.

    If you’re not confused, then you are saying it was either a careless mistake or intentional misrepresentation when you wrote, “Many papers choose to describe the ice mass loss as linear, not because it was the best fit to the data, but as a general descriptor. None of the data presented show a statistically significant trend.” Because that is blatantly wrong. If it was a mistake I would expect you would have owned up to it, so what am I left to assume if you don’t say you were wrong? Simply mentioning both the rate and net ice mass loss isn’t sufficient to lack confusion. You have to use them in the correct context in order to be accurate. If you aren’t confused, you are certainly adding to the confusion in this thread through either laziness or deceit.

    Sadly, we cannot access your Joodaki paper. You are notorious for cherry picking quotes out of papers and misrepresenting them. For example in this very thread when you wrote, “A better analysis would be that ice mass loss has held constant at ~230GT / yr as Rene Forsberg concluded.” When we went and read the paper you linked, Forsberg concluded it was increasing, not held constant. So forgive us if we don’t trust your reading of the literature. I’m sorry, but you can’t take the results of scientists who say it’s increasing but slowly and claim that means it is insignificant. That’s dishonest.

  168. Unsettled Scientist:

    Dan H.

    Here is another example of either your confusion, or an attempt to conflate two separate things in order to confuse laymen. In post #122 you provide a link and cherry pick a quote out of it.

    You write: I think you argument for exponentially increased Greenland ice mass loss is not well supported? Box, et. al. writing in State of the Climate in 2010, noted that “Glacier ice area elsewhere in 2010 (i.e. excluding Petermann Glacier) remained near the average loss rate of 121 km2/yr observed since 2002.”

    What you have done here is conflate “Greenland ice mass loss” with “Glacier ice area elsewhere.” It is obvious that Box et. al are not speaking of ice mass loss in the quote you pulled once one reads the link you provided. You pulled it from the section of the paper on “Marine-Terminating Glacier Changes.” The previous section before that was the section on “Total Greenland Mass Loss from GRACE,” but you didn’t use a quote from there like “Using GRACE data, Rignot et al. (2011) found an acceleration of Greenland ice sheet mass budget deficient during 1979-2010, in close agreement with an independent mass balance model.”

    What you did in post 122 is colossally bad reading and analysis skills showing you cannot understand the difference between ice mass and a select set of glaciers, or it was blatant dishonesty in order to confuse the lay-reader. In that same post you inject your bad analysis and say, “While the GRACE measurements support an increase in annual ice mass loss in its first half of its operation, no such increase can be detected since.” While the link you provided in that post says, “For the hydrologic year 2009/10, i.e., from the end of the 2009 melt season, including October, through the end of October 2010, the ice sheet cumulative loss was -410 Gt, 177% (or two standard deviations) of the 2002-2009 average annual loss rate of -231 Gt*yr^-1. This was the largest annual loss rate for Greenland in the GRACE record, 179 Gt more negative than the 2003-2009 average.”

    So again, don’t fault anyone who doesn’t trust your reading of the literature. You consistently come to different conclusions than the references you provide, and you consistently mix up your concepts comparing apples to motorcycles.

    I hate to keep feeding the troll, so I think I’ll let this be my last word on this subject. Sadly Dan H. is quite prolific throwing up links to references and then misrepresenting them on this site.

  169. Dan H.:

    There is nothing dishonest, in my posts, nor am I confused. Perhaps you are not understanding me correctly. There was nothing careless, nor misrepresented in my statement. Since, you claim that my statement about the papers not showing a statistically significant trend is wrong; you should be able to show me an instance where it does.

    My statement concerning the Forsberg paper is accurate as written. The presentation clearly states recent ice mass losses as ~230Gt +/- 30 Gt. My contention is that “constant” is a better descriptor of the data than “accelerating, but slowly,” since the increase is not statistically significant. Maybe, “held constant,” is too strong a declaration, and “no clear trend” would be a better representation than either Forsberg’s or my statement, since the trend has a poor coefficient of determination, and the uncertainty in the data exceeds the trend.

    There is nothing I can do regarding the Joodaki paper, although I included a link to a relevant graphic from the work. Joodaki showed an average ice mass loss of 225 Gt over an 8-year period, which closely matches the data presented by Forsberg. Here is the concluding statement from the Joodaki paper word-for-word, “Although the mass loss of the ice sheet is not constant, we decided to represent the GRACE observations by a linear trend. We cannot observe a significant acceleration term over whole data series. This trend is also pointed out by various recent research studies as reported in the introduction. This emphasizes the need for continuous observation of ice mass balance and extending time series of ice mass changes estimated from the Earth’s gravity signal provided by GRACE and future missions.”

  170. Hank Roberts:

    No confusion on my part ….
    > …. data shows an increase.
    > Statistically, the increase in not
    > significantly different from zero….
    > … we can say with any reasonable certainty
    > that the trend is increasing….
    > … 8-year trend show an increase …
    > Again positive, but not significantly different from zero.

    Would someone personally adquainted with Dan H.
    look in on him and see if you can help him?

    This is word salad with number sprinkles.

    There may be some science somewhere behind all the words
    but it’s not getting across and the topic’s lost in the fog.

    Perhaps the scientists could sum things up and get it sorted out?

  171. Ray Ladbury:

    Dan H., Expand exp(lt) in a Taylor series in t. Now assume l>>t. Does this make it clearer why researchers might look for a linear trend for data over short periods, regardless of the actual dependence?

  172. tamino:

    Re: #166

    In which Dan H. says

    Visually, the data shows an increase. Statistically, the increase in not significantly different from zero.


    Data from Forsberg:

    Year Loss_Rate
    2003 84
    2004 148
    2005 201
    2006 177
    2007 244
    2008 287
    2009 190
    2010 266

    Result of linear regression:

    lm(formula = x ~ t)

    Min 1Q Median 3Q Max
    -63.464 -18.955 -3.393 33.625 55.071

    Estimate Std. Error t value Pr(>|t|)
    (Intercept) -43011.786 13359.239 -3.220 0.0181 *
    t 21.536 6.658 3.235 0.0178 *

    Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

    Residual standard error: 43.15 on 6 degrees of freedom
    Multiple R-squared: 0.6355, Adjusted R-squared: 0.5748
    F-statistic: 10.46 on 1 and 6 DF, p-value: 0.01781

    The p-value is 0.01781. That’s statistically significant.

    How many more times will you do this, Dan?

    Once again you have been proved wrong. Will you once again ignore that hoping it will go away? Will you once again refuse to own up to your misrepresentation? Will you ever admit that you’re wrong? Will you ever even consider the possibility that your entire belief system is based on wishes rather than scientific evidence? Or, will you simply move on to your next patently, demonstrably, provably false claim?

    How many more times must we endure his kind of garbage?

  173. SecularAnimist:

    Unsettled Scientist replied to Dan H: “That’s dishonest.”

    That two-word sentence is really all that needs to be said in response to each and every one of Dan H’s comments.

  174. MARodger:

    Steve Bloom @156

    Indeed. So clever of me to enable that. With this comment thread swinging from talk of annual ice loss last year to geological timespans, nothing I write or read would immediately surprise me.

    By ‘”feedbacks” I meant that the likes of say a sustained ‘7-year doubling’ of lost ice would quickly overpower the temperature rise that was driving it, this holding true almost as quickly even if such doublings led to icebergs bobbing round the tropics in search of warmth.
    So I speak of “feedbacks” of a temporary delaying nature only.

    Putting numbers onto that assertion, the data from Box et al (Data graphed here) shows the present level of Greenland’s annual ice loss at some 350 Gt pa (Box et al state 430 Gt pa to April 2011). It is thus contributing 1mm pa to sea level rise & requiring 0.12 zJ of latent energy.
    A linear 33 Gt pa increase would yield by mid-century 1,736 Gt pa of ice loss, causing 4.8 mm pa of SLR & requiring 0.6 zJ to melt.
    A ‘7-year doubling’ would yield values 13x bigger and thus the latent energy absorbed in just Greenland’s ice loss will be about equal to the total present-day annual OHC rise.

  175. Hank Roberts:

    “25.05.2012 | Potsdam: The Greenland ice sheet continues to lose mass and thus contributes at about 0.7 millimeters per year to the currently observed sea level change of about 3 mm per year. This trend increases each year by a further 0.07 millimeters per year. The pattern and temporal nature of loss is complex. The mass loss is largest in southwest and northwest Greenland ….”;jsessionid=9A24192AE7E80EDE335359C718135029

    Ingo Sasgen et al., Timing and Origin of Recent Regional Ice-Mass Loss in Greenland, Earth and Planetary Science Letters (EPSL), doi: 10.1016/j.epsl.2012.03.033, Volumes 333–334, 1 June 2012, Pages 293–303

    has an excellent overview with many links to sources.

    The main reference is to:
    Nature Geoscience | Article

    An aerial view of 80 years of climate-related glacier fluctuations in southeast Greenland

    Anders A. Bjørk, Kurt H. Kjær, Niels J. Korsgaard, Shfaqat A. Khan, Kristian K. Kjeldsen, Camilla S. Andresen, Jason E. Box, Nicolaj K. Larsen & Svend Funder

    Nature Geoscience
    5, 427–432 (2012)

    Published online 27 May 2012

  176. dbostrom:

    For what it’s worth here’s the part of the Joodaki paper that is available to the financially unable or unwilling:

    Mass loss of the Greenland ice sheet from GRACE time-variable gravity measurements


    The Gravity Recovery and Climate Experiment (GRACE) satellite data is used to estimate the rate of ice mass variability over Greenland. To do this, monthly GRACE level 2 Release-04 (RL04) data from three different processing centers, Center for Space Research (CSR), German Research Center for Geosciences (GFZ) and Jet Propulsion Laboratories (JPL) were used during the period April 2002 to February 2010. It should be noted that some months are missing for all three data sets. Results of computations provide a mass decrease of −163 ± 20 Gigaton per year (Gt/yr) based on CSR-RL04 data, −161 ± 21 Gt/yr based on GFZ-RL04 data and −84 ± 26 Gt/yr based on JPL RL04.1. The results are derived by the application of a non-isotropic filter whose degree of smoothing corresponds to a Gaussian filter with a radius of 340 km. Striping effects in the GRACE data, C20 effect, and leakage effects are taken into the consideration in the computations. There is some significant spread of the results among different processing centers of GRACE solutions; however, estimates achieved in this study are in agreement with the results obtained from alternative GRACE solutions.

    Meta-comment: The discussion w/the person referencing the Joomaki paper highlights the fundamentally anti-Enlightenment nature of closed-access journals. The content of the article in question is secret, shared only between those who are privileged to read it. Indeed there are legal sanctions against violating this secrecy so as to bring all discussants onto an equal footing.

    Eschewing secrets made the scientific establishment possible but the scientific establishment is now held hostage by tradesmen whose wealth depends on anachronistic, artificially maintained scarcity. How long can this silly tension be preserved?

    Beyond legally required maintenance of ignorance, the other asymmetry here concerns the person who originally cited Joomaki. This person feels comfortable with remaining hidden while routinely leaning on the efforts of others willing to attach real names and real credibility to their work. For my part I’m curious to know whose money this person is spending on journal access; the Joodaki paper is $34.95 for single access while a subscription to the publishing journal itself is ~EUR 1,800/year. Is this an enthusiastic hobbyist, a graduate student slacking off, an employee? Inquiring minds want to know.

  177. Jim Larsen:

    It sounds like Dan H’s primary point is that the the length of record is too short to determine whether the mass loss is going down linearly or exponentially or some other way. Essentially, he’s arguing that the Rule Of Thumb for global temperatures should apply here, and 17 to 30 years are needed to determine a trend. Perhaps someone could address this?

  178. Dan H.:

    I understand why researchers present data as a linear trend over the short term. That does not mean that the correlation is indeed linear, but that there is not enough data to establish a better correlation. The trend could be linear, exponential, sinusoidal, etc. It is an attempt to show was has happened during the measurement period, without making a broad claim as to the actual relationship. Performing linear regression analyses on data with large uncertainties is fraught with error, and can yield values which appear to be much more significant than they actually are. It is a fool’s errand.

    That said, I am not claiming that the rate of ice mass loss is not increasing linearly. The Joodaki data yields a better linear fit than the Forsberg data, which is better represented by a decreasing polymeric or exponential equation.

    As many of the article state, there are several different ice sheet dynamics occurring at different sites and at differnent terminating glaciers. To assign a single characteristic to the entire ice sheet is both difficult and inaccurate. But as Twila Moon (and others) have stated, as more data as been analyzed, the fears of exponential ice mass loss appear to be alleviated (for now).

  179. TimD:

    Congrats to you folks for being patient and methodically and rationally destroying each and every bit of denialist crap thrown out there. I almost feel sorry for the guy, but he actually being civil and I think we owe him that simple courtesy. It is getting old, however. I think a surrender is in order.

    Just got this reference in my email and thought it was most appropriate in terms of what is possible in terms of a worst case scenario. Even if runaway, cascading feedbacks are a low probability, the risk weighted cost means it is economically justifiable to take pretty drastic action immediately. Personally, based on what I know about the paleoclimatology, I don’t think a disaster is that unlikely, but this is an exceedingly complex system that needs several big supercomputers thrown at it to begin to understand the possible outcomes.

  180. SecularAnimist:

    Jim Larsen wrote: “It sounds like Dan H’s primary point is that the length of record is too short to determine whether the mass loss is going down linearly or exponentially or some other way.”

    If that is Dan H’s “primary point” then he’s perfectly capable of saying that — instead of repeatedly and blatantly misrepresenting the sources he cites.

  181. Hank Roberts:

    > Jim Larsen
    > Rule of Thumb

    that’s wrong, there’s no such rule. Statistics looks at any given data set, looks at how variable it is, and tells you how many observations you’ll need to have a good chance of saying correctly that a trend exists in that data.

    Tamino demonstrated how it’s done a few responses back, at 30 May 2012 at 9:44 AM

  182. tamino:

    Re: #177 (Jim Larsen)

    No, Dan H. isn’t applying the “rule of thumb” for temperature data to insist on 17 years.

    He just feels privileged to say whatever he wants to say. Unfortunately for him, he’s in the wrong place for that. Readers here have a tendency to check references and do the math.

  183. dbostrom:

    Further to #178 30 May 2012 at 12:05 PM, here’s some handy insight for the layperson concerning what Twila Moon says:

    Greenland’s glaciers melting faster, say scientists

    Specifically regarding acceleration:

    The researchers analyzed satellite images of the Greenland glaciers taken between 2000 and 2010. These annual images were put through a computer program to detect how quickly the ice is moving. In general, the glacial flow has sped up by 30 percent over the 10 years, Moon said.

    Sounds like a curve, huh? Color me stupid, but what I’ve been taught is that a curve means acceleration, which by extension seems to implicate an exponent in somewhere in the plot.

    Twila Moon has the advantage of not being an anonymous source of comments on a blog so I’m going to hang the credibility flag on her peg.

  184. Dan H.:


    The rest of the article states, “The record showed a complex pattern of behavior. Nearly all of Greenland’s largest glaciers that end on land move at top speeds of 30 to 325 feet a year, and their changes in speed are small because they are already moving slowly. Glaciers that terminate in fjord ice shelves move at 1,000 feet to a mile a year, but didn’t gain speed appreciably during the decade.

    In the east, southeast and northwest areas of Greenland, glaciers that end in the ocean can travel seven miles or more in a year. Their changes in speed varied (some even slowed), but on average the speeds increased by 28 percent in the northwest and 32 percent in the southeast during the decade.

    Only the glaciers in the SE and NW averaged the 30% increase. The rest showed little movement. The curve seems to have gotten quite a bit smaller, according to Twila.

    Her co-author, Ian Howat is quoted as saying, “There’s the caveat that this 10-year time series is too short to really understand long-term behavior,”

  185. dbostrom:

    Did somebody say something? I heard Twila Moon but what was the squeaking sound just after, the thing that sounded a little like a synthetic, ersatz Twila Moon but was plainly wrong?

  186. Unsettled Scientist:

    Dan H.

    The way you quote Ian Howat is dishonest. You use it to contradict the idea that things could be worse, but you don’t even include the entire sentence, you end it with the comma.

    Ian Howat’s entire quote was, “There’s the caveat that this 10-year time series is too short to really understand long-term behavior, so there still may be future events – tipping points – that could cause large increases in glacier speed to continue. Or perhaps some of the big glaciers in the north of Greenland that haven’t yet exhibited any changes may begin to speed up, which would greatly increase the rate of sea level rise.”

    This is what we mean when we say that you misrepresent the scientists and references you use. When we put what your quotes into context, the meaning is opposite of how you used it. Howat’s caveat is that there are conceivable events that could make the ice mass loss far worse than this paper shows, not that we are completely clueless about the ice mass loss or that it isn’t increasing.

    Ugh, I didn’t want to feed into your nonsense again but you continue to cherry pick words and numbers and twist them to make it seem like scientists are saying something they are not. Since I’m here, I’ll point out once again your cognitive dissonance.

    Dan H. “My statement concerning the Forsberg paper is accurate as written”
    Dan H. “A better analysis would be that ice mass loss has held constant at ~230GT / yr as Rene Forsberg concluded.”
    Rene Forsberg “Current changes of Greenland ~ 230 GT/yr … accelerating, but slowly”

    No, your statement concerning the Forsberg paper is not accurate as written! You changed his conclusion and claimed he said what you want to believe, not what was actually in his presentation. Seriously, this mockery of the truth needs to stop. Though it won’t because confusing readers is your intention.

  187. MARodger:

    dbostrom @185
    If I may be so bold as to suggest what was probably intended by the comment @178 “But as Twila Moon (and others) have stated, as more data as been analyzed, the fears of exponential ice mass loss appear to be alleviated (for now).
    The lines preceding this quote (Beginning rather incoherently “As many of the article state,“) do suggest reference to the Moon & Joughin guest post atop this thread and thus to the statement “The observational data now in hand for 2000-2010 show speedup during this period was ~30% for fast-flowing glaciers. While velocities did not double during the decade, a continued speedup might push average velocities over the doubling mark well before 2100, suggesting that the lower number for sea level rise from Greenland dynamics is well within reason.
    The model of speedup being talked of here in terms of double during the decade is that once doubled in speed, the flow-rate would remain constant for the rest of the century. The findings of Moon et al 2012 do not however ‘alleviated fears‘ in this respect because as this BBC report makes plainIn contrast to earlier research that glacier flow would increase before maintaining a fixed velocity, the scientists said they found no indication that the glaciers would stop gaining speed during the rest of this century.
    The ‘alleviated fears‘ perhaps then refer to their conclusion regarding sea level rise. “Considering these results, our data suggest that sea level rise by 2100 from Greenland dynamics is likely to remain below the worst-case laid out by Pfeffer et al.” And Pfeffer et al 2008 set this ‘worst-case’ as a 2 metre sea level rise by 2100, having themselves concluded “increases in excess of 2 meters are physically untenable.

    I do remain confused, however, why it is this site allows the continuation of disfunctional comments as unfit for purpose as is @178.

  188. Mertonian Norm:

    DanH quotes Howitt, “There’s the caveat that this 10-year time series is too short to really understand long-term behavior,” and we get an overblown reaction to that; “dishonest”. Please. I understand we don’t like DanH here, but there’s no need to use that word. Howitt does go on to caution that the long-term behavior could include tipping points, but that he does not go on to say the long-term behavior could also include no tipping points at all is Howitt’s informed choice. That choice takes nothing away from his caveat — there’s not enough data for long-term predictions yet. And this mountain-molehilling over DanH’s choice of “constant” rather than “accelerating slowly” (when the study appears to highlight the “slowly” as much as the “accelerating”) is similarly overblown. I commend DanH for his forbearance in the face of these overreactions, and I refer back to Eric’s reference to “a complex time-dependent glacier response, from which one cannot deduce how the ice sheet will react in the long run to a major climatic warming, say over the next 50 or 100 years.”

    [Response: Not sure why this comment got bore holed but I unboreholed it.–eric]

  189. Radge Havers:

    Unsettled Scientist @186

    “Seriously, this mockery of the truth needs to stop.”

    I suppose the idea of making scientists run around like Keystone cops chasing down false leads could be amusing in some circumstances. But even a running gag gets old. Day after day, month after month, year after year, and it’s just an expression of contempt pure and simple — however politely couched.

    As suggested, perhaps the just using the simple, two word response, “That’s dishonest,” would go a long way toward short circuiting the obsessive pranking. Clarification could be supplied to newbies upon request.

    BTW, anybody got Prince Albert in a can?

  190. dbostrom:

    Despite the Tone Patrol’s cautions about proper comportment in the face of relentless unreliability I’m still not inclined to agree w/inversions of what Twila Moon said.

    1/Twila_Moon =“The curve seems to have gotten quite a bit smaller, according to Twila.”

    Twila_Moon/1 = “In general, the glacial flow has sped up by 30 percent over the 10 years, Moon said.”

    The two expressions are not equal. The former was fabricated– synthesized from dissected parts reconstructed to say something wholly original to this blog comment thread– while the latter statement was directly expressed by Twila Moon.

    After this sort of thing happens often enough it’s not reasonable to expect folks to remain entirely polite.

  191. Dan H.:

    Please read post #187, where MA quotes Twila Moon about the 30% referring to fast-flowing glaciers. You seem to have ignored that feature in the report. That in the 30% only referred to glaciers in the SE and NW, while all others short very little change in speed. Still, a smaller curve than you stated.

  192. Dan H.:

    Ian Howitt could just as accurately said, “There’s the caveat that this 10-year time series is too short to really understand long-term behavior, so there still may be future events that could cause large decreases in glacier speed. Or perhaps some of the big glaciers in the south of Greenland that have exhibited large changes may begin to slow down, which would greatly decrease the rate of sea level rise.” This is pure speculation on his part. There is no reason to expect that only the worst case events could occur.

  193. dbostrom:

    #192 30 May 2012 at 9:54 PM

    Now simply imagining what was said, with quotation marks. Like a verbal functional image of the interior mechanics of the subject brain.


  194. sidd:

    Sasgen et al., Earth and Planetary Science, 2012 is a nice paper, but i wonder if the precipitation term from RACMO2/GR in say Fig 2 could be separated into snowfall and rain ? the latter is far more destructive of ice.

    Nice nevertheless.


  195. Jim Larsen:

    SecularAminist said, “If that is Dan H’s “primary point” then he’s perfectly capable of saying that — instead of repeatedly and blatantly misrepresenting the sources he cites.”

    You’re making a supposition which is counter to previous experience. DanH is unable to give a reasonable question/statement/contribution without immediately falling into the deep end of a sewage pond. Read DanH’s posts, wipe off the goop, and you’ll see that the constant theme is that the data record is too short to determine long-term behaviour. By the way, this sentiment is expressed at least twice in the OP. Dan H quite naturally, and completely beyond his control, expands/calculates/defines this uncertainty so it envelops his comfort zone, where the melt rate will trickle on harmlessly or perhaps even reverse.

    Hank Roberts said, “that’s wrong, there’s no such rule.”

    I limited it to surface temperature trends and we’re talking 90 year horizons, so I think I am correct, though perhaps not as precise as you’d like. I don’t like abusing bandwidth and people’s time, so I often don’t expand “obvious” references. The 17 years was referring to Santer, and 30 years referred to the traditional climate/weather divide. Year to year is weather. 30 years is climate. If that ain’t a rule of thumb, there are no rules of thumb. My opinion I suppose. If you like, substitute whatever numbers and conditions you approve of and change the wording from rules of thumb to _____. It won’t change the core issue – skeptics are correctly bashed for using a decade’s worth of data to determine temperature trends, yet here folks are not just drawing trends, but shaping and extrapolating over the course of the next century — even though one of the primary drivers for the melt rate is weather! Remember the Piomas thread? Arctic sea ice is expected to at least double over the next few decades (though I’d probably bet otherwise). That should counteract a fair amount of acceleration. OTOH, the current temperature plateau has driven us to the bottom half of the probability distribution for temperature, so it is likely that we’ll get a surge in temperature in the near future.

    So, can anybody finish (or modify) the following:

    “Even though 10 years of essentially flat temperatures are woefully inadequate to determine much of anything about long-term trends in surface temperature, 10 years of data are plenty to reasonably estimate the long-term trend for ice sheet melting, along with the trend’s basic shape because _________”.

  196. Hank Roberts:


    it follows the long term trend in atmospheric CO2.

    Don’t just look at the shape of the lines that can be drawn through the various dots on various charts.

    Look at the physical change in the atmosphere causing the change in the ice.

  197. Hank Roberts:

    and, 10 years of that particular data set are enough to do the calculation required as Tamino set out above at 30 May 2012 at 9:44 AM

  198. Hank Roberts:

    ps for Jim Larsen:

    Above you write “Remember the Piomas thread? Arctic sea ice is expected to at least double over the next few decades” (no pointer given).

    Nope, I don’t remember anyone saying that’s expected.
    I looked. I saw that you wrote there that you predicted “a HUGE increase in sea ice volume for September … or … I’m confused” (PIOMAS thread at 28 Apr 2012).

    Was that what you’re referring to?

  199. tamino:

    Re: #195 (Jim Larsen)

    Whether or not you can establish the existence of a nonzero trend from data, doesn’t depend only on the length of time or number of data values.

    What you want to do is separate the signal from the noise. If the signal is bigger, it’s easier to do — so you can do it with less data. If, for instance, global temperature were increasing at a rate of 100 degrees per year (but the noise level remained the same), you wouldn’t need 17 years’ data, you’d know in a single year.

    If the noise is bigger then it’s harder to do so you’ll need more data. If, for instance, the noise level for the year-to-year fluctuations in annual average temperature were +/- 5 deg.C (rather than the actual value of about 0.1 deg.C) the higher noise level would make it hard to detect the trend and you’d need a lot more than 17 years’ data.

    The crucial factor, therefore, is the signal-to-noise ratio. If that’s high enough, you can find a trend with very little data. If it’s low enough, you’ll need a helluva lot to find the trend.

    So to answer your question, it’s because “the signal-to-noise ratio is higher.”

  200. Dan H.:


    because it follows by preconceived notions about what I feel should be happening.

  201. Ray Ladbury:

    Jim Larsen,
    There is nothing magic about the number “30” or the number “17”. They just happen to be the numbers of years required to have a given level of confidence that we can detect a rising signal in a noisy dataset. Signal. Noise. The particular number for another dataset would depend on the relative magnitudes of each.

  202. Hank Roberts:

    Dan H.: what does “significant” mean to you, as you use the word?

    > Dan H. says:
    > 29 May 2012 at 9:04 AM
    > Many papers choose to describe the ice mass loss as linear,
    > not because it was the best fit to the data, but
    > as a general descriptor.
    > None of the data presented show a statistically significant trend.

    Above, you used the word this way, filling in Jim’s blank:
    >> 10 years of data are plenty to reasonably estimate the long-term trend
    >> … because ___
    > 31 May 2012 at 8:36 AM
    > by preconceived notions about what I feel should be happening.

    Is that what “significant” means to you? Personal opinion?

  203. dbostrom:

    Dialing the base period to the absolute minimum, it’s nice and toasty in Greenland just now.

    More to the point of this thread, interesting stat for 2011 from the end of Masters piece: Total ice sheet mass loss in 2011 was 70% larger than the 2003 – 2009 average annual loss rate of -250 gigatons per year.

  204. Unsettled Scientist:

    Hank Roberts said: “because it follows the long term trend in atmospheric CO2.

    Don’t just look at the shape of the lines that can be drawn through the various dots on various charts.
    Look at the physical change in the atmosphere causing the change in the ice.”

    Dan H. said: “because it follows by preconceived notions about what I feel should be happening.”

    That pretty much sums up the difference between how these two people analyze data and choose quotations. It doesn’t matter to Dan H. what Ian Howat actually said, it matters what he “could” have said. That’s precisely my point. He doesn’t care what the scientists are actually saying, he wants to use their credibility to bolster his preconceived notions about what he feels should be happening. So he cherry picks part of Ian Howat’s quote because the rest doesn’t fit with what he wanted. He is trying to steal his credibility to say something completely the opposite of what Howat actually said. To me that is dishonest, and I am not backing down from that. I thought I might overreacted until Dan H. literally put his own words into Howat’s mouth. Words that were 180 degrees from the truth, and he sees nothing wrong with that.

    This has been going on for months. Ian Howat was good enough to quote when Dan H. could support his idea, but once it is shown that Ian Howat was saying the opposite, Dan H. literally just changes the quote to suit his needs. The PDSI is used to support Dan H.’s idea, until we point out that it’s the exact opposite of what he thinks and then he calls its credibility into question.

  205. Dan H.:

    You seem to have a difficult time deciphering the difference between scientific conclusions and personal opinion. I quoted Howat’s scientific conclusion, and you quoted conjecture. Which do you think carries more weight?

    Funny, how you think it is cherry picking, when I quote the conclusion, but leave out the conjecture. There is a difference, in case you did not notice. At no time did I incorrectly state what Howat said.

    Also, I see that sarcasism is completely lost on you.

  206. Charles:

    I have been following this bantering, and cannot help but be reminded of the All in the Family episode where the trade apprentice (young black boy) is eating an apple with a small paring knife, and Archie claims that he was waving a machette in front of him, while Michael claims they was no knife at all. They are both embarassed when Edith pulls out the small knife.

  207. dbostrom:

    Time series:

    Elastic mind attempts to slip one past, 30 May 2012 at 2:58 PM:
    Only the glaciers in the SE and NW averaged the 30% increase. The rest showed little movement. The curve seems to have gotten quite a bit smaller, according to Twila.

    Her co-author, Ian Howat is quoted as saying, “There’s the caveat that this 10-year time series is too short to really understand long-term behavior,”

    CS points out truncation of the above quotation, 30 May 2012 at 4:18 PM:
    Ian Howat’s entire quote was, “There’s the caveat that this 10-year time series is too short to really understand long-term behavior, so there still may be future events – tipping points – that could cause large increases in glacier speed to continue. Or perhaps some of the big glaciers in the north of Greenland that haven’t yet exhibited any changes may begin to speed up, which would greatly increase the rate of sea level rise.”

    Elastic mind disavows complete version of truncated quote, necessitating trashing of formerly convenient source, 30 May 2012 at 9:54 PM:
    “This is pure speculation on Howat’s part. There is no reason to expect that only the worst case events could occur.”

  208. Daniel Bailey:

    Quite frankly, the continued tolerance of Dan H’s behavior by the proprietor’s of this blog now constitute tacit approval of his dissembling. As such, the veracity of this whole blog is now in question.

    Sad, the descent from valued resource to atavism. It didn’t have to be this way.

    [Response: Oh please. People asking that other commenters be banned is tiresome. No-one is obliged to respond to everything other people say (and not feeding the trolls being a very good maxim), and of the responses that have been made there are plenty that demonstrate clearly that Dan H. is a consistent mis-interpreter of the science – and people will draw their own conclusions about his credibility. We have a comment policy which we try to stick to. We moderate for impoliteness, excessive repetition, long-debunked talking points etc.- not whether someone annoys you, and not because they don’t agree with us. – gavin]

  209. Susan Anderson:

    After TimD’s personal, fierce, but quite relevant takedown, I’m returning to spending more time trying to learn than distracting you all from the more interesting parts of what is said.

    While the controversy is continuously annoying, I think perhaps the best thing is for you all to go on discussing real science and ignore the distractions … please? Don’t like it? Don’t feed it.

    But I can’t help wondering why in discussions of time intervals such as 17 and 30, nobody ever mentions that they are in the context of a fairly complete record that goes back to about 1800, or at least 1850, and a fascinating and skilled attempt to reconstruct and quantify the record for a long time before that instrumental record. Nobody takes any particular 17 or 30 years in isolation. The denial/fake skeptic community seizes on these items and takes them out of context, and you all are so used to the context you don’t mention it.

    It is all too easy to forget that while individual events can be treated as noise – distractionalists discredit observable trends by saying, oh, that one was exceeded by a record in [name that year] – it’s foolish to ignore the overall level of excess bunched together in a shortish time period. The recent northeastern heat (shared by Greenland and Scotland) has passed, but that does not erase the excess.

  210. TimD:

    dbostrom @203: Thanks for the Wunderground post. It’s a great summation of the current situation. I think these blogs tend to be addicting. We all think our individual ideas are oh, so important and a site like this is a big megaphone as we stand on our soapboxes. I am trying to give it up since my multiple suggestions to the principals here to correct the obvious errors and horrible tone of the root article has been totally ignored, but can’t help checking in on the back and forth. It is a most disheartening thing to see this site lob a slow ball right over the plate for the denialists at bat, but that is what has happened.

    The back and forth about exponential vs. linear, signal to noise, etc., are amusing, but now getting pretty tedious. As the link by dbostrom shows, the Greenland ice sheet mass loss has been accelerating over the entire record of the decade of GRACE measurements and the latest data shows it continues to accelerate. S/N? The overall signal we see in the GRACE data graph dropping like a big rock, is about 2200 gigatons. The system is clearly very easily resolving the seasonal melt/buildup signal which has an amplitude of less than 200 GT. This seasonal signal is pretty easily removed, since it is highly periodic with a period of precisely one year, but it makes it most obvious that the resolution of the system is well under 50 GT which indicates that the signal to noise ratio is at least 40 to one. There are other sources of noise in the climate system itself, but they are small. There are now about 120 high resolution measurements of a high signal to noise signal. How many points of data do you need to determine the trend of such a data set? A lot less than 120.

    Here’s a fun analogy: Imagine a cartoon of couple of WWII GIs slogging through the mud. All around are signs that say “MINEFIELD!!” or “MINEN”. The winding road ahead has been cleared of mines, but one of the dogfaces says, “Hey, we can save a lot of time by taking a shortcut!” As they slog through the minefield, there is a bright flash under the foot of one of the soldiers. Since this is a cartoon, time can be conveniently stopped and the GIs can take stock of their situation at the instant that the mine is detonated. One asks the other; “Do you think that white hot gas is expanding linearly or exponentially?” The question is kinda moot. They are in a minefield, and in a millisecond or so, the boot of the unlucky soldier will be sailing past his head, with his foot still inside and in a few seconds his body will land in the mud with blood gushing, if his heart is still beating.

    Now, to further clarify the analogy, the current earth’s climate system is like a minefield because, as the Hansen and Sato paper shows ( ), when large ice sheets are present at the poles, the system is dominated by positive feedbacks, and small energy forcings like the orbital variations are hugely amplified. Warming phases in these oscillations are particularly unstable and rapid compared to the cooling phase (it takes longer to plant a mine than it does for it to explode). Once the mine begins to explode, or the Greenland ice sheet begins to collapse, you have very little time to debate the details. It may be too late to avoid the tipping point of ice sheet collapse, but really, we are in ultra slow mo compared to the unlucky soldier and could still be able to turn around and get back to the safe road. That clear road (rapidly cutting GHG emissions) is longer and requires some added effort to walk, but we can’t rationally continue walking in the minefield of hitting an intrinsically unstable climate system with the largest and fastest climate forcing spike in millions of years.

  211. TimD:

    Dear Susan @209: I didn’t mean to be fierce. Stern? Sorry, and didn’t mean to hurt your feelings. But we are, in reality, on the same page and both wishing to discuss the science, so we should be friends. Peace.

  212. Susan Anderson:

    TimD, you were right, that was the important part, and it’s likely others were having the same problem but were too polite to say so. The truth can be painful but it is also liberating. I have an odd relationship to this site – some know about my Dad (PW; please leave it alone, thanks) and I taught drawing at MIT to a lot of scientists – aging faculty brat? I dropped out of MIT absorbing differential equations which leaves me hanging, but my tire-kicking instincts are pretty good and weather is always fascinating:
    (front page particularly vivid today)

    Once I got out of the way, IMHO it turned out you are a valuable addition to the conversation.

    Masters at Wunderground is terrific. So is Neven and a good few others who hang around here.

  213. Susan Anderson:

    oh sigh, *without* absorbing diffyQ’s

  214. tamino:

    Re: that guy.

    Gavin, it’s your blog and you get to decide. There is undeniable merit in not moderating just because people are annoying, or because they disagree with you.

    But I urge you to consider the purpose of this blog. It’s to spread information and combat misinformation. Dan H. has been nothing but a source of misinformation. He hasn’t just disagreed — he has actively distorted the truth. He claims Forsberg says one thing when the opposite was stated, he pronounces as fact the lack of significant trend when it’s easily shown to be present, he quotes selectively even though context contradicts him, then when the full context is posted he disparages the very source he misused. These aren’t mistakes — they are a deliberate pattern.

    You should also consider that, to some small degree, this is our blog too. We work hard — yes, we put real time and effort into it — to further the purpose. We spread information, we combat misinformation. It’s a sacrifice of our time and energy, but we believe in the cause and its importance so we’re happy to help. God knows there’s enough misinformation to combat. Adding to the load is a step backward. It’s a bitter pill to think that his efforts are actually working — both by wasting our time and by sewing doubt in the minds of those (especially the new) visitors who don’t ingest all the details or see all the refutations.

    The stated purpose of the Bore Hole is for comments “that would otherwise disrupt sensible conversations.” So I ask you in all honesty: if Dan H.’s comments don’t fit that description, what does?

    Whatever you decide, we’ll remain loyal to this, the best climate science blog on the internet. And we’ll continue to do our best to spread information and combat misinformation. The continued presence of Dan H. makes it harder.

    [Response: With all due respect I think you are over-reacting here. The rebuttals to Dan H.’s comments have been valuable – people learned what is actually happening in Greenland, what the sign of PDSI represents, the difference between TCR and ECS etc. All issues that have come up elsewhere and where they haven’t necessarily been competently rebutted. Too many of the comments in response to Dan H. have been related to his motives, character and suitability as a commenter – and frankly that is far more disruptive of conversation than either simply ignoring him, or quoting his purported sources to show that they actually contradict the position he was putting forward. Some of his stuff has been bore-holed, some was moderated for cause – as have intemperate or ad hom responses to his posts. But continuous discussions of blog comment policy are tedious, and I’m loathe to continue this one. This stuff is requires quick judgement calls, and I haven’t got the time or energy to justify every single one that is made on a daily basis. Thus there are basically three options – either we drop comments altogether, let them all though, or we continue to moderate in the mostly the same fashion we have been doing – but for that to be sustainable, we can’t spend too much time on it or discussing it. Note that this is a function of traffic as well – if there was less, it might be easier, and if there was much more than it would be more difficult – but these are judgements that we need to make. Please just let this drop and let us get on with it as best we can. There are far more interesting conversations to be had. – gavin]

  215. dbostrom:

    Somebody (Tim?) mentioned albedo here. Just ran across another of mindblowing statistic of the size only available via planetary-scale tampering:

    Darkening of the [Greenland] ice sheet in the 12 summers between 2000 and 2011 permitted the ice sheet to absorb an extra 172 quintillion joules of energy, nearly 2 times the annual energy consumption of the United States (about 94 quintillion joules in 2009).

    Via a post at Meltfactor where there’s more fascinating stuff on albedo of Greenland.

  216. MARodger:

    dbostrom @215
    The quote you present is fascinating stuff but also ambiguity in carnate.
    This extra energy absorbed equals the latent heat required to melt 500 Gt of ice and it’s safe to assume this is an annual figure but is it the average summer darkening or the increase in summer darkening? The paper doesn’t make this clear. I’m inclined towards the former as 500 Gt of extra annual melt seems rather too high, assuming all (or most of) the heat goes that way. On the other hand 500 Gt of annual summer melt is approaching the level of Greenland’s annual rain/snowfall which the laws of physiscs insist must be melted every year for the sole purpose of annoying Dan H.

  217. Lawrence Coleman:

    What I gleaned from all your comments is that it is virtually impossible to predict future glacial retreat based upon past data. It is a very dynamic system and tipping points are/will play a crucial part in future predictions. Decrease of speed of the North atlantic overtuning circulation due to increased fresh water release and accelerating rates of methane release from the many Giga tonnes of thawing methane hydrides in the arctic sea and tundra regions and of course our old friend ice albedo and black soot particulates building up on the once pristine arctic to name the most obvious known to date make it impossible to accurately quantify any change in glacial melt and thus sea level rise. However put it this way the number positive feedback mechanisms currently at work are quite probably unprecedented in paleoclimatology.

  218. Lawrence Coleman:

    Tamino: You have all heard the saying that your most valuable teacher can be your worst adversary. Boy! Politics wouldn’t get far if both sides agreed on all the issues the other was putting forward. Treat Dan H as your teacher and wield your keyboard with all the skill of a master sword fighter as you skilfully cut through his ignorance and misinformation with the ultimate weapon of scientific and irrefutable logic.

  219. Dan H.:


    I endorse your comment #209. I know we have not seen eye-to-eye on many aspects, but I agree with you here. The 17-yr period was particular annoying, as people took Santer’s analysis of the satellite data, and applied it to just about everything else. This was not limited to your denial/fake skeptic community (whatever that is), but was used to show that the 10/12 year temperature hiatus was insignificant.
    In those areas, where we have much more data, it should be used – as you put forth. Where we only have a decades worth of data (i.e. GRACE), that is all we can work with. We can compare it to other methods, such as was the original intent of this thread, and we have proxy measurements dated hundreds and thousands of years prior. Short-term trends are useful, in light of a certifiable forcing. However, we must be careful in extrapolating the short term into the long term, as errors can propagate.

  220. Dan H.:

    I remember that episode, and it is a good analogy. Taking a step back, I recognize my part in the whole fiasco, and hope others do also. That said, the Meathead would like to offer his apology to the Archie Bunkers here.

  221. Susan Anderson:

    re @209, Dan H. misleads again. The 17 and 30 year periods have more meaning in the context of the record; the way he puts it unconstructs my intention. Ben Santer, a top best scientist, has vast experience with phony skepticism and its evil effects on our future if we choose inaction. I believe he does not dismiss the effort to extend the record by whatever means our real world makes available, sediments, ice cores, tree rings, the lot, with more than adequate clarification of the uncertainties involved. There are a whole lot more lawyers than scientists in government, and they skilled at flooding people with real work to do with phony well-sounding demands. Exploiting the meaning of uncertainty and the complexities of scientific efforts to reveal the past in our physical world beyond what is available using instrumental records is a favorite trick to obfuscate. Saying we can’t expand knowledge is not helpful. In addition, the instrumental record would never have been created with this know-nothing argument, which is political rather than scientific.

    When somebody consistently returns to misstate the facts, they are not doing anybody any favors. Visitors inclined to believe these distortions will cite RealClimate as the source of the disinformation. Not all the sources he misconstrues are here to undo the damage, which appears to be far from innocent.

    I get this crowdsourcing stuff from Andy Revkin, and it does not take into account the amount of work it takes to track down the sources and correct the misinformation, as well as the persistent trickle of fuel provided to those looking to discredit scientific findings rather than tease out the truth. In addition, it lays the person doing the work open to attack.

    And of course this has once again detracked the discussion of Greenland glaciers.

  222. Unsettled Scientist:

    > Where we only have a decades worth of data (i.e. GRACE), that is all we can work with.

    “We can’t look at one glacier for 100 years, but we can look at 200 glaciers for 10 years and get some idea of what they’re doing.” – Ian Joughin

    > We can compare it to other methods

    …such as other satellite data such as MODIS or QuickSCAT. Luckily GRACE isn’t our only bird in the sky.

    It is important to look at the totality of evidence, and not just one source of data. We shouldn’t place too much emphasis on any newly published paper. It is the coherence between many avenues of investigation that make AGW clear. Similarly with Greenland’s accelerating ice mass loss, we look at the totality of evidence. Sadly, the rate of ice mass loss is still increasing and even GRACE doesn’t have a single negative year (i.e. one in which rate of ice mass loss didn’t speed up).

    These new papers “add rich detail to our understanding of the ice sheets; they do not change estimates of the magnitude of future sea level rise. The bottom line is that Greenland’s glaciers are still speeding up.” -OP

  223. Dan H.:

    You may need to check the reports a little closer on the GRACE data. The Forsberg data showed a slowdown from 2005 to 2006, and from 2008 to 2009. The Joodaki paper showed the two previous slowdowns, with an additional decrease from 2003 to 2004. Combining these results with the Bergman paper and the Moon and Joughlin paper, yields ample evidence that the rate of increase is decreasing.

    [Response: Science is not a salad bar where you can pick a years worth of data from here or there, spice it up with a creamy dressing and present it as if it was something substantial. It has been demonstrated above that you are simply wishing the acceleration away. Enough with the made up stuff please. – gavin]

  224. dbostrom:

    MARodger says: 1 Jun 2012 at 3:53 AM

    Read the post I linked; obviously you did not, or you’d know that the additional energy absorption happened over the span of ten years. Indeed, it does not seem you even read my comment, where that is fairly clear.

    The distribution of albedo loss is explained in detail and you can learn about it if you suppress your “no” reflex for just a few short minutes.

  225. dbostrom:

    Susan Anderson Jun 2012 at 10:44 AM

    A concise, accurate synopsis. I’d add that the the misinformation is artfully crafted; what appears to be quotation is rearrangement, findings are modified and even reversed while brazenly accompanied by citations and there is no accompanying invective or sprinkling of insulting adjectives to trigger BS detectors.

    Quality stuff, in its own way. As to stopping it Gavin’s explained why that can’t work, so treat the problem as a phenomenon for study and this venue as a lab for developing clinical solutions, as if the problem were malaria or some other subtle parasitic infection.

  226. Dan H.:

    Your response appears to be precisely what I have trying to tell other people here. On several occasions, someone has simply pointed to start and end points, and claimed an x rate of acceleration. Moon and Joughlin have pointed it out to start this thread (a point you have constantly refuted). Others have tried to find significance, where none exists. In most of the references cited here (Hansen excepted), acceleration of ice mass loss was greatest in the earlier years, diminshing or disappearing in the following years. How you can continue to content that the ice mass loss is accelerating exponentionally in the light of all the evidence presented here is beyond me? The data which refutes your position, is not simply “made up.” It exists in the scientific literature referenced here (and elsewhere).

    Enjoy your salad.

    [Response: You are a funny guy. But a clearer case of projection is hard to find. – gavin]

  227. sidd:

    I think Dr. Bindschadler pointed out a while ago that the marine terminating glaciers of Greenland might retreat to escape warming ocean, but that there was no such escape for W. Antarctica. (I note that some large sections of E. Antarctica are also bedded submarine, and most of these Antarctic areas are exhibiting increased ice velocities and mass loss.)

    Now the rate of albedo reduction on Greenland is another positive ablation factor that might make Dr. Bindschadler’s point irrelevant. Greenland can melt in place and drain away, and has as complex hydrology in and below the icesheet as is found in Antarctica. Ice discharge is not the only road to high water.

    And I repeat my plaintive request for a breakup of precip over Greenland into snow and rain.


  228. dbostrom:

    How you can continue to content that the ice mass loss is accelerating exponentionally in the light of all the evidence presented here is beyond me?

    Yeah, don’t believe your lying eyes…

  229. TimD:

    dbostrom@228; yeah, a picture is worth… a lot. Nice use of html. Slightly more recent data shows that the acceleration continues throughout ’11. I do think we need to be clear as to why the GRACE data set is so special. The thing that we are interested in in this discussion is the overall change in the mass of the Greenland ice sheet. Since gravity is directly related to mass and distance from that mass, if you can measure gravity really, really accurately, you can see pretty small changes in mass. The GRACE mission is very important because it represents a quantum leap in accuracy and resolution, since it makes very, very precise measurements very quickly, all over the world. When I was an undergraduate and first used the then state-of-the-art Worden gravity meter, I found that I could accurately measure the difference in the earth’s gravity from the floor to a table top, due to the change in distance from the center of the earth. The GRACE system is hundreds of times more accurate than that, and it can essentially measure the change in gravity continuously as it orbits the earth in a way that guarantees complete coverage of the earth every few days. This new data has revolutionized geodynamics because of the truly exquisite precision and resolution of the information. Check out the two gravity maps of the earth in this file:
    There is a large negative gravity anomaly just south of India that was thought to be due to the earth’s upper mantle flowing north past the thick Indian continent. With GRACE data you can easily see the flow lines of the mantle moving around India like the bow of a ship. The force of this mantle flow is what is continuing to push India into China, constantly renewing the Himalayan Range.

    Measuring changes in the motion of individual ice streams is hard and only measures surface features. The efforts of glaciologists as in the root article are clearly important, but when it comes to the question at hand (Greenland ice mass loss) the GRACE data is much, much better. Given that the graph in dbostrom’s post averages all of the contributions of moving and calving ice over the whole of the region, we are seeing the integrated effect of both warming water and air from top to bottom of the entire sheet. It is a very scary picture, but thank NASA, we have it. It shows conclusively that the statement made in the root article here that “the results put speculation of monotonic or exponential increases in Greenland’s ice discharge to rest” is absolutely false and a disservice to climate science and should be prominently disavowed by the author. I am talking to you, Eric.

  230. Susan Anderson:

    Thank NASA, full of GRACE. Would we were not losing our satellite edge:

    Heidi Cullen seems to have missed your point about GRACE and Greenland?

    Understanding maths is the most important higher power needed for our civilization’s future.

  231. Susan Anderson:

    aargh, *an* important, not *the most* important …

  232. Ray Ladbury:

    The problem with designations like “exponential increase” is exactly the same as that of periodicity–it is rare that you have sufficient data to really definitively call the increase exponential. If you don’t have several doubling periods, all you can really say with confidence is that the increase is “nonlinear”–unless you have physics that supports an exponential increase. Dbostrom’s graph certainly shows nonlinearity. Do we have physics favoring exponentiality.

  233. MARodger:

    dbostrom @224
    I would not do you the discourtesy of commenting in such a manner without having first read the linked papers. You see no ambiguity there. Fine. But I see ambiguity aplenty & have sent an enquiry to the author asking for clarification.

    Re comment @ 228, 229 & 232.
    This is well trampled ground being re-visited. Rather than look for a monotonic, exponential or whatever form of increase within the curvature of a graphed line, a plot of the rate of change may be more easily handled. Hansen & Sato 2010 have one figure 8c in this version of the paper. & I have grafted on the Box et al data bringing it up to 2011 See here (usually requiring a second click to ‘download your attachment.’.

  234. dbostrom:

    MARodger says: 2 Jun 2012 at 10:13 AM
    I see ambiguity

    You do?

    From the post:

    “Satellite observations from the NASA Moderate-Resolution Imaging Spectroradiometer (MODIS) indicate a significant Greenland ice sheet albedo decline (-5.6±0.7%) in the June-August period over the 12 melt seasons spanning 2000-2011. According to linear regression, the ablation area albedo declined from 71.5% in 2000 to 63.2% in 2011 (time correlation = -0.805, 1-p=0.999). The change (-8.3%) is more than two times the absolute albedo RMS error (3.1%). Over the accumulation area, the highly linear (time correlation = -0.927, 1-p>0.999) decline from 81.7% to 76.6% over the same period also exceeds the absolute albedo RMS error.

    Because of extreme 2010 melt and little snow accumulation during the melt season (Tedesco at al., 2011) and afterward, the ice sheet albedo remained more than two standard deviations below the 2000-2011 average in October. Like year 2010, 2011 albedos are more than 1 standard deviation below the 2000-2011 average.

    Darkening of the ice sheet in the 12 summers between 2000 and 2011 permitted the ice sheet to absorb an extra 172 quintillion joules of energy, nearly 2 times the annual energy consumption of the United States (about 94 quintillion joules in 2009).

    This decline is not only over the lowest elevations, but occurs high on the ice sheet where melting is limited.

    A significant albedo decline of 4.6±0.6% in the 2000-2011 period from a year 2000 value of 83.0% is observed for the accumulation area, where warming surface temperatures are enhancing snow grain metamorphosis.”

    Cut and dried. Personally I wouldn’t waste the author’s time just for the purpose of dramaturgy here but you’ll notice at the meltfactor site you can simply ask the author your questions in the comments section of the post.

    As to the graph at 228, sure, it’s an ephemeral curve (really must be because there’s not an infinite supply of ice) but as that curve is what’s actually visible in data, wishing the curve away without fresh data to support curve-free dreams requires speculation more fanciful than the facts we have.

  235. dbostrom:

    Susan Anderson says: 2 Jun 2012 at 8:07 AM
    Thank NASA, full of GRACE.

    Nice turn of phrase!

    Sadly GRACE is an experimental mission, is not classed as an Earth observation satellite. As is so often the case the mission is still functioning at over twice its nominal lifespan. As GRACE is an experiment it does not seem as though replacement will be automatic.

    This is akin to considering the oil pressure warning lamp on one’s dashboard to be “an experiment” wherein if the lamp or circuit fails it is not replaced because “the experiment” is over.

    I don’t understand how it is that missions such as OCO and GRACE are not considered vital instrumentation as opposed to “experiments.” OCO spacecraft were twice attached to salvaged ICBM boosters and subsequently lost even though it’s arguable that these spacecraft are equally as life-safety critical as a “human rated” booster intended for transport of human cargo.

    If I were a researcher working with GRACE data I’d consider no investigation project complete until I’d peppered legislators with copies of resulting publications. Similarly the rest of us armchair researchers should make a point of pestering our lawmakers about this. Seeing this data truncated when some part of one of the GRACE twins breaks will be a bitter pill to swallow.

  236. Hank Roberts:

    “This is the first paper to provide data on *all* the outlet glaciers that drain the Greenland ice sheet into the sea.

    The bottom line is that Greenland’s glaciers are still speeding up.”

    — from the original post

  237. TimD:

    Ray Ladbury@231; “Do we have physics favoring exponentiality?” Yeah, but what we don’t have is good specificity of the mix of positive feedbacks that would allow better predictive models. It is the clear presence in the system of so many potential positive feedbacks in a melting ice system that ensures that the ice loss is accelerating. That the best curve fit equation that effectively de-trends the data has an exponent is the test that the system has an exponential, or accelerating, component. That is clearly the case with the GRACE Greenland data. The obvious positive feedbacks in this system are:
    1) The loss of sea ice, where we observe a large decrease in albedo that leads to increased sea surface temperature that increases melting.
    2) Melt water lakes at low elevations that reduces albedo, again accelerating melting and lubricating ice streams at their base when the water breaks through to the base of the sheet.
    3) Thawing of tundra releasing GHGs that increase temperatures that increases thawing
    4) Reduced ice albedo due to soot that increases melting period that in turn reduces the albedo by eliminating high albedo snow cover for longer periods
    5) Increased basal melting due to infiltration by warmer sea water that increases the capacity of basal ice channels, that increases infiltration rates
    A less obvious, but potentially very important feedback, is non-linear behavior of ice as a fluid. As the body of ice warms due to infiltration of melt and warm sea water, the viscosity of the ice drops, flow rates increase leading to increases of viscous heating, potentially leading to a thermal runaway. There are others. The empirical evidence that there are positive feedbacks in ice sheet systems is the paleoclimate data that shows how small orbital variations in forcing are greatly amplified when ice sheets form in the Antarctic, then the Arctic in the late Tertiary. You can see this in the Sato, Hansen paper previously cited. You can also note that warming phases occur faster than cooling.

    It is the interaction of these positive feedbacks that will allow a reasonable model that could predict how long the accelerating trend will continue. It is obvious that the observed acceleration cannot continue through the end of the century, because we would run out of ice before then.

  238. Ray Ladbury:

    Tim D.,
    Yes, those are positive feedbacks. No, they do not necessarily indicate exponential decay. Specifically, is there some reason to think dx~axdt? That is what is required for a truly exponential system. Nonlinearity does not equal exponentiality.

  239. Hank Roberts:

    > the end of the century, … run out of ice

    That would be rather fast.

    It would be interesting to see a chart of the rates published over time and how those have changed. Kind of a meta-study.

  240. TimD:

    Ray, I think you are putting too fine a point on it. If there are positive feedbacks dominating in a dynamic system, that system will tend to accelerate and its average behavior will take the form of an accelerating function that can be fit with an exponential curve, which is clearly the case with the GRACE Greenland data. The important point is that when we see this sort of behavior in a system dominated by positive feedbacks, we need to quickly determine what positive feedbacks are most important and create models that accurately duplicate past behavior based on that understanding and then may allow us to compute the range of possible future states. At present, we don’t really know whether the current behavior of Greenland’s ice sheet is a minor decadal bump or a major tipping point that will lead to rapid coastal flooding and constitute the greatest disaster in human history. Inquiring minds want to know!

  241. TimD:

    Hank @239: “That would be rather fast.”

    Right. That is the nature of exponential growth. It quickly gets ridiculous. If the cumulative loss continues to double every 7 years or so, there are about 12 doubling periods to the end of the century. Starting with 1400 GT lost in the first 7 year period of Grace data, you would be, at that rate of acceleration, get rid of some 6.16 million km^3 by the end of the century, more than the total volume, estimated at 2.85 million km^3. That’s why I said that we can’t go through too many 7 year doubling periods before negative feedbacks inevitably kick in to change the trend. But that also means that the earth’s climate will be very much different than the average Holocene conditions and we will all, effectively, be living on a different planet.

  242. David B. Benson:

    TimD @240 — Ray Ladbury has the right opf it. A so-cfalled positive feedback does not necessarily imply exponential growth. Read any text on linear system analysis.

  243. Ray Ladbury:

    Tim D., The defining character of an exponential is that the change in the quantity is proportional to the quantity at a given time.

    Exponential=/=rapidly increasing.

  244. TimD:

    Ray, Exponential growth doesn’t have to be fast, and can be negative. Here is a good exponential curve fit for the GRACE data from dbostrom’s graph @228.
    M(T)= M(T-1) – (135 * (1.105 ^(T – T(0)))) Where M(2002)=800 and T(0)=2002

    It has a doubling time of about 7 years and fits the data through 2011. Plug it in to a spreadsheet and see how long the ice loss stays exponential. The value exceeds the total Greenland ice mass before 2080.

  245. Ray Ladbury:

    Tim D., I have a passing familiarity with the exponential function. I also know that for short time series (less than 2-3 doubling times) it is very hard to distinguish exponential growth from, say, a power law–or, if the time series is short enough a linear trend + a sinusoidal variation.

    Curve-fitting is fun. By itself, it isn’t science.

  246. Hank Roberts:

    Tim, nobody’s saying the ice just decided it’s going to change on its own.
    It’s changing as the result of forcings; the question is how sensitive is the ice, how quickly does it show the effects and what changes happen. Look at the recent work with old photographs — the ice — in that area, at this time — may be a more sensitive indicator rather than the last thing to start changing when the climate warms. It’s a local effect of multiple causes.

    Nobody’s claiming it’s a specific mathematical curve.

  247. TimD:

    Ray, How very heavy of you. Please feel free to fit any curve you wish. There is a reason to fit an exponential curve to the GRACE data that seemed compelling to perhaps the most accomplished climate scientist in the world, one J. Hansen. That is because systems dominated by positive feedbacks, when strongly forced (which is the current situation in the arctic) frequently experience periods of exponential growth, typically when that system is beginning to approach a tipping point and basically blow itself apart. Please feel free to ponder the science behind a sinusoidal curve fit, but I don’t think I need your help.

  248. dbostrom:

    Dumb question from a relative ignoramus: Does exponential growth axiomatically imply growth without limit? Is it considered cricket that growth may be considered exponential for some limited period of time?

    Looking (advisedly) at Wikipedia, I see these examples:

    “The number of microorganisms in a culture both will increase exponentially until an essential nutrient is exhausted. “


    “Heat transfer experiments yield results whose best fit line are exponential decay curves.”

    The curve in the graph above is bent, not linear, so surely describing the curve must involve an exponent, implying that for the period of time observed loss has grown exponentially?

    My naive interpretation is that “exponential” need not lead to no ice; right now loss of ice is swiftest at the margins of Greenland’s ice sheet where due to geometry the area encompassing loss is greatest. It’s not surprising to see a curve in the affair.

    Looking at the physics of situation (albedo loss at margins, attack by warmer water also at margins) linear loss early in the game seems the least likely scenario. Presumably we’ll eventually see the curve in the graph above reverse itself because the conditions of loss right now are limited in their scope.

    Again, opinions of a naif. Perhaps the discussion here of “exponential growth” is on a much more formal level.

  249. Hank Roberts:

    Would you cite exactly what Hansen says and where?
    See also: (page down a few times to get to the content)

  250. Hank Roberts:

    PS, Tim, are you referring to this?
    Paleoclimate Implications for Human-Made Climate Change
    James E. Hansen, Makiko Sato
    (full text pdf link at the web page)

    “… These data records suggest that the rate of mass loss is increasing, indeed nearly doubling over the period of record, but the record is too short to provide a meaningful evaluation of a doubling time. Also there is substantial variation among alternative analyses of the gravity field data (Sorensen and Forsberg, 2010), although all analyses have the rate of mass loss increasing over the period of record.
    We conclude that available data for the ice sheet mass change are consistent with our expectation of a non-linear response, but the data record is too short and uncertain to allow quantitative assessment. A 10-year doubling time, or even shorter, is consistent with the gravity field data, but because of the brevity of the record even a linear mass loss cannot be ruled out. Assessments will rapidly become more meaningful in the future, if high-precision gravity measurements are continued.”

  251. TimD:

    Hank @246, I guess I am saying that seeing signs of exponential growth is important in this context, basically because it is saying that something very interesting is happening to the system experiencing that type of growth. The growth of the Chinese GDP, which has a growth rate similar to GRACE data of Greenland’s ice loss, of about 10% per year that has been maintained for some 30+ years, is not a function of any intrinsically exponential activity. Chinese economic growth is, in fact, due to trillions of individual economic transactions every year, that individually, don’t have any real relationship to “exponentiality”.'s_Economic_Growth_and_the_Environment_Fa_08
    But it is very clear that the overall behavior of that system is very interesting and something we need to understand, since they are totally kicking our ass in the economic sphere. That is, in the same way, why I have said several times, that the appearance of exponential growth is an alarm bell that says something interesting is happening to the growing mass losses in the Greenland ice sheet system that needs to be studied with urgency and understood. Hansen fit an exponential curve to the data when it was only available through 2008. That curve still fits through 2011. When someone in a prominent public position claims that the exponential growth is not exponential and that the issue of rapid exponential growth “has been put to rest” that person is acting irresponsibly by arguing against the urgency to rapidly come to understand the system. I’m talking to you Eric.

  252. Hank Roberts:

    Tim, if you’re talking about that Hansen paper — note the discussion there around Fig. 7.

    “Alley (2010) reviewed projections of sea level rise by 2100, showing several clustered around 1 m and one outlier at 5 m, all of these approximated as linear in his graph. The 5 m estimate is what Hansen (2007) suggested was possible under IPCC’s BAU climate forcing. Such a graph is comforting – not only does the 5-meter sea level rise disagree with all other projections, but its half-meter sea level rise this decade is clearly preposterous.
    However, the fundamental issue is linearity versus non-linearity….”

    Point of Fig. 7 is that the “Exponential (10-Year Doubling)” is much _slower_ to rise — sea level barely changes up through 2050 or so — then takes off.

    And Fig. 8.: Greenland (a) and Antarctic (b) mass change deduced from gravitational field measurements by Velicogna (2009) and best-fits with 5-year and 10-year mass loss doubling times.

    These are hypotheticals — spooky for sure. He’s saying this could happen, we can’t yet tell if it’s happening, and pouring CO2 into the atmosphere as we are means there’s no reason it wouldn’t be happening.

    If we come across some idiot throwing fuel onto a fire, we don’t argue about the rate of change and whether the fuel’s going to make the problem significantly worse.

  253. David B. Benson:

    dbostrom @248 — For micro-organism growth, fit an S-shaped curve such as the logistic function. That appears exponential, approximately, up to the inflection point. I opine that the same is, approximately, the case for Greenland ice.

  254. dbostrom:

    Thank you, David. S-shaped is indeed what I was picturing.

    Swerving into repeating myself, I sure hope we’ve slotted in a replacement for the GRACE twins when the one of the pair inevitably shuffles off this mortal coil. They’ve proven wildly successfully for all sorts of applications, far beyond expectations. What a bummer if the austerity fad means we blind ourselves.

  255. Ray Ladbury:

    Tim D., I never fit a single curve to any dataset that I am serious about analyzing. Multiple fits give you a lot more information–even if none of them is the “correct” fit.

    Given the current data, it is irresponsible to say that the increase IS exponential for the same reason that it is proper to be concerned that it COULD BE exponential–namely because of the implications of such growth. The fact remains though, that I know of no period in paleoclimate where we saw such catastrophic collapse. I’m a wee bit more concerned about the possibility of it here than I am about, say, the simultaneous release of all the Arctic’s methane as mooted by our last catastrophist. The reason is that the rate of warming could play a much bigger role for the ice sheets. Still, I think sustained catastrophic collapse of the Greenland ice sheet by the end of this century is unlikely.

  256. Ray Ladbury:

    Indeed to amplify on what David said above, I can’t think of a single instance of sustained exponential growth in nature–be it if bacteria, cancer cells, nuclear fission…

    Exponential growth always leads to catastrophe–in the sense that the physics of the system changes dramatically. One interesting system was the inadvertent creation of a pulsed neutron generator by Japanese nuclear workers.

    Running behind schedule mixing solutions of enriched uranium, they doubled the amount in the mixer, causing the system to go critical (exponentially at first). The heat of the fissions heated the solution, causing it to expand, decreasing the rate of fission, cooling it… This bit of ingenious stupidity caused the untimely death of the two workers, but I don’t think it ever got its well deserved Darwin award.

  257. flxible:

    When someone in a prominent public position claims that the exponential growth is not exponential and that the issue of rapid exponential growth “has been put to rest” that person is …
    …. Talking about something other than what TimD has hijacked this thread over. I would expect that I’m not the only one here to take exception to TimD’s repeated “calling out” of our host, using a misinterpretation of the introduction to the post [by invited guests], which concerns Greenland’s ice discharge, NOT the mass (loss). In addition, the entire paragraph from that introduction makes it entirely clear what is under discussin in the post, regardless of TimD’s pet fixation, particularly the entire phrase, which includes “speculation of monotonic or exponential increases …” and “… one cannot deduce how the ice sheet will react in the long run to a major climatic warming”, although TimD appears to think he can make that deduction. Maybe TimD could submit his analysis to Science as a response to the Moon et al paper so we can put the exponential digression here to rest.

  258. Hank Roberts:

    “has been put to rest” is a quote from where?

    Look at Hansen’s Fig. 7 – “exponential” growth there is pictured — it’s _slower_ than linear growth up through around 2050, and until 2100 not as much melted as with linear growth.

    It sounds like you think “exponential” has to mean “rapid” and that’s not necessarily so.

  259. TimD:

    Hank, I don’t see much that we disagree about. I like your parable and would add that if we saw a man beginning to throw fuel on a small fire consuming a wooden house, we would think an onlooker completely crazy or an accomplice to the arson if he were to say “Oh, the fire is not so fast.”

  260. flxible:

    Hank @258 – See comment by TimD @22 May 2012 @ 12:51 AM with Erics response, and his further misinterpretation @ #78. Maybe TimD should investigate Erics “day job”.

  261. David B. Benson:

    Ray Ladbury @255 — 8.2 kya event. From memory only, the largest of the various Laurentide proglacial lakes suddenly drained through the Lauerntide ice sheet and out to sea via Hudson’s Bay. It just occured to me it would be of some paleoclimatological interest to have an estimate of how much SLR was due to that single event (as it was over in a matter of at most a few weeks). Unfortunately I haven’t the time to attempt to find an estimate these days, being intensely busy with something else.

  262. TimD:

    flxible@257: The exact quote is “The bottom line is that Greenland’s glaciers are still speeding up. But the results put speculation of monotonic or exponential increases in Greenland’s ice discharge to rest”. My paraphrase is reasonable although I will admit I should have included a “…”. Given that both Eric and the guest authors discuss melt and the relevance of Greenland ice loss in general on sea level rise, it is important to reconcile the very significant discrepancy between their study, which shows a 30% increase in ice stream velocity/discharge while the GRACE data, which is intrinsically more relevant, complete and accurate, shows about a 120% increase in the rate over the same period. By not discussing that discrepancy Eric has no business at all in saying that anything regarding ice mass loss, including discharge, has been “put… to rest”. That sort of language is a sweet slow ball for the denialists, and that is my primary beef with Eric. I asked him nicely to discuss that discrepancy and he has consistently refused to get involved. As far as I am concerned, if he is not prepared to take the time to discuss and clarify his positions relevant to inflammatory statements in his work product on this site, he should delegate that responsibility. This is a prominent public forum in the global warming debate and it should serve to inform the public at large about important aspects of climate studies. His article grievously misses the most important aspect of Greenland ice loss and his sloppy language damages the cause that this forum claims to serve. And you are flat out lying when you say that I claim or “appear” to claim to know how the mass loss will proceed into the future. I have, in fact, consistently stated that it is, instead, a call to redouble our efforts to understand the underlying mechanisms of that observed, very disturbing loss record. Tell the truth!

  263. Hank Roberts:

    > the most important aspect of Greenland ice loss

    Measures vary, and we don’t know how it’s going to proceed. Glaciers vary and their responses to the varying weather over the past few decades is much more sensitive than had been thought. Nobody’s missed this.

    Read Joe Romm on how climate discussions get taken over by the alarmists and denialists, who between them claim the entire conversation and stifle scientists who won’t take either side and shout down those trying to learn rather than proclaim they know the truth.

    > pulsed neutron generator

    The Japanese event wasn’t the first — a similar criticality happened June 16, 1958, at the Oak Ridge Y-12 Plant.

  264. Brian Dodge:

    “…it would be of some paleoclimatological interest to have an estimate of how much SLR was due to that single event…”

    “We present a high-resolution early Holocene sea-level record from the Mississippi Delta that documents a distinct sea-level jump, marked by a characteristic stratigraphic succession that is corroborated by paleoenvironmental reconstruction. The 0.20–0.56 m local sea-level jump occurred within the 8.18 to 8.31 ka (2σ) time window and is attributed to the final drainage of proglacial Lake Agassiz– Ojibway (LAO). Since the timing of the sea-level jump is indistinguishable from the onset of the 8.2 ka climate event, this study provides compelling evidence for a nearly immediate ocean–atmosphere response to the freshwater perturbation. In addition, the total inferred eustatic sea-level rise at 8.2 ka (after correction for gravitational effects) amounts to 0.8 to 2.2 m, considerably higher than previous estimates for the final stage of LAO drainage.” Synchronizing a sea-level jump, final Lake Agassiz drainage, and abrupt cooling 8200 years ago, Yong-Xiang Li a, Torbjörn E. Törnqvist, Johanna M. Nevitt, Barry Kohl

  265. David B. Benson:

    Brian Dodge @264 — Thank you vary much. This may well resolve an issue regarding the almost complete disappearance of near-shore (tidewater) ocean organisms on along the east coast of South America at some (rather uncertain) time betwen LGM and the Holocene. As I understand it, this coast was only repopulated around or after HCO.

    The other possiblity is Meltwater Pulse 1A. However, despite the rather large SLR, this event is spread over a millenium or so and therefore one supposes the tidewater organisms could keep up with the change. It hadn’t occured to me until yesterday to consider the 8,2 kya event. So thank you again for your research.

  266. Dan H.:

    Reference to this discovery with the article abstract was posted on another thread. It seems more appropriate to the discussion here, especially concerning the effects of increased SST on glacial loss.

  267. Hank Roberts:

    > 266
    More info and links on the paper Dan mentions — it’s the one on the historical archive of glacier photographs — posted above, earlier in the thread at 30 May 2012 @ 10:43 AM

  268. Unsettled Scientist:


    Some points I found interesting from the article linked in 266:

    “From 1943-1972, southeast Greenland cooled – probably due to sulfur pollution, which reflects sunlight away from the earth.

    “The important point is not that deadly pollution caused the climate to cool, but rather that the brief cooling allowed researchers to see how Greenland ice responded to the changing climate.”

    And a quote from Box in the article:

    “From these images, we see that the mid-century cooling stabilized the glaciers,” Box said. “That suggests that if we want to stabilize today’s accelerating ice loss, we need to see a little cooling of our own.”

  269. Dan H.:

    Also noteworthy, is that the higher land temperatures of the 1930s resulted in greater melting of the land-terminated glaciers, while higher Atlantic ocean temperatures recently has resulted in greater melting of the marine-terminating glaciers.

    [Response: It’s worth pointing out that the glaciers are substantially more ‘melted’ now than they were in the 30s in both domains. – gavin]