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Comments 118951 to 119000:

118951. PaulK at 11:53 AM on 21 May 2010
        There'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.
118952. michael sweet at 11:36 AM on 21 May 2010
        Unprecedented 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.
118953. PaulK at 10:51 AM on 21 May 2010
        There'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!
118954. Rogerthesurf at 09:53 AM on 21 May 2010
        Climate'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 Roger
        Response: "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 :-)
        
118955. Albatross at 09:44 AM on 21 May 2010
        Unprecedented 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.
118956. dhogaza at 09:20 AM on 21 May 2010
        Unprecedented 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.
118957. johnd at 08:56 AM on 21 May 2010
        Unprecedented 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.
118958. scaddenp at 08:33 AM on 21 May 2010
        Climate'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)
118959. Marcel Bökstedt at 08:23 AM on 21 May 2010
        Unprecedented 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.
118960. Berényi Péter at 07:52 AM on 21 May 2010
        Has 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?
118961. Doug Bostrom at 07:47 AM on 21 May 2010
        Climate's changed before
        Roger, I'm not spotting the tautology. Which part of the physics do you disagree with?
118962. Rogerthesurf at 07:25 AM on 21 May 2010
        Climate'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.
118963. Riccardo at 06:54 AM on 21 May 2010
        Has 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?
118964. Albatross at 06:41 AM on 21 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        I'd like to second Doug's comments at #32. Thank you Dr. Tierney.
118965. Doug Bostrom at 05:53 AM on 21 May 2010
        Unprecedented 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.
118966. jtierney at 05:47 AM on 21 May 2010
        Unprecedented 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
118967. embb at 05:26 AM on 21 May 2010
        Unprecedented 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 ?
118968. Albatross at 05:21 AM on 21 May 2010
        Unprecedented 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.
118969. embb at 04:38 AM on 21 May 2010
        Are 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?
118970. johnd at 04:14 AM on 21 May 2010
        Unprecedented 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.
118971. Marcel Bökstedt at 03:40 AM on 21 May 2010
        Unprecedented 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?
118972. mspelto at 02:03 AM on 21 May 2010
        Unprecedented 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.
118973. Berényi Péter at 01:52 AM on 21 May 2010
        Has 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).
118974. Philippe Chantreau at 01:49 AM on 21 May 2010
        Has 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.
118975. Phila at 01:39 AM on 21 May 2010
        Unprecedented 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.
118976. Philippe Chantreau at 01:38 AM on 21 May 2010
        Has 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).
118977. e at 01:31 AM on 21 May 2010
        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.
118978. Marcel Bökstedt at 00:55 AM on 21 May 2010
        Unprecedented 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.
118979. jtierney at 00:39 AM on 21 May 2010
        Unprecedented 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
118980. thpritch at 00:32 AM on 21 May 2010
        Unprecedented 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.
118981. Riccardo at 00:02 AM on 21 May 2010
        Has 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.
118982. tobyjoyce at 23:54 PM on 20 May 2010
        Unprecedented 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.
118983. dhogaza at 23:53 PM on 20 May 2010
        Unprecedented 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.
118984. dhogaza at 23:52 PM on 20 May 2010
        Unprecedented 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.
118985. Turboblocke at 23:31 PM on 20 May 2010
        Unprecedented 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.
118986. Ari Jokimäki at 23:10 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        #5 paulm: This might be good place to look for lake reconstructions: NOAA Paleoclimatology, and here's their lake reconstruction index.
118987. michael sweet at 23:10 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        CBDunkerson x2. This blog describes the effects of global warming. That does not mean that the authors of this paper think deforestation is not important. The effects of deforestation are additional anthropogenic caused changes. Most changes in large biological systems will have multiple causes. Determining how much is due to different causes is the interesting science. This paper claims warming is a major cause of the decline of fisheries in this lake and provides data to support their claim.
118988. CBDunkerson at 22:40 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        Lake sediment analysis seems to be becoming an increasingly common proxy for temperature reconstructions. Hopefully this means that future studies will have more extensive southern hemisphere data to draw upon. As to whether temperature or land use change has impacted the fish... well, the Tierney 2010 paper seems to show that temperature has consistently done so in the past. Therefor, it seems likely to be doing so now as well... but that doesn't preclude the land use issues from ALSO being part of the current problem.
118989. sylas at 21:20 PM on 20 May 2010
        Has the greenhouse effect been falsified?
        Berényi, you are right again. You currently my new best friend, and I really appreciate the editing work you are doing for me. D'oh. I was looking at the lines as being 20K separated, but of course it is 10K, and so the numbers in the post need to be fixed. I put this together in a bit of a rush before going on an overseas trip... and in fact I am posting this now from an airport hotel. As for the 80% transmittance, I think we may need to be a bit careful. There's a difference between the general mean over the whole planet and a specific spectrum observed at a certain time and place, which I am told was under clear sky conditions. But for the time being the worst error is with the numbers and I'll get that fixed first. What I am trying for here is something that is as straightforward as I can make it, suitable for a wide range of readers. I do appreciate there are all kinds of subtleties involved in obtaining surface temperatures with microwave brightness, but I did think these particular two spectra, which were taken simultaneously, gave one of the clearest direct observations of the greenhouse effect I have seen. I know that Tobin's team did take measurements over Barrow, but I am not 100% sure that this is from there. The diagram itself is not from a published paper, but from data that David Tobin provided to Grant Petty, and which he plotted for his text book. If you have concrete suggestions for better wording in any part of the essay, please go ahead and made the suggestions. You've been a great help! Sorry if I am a bit rushed over the next week or two, but I'll try and pop in here periodically while I am on the road.
118990. Arkadiusz Semczyszak at 21:06 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        1. "The deforestation that has occurred in Mt Kenya, Mau, Aberdare, Mt Elgon and Kaptagat forests has negatively affected watersheds." "Due to the loss of forest cover, the ability of water catchment areas to regulate run-off has been reduced, with subsequent flooding. The area under forest cover has rapidly diminished from 165,000 hectares in 1988 to 80,000 hectares in 2003." "The deforestation of the Mau Forest has continued unabated, Nuttal said, noting that charcoal burning and farming activities were the main causes of the destruction. An estimated 11,000 sq km of the forest have been affected by the destruction. Contrary to conventional wisdom, an estimated 62 percent of precipitation occurs over land as a result of evapotranspiration from lakes and wetlands and dense vegetation, particularly forests, which pump ground water into the sky ." Kenya's annual deforestation rate in 1990 - 2005: 12,000 ha / year (...) Does this anthropogenic pressure does not affect on the fish? 2. Palynological evidence of climate change and land degradation in the Lake Baringo area, Kenya, East Africa, since AD 1650, Lawrence M. Kiage and Kam-biu Liu, 2009, "The dry environment is punctuated by a succession of centennial- to decadal-scale wet and dry episodes, disjointed by SHARP TRANSITIONS, including two intense dry episodes that led to drying of the lake at ca. AD 1650 and AD 1720 which coincide with the Little Ice Age (LIA) period in Europe." It is worth noting, that Mann's team and other "hockey teams" - in their reconstructions - multi-proxy; not indicate significantly MWA and the LIA, or the difference between the current temperature (contra MWP) there is significantly greater, than in Tierney 2010 ...
118991. Berényi Péter at 20:48 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        Before concluding it is just another consequence of global climate processes induced by increasing atmospheric carbon dioxide levels, some reality check is advisable. Effects of Landscape Disturbance on Animal Communities in Lake Tanganyika, East Africa Simone R. Alin at al. Conservation Biology, pp. 1017-1033 Volume 13, No. 5, October 1999 Sediment inundation resulting from large scale watershed deforestation, soil erosion, municipal and industrial discharges, road building, high and ever increasing population density, refugee influx from war zones, etc. may have something to do with decreasing fish production. These local disturbances can even influence lake surface temperatures.
118992. Riccardo at 19:53 PM on 20 May 2010
        There's no empirical evidence
        PaulK, if the system reached the saturation level of the OLR any change in slope of the forcing, not a reduction, will produce a temporary rising/lowering of the OLR. More, any deviation from perfect linearity of the forcing will produce a trend in OLR as well. The only LW output from climate models i can remember right away is in Forster and Taylor 2006.
118993. Berényi Péter at 19:32 PM on 20 May 2010
        Has the greenhouse effect been falsified?
        Chris Ho-Stuart at Wednesday, 19 May, 2010 wrote: When you look down from aircraft at 20km altitude (Fig 1a), what is "seen" is the thermal radiation from Earth that gets out to that height. Some of that radiation comes from the surface. This is the parts of the spectrum that follow a line corresponding in the diagram to about 275K. No. The part of the spectrum in the atmospheric IR window (between 8 and 13 μm, i.e. wavenumber 770 and 1250 cm^-1) has an approximate temperature of 268 K (-5°C), not 275 K (+2°C), provided the dashed lines do stand for blackbody radiation of temperatures indicated by labels in the figure. A 7 centigrade difference is not negligible. However, not even all of this radiation is coming from the surface. As you can see, clear sky atmospheric transmittance in window is below 80% at all frequencies, variable. Therefore some of the IR window radiation is absorbed on its way up, thermalized on a different local temperature and re-emitted, quite possibly on frequencies outside the window. This is why determining actual surface temperature of the ice sheet below (near Barrow, Alaska) from IR window radiation can get quite tricky, even if emissivity spectra of ice and snow makes them almost perfect blackbodies in this frequency range. Anyway, an ice sheet surface temperature of 275 K as claimed is not possible.
118994. HumanityRules at 18:57 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        Thanks for the reply. it's just in previous discussions of paleoclimate reconstructions there has been a suggestion that they don't capture the most recent past including the dramatic past 30 years and generally miss the end of the blade of the hockey stick. My memory is that the blade on the Mann reconstruction only becomes greater than the natural variation of the past when you splice on the instrument record. Anyway, I discovered some further reading on the subject. There was a similar paper in Nature in 2003 Nature 2003 A comment by Willis W. Eschenbach Eschenbach comment And a reply to that by the original authors Reply to Eschenbach
118995. HumanityRules at 18:30 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        Sorry John I know you said no MWP here but everybody else is, and I have to follow the crowd. It's worth noting if Johns global MWP global image is from Mann 2009 then there is only one single data set for the whole of Africa on that reconstruction. My understanding of that Mann global is from the scarse data in the MWP they have assumed a La Nina type weather pattern and have filled in the large expanses of the globe that have no data. #4 Barry If there are 40-odd data sets covering teh MWP then very few (~6) cover the whole of the SH. John do you have any idea what date the sediment record would be measuring to? (i.e. does this technique capture the temperature of the past few decades?)
        Response: "I know you said no MWP here but everybody else is, and I have to follow the crowd"
        
        I lose control of the class all too easily :-(
        
        "do you have any idea what date the sediment record would be measuring to?"
        
        A close-up of their temperature reconstruction (in the paper, the Figure 1a inset) seems to indicate the data ends in the late 1980s (best guestimate from eyeballing the graph is 1988) but I can't find anything stating that date explicitly. Maybe it's in the supplementary material which I don't have my hands on right now.
        
118996. thefrogstar at 18:21 PM on 20 May 2010
        Has the greenhouse effect been falsified?
        .....but if it was so cold that the water vapor froze out of the atmosphere, then life might not have evolved, so the earth might still have a reducing atmosphere with lots of ammonia and methane which might warm the earth up so that life could evolve which....... !!!!! Is LOL the word?
118997. tobyjoyce at 18:11 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        @barry & sceptical student, Sorry to bang on about the Medieval Waming Period,but its seems to me to begin later in the Lake Tanganyika chart (more like 1100 than 950, which is usually considered the start of the European MWP), so it is offset from the European phenomenon - which is what John stated.
118998. Paul D at 18:02 PM on 20 May 2010
        Has the greenhouse effect been falsified?
        35 Monkhausen, re water vapour. There is a significant difference between water and CO2 though in the range of temperatures that exist on earth. That is water can rapidly change between gas, liquid and solid. CO2 doesn't. Hence it is more likely that CO2 will influence water, eg. more or less water vapour, depending on how much CO2 is in the atmosphere. Making water a feedback mechanism. Although water vapour may be a greenhouse gas, I think water in general and its relation to CO2 at earth temperatures gives a bigger and better 'picture'.
118999. Paul D at 17:50 PM on 20 May 2010
        Has the greenhouse effect been falsified?
        Thanks Chris @ 28. A nice and clear explanation.
119000. Arkadiusz Semczyszak at 17:47 PM on 20 May 2010
        Unprecedented Warming in Lake Tanganyika and its impact on humanity
        "... and that the recent anomalous warming is a response to anthropogenic greenhouse-gas forcing." East Africa is the least appropriate place is to prove similar assertions. 1st Over the past half century there has been unimaginable to the land-use change - deforestation. 2nd At this time there appeared a huge natural increase - the largest in the world and human history. "In addition to land use change, aerosol forcing in the NBL may play a role. In East Africa the common practice of burning biomass for warmth, cooking, and light, especially in the early evening, tends to fill the shallow NBL of these communities, where most weather stations are sited, with a visible layer of smoke. Additionally, the large smoke aerosols, smaller hygroscopic aerosols, and larger coated organic aerosols may readily swell when the humidity reaches 80% (common in East African evenings). In combination, these produce a nighttime pall that is characteristic of the underdeveloped world. Although the magnitude of aerosol forcing in East Africa is not known, model studies in Los Angeles, California, where the concentration of large thermally active aerosols is likely much smaller than East Africa, showed that the presence of aerosols accounted for an enhancement of nocturnal downwelling radiation of 13 W m~2 (Jacobson 1997). A recent study in India, where aerosol forcing may be similar to East Africa, attempted to account for their role and estimated a daily mean of downwelling radiation enhancement from aerosols of 6.5 to 8.2 W m^sup -2^ (Panicker et al. 2008.)" - Surface Temperature Variations in East Africa and Possible Causes, Journal of Climate 2009, Christy et. al. 3rd Although the final proposal, however, the work is valuable - makes clear MCA (which everyone noticed).

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