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johnd at 20:07 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
scaddenp at 14:51 PM and Jeff Freymueller at 15:09 PM, read carefully, I did not suggest doing the lab tests on site, merely considering the possibility that perhaps the coring equipment remained on site until results were known. What I saw was a big risk expending so much time, effort and money to return with only two small core samples. There was no fall back position if the cores were unable to be tested properly or more importantly they yielded conflicting or confusing results. The more cores, the lesser chance of such possibility, and if money is really tight then being penny wise can often end up being pound foolish. Simple really. It is different for someone digging in their own backyard, but if it requires travelling to a remote location on the other side of the world, and funding is so tight that there is only one chance, then it simply has to be done right. It leaves me wondering how many other such research projects have failed to see the light of day because the data collected was so bare bones that it was unable to be used. It would be those that fail that make funding even harder to get, not those that achieve the objectives. -
Riccardo at 19:54 PM on 21 May 2010There's no empirical evidence
PaulK, actually what you call the "Schwartz model" is just the standard energy balance equation, widely used even in the scientific litterature. I think that you are confusing the equation written for absolute temperature with the one for temperature anomaly. You'll find a step by step explanation in the page i linked before. Indeed, it should be clear from the solution given by Schwartz that he's not solving dT/dt ∝ F(t); after linearization the equation is instead
dΔT/dt ∝ F(t)−λΔT. My evaluation of the OLR comes from the assumption that the forcing is only due to an increased IR absorption which directly influences the OLR. A linear increasing forcing then comes from an exponential growth of CO2 concentration, given the aproximate but quite reasonable relation F=5.35*ln(C/Co) W/m2 where Co typically is the pre-industrial CO2 level. -
Lars Träger at 19:16 PM on 21 May 2010Why are there fewer weather stations and what's the effect?
re #8: I did - and I certainly noticed that some of the least densely populated areas of Europe (like parts of Spain and France, West Scotland and Southern Scandinavia and the islands in the North Sea and Baltic Sea) are red, while some densely populated areas (like the Mediterranean coast and that lone spot in the middle of England) are not red. Blaming it all on the UHI effect is clearly wrong. re #28 On the fraud issue: that kind of fraud (Missing trader fraud) has nothing to do with what is traded (as it has been done with just about anything that can be traded) - the fact that this story was picked up by the Skeptosphere falls fully in line with why it does what it does the way it does. -
Riccardo at 18:49 PM on 21 May 2010Has the greenhouse effect been falsified?
Berényi Péter, the one I evidenced before, to begin with. Beyond that, what we know is that the measurements in fig. 1 behave like basic absorption/emission in the atmosphere dictates, the spectra nicely follow what's expected they should do, they also match what can be calculated from MODTRANS code. You, instead, throw in the discussion strange theories on the thermalization based on a descriptive graph found on Wikipedia to conclude that either those cannot be real measurements or that some "undocumented trick" (fake data?) has been used. Astonishingly. -
HumanityRules at 17:27 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
It is great to see Jessica posting here. If you have more time to post I'd be interested in your thought on local/regional changes around the lake that may contribute to change. Your paper seems to put all change down to processes controlling global climate change which would leave little room for local changes having any affect. I've been trying to find an estimate on population change around the lake, with little success so assume it's impressive, and others have raised land use changes as a possible contributer to reduced productivity. I'd be interested in your thoughts? I guess another way of looking at this is any attempt to monitor and control local processes completely pointless giving the overarching control by global processes suggested by your paper? (Completely OT. I just came across this new paper on ocean heat content which has been a recent topic here. Authors include Josh Willis. Enjoy! http://www.nature.com/nature/journal/v465/n7296/pdf/nature09043.pdf) -
Doug Bostrom at 16:29 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Some folks would be well served to be more self-conscious about the rather paltry level of effort they're expending on this topic, versus that exerted by others. It's quite extraordinary how conspicuous is the difference. The reason why self-inflicted embarrassments of this kind matter is because most observers will find somebody sitting in their armchair lazily casting factually unsupported judgment on hard work, scrupulous attention to detail and articulate presentation of new facts performed by others quite unpersuasive. Enlightened self-interest suggests that more work is required in order to save face let alone sway opinion. Imitate Berényi if you want to follow an example of someone approaching genuine skepticism, which requires a substantial investment of time and energy in order to have any hope of being genuinely productive. The bar gets higher all the time, so expect to pedal harder and faster in order to keep up. -
Doug Bostrom at 16:10 PM on 21 May 2010Climate's changed before
Roger, you appear to be missing a lot of important information which I suspect is why you're not connecting the dots here with regard to the order of precedence of discovery leading to present conclusions about climate behavior. Theories and observations originally unrelated in both primary intellectual domain and chronological order led to our ability to understand gross climate behavior and subsequently to the notion of anthropogenic climate change. It's not a matter of imagining that we might change the climate and then hypothesizing mechanisms that might cause such to happen. You've got it quite backwards. I sincerely suggest you temporarily set aside your internally generated hypothesis of how AGW appeared on our collective radar and start from the beginning. Dr. Spencer Weart's Discovery of Global Warming. Weart's book begins from first principles in a number of different scientific domains and spells out pretty comprehensively how what we know of physics and earth sciences leads ineluctably to the conclusion that we can in fact change the climate all by ourselves. Really, you owe it to yourself to read Weart. If you're looking for -actual- gaps in our understanding of climate and how humans may change climate, his book is your best place to start. -
Jeff Freymueller at 15:09 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
#40 & #43. I missed the suggestion by johnd that you do the lab work on site. You might as well suggest doing the lab work on the moon. Even on a fully-equipped scientific drilling ship (like the Integrated Ocean Drilling Program ships), there are limits to what you can do on the shipboard labs. The limits of what lab work you can do in an African hotel room are far more severe. Jessica Tierney may check back in, but my guess is that you might not even dare split the core in the field for risk of losing everything. Get the samples, protect them like crazy, get them back to where you can do real work on them. -
scaddenp at 14:51 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Do the testing while still on site???? This lab work looks expensive and very unlikely that you could schedule it while still on site. You could write to the author and ask but I would suspect that there was some delay between getting core back to lab and getting all that analysis done. If my institute were doing it, you would wait months or longer. Consider the ice coring. With only one core, there is indeed all kind of questions you couldnt answer for sure till more coring had been done. However, demanding a comprehensive sampling program from the GISP or Summit programmes would have asking a lot. I dont see this is much different. -
Jeff Freymueller at 14:34 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
In almost every funded research project I have had, I have stretched funding to the limit to always collect more data in the field than originally proposed. And yet, sometimes I dearly wished I had collected a little bit more. But you have to keep the money to pay the graduate student, even when you might risk being able to pay your own salary. Funding is always tight, because in (probably) every field there are more good research proposals than there is money to fund them. So the funding agencies almost always dole out as little as they can to every project, to spread what they have around, and you get pretty close to the minimum possible to do your project. I have had projects where the mobilization cost was a depressingly large fraction of the total field cost, and there was nothing I could do about it -- what I had was what I had. All of that is a long way of saying that criticism of Tierney et al. for only having gotten two overlapping cores seems pretty ridiculous to me. I'm sure they got as much data as they possibly could with the funds that they had. And I think it would be more useful to get cores from some of the other rift valley lakes rather than trying to pepper Lake Tanganyika with more cores -- if the other lakes did not tell the same story then you would go back and do more systematic sampling. -
Bern at 14:01 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
johnd at 13:51pm on 21 May, 2010: Yes, you're right, the mobilisation costs might well have been a very large component of the total cost of obtaining the cores. However, given the scarcity of funds for many scientific investigations, it might be that there simply wasn't enough money to get more cores, when you consider extraction, storage, transport, and analysis costs. I'm inclined to agree with michael sweet at #37 - while it would have been nice to get a comprehensive set of data for this one lake, it might be better to spend additional funds to do similar investigations of other lakes through the southern hemisphere, to improve the coverage of climate data. -
johnd at 13:51 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
scaddenp at 13:11 PM, the reality is that the biggest expense would have been mobilising the equipment and personnel. The operating cost to obtain each additional core a lesser cost, lab time a relatively minor expense. The danger always is that after going to all the trouble to undertake the project, stopping after only taking 2 small cores is that if the cores are not usable or yield conflicting results, then all the time and expense has been totally wasted. On the other hand if the cores are tested whilst the equipment is still on site, is it right to stop just because part of each the first 2 cores gave the right answer. There is no basis on which to establish the level of confidence that a proper sampling regime would be designed to produce. -
scaddenp at 13:11 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Wow! And all the laboratory time is free? Considering how much is inferred from just one oil well I find this a bit precious. Undoubtedly more data would be better - it always is - but real world intrudes on our desires so we do what we can. Just regard this as one more brick among a great many others. Please suggest to your local politician that science needs more funding. I for one never have enough data and given price of oil wells, I am not likely to get it either. -
johnd at 13:01 PM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
michael sweet at 11:36 AM, I appreciate that more data means more time, effort and expense, however your estimate of years to obtain extra data seems unrealistic, I think days should be closer to the mark. Because I am aware of the difficulties in undertaking similar such work, I cannot help but wonder why after taking the trouble to mobilise equipment and personnel to such a location, why only take one or two cores each about 1.5 metres long when all the hard work has already been done? It would be interesting to see how long was spent getting mobilised and how long actually spent sampling. However, at the end of the day, irrespective of the reasons, the reliability, or the confidence that can be expressed in the results obtained is primarily a function of the sampling regime more so than the accuracy of any laboratory analysis or data processing. -
scaddenp at 12:20 PM on 21 May 2010Climate's changed before
Roger - where are you getting this idea from? Besides the papers that John's article points to you (especially Harries and Evans) you might consider your "previous warmings disprove this hypothesis". They do? How? Do you consider that fact that, say, more energy from sun earlier caused a warming as proof that GHG isnt warming us now when there is no extra energy from the sun? If you look at the IPCC WG1, chapter on paleoclimate you will see reference and outputs from numerous models that consider past forcings and compare with past temperature. The physical model that climate change is function of solar, albedo, GHG and aerosol works very well to explain past climate (eg see Benestad & Schmidt 2009) and that model also leads us to conclude that humans, especially through our emissions, are changing climate. Consider the scientific process involved too. A model is derived out of basic physics - at heart it is a heat balance based on conservation of energy. From the model come a lot of predictions about what we should be observing. The match of observations to prediction gives us confidence. We can also apply it to the past to see that previous climate change is accounted for within model (within the very considerable error bounds imposed by the uncertainties in past forcings and observations of climate). Because it is a physical model, not a statistical model, you can compare predictions for say a solar forcing to a GHG forcing (eg and especially stratospheric cooling). All in I would say that gives very considerable support to current climate theory. -
PaulK at 11:53 AM on 21 May 2010There's no empirical evidence
Riccardo, Thanks for the Forster and Taylor reference. I am still digesting, but it looks as though the GISS models along with all of the other models overestimate LW positive feedback and hence underestimate OLR in the observational period. The information here is not definitive, but sometimes if something looks like a duck and quacks like a duck... Thanks again. -
michael sweet at 11:36 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Johnd, I think you are asking for unrealistic amounts of data. As you point out the data from Lake Tanganyika are limited and do not provide 100% certainty. On the other hand, it takes an enormous amount of time and funds to obtain this data. If Dr. Tierney went back she would have to work for years to obtain a small improvement on the data. I think her time is better spent collecting data somewhere else. The Lake Tanganyika data is validated and supported by the data collected elsewhere. When we see a pattern of data from a variety of sources it validates all the data. Ten lakes that all have similar data sets are more informative than one lake extensively surveyed. No one would suggest making economic decisions about AGW based solely on this data. This data adds to the rest of the data on AGW to give compelling reasons to take action. -
PaulK at 10:51 AM on 21 May 2010There's no empirical evidence
Hi Riccardo, As promised, I have considered the Schwartz model in a little more detail and think I now understand where the confusion is arising. You need to consider carefully what the forcing term, F, actually means in the Schwartz 2007 paper, because I think it is misleading you (as it did me before I tried to reconcile my results with Schwartz). Consider Equation 6. The F term here is NOT equal to F(t) = Q-E. (If F = F(t)=constant, the temperature could not asymptote to a constant as t becomes large; temperature would continue to increase linearly with constant F(t). F(t) in reality must decrease to zero over time as equilibrium is restored.) It is clear from this, and also from the definition of climate sensitivity that the F in this equation is actually equal (only) to the instantaneous imposed forcing at time t = 0. Now consider Equation 11 for F = bt. Equation 11 is the solution of the convolution integral for Equation 6. In other words, it is the continuous summation in time of a series of Equation 6 terms in order to stack temperature changes. F = bt therefore can be thought of as the continuous stacking of NEW forcings. Or perhaps easier to visualize, d F/dt = b is the rate at which new forcings are added in time. Since the effect of the forcing added at time t1, say, has declined by tn, the actual net forcing at TOA at time tn is therefore NOT equal to F=b*tn. Once again F = bt is NOT equal to Q-E. In conclusion, your attempts to derive an expression for OLR were based on a misunderstanding of the F term, I believe. Your statement that a linearly increasing net forcing (or linearly decreasing OLR for constant TSI) corresponds to a geometric growth in CO2 is incorrect. However, it would be correct to say that a geometric growth in CO2 would give rise to a constant rate of addition of new forcings and a linearly increasing temperature at t>>tau. To highlight how different these statements are – note that the linearly increasing temperature implies a constant dH/dt i.e. a constant net forcing of Q-E even though the F term in the Schwartz model is linearly increasing! -
Rogerthesurf at 09:53 AM on 21 May 2010Climate's changed before
Phil and Doug, Thanks for your answers, please consider the opening statement to the answer of the question on this page. "If there's one thing that all sides of the climate debate can agree on, it's that climate has changed naturally in the past. Long before industrial times, the planet underwent many warming and cooling periods. This has led some to conclude that if global temperatures changed naturally in the past, long before SUVs and plasma TVs, nature must be the cause of current global warming. This conclusion is the opposite of peer-reviewed science has found. Our climate is governed by the following principle: when you add more heat to our climate, global temperatures rise." The above opening statement in the "explanation" as to why there were previous warmings (when there was no anthropogenic CO2) neatly sidesteps the question. The question, which is a very good one, is - "If there are previous warmings, why do we blame this one on CO2?" The answer is "Because an increase in CO2 which is a greenhouse gas, is the cause THIS TIME". So I am saying, where is the empirical proof of this cause. All that is in the explanation is a lot of theory which is not based on anything empirical, in fact like I have mentioned above, the explanations assume that the "Anthropogenic CO2 causes Global warming" hypothesis is fact when in actual fact there is no emperical support whatsoever. In fact previous warmings disprove the hypothesis. Hope you can understand my point. This comment and your answers are posted on http://www.globalwarmingsupporter.wordpress.com for the benefit of my readers. Cheers RogerResponse: "where is the empirical proof of this cause?"
There are multiple lines of empirical evidence that CO2 is causing warming. We have a number of different satellites from NASA and Japan finding less infrared radiation escaping to space at CO2 wavelengths (Harries 2001, Griggs 2004, Chen 2007). Surface measurements from thousands of ground based stations are also finding more infrared radiation returning back to the Earth's surface (Wang 2009). A close examination of the infrared spectrum returning back to Earth finds more infrared radiation at CO2 wavelengths (Evans 2006).
So we have independent measurements finding the same answer - which is consistent with lab measurements and simulations of an increased greenhouse effect caused by rising CO2.
If you could post this answer on your blog, would be much appreciated :-) -
Albatross at 09:44 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Marcel @34 "which are melting but appearantly not beacuse of AGW, but because of deforestation." Marcel, this is OT, but I take issue with your argument. It has been hypothesized that deforestation has been responsible for the glaciers' retreat on Kili. However, as far as I know, it has not been demonstrated that the reduction in ET associated with the deforestation has actually affected precipitation on the summit. People tend to forget that changes in moisture flux ET into the boundary layer, does not affect moisture in the free atmosphere, certainly not the mid-troposphere (the summit is almost 6000 m above MSL)unless it affects convective precipitation. And even then, by how much would it reduce the precipitation on the summit, if at all? Impacts on precipitation on the mountain's slopes (arising predominantly from orographic lift/upslope flow) is far more likely to be associated with reduction in ET. Dr. Pierrehumbert has addressed the deforestation hypothesis at RC and found it to be "egregious" and to have rather dubious origins. Also, the deforestation/drying hypothesis does not explain why the glaciers on the summit have managed to survive much drier periods in the past 11 000 years. One way to explore deforestation hypothesis would be to look at TRMM and NDVI data, as well as to examine changes in the large-scale circulation patterns (e.g., monsoon) arising from changes in SSTs from AGW, for example. Alas, those data are for a relatively short period, but may also be useful for conducting sensitivity studies using a model. Anyhow, just as it is perhaps an exaggeration to claim that AGW is solely responsible for the demise of the Kili glaciers, the same holds true for claiming that deforestation explains it all. Something definitely unprecedented in the glaciers' history is occurring in the last 100 years, and especially the last 30 years. Truth is that there are probably several factors at play, but that does not preclude or exclude AGW from being one of them. -
dhogaza at 09:20 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
I third Doug's comment at #32, thanks for taking the time to show up, jtierney. -
johnd at 08:56 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
jtierney at 05:47 AM, I thank you also for coming here and appreciate such a prompt reply. The reason I am interested in this particular aspect is because I do know about the difficulties involved in getting core and other samples, often in remote locations with improvised equipment, and always the temptation to take shortcuts when the going gets tough. But I also appreciate how crucial it is to get sufficient viable samples to ensure they are a fair representation of the area or object being studied because individual samples can wildly vary. Relying on just one sample in the natural world simply because it displays expected results can more often be a trap rather than early confirmation. For me, the sampling is always of more importance than the analysis of the sample, and the place where margins of error and confidence levels are determined. For a lake covering about 700km by 50km with a number of major and minor inflows and outflows, one complete or perhaps two part core samples seem simply nowhere near adequate to draw conclusions that are required to fall within small margins of error. Depending on the location, a single core sample could quite possibly provide results relevant to a region remote from the lake, the sediment transported by a river inflow. These views may or may not be relevant for this particular field of study, but they are certainly relevant to other areas involving the study of the natural world where it is vital to compile an accurate assessment before any conclusions are reached or decisions are made that individually are of far less importance than the issue of climate change. -
scaddenp at 08:33 AM on 21 May 2010Climate's changed before
Roger, what exactly in the theory of climate that underlies the above that you are objecting to? That, when you add more heat to our climate, global temperatures rise? That CO2 is a greenhouse gas? That greenhouse effect is real? These questions of climate physics are better addressed on other threads. For past climate, it is better to realise that it is primarily where models can be tested and constrained. Phil (also from NZ) -
Marcel Bökstedt at 08:23 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Jessica Tierney> Yes, I see the argument. The present warming of the lake is unprecedented, so it should be the effect of unprecedented causes. One such unprecedented cause is global warming, so therefore it is a likely suspect. Still, I think that from the data given, other effects of industrial society could play a role. One has to be careful. Remeber the snows of Kilimanjaro, which are melting but appearantly not beacuse of AGW, but because of deforestation. I looked at the supplementary material, and I'm kind of mystified by the "reversed age" in core KH1. Is it just that we are close to the limits of the C14 method, or could there have been some mixing of layers? Anyhow, I congratulate you and your coworkers on making an interesting contribution. -
Berényi Péter at 07:52 AM on 21 May 2010Has the greenhouse effect been falsified?
#47 Riccardo at 06:54 AM on 21 May, 2010 you started with a false premise Which one do you mean? -
Doug Bostrom at 07:47 AM on 21 May 2010Climate's changed before
Roger, I'm not spotting the tautology. Which part of the physics do you disagree with? -
Rogerthesurf at 07:25 AM on 21 May 2010Climate's changed before
"71.Rogerthesurf at 12:52 PM on 8 April, 2010 "What does past climate change tell us about global warming?" In case you dont know it, your explanation uses the AGW theory to explain the question when the question is really asking for some proof of the AGW theory. Cheers Roger http://www.rogerfromnewzealand.wordpress.com 72.doug_bostrom at 13:53 PM on 8 April, 2010 Rogerthesurf, you'd do better to explain yourself. Failing that, presumably you won't care if your post is deleted? " Sorry your reply did not show up on my "My Comments" page. Thank you for editing my comment (not) However my point is simple. Correct me if I am wrong, but at no point does your explanation discuss the validity of the "Anthropogenic CO2 causes Global Warming" hypothesis. Instead your host of explanations which are all based on the assumption that it (the above hypothesis) is fact, which actually it is not fact but as yet simply an unproven hypothesis. Therefore all your explanations are no better than this unproven hypothesis. I trust that is clear. Cheers Roger I also always post my comments and replies on my other site http://globalwarmingsupporter.wordpress.com where my readers can evaluate my questions and your answers. Check under your url and post title. -
Riccardo at 06:54 AM on 21 May 2010Has the greenhouse effect been falsified?
Berényi Péter, "Fig. 1 can not be produced by actual measurement or if it was, what is shown is a scaled up version of values measured. Undocumented tricks like this are not helpful." Well, you started with a false premise and arrived to the wrong conclusion, no surprise. And to cast unsupported doubts is not helpful. Didn't you notice any difference between the data shown here and the one you linked to? The transmittance is zero above 14 μm and below 8 μm. Is this an undocumented trick as well? -
Albatross at 06:41 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
I'd like to second Doug's comments at #32. Thank you Dr. Tierney. -
Doug Bostrom at 05:53 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
A sincere Thank You to Dr. Tierney for putting in a appearance here. To be treated to such detailed attention from the first author of this paper is remarkable gift. I hope everybody here appreciates our good fortune whatever quibbles some of us may have with the paper in question. -
jtierney at 05:47 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Hi, #27 and #28, thanks for writing good questions. First #27, how do we know that the local temp. rise in East Africa is due to global warming? Well, in part that was why we chose in our study to reconstruct the "history" of temperature in this region by using a proxy. Instrumental data from the Lake already have shown that the lake is warming (cf. O'Reilly et al., 2003 Nature and Verburg et al., 2003 Science) but what we didn't know before now was whether such warm temperatures could happen by chance or in response to natural climate forcing vis a vis AGW. That's because the instrumental data are sparse, and only go back to 1913. What we we've shown now with our new proxy data is that we don't see 26 degrees occurring naturally in the lake in the recent past, and in fact on my website I show that it is likely that we haven't seen that the lake is as hot as it is now since 6000 years before present! So that suggests that something is happening right now that is distinctly different. We know that the planet is warming, and that humans are causing it, so it is very likely that that is the culprit. In terms of the match between NH temps and our record, you are right that they are different in places. I think the post above re: the temp. distribution during the MWP illustrates that there is a lot of spatial differences in temp. change in the past. In other words, you might not expect a perfect match between our local record and the global average. But BOTH records do show the same trend during the past 150 years - a big warming. #28: Great question, and in an ideal world we would have sediment cores from a lot of locations in the lake. However, as you can imagine is it pretty difficult to get these cores...we are operating in 100s of meters of water out of modified shipping or fishing boats, in a very remote place of the world! Again, as I mentioned in response to #27, previously published work shows that instrumental data from the lake show a warming. These data are plotted in the inset which you can see on my website. They are from farther down the water column, so the warming is not as big as at the surface, but the trends are clear. To the extent that our proxy data agree very well with these water temperature trends as well as air temperature trends, we trust that our cores are doing their job. btw, the reason why we "spliced" the core records was because only MC1 had sediment coming up to present; the top of KH1 was not recovered by our corer. So we had to combine two cores and overlap to get a full record. Hope that helps -Jessica -
embb at 05:26 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
If I understand the argumentation correctly the people living around the lake are not responsible for the environmental degradation as "these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery." No overfishing, deforestation or any other local environmental effects play a decisive role - the damage comes from AGW. It also follows that aside from fighting the CO2 emissions globally there is no point in starting local environmental actions, as they are clearly pointless against AGW. As truths go this must be really convenient. I wonder if it is also true ? -
Albatross at 05:21 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
This is an interesting study and the results are, IMO, concerning. Some here seem to be making some rather odd critique of the paper and analysis. For example, it is odd to make unsubstantiated statements that the analysis is compromised because alleged logging in the area (and other land use changes) may have affected the lake temperatures or sediment deposition. Scientists who work with these sediment data are, of course, very well aware of the processes which both generate and affect the sediments. The sampling site at Lake Tanganyika is located near 6 degrees south, so it is debatable whether either the N or S hemisphere temperature reconstructions are appropriate. They used the N. Hemi., and that is probably acceptable given the close proximity of the site to the equator and the fact that the N. Hemi reconstructions are more reliable. Anyhow, that critique in no way refute this work or calls it into question and is really just a red herring being used by Eschenbach (and Eschenbach is definitely not an expert on lake sediments). If there were a proxy dataset close by, then that could perhaps have been used. Someone asked when their reconstruction ended; their last sampling point corresponds to 1996. What some people seem to be ignoring is the significance of cumulative impacts. The lake is a critical food source and is subject to numerous stresses, including over fishing, degradation of water quality from anthro activities etc. Now a new stress has been added to the system, rapid warming of water temperatures. Indications are that this warming is associated with the energy imbalance arising from higher levels of GHGs from human activities. Claiming that deforestation in the region is somehow warming LSTs of the second largest lake (by volume) on the planet by 2 C since 1900 is a huge reach and, as with many contrarian arguments, unsupported. The authors did compare the TSI and LST records and found that while in the past they were in fairly good agreement, they note that "...TSI variability clearly does not explain the dramatic twentieth-century increase in LST..". The fish have adapted to conditions in the lake, and cannot simply move on to more favourable habitat. The authors note that "our data demonstrated that the LST and primary productivity are are closely related in both the pre-anthropogenic and anthropogenic eras, confirming that warm surface temperatures increase the degree of stratification within Lake Taganyika and reduce primary productivity. Apart from fishing intensity, the present decline in primary productivity is likely to impact the clupeid fishery, with potential dire implications for the communities". So yes, other factors may be affecting productivity and lake temperatures, but they alone do not explain the dramatic increase in temperatures observed since 1900. Eschenbach and other critics are clearly grasping at straws and trying to detract from yet more evidence of the detrimental impacts of the enhanced greenhouse effect. Colour me unsurprised. -
embb at 04:38 AM on 21 May 2010Are we too stupid?
Jacob, you do not answer my question sohere it is again: How is this going to look like in real life: WTO-consistent border adjustment mechanism so that there won't be any "carbon leakage" of companies manufacturing things overseas in countries that don't manage their emissions. Imports from those countries will have to pay a fee at the border. Starting next year, say, the US will raise customs tax equivalent to the carbon tax on every product coming from a country that does not have an equivalent tax? Yes/no? Any thoughts you have on the impact of such a tax on the world economy? -
johnd at 04:14 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
jtierney at 00:39 AM, I visited your website and I notice from the calibration data in the supplemental information that it appears only two core samples were mentioned, MC1 and KH1, and then only part of each were combined to provide the one set of data. Were these core samples the only ones taken, and if so, how confident are you that they are truly representative of the lake as a whole, especially given that a portion of each had to be combined, and the anomalies at the bottom of KH1? If more than these two core samples were taken, why were the others discarded, and why was only a portion used of each of the two that were analysed? It is one thing to look for consistency within one sample, but it is more important to ensure that the sample used is truly representative of the subject being analysed and that confidence level can only be attained through multiple sampling. -
Marcel Bökstedt at 03:40 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
J Tierney> Hey you! It's really great that you take the time to visit us and comment on our attempts to discuss your article. e> Yes, I had missed that sentence in the introduction, they actually do state that the rise in local temperature is due to anthropogenic global warming. In the text of the article the formulation is a little weaker. They write that "the dramatic twentieth-century increase in lake surface water temperature, as global temperatures, is probably a response to greenhouse-gas forcing." The main argument for this is a diagram comparing the reconstructed local temperatures to North Hemisphere anomalies, but I don't see that diagram as a very close fit. Maybe I don't understand how the color coding works in the diagram. Anyhow, there is no statistical analysis. It is true that global temperature rises through the last century (almost certainly to a large extent due to AGW, but that is not the subject of this post), and it is also true that local temperatures rises in the same period. The part where I feel that the argument is not completely convincing is in the link between global and local temperature, that is, do we know that the local unprecedented rise in temperature is caused by AGW? -
mspelto at 02:03 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
The warmth of Lake Tanganyika parallels the demise of the glaciers in the nearby Rwenzori Mountains , Mountians of the Moon. Which have lost more than 75% of their area in the last century. -
Berényi Péter at 01:52 AM on 21 May 2010Has the greenhouse effect been falsified?
#44 sylas at 21:20 PM on 20 May, 2010 You currently my new best friend You are welcome :) As for the 80% transmittance, I think we may need to be a bit careful I think the atmospheric transmittance spectrum is for clear sky conditions. It can't be a global average, since about half the skies are covered by clouds at any moment and they are opaque to IR (zero transmittance). However, it is far from being opaque in the mid IR window (optical depth ~0.22). Still, Fig. 1 (a) has a problem. Using Planck's formula for blackbody radiation
with ν = 100cκ (c is the speed of light, κ is wavenumber in cm-1) at 260 K peak of spectral radiance is found at 510 cm-1 to be 100 mW m-2 sr-1 cm indeed as shown by the second dashed line from above in Fig. 1 (a).
On the other hand, since IR transmittance in window is ~80%, spectral radiance coming from the ice sheet surface and measured at an altitude of 20 km can not be proper blackbody radiation, it must be an attenuated version of it. In other words the surface is seen as a grey body from there with emittance around 0.8 even if the surface itself is a close approximation of a black body in this frequency range. This must be so as in the stopband atmospheric absorptivity is orders of magnitude higher than in the window, therefore according to Kirchoff's law, almost all of the absorbed radiation after having got thermalized, is re-emitted outside the window.
It means the radiance curve in Fig. 1 can not be produced by actual measurement or if it was, what is shown is a scaled up version of values measured. Undocumented tricks like this are not helpful.
BTW, there are some actual IR transmission data for two observation sites (Cerro Pachon, 2700 m and Mauna Kea, 4200 m). It looks like at high altitudes with low atmospheric moisture IR windows get quite transparent. However, Barrow, Alaska is at sea level (elevation 3 m).
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Philippe Chantreau at 01:49 AM on 21 May 2010Has Arctic sea ice returned to normal?
And Robhon, to answer your question @52, the folks at WUWT are probably not being totally disingenuous, at least not all of them. Some genuinely do not realize that there is no sunshine up there during winter time. Nofreewind's complete lack of comprehension of your question and his ensuing post, talking about other things, should give you a clue. -
Phila at 01:39 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
#22 Marcel Bökstedt "This could be due to global warming, but in principle it could also be due to other factors. Bérenyi Péter bring up deforestation, that is certainly an alternative to consider." AGW and "other factors" are not mutually exclusive, of course. -
Philippe Chantreau at 01:38 AM on 21 May 2010Has Arctic sea ice returned to normal?
Checking again NSIDC today, it seems the recent slope has persisted and extent is now below the 2007 extent, over 2 standard deviations below average. That makes it a rather fast spring melt and it interestingly correlates with M. Pelto comment on this spring's fast snow melt. Anyone claiming that Arctic sea ice has returned to normal needs to have his/her head examined (and not by a blog scientist). -
Unprecedented Warming in Lake Tanganyika and its impact on humanity
Marcel writes "The article in question seems to establish that a rise in the local temperature of lake Tanganyika leads to a drop in biological productivity. It does not really discuss whether the local warming is related to global warming." Actually that's exactly what it does. From the abstract: "We conclude that these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery." They conclude this based on close correlations between lake surface temperatures and global temperatures over the last 1500 years. -
Marcel Bökstedt at 00:55 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
The article in question seems to establish that a rise in the local temperature of lake Tanganyika leads to a drop in biological productivity. It does not really discuss whether the local warming is related to global warming. Even in the majority view, the relation is not so simple : There is supposed to have been local warming during the "Medieval warm period" but no global warming. Also, the local warming at Tanganyika is estimated by Tierney etc. to about 2 degrees from 1860-1990, much more than the usual estimates of global warming during the same period. In addition to this, the paper argues that the local warming during the last century has been unprecedented. This could be due to global warming, but in principle it could also be due to other factors. Bérenyi Péter bring up deforestation, that is certainly an alternative to consider. -
jtierney at 00:39 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Hi Skeptical Science, thank you for your excellent post on our research! Brief comment about Willis' critique (Willis as many readers know is a climate change denialist). We did indeed calibrate our proxy, and the calibration equation and data are available in the supplemental information which Willis himself provides a link to. For more info. on some of the common misunderstandings of our work, please visit the page on my website: Lake Tanganyika Warming -
thpritch at 00:32 AM on 21 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
I find it interesting that the two trend lines showing a decrease in surface air temperatures both stop at 1975 when all the actual recorded temperatures start to show a significant positive overall slope. I will concede however that the Tieney proxy lineis not accurately reflecting the temperature trends for the 1950-1975 time period probably due to some other factor affecting that proxy data. But after 1975, the proxy data seems to generally follow the rise in surface temperatures actually being recorded. Again, it is not an exact match but that is likely due to the contribution of whatever factor(s) was throwing of the 1950-1975 data. -
Riccardo at 00:02 AM on 21 May 2010Has the greenhouse effect been falsified?
sylas, we definitely need to be carefull before claiming something based on a graph which we do not know what's showing, as Berényi Péter did. Indeed, although the overall behaviour is similar in all the spectra one can find over the internet, typically they are just to illustrate the general behaviour, not intended for quantitative analysis. Here's an exaple of two spectra from the same site, one shows 90% trasmittance, the other 100%. But there's one more fundamental error that Berényi Péter did. He apparently thinks that there's a direct relation between transmittance level and temperature. Even without other light extintion mechanisms (e.g. scattering), there's no such relation except in the saturated part of the spectrum. Indeed in the intermediate cases scientists talk about brightness temperature, not temperature alone. Then, i find your claims in the context of the general description perfectly valid. -
tobyjoyce at 23:54 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Willis Eschenbach has posted a critique of the paper at WUWT, of which the above is the centrepiece.
Bujumbura and Mbala are two weather stations on the lake, and the chart sows the air temperature. he therefore attacks the statement "The surface temp. tracks with the air temperature over the last half-century". However, WE conveniently takes the "last half-century" back to 1950.
His other criticisms may have more merit: showing a comparison with the Northern Hemisphere, rather than the Southern, since the lake is in the souther hemisphere.
He also claims the numbers disagree with a paper of the same authors published in 2008.
Another criticism which I do not understand is "not calibrating their proxy."
"It turns out that they used a proxy called TEX86, which has been used in other studies. But how did they calibrate the proxy to the lake surface temperature (which they call “LST”)?
Well … they didn’t calibrate it. In their theory, no calibration is needed. However, that seems like a very problematic assumption, as there are always confounding factors for proxies that mean that they need to be calibrated to the instrumental record. Some of these factors are listed in their Supplementary Information."
On balance, I don;t think any of these stands up, except maybe for the last one. He did not mention the decline in productivity of the lake.
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dhogaza at 23:53 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Oh, that should be "described" species - there are undoubtably more. The lake is big, as was pointed out above by someone. -
dhogaza at 23:52 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
This lake also has the most diverse cichlid population in the world, biological diversity which is at risk. Here's a chart showing a single genera: http://www.uni-graz.at/~sefck/Lake.jpg and there are something like 40 genera and 150 cichlid species endemic to the lake. -
Turboblocke at 23:31 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Surely land change uses etc are irrelevent for the surface temperature of a lake that's nearly 700km long and 50 wide? Looking at it on Google Earth, it doesn't seem to be densely surrounded by habitation.
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