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Climate Hustle

Unprecedented Warming in Lake Tanganyika and its impact on humanity

Posted on 20 May 2010 by John Cook

Lake Tanganyika, in East Africa, is the second largest lake in the world (by volume). The lake supports a prodigious sardine fishery which provides a major source of animal protein for the region as well as employment for around 1 million people. Direct observations over past 90 years find that Lake Tanganyika has warmed significantly. At the same time, there's been a drop in primary productivity in the lake impacting sardine populations. To further explore this matter, geologists took lake cores to determine the lake's surface temperature back to 500 AD (Tierney 2010). They found that warming in the last century is unprecedented over the last 1500 years.

Lake Tanganyika lake surface temperature
Figure 1: Lake Surface Temperature from Lake Tanganyika palaeorecord for the past 1,500 years, measured in core KH1 (red line) and MC1 (dark red line). Orange shading is 95% error bars.

What effect does temperature have on the lake's sardine population? To answer this question, a proxy for primary productivity was also reconstructed from the lake cores. Primary productivity was determined from the percentage of biogenic silica in the sediment. They found that over the last 1500 years, when temperature rose, primary productivity fell. In the last 150 years, productivity plummeted from relatively high levels during the early 1800s to some of the lowest sustained values during the past 1,500 years.

How does temperature affect primary productivity? When the surface of the lake warms, the waters become more stratified. This makes it harder for cold currents to rise from the bottom. These currents carry nutrients from the depths toward the surface as food for algae. Sardine then feed off the algae. A less productive lake means fewer fish and therefore less food and income for those living in the region.

The stratification is confirmed by deep-water instrumental measurements which find less warming at deeper layers, revealing an increased temperature gradient. Nevertheless, another possible cause in changing rainfall is explored. Higher rates of precipitation may increase primary productivity. Charcoal levels in the lake cores were used as a proxy for humidity (eg - low humidity leads to drought which corresponds with more bushfires). However, they found a weak correlation between charcoal levels and productivity. The stronger relationship between temperature and productivity led the authors to conclude that it's temperature, not rainfall, that is largely controlling primary productivity.

There's also a strong match between Northern Hemisphere temperature reconstructions and the Lake Surface Temperature reconstruction. Temperatures on Lake Tanganyika have largely followed global trends over the past 1500 years as well as the past half-century. From this, the authors infer that surface temperatures in this region vary in concert with the global average and that the recent anomalous warming is a response to anthropogenic greenhouse-gas forcing. As lake temperature and primary productivity are closely related, this is evidence of another impact of man-made global warming on humanity - in this case, the communities and regional economy around Lake Tanganyika.

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Comments 51 to 100 out of 160:

  1. chris at 21:37 PM, I inferred nothing of the sort.
    What does seem to be inferred by those who disagree with my concerns about whether the sampling provides representative data, is that one or two 2" core samples are sufficient to draw a conclusion about whats been deposited under a body of water covering 32,900 km².
    With a shoreline close to 2000 km and a wide variety of conditions and activities that affect the localised inflows and thus the sediments that collect on the lakes bottom, what are the scientific odds of being able to take one sample that yields results that represent the entire lake.
    Any prior work would have had to been very extensive in order to select such a target.

    Of course armchair wannabees who have had little contact with the realities of the physical world, and even less appreciation of the infinite variability of all things natural, but instead see the world through lenses carved from ready made blocks of homogenised data interpreted by others may disagree. But hey, thats life.

    Your impression about the low tech element is probably right. Core sampling of sediments is generally a low tech operation, even in a high tech world.
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  2. johnd,
    a discussion based on unsupported hypothesis (too long shorelines, human or natural influences, etc.) and, above all, on the premise that scientists are more or less blind to all these things, is really pointless.
    If you have any real reason to think that the data in the paper are invalid or too limited, please enlighten us. Otherwise it's safer to assume that those who have been working in the field for years know better. First study the problem, then ask questions; and only then one may have a well founded idea.
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  3. 'Skeptic' A: 'Climate science is all a huge hoax to get billions in grant money'.

    'Skeptic' B: 'Climate science is too poorly funded to get 100% incontrovertible results and thus should be ignored'.

    Well, at least they've got all the bases covered.
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  4. Just to yank us back to reality here, let's remember that the signal extracted from the cores obtained by Dr. Tierney is substantially consistent with -other- examples obtained elsewhere via different proxies. To the layman such as myself that alone is an indication that we're actually viewing a signal as opposed to some artifact or product of sample incoherence. It rather beggars belief that such a familiar shape should emerge by coincidence from a faulty sample.

    If Jessica is still hovering in the vicinity, perhaps the most valuable input she could contribute at this point would be a quick (if such is possible) synopsis of how one determines if a core is in fact reasonably intact, has not been mangled by previous bioturbation etc.?
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  5. Just as a data point here, we had a seminar speaker a month or two ago about the drilling project at Lake El'gygytgyn in the Russian Far East (also a paleoclimate project, but aiming to go back several million years to pre-glacial times). That was a much larger scale of project, with a drill rig and many tons of gear mobilized to a very remote part of Russia, set up on the lake ice, and drilling much deeper. We're talking about millions of dollars. That project got two cores. A third was planned, but drilling problems meant they just got two.

    All of this was done after extensive work of studying the lake water, multiple seismic lines, etc, to choose the ideal sites. I don't do this kind of work, but I am absolutely sure that the people who do are keenly aware of what conditions must be met for a sedimentary record like this to be considered a viable proxy for temperature, including the people who reviewed the paper. The fact that this project followed the same approach as other similar studies, followed extensive preparatory work, and was published after peer review from people who work in the field carries far more weight than the objections of someone who doesn't appear to have any conception of the scope of work needed to collect the core or go from core to paper, and doesn't appear to have even looked very hard for more information....
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  6. johnd at 22:50 PM on 21 May, 2010

    johnd, I doubt anyone would disagree that one core is not going to define every possible core that could be drilled in Lake Tanganyika. However the core and interpretations thereof are likely to have been considered in relation to a rather large body of work including:

    (i) prior studes to determine suitability for coring in lake Tanganyika, optimising coring sites and associated limnological analyses.

    (ii) A considerable amount of prior study to determine the suitability of the particular temperature proxy for paleotemperature analysis from lakes like Tanganyika (e.g. this detailed analysis [***])

    (iii) Knowledge from analysis of surface temperatures in lake Tanganyika that seasonally-averaged temperatures from multiple sites in the lake (near Bujumbura, Kigoma, Lubugwe, Kibwesa, Kipili, Kipanka, Bujumbra), show very similar temperatures, indicating that sampling surface temperatures at single sites is representative of sites throughout the lake, particularly when averaged over significant time periods (

    (iv) That direct sea surface and time-averaged air temperatures in many lakes, including Lake Tanganyika are strongly correlated, indicating that sea surface temperature measures and those from proxy analysis are likely to be well-correlated with air temperature at the times the surface temperature proxies were sampled.

    (v) That very extensive analysis of surface temperature measures shows that these are strongly correlated (rise and fall similarly) over long distances as yearly or decadal averages (NASA Giss establish that these correlations hold for distances of up to 1200 km).

    (vi) That the analysis of the direct measures of lake surface temperature, air temperature and primary productivity during the last century, indicate that the correlations assessed by analyses of the proxies are robust...

    ...and so on...

    In other words just like all scientific research, this study was done in the context of considerable prior research, and within a framework of strong knowledge of relevant climatology.

    Now this isn't my research area at doubt the practitioners of this study have an almost infinitely (!) greater knowledge of this subject than I have, and thus considerably more insight into establishing the proper context of their work.

    [***] L. Powers et al (2010) Applicability and calibration of the TEX86 paleothermometer in lakes Organic Geochem. 41, 404-413
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  7. johnd at 22:50 PM on 21 May, 2010

    "Of course armchair wannabees who have had little contact with the realities of the physical world, and even less appreciation of the infinite variability of all things natural, but instead see the world through lenses carved from ready made blocks of homogenised data interpreted by others may disagree"

    That's an interesting statement that bears on philosophical ideas about the nature of knowledge (or personal knowledge).

    I would say that my knowledge of the world is to a significant extent "based on ready made blocks of homogenised data interpreted by others". What's missing from that attempt at a perjorative are the truisms that (i) those "blocks" shouldn't contradict my personal experience and (ii) that the "blocks" can be accommodated within my mental picture of a subject formed from everything that I happen to know, also bearing in mind that the natural world has inherent degrees of order and that things "make sense".

    So I'm inclined to take what I read in the scientific literature at face value and afford it the presumption of "correctness" unless I have reason not to. I find this is a pretty useful approach in my own research.

    The notion that skepticsm involves the presumption of incorrectness is pretty self-defeating I think. The arrogance of assuming that one knows better than the practitioners of the research at hand, and that all the negative things you can think of that might be a problem, actually are a problem, doesn't help understanding. It tends to stop you investigating further. Far better if you think something might be a problem to do a bit of research, or enquire to the authors of the work. It's very likely that the negative things you've thought of have already be considered by the you might actually learn something!
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  8. Chris thanks for that. The same approach and conclusions apply to a plethora of cases similar to this; folks leap to judgment based on their supposition they're reading research findings that are somehow atomic and self-supporting, when of course they're not.

    Another question for Dr. Tierney if she's about, not related to temperature per se. Inspired by johnd I was attempting to do what Chris just did and noticed you're looking at biomarker carbon isotope compositions and presumably ratios in your samples. By any chance, have you looked for the same recent shift in isotope ratios we see in the atmosphere and which are used to identify fossil fuel contributions to the carbon cycle? I expect we would see that if we were looking for it but am curious to know if you've followed that side path. It seems like that might be a way of identifying the first environmental fingerprints of our vast combustion project. I'm giving strong odds that this is something totally obvious to anybody working in the field and I'm simply oblivious, heh!

    Anyway, the methods you're developing and employing seem to have broad applicability and it'll be interesting to see what we discover as they're more broadly deployed.
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  9. ooops...can I point out that in my post 57 above [under (iv)], when I say "sea surface temperature" I mean "lake surface temperature"!
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  10. Maybe I missed it somewhere, but I did not see any mention of this lake's level lowering and a possible correlation to temperature. It doesnt take much internet search effort to find that the level has changed historically and recently as well due to water being deviated by man. Down at the bottom of the lake there just happens to be a continental rift as well. The lake's temperature therefore doesnt seem like the best example for convincing Skeptics (like me).
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  11. RSVP,
    as for the rift, i'd not call skepticism when not reading the information available. Indeed, you should read Tierney's page she linked before and, if not convincing, eventually comment on the explanation provided there.
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  12. Second Riccardo's remark regarding the rift. Do more work before launching speculations. Again, use BP (our BP, not the oily BP) as a model for emulation. Though BP is frequently wrong he comes up with original ideas, puts a lot of effort into his ruminations, has good math chops (better than mine, that's for sure) and is also (and this is a key point) capable of recognizing and acknowledging those times when he's obviously incorrect.

    It's not guaranteed of course, but generally if you see a blindingly apparent feature such as the African Rift unmentioned in a paper you may safely conclude that it's not relevant.

    It helps to remember, though in the space we occupy here there's an artificial atmosphere of controversy, in the actual mainstream research community anthropogenic warming is not even slightly controversial, so it is not considered necessary to explicitly address every possible niggling objection that may be raised by folks unprepared to understand or accept research findings.
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  13. Albatross> I must admit that I was relying mainly on John Cook's remarks on the glaciers of Kilimanjaro on this site. They still make sense to me. If you want to question this, why don't you go to that "skeptic argument" and repost there? Then we could try to figure out what is true in the proper thread.
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  14. chris at 00:55 AM, the reason I focused on this particular aspect is because I do have some practical knowledge of what is required and involved with relation to the subject of taking of samples.
    Granted it is in a different field with different objectives, geophysical, mineral exploration, bulk commodities, natural fibres, where the objective is not to get a confirmation of what we assume we know, but to quantify what we don't know.
    We might assume that the ground might be able to support a heavy structure, and a test at one corner might confirm that, but often that will not apply to the other corners.
    Whether taking simple surface sediment cores or cores from deep below in the search for natural resources, there is a strict regime on what is required to satisfy firstly those who will decide whether to proceed further or not, and an even tighter requirement for it to become part of a bankable feasibility study, and then even tighter beyond that.
    In bulk commodities where a degree of consistency is easily assumed, there is an even stricter sampling regime that acknowledges the wide variation that can occur in all natural products.
    With natural fibres, wool in particular, it is accepted that the variation of micron within a single fleece is greater than the variation across the entire flock. Those who prepare the fleeces are well aware of this and often will go to one particular part of the fleece to extract a handful of wool that will make up a bale of special wool that ends up being awarded accolades as the worlds highest priced wool. However those who understand the game being played know that overall the flock that produced such wool is little different from the more run of the mill flock belonging to the next door neighbour.
    That might be comforting to those who wonder why the wool that gets pulled over their eyes often is so soft and subtle they are hardly aware of it's presence. ;-)

    In all fields it is relatively easy to take a sample that will confirm what anyone may want it to confirm is so desired, but in the field of commerce that desire is well recognised hence the strict regime and rules that apply, and it is from this perspective that I look to see if what is being presented as being representative of something bigger, does qualify in fact.
    Nothing more, nothing less.
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  15. Perhaps the latest study of global ocean temperatures which includes over 3200 Argo floats will help to convince you that the warming in Lake Tanganyika is consistent with enhanced global climate change.

    New Study Finds Ocean Warmed Significantly Since 1993

    Quote: "The upper layer of Earth's ocean has warmed since 1993, indicating a strong climate change signal, according to a new international study co-authored by oceanographer Josh Willis of NASA's Jet Propulsion Laboratory, Pasadena, Calif. The energy stored is enough to power nearly 500 100-watt light bulbs for each of the roughly 6.7 billion people on the planet."
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  16. Ron Crouch at 09:08 AM, my understanding of the study is not whether the lake is warming or not, but rather that the primary productivity of the lake, both currently and for the past 1500 years, is solely a function of global temperatures, to the exclusion of all other local and regional factors, and thus can be taken as a proxy for anthropogenic climate change.
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  17. Looks like in johnd we have another classic denier argument - that is that no sample, no sample size, is ever big enough or comprehensive enough to demonstrate global warming, in fact, it seems, no sample can ever BE big enough. Here is another independent study which matches what every other study shows, and it comes from a new and very different location. And it's not just one core sample, but two. Worth remembering that sediments by their very nature are averaging out conditions over wide areas and over time.

    And the response? Not enough samples. I am not a betting man, except on sure things, and I bet that if there had been three cores, 4 would have been demanded, 4 needs 5, and so on to an infinity of samples from every square metre of the lake floor. And we would then be told that this was just one lake, that we couldn't possibly conclude anything until a second lake had been cored. Oh, you have 2, 3 are needed, and so on. And then, what, only lakes in eastern Africa? Only lakes in Africa, southern hemisphere, the world?

    It would be nice to see, just once, a denier come to terms with the fact that we now have masses of evidence of very different kinds and from all over the world all of which support and strengthen each other. As Charles Darwin said, in a slightly different context, it would only take one example to prove the theory wrong. The converse is not true, cherry-picking in the sense that every individual study has to somehow completely stand alone with 0 error bars might be a recipe for delaying action on climate change, but it has nothing to do with science.
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  18. Without my having to say so David Horton has summed things up very nicely.

    Quote: "It would be nice to see, just once, a denier come to terms with the fact that we now have masses of evidence of very different kinds and from all over the world all of which support and strengthen each other."

    On their own the individual studies don't really represent that much, however when one starts to stitch them together and the mosaic begins to appear, the overall picture of the health of the planet starts to become clearer. But then I don't expect all to have an eye for Picasso, most prefer Rembrandt.
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  19. Johnd, I don't think I'm being hyperbolic or unnecessarily pejorative to categorize that remark as rubbish.

    Can you please state exactly where the study concludes "the primary productivity of the lake, both currently and for the past 1500 years, is solely a function of global temperatures?"

    If you can't do so, do you have the grace to retract your remark?
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  20. "It doesnt take much internet search effort to find that the level has changed historically and recently as well due to water being deviated by man."

    Not to pile on, but this sentence may be the best illustration I've ever seen of the problems with "skeptical" logic.

    Not only is there an assumption that you can rebut scientific papers by Googling, but there's also an assumption that the easier it is to Google an alleged counterargument, the more damning it is.

    In reality, as Doug Bostrom says, if a problem of this type seems "obvious," there's a pretty good chance that it's not a problem at all.

    True skepticism requires discipline, knowledge and humility. Unless it's backed up with actual evidence, a statement like "it is relatively easy to take a sample that will confirm what anyone may want it to confirm" comes across as a lazy -- and ultimately nihilistic -- attempt to muddy the waters, IMO.
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  21. Ok I have been ostracized for putting out information without evidence to back it up.
    I've done some considerable research over the last week or so since this originally came out. John was a little slow on the uptake on this one, no doubt to his eager anticipation of the Heartland institutes summit on Climate change last week. :-)
    So I'm breaking this down into two sections to make it short as requested by John C.
    Part 1.
    I have been researching this whole issue for the last couple of days.
    At someone's suggestion I went to check out the following article but unfortunately they only provide Abstracts through ProQuest and I can't afford to sign up for their membership. Hydrothermal vents in Lake Tanganyika, East African Rift system
    Pflumio, Catherine, Castrec, Maryse, Boulegue, Jacques, Gente, Pascal, et al. Geology. Boulder: Jun 1993. Vol. 21, Iss. 6; pg. 499

    One would think that if there are active thermal vents that we've known about since at least 1990 this could have something to do with the issue.

    It would also appear that there is a massive overharvesting of fishing going on that makes the gillnetting/long lining of salmon look like a drop in the bucket.
    Also there is a massive problem with land use issues.
    Granted the last two issues are man caused but have absolutely nothing to do with AGW.

    I also read an article that shows that there have been higher than normal wind conditions which inevitably dry out the surface which is going to cause conflicting temperature anomalies.
    I’ve also read about Gustave the killer Croc which could be eating up large amounts of fish. A much more viable option than AGW, especially since the authors admit that they only took two samples from a huge body of water.
    The above is a link to a scholastic database of a National Geographic Article.
    Is an interesting article about how the two major species of fish have major variances in population.
    Limnological variability and pelagic fish abundance
    (Stolothrissa tanganicae and Lates stappersii)
    in Lake Tanganyika
    P.-D. Plisnier Æ H. Mgana Æ I. Kimirei Æ A. Chande Æ L. Makasa Æ
    J. Chimanga Æ F. Zulu Æ C. Cocquyt Æ S. Horion Æ N. Bergamino Æ
    J. Naithani Æ E. Deleersnijder Æ L. Andre´ Æ J.-P. Descy Æ Y. Cornet
    Received: 24 June 2008 / Revised: 12 December 2008 / Accepted: 2 January 2009 / Published online: 2 February 2009
    _ Springer Science+Business Media B.V. 2009
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  22. Part II -
    The effects of windstorms on nutrient of Lake Tanganyka
    Effect of wind induced water movements on nutrients,
    chlorophyll-a, and primary production in Lake Tanganyika
    V. T. Langenberg,1∗ J. Sarvala,2 and R. Roijackers1
    1Aquatic Ecology and Water Quality Management Group, Agricultural University, Wageningen, The Netherlands
    2Department of Biology, University of Turku, Turku, Finland
    *Corresponding author: Aquatic Ecology and Water Quality Management Group, Agricultural University, PO Box 8080,
    Wageningen, the Netherlands; Tel.: +31-629433225; Fax: +31-317484411; E-mail:
    Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa.Full Text Available By: O'ReiIIy, Catherine M.; AIinl, Simone R.; Plisnier, Pierre-Denis; Cohen, Andrew S.; McKee, Brent A.. Nature, 8/14/2003, Vol. 424 Issue 6950, p766, 3p; DOI: 10.1038/nature01833;
    There have been numerous peer reviewed articles that have talked about an increase of fish, including the one above. The only species of Cichlids that are declining are the rock fish that are suffering from their habitation being destroyed by erosion of rock shelve strata by over use of the area.
    Nature and Science are the only two journals that have any articles about global warming causing issues and they’ve been by the same authors, using similar test methods to this recent one. The latter not using any surface temperatures across the lake or more than two core samples. This lake is over 10,000 sq. miles.

    [pointless, irrelevant and insulting analogy removed]

    And if you notice, I even used information from a "Nature" article.
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  23. Skepticstudent, lots of work but besides hydrothermal vents, what does it all have to do with the temperature of the lake, which is the actual signal being assessed?

    Regarding the hydrothermal vents, what is their output in watts and how much is that output capable of changing the temperature of the lake?

    In general you need to produce numerical results to be persuasive.

    You've got more work to do.
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  24. Thermophilic Sulfate Reduction in Hydrothermal Sediment of
    Lake Tanganyika, East Africa
    Universite Pierre et Marie Curie, Paris 6,1 and Centre National de la Recherche Scientifique,2 Station Biologique de
    Roscoff, F-29682 Roscoff; France; Centre de Recherche en Sciences Naturelles, Station d'Uvira, Uvira, Zaire3;
    and Max Planck Institute for Marine Microbiology, D-2800 Bremen 33, Germany4
    Received 21 October 1993/Accepted 18 February 1994

    I just discovered this article that could possibly shed some light on this issue.
    I know I’m no PHD but it makes one curious.

    The Max Plank Institute is a pretty respected organization so it’s not like I’m speaking out of my ear.
    I googled: Hydrothermal vents in Lake Tanganyika, East African Rift system Pflumio, Catherine, Castro, Maryse, Boulegue, Jacques, Gente, Pascal, et al. Geology. Boulder: Jun 1993. Vol. 21, Iss. 6; pg. 499
    And I came up with the above article from the Applied and Environmental Microbilogy journal.
    I'd be very curious where they did their coring for the thread article? Did they know about the thermal vents at the bottom of the lake in numerous locations before they wrote this article and spent all that time?
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  25. regarding doug_bostrom

    that's my whole point. They don't really describe much about where exactly they took their 2 whopping samples.
    but one would assume that if they're taking samples from the lake bed that would be close to the vents which apparently are from all over the lake. when you're digging into sediment of a lake with Volvanic vents all over the place does one really have to worry about wattage output into the water to wonder if they could output heat into the lake?

    One would also have to admit that these thermal vents are pushing co2 as well as sulphur to the surface along with heat towers.

    One thing that seems to escape notice in this website by many people such as yourself is that I'm not trying to say this is a died in the wool for sure cause of any and all temperature inclines in the area.
    However to the opposite I'm attempting as do the majority of skeptics to show that there are many natural causes that add to the whole.
    Besides one would have to assume that since there isn't much in the line of industry in Africa being the poorest continent in the world, where would the anthropogenic warming effect be coming from.
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  26. Skepticalstudent, you need to be a little more thorough in your research.

    You might find it informative to visit J Tierney's website (link in her first post above) where she comments on the influence of those thermal vents .

    "Besides one would have to assume that since there isn't much in the line of industry in Africa being the poorest continent in the world, where would the anthropogenic warming effect be coming from."

    That's not a serious comment, is it? You do need to do some very basic reading to clarify for yourself how CO2 and greenhouse gases affect climate and induce warming.
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  27. skepticstudent,
    it could be helpful if you link directly to the paper instead of copy/paste author, title, affiliation and address.

    What Doug was trying to say, I guess, is that one has to be quantitative in their hypothesis. No one is saying that there is no volcanic activity in the lake. The point is the impact on the overall behaviour of the ecosystem.
    For sure Dr. Tierney and co-workers are well aware of the presence of vents in the lake and we can take it for granted that their hole was not digged near one of such vents, even if not stated explicitly. Remember, research papers have no didactic intent (by definition, i'd say). And while we are all welcome to have a read, it's absurd to criticize them for not being explicit enough on many things. Even worse if you question author's skill in doing accurate research. Do you really think you have something to teach them on how to choose the proper drilling site? Do you really think that one day they just dropped some instruments on a boat and start drilling at random? Not even a newbie fisherman would do this, his first question would be where to go.
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  28. Skepticstudent, you're not keeping up and you're making yourself look foolish.

    To wit:

    ....does one really have to worry about wattage output into the water to wonder if they could output heat into the lake?

    How much heat? You do realize, the heat energy released into the lake versus the mass of water contained in the lake determines whether the hydrothermal vents will have any significant impact on the temperature of the lake compared to other inputs? Right? So you need to quantify that or you're not making a argument with any effect.

    One would also have to admit that these thermal vents are pushing co2 as well as sulphur to the surface...

    Ok, that last statement is completely diagnostic of your traction problem. You need to start at the beginning.

    Read this:

    Weart's Discovery of Global Warming.

    See, getting your head around Weart's book or the complete equivalent is a prerequisite for conducting useful discussion of the entire topic of AGW including the little fragment we're treating here. You can't do long division before you know how to add and subtract. You can't be a "skeptic" without knowing enough about the topic to avoid making blunders such as imagining that C02 entering the lake from hydrothermal vents will somehow affect the temperature of the lake in the same way C02 in the atmosphere at large helps to control the temperature of the lake.

    Really, do yourself a favor and read Weart. It'll take you some hours but for anybody who is inclined to spend time noodling around on Google Scholar-- such as yourself-- it's actually quite entertaining. And it's free, the web edition that is.
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  29. In terms of the comments on Kilimanjaro glaciers, I referenced Rwenzori glaciers because they are closer and to the wetter environment, do not lose mass significantly via evaporation. Thus, it is only temp and ppt. that matter more typical. The glaciers are also at a lower elevation which yields climate more in line with their surroundings.
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  30. Skepticstudent writes "Did they know about the thermal vents at the bottom of the lake in numerous locations before they wrote this article and spent all that time?"
    Actually the authors were well aware of geothermal activity in the lake. The issue is addressed in their comments here.

    >"... I'm attempting as do the majority of skeptics to show that there are many natural causes that add to the whole."
    Why do you and a majority of skeptics constantly assume that climate scientists are so incompetent as to be unaware of this fact? You are shown to be wrong time and time again yet you continue to make these assumptions.
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  31. Skepticalstudent...looks like you agree with Willis then who concludes in his article

    "My point is, the Tierney 2010 report is a study of the change in Lake Tanganyika surface temperature over time, which contains no measurements of the change in LST over time, and which has exactly three actual surface temperature measurements, which are poorly cited, are from different parts of the lake, and are all from 2003 …"

    Jessica, is he right?
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  32. Skepticstudent,

    Please try to bear in mind that you're essentially accusing real people whom you've never met of incompetence or worse. Basic human decency would require you to offer very strong evidence, even if the scientific method didn't.

    You should also bear in mind that as you labor to discredit every single study you don't like by dreaming up alternative explanations, you're creating a highly counterintuitive picture: An accumulation of data from all over the world that combine, coincidentally, to present the "illusion" of AGW. At some point, you have to understand that this is a far more improbable scenario than the one you're so desperate to debunk.
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  33. E at 79.

    I agree with the sentiment here -climate scientists are not incompetent or indeed involved in a conspiracy. But Jessica (at 30) admittted that again it is a case of blaming CO2 as the likely culprit.

    Hardly a convincing argument.
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  34. Another young student, Victor Langenberg’s 2008 thesis (Wageningen University) On the Limnology of Lake Tanganyika

    should make for an even more interesting comparison.
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    Moderator Response: Perhaps you're new here and don't know, if you provide a link to a paper or other resource at SkS you're expected to explain why you think it significant to the discussion.
  35. Si, it's worth thinking for a moment about what the implications would be if Tierney had -not- found a temperature signal resembling that found elsewhere. Really, take a moment to ponder that. Blame does not really enter into the equation.
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  36. Si, Willis appears to be committing a mistake that we (and especially folks at WUWT) should have left behind a long time ago.

    Willis is missing the forest while scrutinizing pine needles, conflating the significance of temperature trends w/ the importance of absolute accuracy of temperature measurements. The instant he latches onto problems with accurate calibrations is when he runs off the rails and misses the big picture. The fundamental objective here is to look for trends, not what exact temperature it was on a given day. Tierney necessarily needs to establish some sort of base temperature around which to hang the data she derived from her cores, but in point of fact that choice is not really important, it's the shape of the graph that is noteworthy.

    It's interesting to observe that comments on Willis at WUWT note the resemblance of Tierney's graph to others including of course Mann's famous example. They allude of course to incompetence, etc. because they have nothing else to say but fail to explain why so many sources of data should resemble one another in the shape they present when plotted.
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  37. Phila quotes doug_bostrom about my remark etc.
    "In reality, as Doug Bostrom says, if a problem of this type seems "obvious," there's a pretty good chance that it's not a problem at all."

    I see the article as directed to the less initiated (sort of an intro into this subject about the temperature of the largest lake in Africa). As such, it might be good to dispell these "obvious" issues and not make assumptions about what the reader is inclined to believe.

    Aside from this point, were'nt local temperature conditions suppose to be irrelevant in terms of proving or disproving global warming?
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  38. RSVP, you think Nature is a journal aimed at the layman? It's not. Publishing in Nature guarantees an audience beyond any narrow domain of research but that audience is well versed in the practice and conventions of scientific publication. As you know.

    Temperature trends are a key metric of climate behavior. As you well know.
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  39. #86

    "it might be good to dispell these "obvious" issues and not make assumptions about what the reader is inclined to believe."

    That sounds great in theory, but in practice it would be very hard to anticipate every single issue that a "skeptic" might seize on while looking for an excuse to downplay or disregard scientific findings.

    The problem isn't that Nature is making incorrect assumptions about its readership. The problem is that a small group of amateurs has decided to hold climate scientists to an impossibly high standard that most of them apply to no other field.

    Any science that tried to appease this degree of contrarianism would be doomed to stasis at best.
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  40. John the relevance of Langenberg to Tielney is that he is another young student studying the lake but comes to different conclusions - of course they are not attention headline grabbing ones but such is life.

    In brief (and not my summary but from Pat Moffat)

    • No evidence of increasing lake clarity as a result of secchi measurements since 1946
    • The interplay of stratification and plankton productivity are not “straightforward”
    • Challenges O’Reilly’s assumption on the correlation of wind and productivity -the highest production is on the end of the lake with the lowest winds
    • A strong caution using diatoms as the productivity proxy (it is one of two different lake modes)
    • No ability to link climate change to productivity changes
    • More productivity from river than allowed for in Nature Geopscience article
    • Externally derived nutrients control productivity for a quarter of the year
    • Strong indications of overfishing
    • No evidence of a climate and fishery production link
    • The current productivity of the lake is within the expected range
    • Doesn’t challenge recent temp increase but cites temperature records do not show a temperature rise in the last century
    • Phytoplankton chlorophylla seems to have not materially changed from the 1970s to 1990s
    • Disputes O’Reilly’s and Verbug’s claims of increased warming and decreased productivity
    • Rejects Verburgs contention that changes in phytoplankton biomass (biovolume), in dissolved silica and in transparency support the idea of declining productivity. A large part of the lakes production may be picocyanobacteria
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  41. doug. I dont think Willis makes the mistake you mention. He is having a critical look at Jessica's paper - thats what scientists do.

    I think he makes some interesting points and gets even better comments in the thread eg Hu McCulloch's- odo take a look.
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  42. Phila

    "The problem is that a small group of amateurs has decided to hold climate scientists to an impossibly high standard that most of them apply to no other field.

    Any science that tried to appease this degree of contrarianism would be doomed to stasis at best."

    I think not. The more critical we are the better the science will be. That papers get picked over and pulled apart (Teardown you call it in hardware) means that Climate Science will move out of the cosy club it has been and become a much more robust science. This site is helping in that by questioning your 'small group of amateurs' (I think Richard Lindzen et al might object to that description).
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  43. Si, you don't think Willis is swerving into misplaced concerns with absolute accuracy? Can you explain what he's writing about, if it's not absolute accuracy? Why are he and you, too, apparently so disturbed by by the relative paucity of calibration data?

    Regarding your later remark, the utility of criticism depends on its validity and ability to further progress. So far I've seen little evidence of that; Lindzen is about the best data point available but he appears to have become entirely fixated on a hypothesis that has proven unable to improve on others' work.
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  44. Thanks for the clarification (pun?) on Langenberg, Si. A lot of observations but apparently none to rebut Tierney's central finding, that of a temperature record closely resembling that produced by numerous other measurement methods from a diversity of other geographically dispersed situations.

    Now, one could say Tierney's wrong somehow, but that leaves hanging the question of why the record she's derived bears such an uncanny resemblance to so many others, which of course also mutually coincide.

    Any hypothesis to explain this resemblance should include a mechanism yielding such a set of coincident signals. We have that mechanism at hand, predicted by fundamental physics and apparently confirmed by a host of observations.

    At WUWT I read misplaced concern about data points as opposed to statistical lessons from data collections, innuendo about Mann, sophomoric remarks about "Hockey Teams" and the like but I see absolutely nothing that will coherently explain how Tierney's results are so closely congruent with what we expect to see and in fact have seen in numerous other data sets.

    So, no useful contribution, just a lot of "I doubt it" or elliptical departures from the objective of Tierney's work. No utility of the kind you refer to, Si, when you extol the virtues of the activities at WUWT and elsewhere.
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  45. Si >"The more critical we are the better the science will be."

    Yes, but true scientific criticism generally comes from other practicing scientists, especially those in related fields of study. This ensures that those employing the criticism are well versed in topics relevant to the field. If scientists tried to address all the criticisms of amateur skeptics, they would be spending all their time rehashing basic principles and never moving the science forward.

    For sure, there are legitimate scientists on the skeptic side (Lindzen being one), but their number is tiny compared to those accepting the mainstream position. It seems that an inordinate amount of criticism of AGW comes from amateurs who feel that their every issue and misunderstanding must be addressed before the science should be considered robust. I can't think of any scientific discipline that holds itself to such an impossible standard.

    In the end though, I think you are right that it makes the science more robust. In that regard, it is telling that the scientific consensus supporting AGW has only grown stronger in the face of this overwhelming scrutiny.
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  46. #91

    "I think not. The more critical we are the better the science will be. That papers get picked over and pulled apart...."

    Yes and no. If someone like Lindzen is critical, that's one thing. But if someone who doesn't understand the basic concepts of AGW is critical, and routinely mistakes lazy contrarian speculation for a new and improved form of "peer review," that's not really useful, IMO.

    I think it'd great to have a "more robust science," and I'm sure everyone here agrees with me. But if skeptics want to contribute to that result, they need to become conversant with the basic science and the rules that govern it, at the very least. You can't simply leapfrog over these requirements and present yourself as a climatologist's peer or inquisitor. What I object to is not the desire for democratization, but the assumption that there is or should be no entrance fee, in the form of doing one's [let's be civil, please!] homework.

    I'm sure you'd like astrophysics and virology to be more robust sciences too, but I suspect you don't spend much time instructing scientists in those fields on First Principles.
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  47. [let's be civil, please!]

    Sorry! That's what comes of not hitting "preview."

    Thanks for the gentle reminder.
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  48. [let's be civil, please!]

    Sorry! That's what comes of not hitting "preview."

    Always good to be reassured someone's actually reading all our blather. :-)
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  49. doug_bostrom at 11:52 AM, perhaps if we go back to the basics and look how the proxy was developed.
    A direct link was created between the deposits of biogenic silica (BSi) found in the core sample and lake temperatures.
    The lack of correlation for the charcoal obtained from the core was used to rule out rainfall as an influence on the rate of deposition.
    Other indicators as to whether the replenishment of nutrients from any of the many inflows or any part of the shoreline were excluded from consideration by the limited core samples taken that could have identified possible sources remote from the lake itself or activity close by.
    Logic dictates that if any material is being deposited in the sediments it must be replenished from somewhere unless it is in a constant decline, and if the rate of replenishment varies that would be reflected in the rate of deposition.

    If you haven't read this study referenced below you may find it interesting if read carefully, particularly the advice on site selection within the lake if undertaking paleoclimate reconstructions,
    the accepted methods they used to take multiple samples along transects,
    but in particular, I repeat, in particular, the extremely wide variation of the BSi content within the numerous samples collected.
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  50. Thanks johnd, that was indeed an interesting read.

    I'm unmoved by your speculations; Tierney's methodological explanation is vastly superior in actual detail compared to "maybe something went wrong with the samples."

    Besides which we still have the congruency to explain.
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