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Comments 118701 to 118750:

118701. HumanityRules at 16:38 PM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        Is that a seasonal signal in Fig 1 or an artifact of the measurement method? Sorry for the dumbness but I can't get my head around what it's showing in Fig 1. "the amount of acceleration". Does that mean for example that for Iceland the rate of acceleration slowed from 1995 to 2000 and then picked up again?
        Response: I don't recall off the top of my head if the paper says either way but I do believe it is a seasonal cycle. Makes sense - ice melts in summer, less ice, base uplifts.
        
        Re Figure 1, I confess I did have to stare at it for a while before the truth emerged. Take Iceland for example. What the graph shows is essentially the height of the base (or more technically precise, the anomaly of the height). At the beginning of the measurement period, Iceland is subsiding. But this subsiding is slowing down, stopping, then rising. The acceleration rate is fairly constant through this whole period.
        
118702. scaddenp at 12:38 PM on 25 May 2010
        It's cooling
        michaelkourlas - why do you think John spends time on discussing the ocean heat above? Pay particular attention to John's first 2 sentences above.
118703. HumanityRules at 12:18 PM on 25 May 2010
        Robust warming of the global upper ocean
        33.Riccardo It is a good job that Lyman do in pulling together the available data on OHC. The problem for me comes in the robustness of conclusions. The only tools designed to do the job this paper describes are teh Argo floats. These have yet to find a warming signal in the 5 or so years they've been operating. It seems extra-ordinary based on this fact alone that you would come to the conclusion this paper has. Place this data in the real world and as Trenberth says it still doesn't account for the missing heat. Having said that speculation on the missing heat seems even more wild given there doesn't seem to be any attempt to link the missing heat with any real world physical process that would allow the heat to go missing. It seems a really strange time to make such a forthright statement on this aspect of climate change when the data would not seem to fully support the climate change hypothesis.
118704. Eric (skeptic) at 12:00 PM on 25 May 2010
        Volcanoes emit more CO2 than humans
        JMurphy, I posted a response earlier, but it may have been deleted or I might have screwed up. I didn't say much more than I disagree mainly because the EU cuts (and naturally the volcano) are inconsequential for climate. But that argument probably belongs on a different thread.
118705. Eric (skeptic) at 11:45 AM on 25 May 2010
        Arctic sea ice has recovered
        Riccardo, keep in mind the "perfectly able" is qualified by the need for parameterizations related to the forcings. As a simple example, the extent and temperatures of ocean currents under the ice. Those calculations are very similar to a prediction except used for the present time. I can't interpret the graph you show without the description of how it was derived, but from the looks of it, the model is verifying about 5 years of actual volume measurements. I understand how the GCM adds both predictive value and uncertainties, but those are certainly not the only source of uncertainties in the model (except in the hypothetical case of a perfect model).
118706. HumanityRules at 11:45 AM on 25 May 2010
        Robust warming of the global upper ocean
        1.tobyjoyce I guess robust means 16years. And those 16 years can be separated into three phases. 4 years of little to no warming, 6 years of intense warming and finally 6 years of no warming. That would be what robust means. But this sort of detail gets in the way of the message which is the oceans are warming.
118707. Eric (skeptic) at 11:38 AM on 25 May 2010
        Arctic sea ice has recovered
        doug, I think the latter part of the curve has been verified, which I believe is about 5 years worth of data. Prior to that the verification relies on measurements of the same factors to calculate volume that were used in the volume and extent prediction (made in 2007 for 2008), namely forcings like weather and ENSO. Obviously those are well known for the past rather than predicted for 2008, but the ensemble used a variety of them to attempt to predict 2008 which all resulted in an underestimated ice extent. Not useless and the trend is correct, but I don't know how accurate the long term slope is.
118708. Doug Bostrom at 11:35 AM on 25 May 2010
        It's cooling
        Michael, I think one of the things you're missing is taking a moment to read John's post, or if you have and believe you've found something wrong there, perhaps you could mention it?
118709. Pat Moffitt at 11:29 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        BSI is being used as a proxy for productivity. Generally using BSI requires that diatoms comprise the majority of the primary producers. A recent paper by Stenuite et al in the J. of Plankton Research "Photosynthetic picoplankton in Lake Tanganyika: biomass distribution patterns with depth, season and basin" http://plankt.oxfordjournals.org/cgi/content/short/31/12/1531 found that picocyanobacteria ranged from 44 to 99% of total phytoplankton biomass. On the limnology of Lake Tanganyika- Victor Theodorus Langenberg thesis-rejects Verburgs (used by Tierney as suport for BSI proxy) contention that changes in phytoplankton biomass (biovolume), in dissolved silica and in transparency support the idea of declining productivity.
118710. michaelkourlas at 11:13 AM on 25 May 2010
        It's cooling
        I'm sorry but I think I'm missing something. Both surface and atmospheric measurements show cooling, or, at least, minimal warming since 2002. How can the planet be accumulating heat when over the course of 8 years global temperature records show it has not really warmed at all?
118711. Jeff Freymueller at 09:51 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        #29 Joe Blog, I don't know much about the details of pre-20th century glacial history of Greenland, but I think you are correct that there were general glacial advances over the last millenium. When the glaciers and ice sheet gain mass, the land will subside just as it is uplifting now as the ice is melting. In fact, you can see prominent annual cycles of uplift and subsidence in many of the time series shown in the main post, and most of that variation is due to the load change from the accumulation of snow and ice in the winter and its melt in spring through fall. See Grapenthin et al. (2006) for the case of Iceland.
118712. michael sweet at 09:17 AM on 25 May 2010
        Robust warming of the global upper ocean
        It strikes me that for amateurs to dismiss a paper by professionals published in Nature as 'Just nonsense" and "not measured in any reasonable sense" based on eyeballing their graphs is just nonsense and not reasonable. Please provide citations of reviewed papers that show the problems you claim are obvious.
118713. chris at 08:56 AM on 25 May 2010
        Southern sea ice is increasing
        GFW at 08:16 AM on 25 May, 2010 GFW, this isn't exactly what you're asking for. However many early models of the 80's/90's showed greatly delayed Antarctic warming compared to rapid Arctic warming. This is due (a) to the very large Southern hemisphere oceans and (b) different S and N polar ocean circulation which gives more efficient mixing of surface and deeper waters in the deep S hemisphere, transferring heat from the surface. So, quoting from a recent review of ocean circulation modelling in which the mechanisms for hemispheric warming asymmetry are described illustrates that highly delayed Antarctic Circumpolar ocean warming has been predicted since the early 1980’s. Here’s a bit of a summary from (direct excerpts are in blockquotes): S. Manabe and R. J. Stouffer (2007) Role of Ocean in Global Warming J. Meterolog. Soc. Jpn. 85B 385-403. General point about ocean modulation of surface warming:

        “In response to the increase in greenhouse gas in the atmosphere, the positive temperature anomaly initially appears in the well-mixed surface layer of the ocean called the “mixed layer”. Gradually, the anomaly spreads from the mixed-layer to the deeper layers of the ocean, thereby increasing the effective heat capacity of the oceans. The increase of effective heat capacity, in turn, results in the reduction of the rate of increase in surface temperature, reducing and delaying the warming as shown by Hoffert et al (1980) and Hansen et al. (1984).”

        Discussing the early models of Schneider and Thompson (1981) to evaluate the delay in the response of the sea surface temperature to gradual increase in CO2, Manabe and Stouffer say:

        "Their study shows that the time-dependent response of zonal mean surface temperature differs significantly from its equilibrium response particularly in those latitude belts, where the fraction of ocean-covered area is relatively large. Based upon the study, they conjectured that the response in the Southern Hemisphere should be delayed as compared to that in the Northern Hemisphere because of the inter-hemisphere difference in the fraction of the area covered by the oceans.”

        In a later model Bryan et al (1988) made the same sort of analysis, investigating the role of the oceans in modulating the response of surface warming to enhanced greenhouse gases.

        "They found that the increase in surface temperature is very small in the Circumpolar Ocean of the Southern Hemisphere in contrast to high latitudes of the Northern Hemisphere where the increase is relatively large.”

        It’s not just the oceans per so of course. It’s also ocean and air currents, and particularly the mechanisms governing the efficiency of surface heat transfer into the deeper oceans. If this is efficient, the deep oceans will absorb heat and there might be little measured surface warming, at least for a while. So (speaking of Bryan et al (1988)) again:

        "However, the detailed analysis of the numerical experiment reveals that the absence of substantial surface warming in the Circumpolar Ocean is attributable not only to the large fraction of the area covered by the oceans but also to the deep penetration of positive temperature anomaly into the oceans.”

        Later models predict the same hemispherical asymmetry that is seen in the real world. e.g. discussing the simulations of Manabe et al (1992):

        “Figure 3 also reveals that there is a large asymmetry in surface warming between the two hemispheres. In the Northern Hemisphere, the surface warming increases with increasing latitude, and is particularly large in the Arctic Ocean. This is in sharp contrast to the Southern Hemisphere, where warming is relatively large in low latitudes and decreases with increasing latitudes. It becomes small in the Circumpolar Ocean of the Southern Hemisphere, particularly in the immediate vicinity of Antarctic Continent.”

        Why is this, one might ask?! Here’s what Manabe and Stouffer say:

        "One can ask: why the polar amplification of warming does not occur in the Southern Hemisphere, despite the existence of extensive sea ice which has a positive albedo feedback? As discussed in the following section, the absence of significant warming in the Circumpolar Ocean of the Southern hemisphere is attributable mainly to the large thermal inertia of the ocean, which results from very effective mixing between the surface layer and the deeper layers of ocean in this region. This is in sharp contrast to the Arctic Ocean, where very stable layer of halocline prevents mixing between the surface layer and the deeper layer of the ocean" ......."In view of the absence of significant surface warming, it is not surprising that the area coverage of sea ice hardly changes in the Circumpolar Ocean despite the CO2-doubling.”

        n.b. remember this is a prediction from a model involving the response to [CO2] doubling; we’re nowhere near CO2 doubling yet. However these early models predicted what we're seeing in the real world today.
118714. billkerr at 08:53 AM on 25 May 2010
        Robust warming of the global upper ocean
        roger pielke snr's article, My Perspective On The Nature Commentary By Kevin Trenberth is relevant to this discussion
118715. GFW at 08:16 AM on 25 May 2010
        Southern sea ice is increasing
        John, I swear it was somewhere on this site, but I can't find it ... There's a paper from the early 1990s where the GCM the authors were using predicted increasing antarctic ice, which puzzled them, and they found it was the increased precipitation (lowering surface salinity) that was doing it (in the model). It's really quite a coup to have predicted the increase and to have attributed it to one of the mechanisms now believed to underlie the observed increase. If you know what paper I'm talking about, it deserves a shout-out from this page. Thanks!
        Response: I think you must've seen that paper somewhere else - the only papers I include on Antarctic sea ice analyse the trends after the event. But if you do track down this paper, please do post the URL here, thanks!
        
118716. J Bowers at 08:16 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        @ 26 The Ville What's gained in the UK at one end is lost at the other. Greenland is gaining at both ends. Last I heard, Britiain's isostatic rebound wasn't accelerating either, nor have each ends' rebounds decided to go in the opposite direction in the past few years. Different situation.
118717. Riccardo at 08:07 AM on 25 May 2010
        Arctic sea ice has recovered
        Eric, suppose that the ice volume model is perfectly able to calculate the true ice volume when you plug in past and current measured data. You then try to predict next season and plug in a GCM projection of the relevant physical quantities, i.e. weather evolution. It may well turn out to be wrong. What do you conclude? Sure the input data were wrong. Hence, a wrong forecast does not invalidate the ice volume calculations. So it is essential to separate the problem in two parts. The first is validation of the model calculation of ice volume. It has been done and it is shown here. And this is also the topic in this post. If the authors are confident with the results, they may want to try a forecast, but now they're adding the uncertainties of the GCM and chances are they dominate for the reasons you said. I can't tell if something went wrong or if it was just the expected uncertainty, one really need to be an expert on arctic ice behaviour. You might want to ask directly to the authors.
118718. Joe Blog at 08:00 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        I have a question that hopefully some of the informed commentators here can enlighten me on. Ok so its generally agreed by both sides o the AGW debate (and ice cores show) that Greenland was warmer some 1kybp. So during that time, is it likely that rebound would have been similar to today? And during the cooling of that land mass that ensued in later years, did it subside? or has rebound generally been positive since the last glacial maximum?
118719. Doug Bostrom at 07:45 AM on 25 May 2010
        Arctic sea ice has recovered
        Not to barge in, Eric, but how -much- of figure 2 is inaccurate, in your estimation? How wrong is it? Is it useless? Is the trend reflected in the figure entirely absent?
118720. Riccardo at 07:38 AM on 25 May 2010
        Robust warming of the global upper ocean
        Berényi Péter, i'm not going to follow you along this path. You are arbitrarly forcing the dichotomy yes/no, right/wrong, to make your preconceived point. The reality of good research is different by definition. As pointed out in my previous comment we all agree and know that there are problems and science is finding problems and trying to solve them as best as we can. This is what Lyman et al did and it's a good job. You've not been able to find any valid reason to dismiss the paper and it is only your a-scientific dichotomy that allos you to say that it's all wrong. In this way you're putting yourself outside the realm of science. And this is why I won't follow you.
118721. mspelto at 07:29 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        GFW it is an interesting question. However, we do not have an undermine issue in Greenland, there is not a danger of the major glaciers or the ice sheet developing into ice shelves. Yes some the very end of marine terminating outlet glaciers in the south are afloat and larger sections of some of the marine terminating northern glacier are, see Petermann Glacier are afloat. MS is right this is not a meaningful change.
118722. Eric (skeptic) at 07:27 AM on 25 May 2010
        Arctic sea ice has recovered
        Riccardo, thanks again for keeping track and responding. You are right that the figure is based on a model of the past which is different from a prediction of the future. But it is the same model. Many of the same factors are used both to model the past and predict the future, ocean and air temperatures being major examples. There are other factors can't be predicted or are very difficult to predict due to chaotic effects, like weather patterns and El Nino. As you point out, they use an ensemble for that purpose using the historical factors for the previous 7 seasons. However all of the ensemble predictions were less than the 2008 actual. So either 2008 was a very unusual year weatherwise or the model fails to properly integrate the recorded weather into the calculated ice volume. I'm inclined to believe the latter which is why I don't believe fig 2 above is accurate either.
118723. Doug Bostrom at 07:26 AM on 25 May 2010
        Robust warming of the global upper ocean
        Berényi I just read your post more carefully and I should amend my question. Do you see a possibility that OHC has in fact increased during the period examined by Lyman et al, and if so do you have a reasonably complete mechanism in mind to explain how it may have completely failed in reliability after ~2003? I think you need to supply more detail to describe how the failure you see has occurred.
118724. Doug Bostrom at 07:17 AM on 25 May 2010
        Robust warming of the global upper ocean
        Berényi, can I take your analysis as a "yes" on my question of whether anybody believes the current OHC measurement capability is entirely unable to detect a trend in temperature? Assuming that to be the case, is it capable of any useful measurements at all? Can you place any boundaries on its accuracy, and if so can you show how?
118725. michael sweet at 07:10 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        GFW, The glaciers can be more than 1,000 meters thick at the melt front. If the uplift is 1 cm/year, it will take forever to get a meaningful change. It was an interesting question.
118726. Paul D at 07:09 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        J Bowers @ 24 I'm at the South End. It's the same situation in that the reason for it is ice. The fact the ice melted thousands of years ago, is why the rising and sinking here in the UK is small compared to Greenland.
118727. Doug Bostrom at 07:09 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        GFW that's an interesting idea. Probably could be modeled? With known rates of rebound exceeding 3cm/yr in some places I'm guessing it may already be included in projections. On a general note there's a pretty good article on rebound here on Wikipedia. It's rather an amazing phenomenon.
118728. Berényi Péter at 07:04 AM on 25 May 2010
        Robust warming of the global upper ocean
        #26 Riccardo at 01:20 AM on 25 May, 2010 As for TOA imbalance, OHC trend and the like TOA imbalance is extremely important. Below is satellite measurement for the last ten years: These measurements have low accuracy but reasonable precision. It means that the curves above have an arbitrary offset (within several Wm^-2), but would show a marked level change whenever accumulation rate of thermal energy changes in the climate system. Nothing like that is seen between 2002-2004. Therefore either satellite data are absolutely useless or the 6-8×10²² J heat accumulation in the oceans after 2000 followed by a more or less level plateau from 2004 on is an artifact due to transition to ARGO. There is no other possibility. Net TOA radiative imbalance should be very nearly identical to the temporal derivative of OHC, because there is no heat storage capacity in the climate system comparable to the oceans and all energy exchange between Earth and its environment is mediated by electromagnetic radiation (any other forms of energy transfer, e.g. tidal breaking are many orders of magnitude smaller). For scientists it is left as an open question, as it should. The open question is not the "missing heat" but inconsistency between satellite and buoy measurements of energy budget and inconsistency between measurements and computational model predictions. The often quoted more than 0.5 Wm^-2 positive global energy imbalance is not measured in any reasonable sense. It is a model prediction, all but falsified by now.
118729. johnd at 06:30 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        chris at 04:46 AM, the abstract for the article gives the impression that "productivity" and "primary productivity" are somewhat more closely related rather than separate, and perhaps like both Reuters and The Straits Times they should have made it clearer also. Thats the trouble, all put their own spin on everything. Just to be precise, the study measured biogenic silica BSi, the production of which is controlled by the availability of silica and other nutrients amongst other factors, as the proxy for primary productivity.
118730. J Bowers at 05:43 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        @ 11 The Ville While the northern end of the British Isles is rising, the southern end is sinking, both ends at roughly the same rate. It's not the same situation as Greenland.
118731. GFW at 05:30 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        If the rebound of Greenland is in some places faster than the sea level rise, could that at least reduce the basal undermine/melt problem along the outlet glaciers?
118732. Jim Eager at 05:01 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        Based on the fact that Iceland sits astride the mid-atlantic ridge created by the spreading of the Eurasian and North American plates while Greenland sits entirely on the North American plate means that Greenland's glaciers are almost certainly not warming from the bottom due to volcanic activity. It's a shame that the AGW denial fanatics are so fixated on latching onto any and all possible and imagined causes other than AGW that they forget that grasping at straws does not hold up in the world of real science.
118733. chris at 04:46 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        johnd at 02:59 AM on 25 May, 2010 Two seperate issues are being conflated, johnd. 1. Primary productivity "Primary productivity" relates to the generation of biomass at the bottom of the foodchain largely by fixing of CO2. So in marine/lake environments this is normally measured as algal load or density. This is the measure that Tierney (and others) report on both as contemporary measures and as a proxy. So "primary productivity" has a particular and specific meaning. 2. Productivity in relation to fish yields. This is a different issue, and is the one that is subject to "other factors". This has got nothing to do with Tierney et al's proxy for primary productivity which is something else entirely (see 1.). As is very clear from the paper, the reduction in fish catch in recent decades may have some relation to the reduction in primary productivity (see 1.), but is more likely due to over-fishing: so Tierney et al. (2010) state:

        Specifically, from AD 1913 to 2000 the lower metalimnion (~110 m depth, just below the thermocline) of the lake warmed by 0.9 °C, the hypolimnion (below ~300 m depth) warmed by 0.2 °C and phytoplankton biomass between 1975 and 2000 decreased by 70% (ref. 2). The late-twentieth-century drop in primary production in Tanganyika may have contributed1 to declines in catch per unit effort during the late twentieth century (absolute catch increased between the 1950s and 1990s; refs 4,6), although most of this short-term change is probably the result of changing fishing intensity and technologies4.

        This is quite clear from reading the paper. I don't think anyone is "admitting" anything. They're simply describing what the evidence indicates.... Incidentally, the Straits Times headline: "Lake Tanganyika's life is dying" is rather overwrought! And both the Straits Times and Reuters accounts fail to seperate the two meanings of "productivity" clearly. So they also give the impression that there is a causal chain from warming to reduced fish catch, whereas the causal chain as described in the paper is from warming to reduced primary productivity (fixing of carbon into biomass at the bottom of the food chain). This (loss of PP) may have impacted fish catch, but the main contribution in the short term is likely over-fishing.
118734. Doug Bostrom at 03:52 AM on 25 May 2010
        Robust warming of the global upper ocean
        It'll be interesting to see what does come of the pressure sensor problem. I should take my own advice and go try to find out how many buoys are suspect, whether the manner in which the buoys are run can cause a measurement error in gross heat content as opposed to simply making it more difficult to obtain a depth/heat profile. I suppose that's already been done by the operators for that matter. Great website, Ari. A tremendous compendium of papers; well done!
118735. Ari Jokimäki at 03:43 AM on 25 May 2010
        Robust warming of the global upper ocean
        Doug, remember that the world ocean database document is only for the data analysis in NODC. The "official" situation of Argo can be found from Argo website. The Argo information centre there is the interesting thing for the discussion here. There is an item in the news list saying "Advice on Pressure Biases in the Argo Data Set", it says: "A part of the global Argo data are subject to biases in reported pressures. These biases are usually less than 5db, but occasionally can be larger (> 20db). These bias errors are being steadily removed by the reprocessing of historical Argo data. We expect that by the end of 2010 these errors will be removed from the global Argo data set in both the delayed-mode and real-time data." So it seems that next year we will have a better idea of how much of less warming of post-2003 has been due to the pressure sensor problem. So far studies have just rejected the bad Argo floats from the analysis (this latest study included), so it will be interesting to see the end result, when the data has really been corrected. But I bet there's still something else biasing the Argo-data that we don't know about.
118736. Doug Bostrom at 03:41 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        I wonder what mechanism of error would produce Tierney's graph, what the coincidence of problems would be that would yield such an image that resembles others we've seen? Stuck at this point, it seems, until somebody extends the path of research. Thanks for the link, johnd.
118737. johnd at 02:59 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        Subsequent to the study being published, Jessica Tierney did a telephone interview with Reuters which is reported here. http://www.straitstimes.com/BreakingNews/TechandScience/Story/STIStory_527551.html Interesting the final note from Reuters about how the paper apparently admits that other factors, like overfishing, may be doing more harm than any warming. If the study considers that "other" factors may be more significant in falling productivity than any warming, then logically the study must have had to quantify those other factors before being able to calibrate the proxy chosen for productivity, namely BSi, and the temperature data from the relevant instrumental records available. Does anyone have any information on the proportions allocated to the various factors to allow the calibration? 'INTENSE WARMING' MOST climate change studies have focused on the atmosphere, but increasingly scientists are studying the effects on the oceans, seas and lakes, which all absorb a huge amount of heat. The paper argues that recent rises in temperature are correlated with a loss of biological productivity in the lake, suggesting higher temperatures may be killing life. 'Lake Tanganyika has become warmer, increasingly stratified and less productive over the past 90 years,' the paper says. 'Unprecedented temperatures and a ... decrease in productivity can be attributed to (human) ... global warming.' The rise in temperature over the past 90 years was about 0.9 degrees Celsius and was accompanied by a drop in algae volumes. 'We're showing that the trend of warming that we've seen is also affecting these remote places in the tropics in a very severe way,' Tierney said by telephone from the United States. 'We've seen intense warming in recent times ... not down to natural variations in climate.' She said the lake life had been harmed because in a lake as deep as Tanganyika, the nutrients form at the bottom but the algae needed to make use of them live at the top. Higher surface temperatures mean less mixing of waters at the top and bottom.' That's why a warmer lake means less life.' But the paper admits that other factors, like overfishing, may be doing more harm than any warming. -- REUTERS
118738. Riccardo at 02:43 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        Thank you Jeff for elaborating on ice-quakes. I've been too lazy to do it myself and I sure have not your competence on this. :)
118739. Steve L at 02:18 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        Jeff @17: thanks. I was wondering how come more hadn't been said about this basal heating over the last couple of years subsequent to the preliminary finding. Now I have a some idea.
118740. Jeff Freymueller at 02:16 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        #13 Riccardo, actually there has been an increase in seismic activity in Greenland, but it is all in the form of low-frequency earthquakes that originate in the ice, not regular earthquakes in the rock. These events increased in rate at about the same time that the GPS says the ice load began to decrease and glaciologists observed that the outlet glaciers sped up. See Ekstrom et al. (2006) for details. It is yet another independent piece of evidence that there has been a fundamental change in the behavior of the ice sheet and its outlet glaciers.
118741. Doug Bostrom at 02:10 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        That's an excellent point, Jeff, and in fact it makes Jiang's result all the more striking since by extension it would appear the rebound spotted in his analysis has overwhelmed the prior adjustment process.
118742. Jeff Freymueller at 02:09 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        #9, #12. No, volcanoes under Greenland are not the cause of this. As pointed our already, Iceland is located on the Mid-Atlantic Ridge and Greenland is not, and Greenland is about as tectonically and volcanically active as the Canadian Maritimes (which is to say, not at all). I looked up the abstract for the meeting presentations that the news article cited in #12 was based on, and it is pretty vague. The URL to the abstract is about as long as the abstract, so here's the abstract: "Rapid ice flow in the northeast quadrant of the Greenland Ice Sheet is associated with unusually high heat flow. Heat flux can be greatly increased in deep valleys to promote basal melting with additional feedback due to locally increased friction. However, crustal thinning can also enhance heat flow because the relatively thermally conductive mantle is closer to the surface. In addition to incised topography, relatively shallow Moho also occurs beneath the northeast quadrant of the Greenland Ice Sheet. We made regional three-dimensional thermal models that include the effects of topographic and mantle relief. These effects can strongly enhance the heat flux at the base of the ice sheet. " The Moho is the seismic discontinuity between crust and mantle, so they are talking about a change in crustal thickness. Typical crustal thickness is 30-40 km, and if you cut that in half you would double geothermal heat flow, which would still be pretty small compared to the changes in heating from the top. I'd say the news article is overblown. In any case, even if geothermal heat flow in NE Greenland is higher than average and has an effect on the ice there, the heat flow would have been high for millions of years (so no change around 2002-2003), and all of the data in the paper came from SE and W Greenland, so this argument is just a big red herring.
118743. Doug Bostrom at 02:05 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        Chris also takes the time to digest his findings and produce synopses with some useful remarks on relevance. Worth emulating, if you're claiming to have better insight than experts.
118744. michael sweet at 02:00 AM on 25 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        I hope that people appreciate the amount of time it takes people like Chris to find and reference all the papers he brings to our attention. This allows us to read the original data and see the science develop. Thanks for your carefully researched posts Chris
118745. Doug Bostrom at 02:00 AM on 25 May 2010
        Robust warming of the global upper ocean
        Further to my earlier remark, for those wishing to dismiss the entire collective anomaly apparently revealed by OHC measurements you'd do well to begin by reading and comprehensively understanding the item pointed out by Ari, the WORLD OCEAN DATABASE 2009, then extend your effort to a point where you feel your expertise exceeds that of the authors of this study. At that point you'll be prepared to offer some useful critique. Short of that-- short of some miracle-- your offering will inevitably reside in the "I doubt it" arena in terms of utility with drawing conclusions.
118746. e at 01:57 AM on 25 May 2010
        There's no empirical evidence
        PaulK, Riccardo, I was attempting to address this comment from PaulK > "Quote Now suppose that prior to our starting time, climate forcing was constant and equal to zero, and temperature departure was constant and equal to zero. After time t0, climate forcing increased to 1 W/m^2 and stayed there. Then the solution turns out to be: Theta(t) = (1 – exp(-lamda*t/C))/lamda Endquote It is hopefully evident to you that Theta (t), the temperature change from the forcing, must asymptote mathematically from this expression to a constant 1/lamda at large values of t. So now ask yourself the question whether it is possible in terms of first law of thermodynamics to have an imbalance of TOA radiative energy for an infinite time which results in a finite (constant) change in planetary temperature. If you can truly answer yes to this question , then I think that I am going to sign off, since I am wasting my time here. " I'll admit I probably misunderstood what you were trying to say Paul. I don't see what is wrong with Tamino's solution for Θ(t) in his scenario. To repeat what you said in your recent post: "As the system heats up, it will increase its power output until the temperature restabilises at a new constant value." Isn't this exactly what Tamino was showing in his solution for temperature departure Θ(t) in his scenario? How does this violate the first law of thermodynamics?
118747. Jeff Freymueller at 01:56 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        #6, #8, about isostatic rebound. Greenland may have been subsiding just a bit because of isostatic rebound from the Laurentide ice sheet. When the ice sheet was at its maximum, Greenland was on or close to the forebulge that surrounds the central depression. Collapse of the forebulge after the ice was gone goes hand in hand with uplift of the depressed area. As I recall the signal was very small, which is consistent with the data prior to about 2002-2003. The earth is viscoelastic (think spring + shock absorber). When you remove a load from the surface, there is an immediate elastic response, and then a delayed viscoelastic response, which can last a very long time depending on the spatial scale of the load. Parts of Canada and Fennoscandia are still uplifting at about 1 cm per year due to the melting of ice sheets after Last Glacial Maximum. What we are seeing in Greenland now is almost entirely the immediate elastic response to removing the load. The reason for the change in trend in the GPS vertical measurements is because there has been a drastic increase in the rate of ice loss.
118748. Doug Bostrom at 01:50 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        Sheer speculation, picking any explanation other than what's shown by scrupulous measurement to the very best of our ability is not an argument that is even remotely persuasive. If a wild guess is extended and made concrete with a plausible hypothesis and subsequently observations that are sufficiently solid, it might become useful. Otherwise it falls in the large but vacuous category of "I doubt it."
118749. Riccardo at 01:33 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        Tony O, what is measurend is the fast elastic response which need to be discriminated from the annual cycle (yes, strange as it may appear, there's one) through carefull analisys. You can find some details in the supplementary informations.
118750. Steve L at 01:23 AM on 25 May 2010
        Greenland rising faster as ice loss accelerates
        If sea level rises, but the Canadian archipelago doesn't, I wonder if sea ice will more easily float out of the Arctic. Probably I'm getting a little 'carried away'. #9 may not be as far adrift as I first thought. I did a brief search for magma and greenland and found this mention of a study indicating a hotspot in northeast Greenland. I couldn't find any update.

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