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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. -
Ari Jokimäki at 23:10 PM on 20 May 2010Unprecedented 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. -
michael sweet at 23:10 PM on 20 May 2010Unprecedented 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. -
CBDunkerson at 22:40 PM on 20 May 2010Unprecedented 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. -
sylas at 21:20 PM on 20 May 2010Has 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. -
Arkadiusz Semczyszak at 21:06 PM on 20 May 2010Unprecedented 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 ... -
Berényi Péter at 20:48 PM on 20 May 2010Unprecedented 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. -
Riccardo at 19:53 PM on 20 May 2010There'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. -
Berényi Péter at 19:32 PM on 20 May 2010Has 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.
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HumanityRules at 18:57 PM on 20 May 2010Unprecedented 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 -
HumanityRules at 18:30 PM on 20 May 2010Unprecedented 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. -
thefrogstar at 18:21 PM on 20 May 2010Has 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? -
tobyjoyce at 18:11 PM on 20 May 2010Unprecedented 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. -
Paul D at 18:02 PM on 20 May 2010Has 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'. -
Paul D at 17:50 PM on 20 May 2010Has the greenhouse effect been falsified?
Thanks Chris @ 28. A nice and clear explanation. -
Arkadiusz Semczyszak at 17:47 PM on 20 May 2010Unprecedented 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). -
MarkR at 17:42 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Skepticstudent; it may be another case of how many graphs you're shown are cut off in 1950. If you cut the Tanganyika graph off in 1950 it looks like the MWP was comparably warm there, which is a reasonably common outcome. Like barry, I'm interested in how you've concluded that a) it was warmer on a global average and b) it was probably therefore warmer everywhere than today, when most composites say different. -
thefrogstar at 17:20 PM on 20 May 2010The significance of the CO2 lag
fydijkstra (#29) Your first paragraph: Good point, I think. I think it helps illustrate some of the problems with feedback-effects in what I would loosely call "self-referencing systems" By way of a verbal analogy (and with no political point), this reminds me of "strong market" Economists who can be very fond of heavy-duty mathematics without emphasizing some of the pitfalls. Strong- (or "efficient")-market theories hold that the movements of markets are forward-looking, efficiently and rapidly incorporating all important information as it becomes available. So (in the absence of earthquakes etc) stock-market prices today already efficiently anticipate the future, which is why individuals can't "beat the market". And there are some good reasons to believe this, not least because central bankers effectively tell banks what the next interest-rate movement will be, (even though they won't tell the rest of us.) But as soon as you ask the question "So do efficient-markets anticipate the actions of the market itself ?" then it rapidly appears that you may have stumbled on a paradox, and that "The Emperor has no Clothes". -
Paul Magnus at 17:14 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
Thought the MWP was only in Europe? Do we have any other lake reconstructions? That would be interesting? -
barry1487 at 17:12 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
skepticstudent, Can you not see a warming bump around the MWP period in that time series? It looks to be in roughly the right place - 1100 to 1400 AD. From where do you get the notion that medieval temps were warmer than today's? The mainstream conclusion is that this is unlikely (though not absolutely certain) - for the Northern Hemisphere. How does a 'skeptic' arrive at a certain opinion on the MWP? You may be familiar with this map from skeptical webssites, entitled "The Medieval Warm Period - A Global Phenomenon". However, an examination of the time series therein shows that MWP for different regions are offset by as much as 500 years. From the 40-odd data sets, we see that MWP was a regional event, with the timing quite different in different parts of the world. Crunching the numbers we get an MWP from ~950 to ~1250 with a lower amplitude than that suggested by certain data sets. Paleoreconstructions of the period rest on anywhere between ~20 to hundreds of data sets. What study/s gives you absolute confidence that "the temps then were much higher", and how do you manage to hold that opinion when the weight of evidence (the great majority of scientific studies) posit alternatively? http://agwobserver.wordpress.com/2009/09/08/papers-on-the-mwp-as-global-event/ Note: the IPCC considers MWP for the Northern Hemisphere, assessing that there is not enough data for a global analysis with much statistical significance. Lake Tanganyika is just below the equator. -
skepticstudent at 16:38 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
I am kind of curious that even though their graph looks like it has no corellation to the medevil warming period like a certain other chart mentioned in comments 1 and 2. How do they correlate no high temperatures in the lake at a time when the temperatures were considerably warmer than they are now? Shouldn't the left of that chart be much higher than it is since the temps then were much higher than the right side of the chart? I know I'm not a scientist but something just seems wierd. I suppose one could stretch the hypothesis by saying that it was cooler regionally in this particular spot than the rest of the known world.Response: It's an interesting question and in fact, the paper does compare the Lake Surface Temperature (LST) to the Northern Hemisphere temperature reconstruction. I left that part of the paper out of my blog post for reasons of brevity (okay, I was lazy, are you happy?!). Here's the graph with the black area showing the LST and the coloured range showing the Northern Hemisphere 'hockey stick':
Note that while certain regions during the Medieval Warm Period were hotter than current condition, the global average was cooler than today. Here's a temperature map of the Medieval Warm Period. Temperatures are relative to the 1961 to 1990 period. So if a region is yellow, orange or red, it's warmer than the 1961 to 1990 period. There are various regions that were warmer than the late 20th Century. But there were other regions that were cooler also, denoted by the blue regions.
I suggest discussions of the Medieval Warm Period are best conducted at the Medieval Warm Period page. -
Bern at 16:23 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
doug_bostrom: yes, it does look somewhat familiar... would that be an MCA in the middle and a (shock!) 'hockey stick blade' at the right? :-D It's interesting, though, to see more papers like this coming out, where scientists are tying reconstructions of temperature to other data types, and working out the potential effects of temperature change. -
HumanityRules at 16:22 PM on 20 May 2010Has the greenhouse effect been falsified?
33.chris Thanks Chris very clear, I think it was the word "required" that's throwing me. I'm going to say I get it now. -
Doug Bostrom at 15:20 PM on 20 May 2010Unprecedented Warming in Lake Tanganyika and its impact on humanity
"Salmon then feed off the algae." I'm thinking you meant sardines there, John! That graph has an eerily familiar shape to it.Moderator Response: Oops, thanks for spotting that. Fixed. -
scaddenp at 14:58 PM on 20 May 2010Has the greenhouse effect been falsified?
Actually this has been both discussed and calculated. See the detail with links to calculation and code at: Calculating the greenhouse effect Short answer - it would be very cold without water. Around 20 deg colder. -
shawnhet at 13:46 PM on 20 May 2010The significance of the CO2 lag
A couple of points to keep in mind here: CO2's feedback effect is very small, compared, say to the hypothetical water vapor feedback. A degree C increase leads to a release of ~10ppmv of CO2, which by the logarithmic relationship of CO2 and temperature increases the temperature by ~.1 times the sensitivity. Ultimately, this means that we can't use the CO2 time lag to diagnose sensitivity in *either* direction(as either positive or negative). Secondly, it is pretty hard to take the 20ppmv/deg C number seriously, when just by eyeballing the graph of CO2 and temps, we see that there the actual relationship is more like 10ppmv/deg. C. If, in fact, the 20ppmv number were the correct one, we would be forced to conclude that the correct pre-industrial value should be approximately 340ppmv CO2(ie the depths of the ice age had temps 8C lower at a CO2 concentration of ~180ppmv if each degree of warming released 20 parts of CO2, the 1600s should've had an atmospheric CO2 level of ~340ppmv. Cheers, :) -
kdkd at 11:31 AM on 20 May 2010There is no consensus
Poptech #215 I think you mistake science for some kind of democratic process. Generally we weight the opinions of scientists on a topic as to whether they have a publication record in good quality peer reviewed journals related to the topic on which they have an opinion. To illustrate why your democratic approach is faulty, consider biological sciences. Ecology and molecular biology are both important fields. Ecologists use a lot of molecular biology technologies, but are not domain experts in the subject - they follow procedures rather than have a deep understanding of the underlying science. Molecular biologists can create organisms that alter ecosystems, but with a small number of exceptions, their education in ecology is almost non-existant. As a result it would be very wrong to use the opinion of a molecular biologist on the topic of ecology because they don't know anything about it. I reckon the same is very likely for the people you describe as scientists who contribted to the petition. It has very little meaning as far as the science goes, it's a political action which is entirely unrelated. -
Joe Blog at 10:18 AM on 20 May 2010Has the greenhouse effect been falsified?
monckhausen Well, technically if yer look at it extremely simply, if all the water vapor was stripped outta the atmosphere the average temp would be below freezing... but then again yah would have a reduction in clouds... and you would also have a massive albedo change of the globe... simple put, its not a simple question, with a simple answer. -
scaddenp at 09:35 AM on 20 May 2010Climate Change and the Integrity of Science: a letter to Science
Roy, "15 years of no global warming cannot be reconciled with the claim that human-produced CO2 dominates climate. The climate record is out of the 95% bounds of the models. I think you believe things that are not true. On the "no warming" try no warming since 1995. It seems to me that you are relying on very unreliable source. Check it yourself. Numbers easily available. As for out of 95% bounds of model - huh? For starters on whether it can be "reconciled" you could try Dont be fooled again. However, 15 years is not climate. 16 year trend is significant warming, but 30 year trends is what climate models predict. -
PaulK at 09:29 AM on 20 May 2010There's no empirical evidence
Riccardo, I plotted out the GISS model data you referenced, and agree that it shows a small change in the gradient of GHG forcing after 1990. However, even with this small gradient change, the modelled GHG forcing is still MONOTONIC INCREASING, suggesting that, all else being equal, OLR should be decreasing unless overwhelmed by other factors. If we look at the total forcing, we see that it INCREASES over the period fairly steadily if one ignores a couple of spikey excursions associated with volcanic events, but that it is always less than the GHG forcing. Hence, (excluding GHGs) all of the other forcings combined are negative in aggregate effect, and thus reduce the heating effect of the putative GHG forcing. Given this, I would guess that this model run would consistently underestimate observed OLR. But perhaps you have the integrated OLR output from the run to prove me wrong? -
Rob Honeycutt at 09:20 AM on 20 May 2010Has the greenhouse effect been falsified?
@monckhausen... I'm definitely not a physicist but I'd have to think that's impossible. It's a good question for some of the better trained folks here. What would happen if you pulled ALL the other GHG's out of the atmosphere? What would happen to water vapor? For that notion to hold true CO2, I believe, would have to have virtually NO IR absorption properties, and we know that's not true. You can prove that with a very very simple lab experiment. -
Riccardo at 09:11 AM on 20 May 2010There's no empirical evidence
PaulK, I think that you should think at the response time as a sort of weighted average. There are several processes at play operating at different time scales, from years to several centuries, so it's not well defined. Depending on the time span you're looking at you're testing one or a few of them. I see many problems in using the simple heat balance equation for quantitative analysis. It's nice, simple and useful to understand the general behaviour of the system but, as said before, we should not push it to the quantitative comparison with actual data. To have a linear forcing you need an exponential growth of CO2 concentration (the former is roughly logarithmic with the latter), which is about what we're experiencing now. The result correctly is a constant imbalance and a linear increase in temperature. -
monckhausen at 08:31 AM on 20 May 2010Has the greenhouse effect been falsified?
#30 robhon But then, the skeptic could and will argue water vapor is the most abundant greenhouse gas - and it alone causes the T increase and thus the feedback. Really difficult to argue with someone who does not accept facts. I just checked Wattsupwiththat...they come up with all sorts of stuff for anything: e.g. that science is controlled by 50 'believers' and that the current Heartland conference is attended by 700 of the world's best scientists... I collected more CO2 'skepticism' here: http://friendsofginandtonic.org/page4/page7/page7.html The problem is that you have to do a lot of reading to debunk this...and then you are still arguing against someone who refers to you as a believer. You cannot win against someone who argues from a position of ignorance. -
Phila at 08:00 AM on 20 May 2010Has the greenhouse effect been falsified?
#1 RSVP "I think there is a typo needing correction here, but if not, (as in the last article), taken on face value, the implication is another runaway scenario." In the last article, chris and others addressed your concerns about a runaway scenario. -
PaulK at 07:50 AM on 20 May 2010There's no empirical evidence
Riccardo, Thanks again. With regard to your second paragraph above, Schwartz produced an updated paper where he re-estimated the climate system response time at 8.5 years. I agree with you that if one accepts this equilibration time (or a similar time) , there is no problem explaining a flat or increasing OLR over the period of interest. On the other hand, this equilibration time is an order of magnitude smaller than that assumed in the IPCC model suite. With respect to the Schwartz formulation, I have two fundamental problems with the underlying assumptions, and need to spend some further time on it. One problem is easy to explain:- the ingoing and outgoing fluxes are both defined at TOA, but the estimate used for outgoing then becomes S-B applied at the SURFACE; since we are interested in transient affects before equilibrium, this introduces an error. The second is more complicated and I really have to spend more time thinking about it, but basically the assumption of a linear change in F with time gives rise to a bizarre animal when we start asking what CO2 profile could bring about such a profile in TOA forcing. A geometric growth model in CO2 goes flat at equilibrium time (F = constant) and temperature then becomes linear with time. To get F to continue to increase after equilibration time requires a doubling of the rate of growth of CO2, and then a quadrupling after twice the equilibration time, and so on. Equally bizarrely, for t < equilibration time, the impulse response function which stacks into a linear relationship between F and t is a Fourrier step or uniform distribution on (0,te), and this does not seem very physical. I will invest a few more neurons. -
chris at 07:22 AM on 20 May 2010Increasing CO2 has little to no effect
babelsguy, you and I have just written more or less the same post in two different contexts (see here) I think that says a lot for the fundamental nature of scientific knowledge ;-) -
Doug Bostrom at 07:08 AM on 20 May 2010There is no consensus
Breaking Consensus Update... U.S. National Academies today issues three reports from the National Research Council detailing climate change research results and remaining challenges, mitigation possibilities, adaptation requirements and hurdles. This is where scientific consensus leads: Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. Summary, links to reports here: Strong Evidence On Climate Change Underscores Need For Actions To Reduce Emissions And Begin Adapting To Impacts The petition Poptech mentions is not very useful compared to what NAS has just published. -
babelsguy at 07:04 AM on 20 May 2010Increasing CO2 has little to no effect
Well I have now worked out on my own why the bigger temperature difference between atmosphere and space does not cause an energy loss that lets global warming collapse again: There is no bigger temperature difference. Due to the absorption length of GHGs being much shorter than the height of the atmosphere, the only place that matters for outward radiation is the upmost layer of the atmosphere that radiates at all - minus the absorption length to any reasonably small non-absorbed residue. Because the GHG concentration change effectively shifts this outward radiating layer upward into colder heights, and the atmosphere below has an increasing temperature gradient towards the ground, the ground has to heat up "a lot" to let the boundary layer also heat up sufficiently *until is as warm as before*, so it can radiate enough to re-establish equilibrium! Q.E.D. So the guy's conclusion is wrong because his whole presupposition is wrong. Garbage in - garbage out. -
chris at 06:55 AM on 20 May 2010Has the greenhouse effect been falsified?
HumanityRules at 00:46 AM on 20 May, 2010 re your comments on a phrase and sentence from the top post:"The Earth's surface is about 33 degrees Celsius warmer than required to radiate back all the absorbed energy from the Sun. This is possible only because most of this radiation is absorbed in the atmosphere, and what actually escapes out into space is mostly emitted from colder atmosphere."
This makes perfect sense HR, if you read the half sentence you referred to in the context of Chris’s two sentences above. The Earth absorbs around 240 W.m-2 of radiation from the sun. Obviously in order to maintain radiative equilibrium it must radiate this energy back to space. If this was achieved by direct emission to space from the surface then the Earth's surface need be only 255K (around -18 oC). This is easily calculated from the Stefan Boltzmann equation [240 W.m-2 = (255 K)^4 . 5.6704 x 10^-8 W.m-2.K^-4] However since the Earth's atmosphere is strongly absorbing of long wave IR of these "temperatures" (energies) due to greenhouse gases, radiative equilibrium can't be achieved by direct emission to space from the Earth's surface. Radiative balance is achieved by emission to space from the atmosphere. On average the emission will occur at an altitude where the temperature is around 255K. Clearly if a region (layer) of the atmosphere has a temperature of 255K, then the layers below, right down to the surface, will be warmer than 255K. In other words the greenhouse effect can be thought of as retaining energy in the system until the temperature of layers of the atmosphere where LWIR is radiated to space is “pushed up” to 255K. All the layers below this warm up (including the surface). As you increase the greenhouse gas concentration the efficiency of LWIR emission to space from any layer of the atmosphere decreases further, and so the average height of long wave IR emission to space increases. Since the atmosphere gets colder as one goes higher, emission becomes less efficient. Thus energy tends to build up in the system (positive radiative imbalance) further warming the atmospheric layers (right down to the surface) until the regions of the atmosphere where LWIR are emitted to space reach 255K. -
KR at 06:48 AM on 20 May 2010Has the greenhouse effect been falsified?
The Ville, a vibrating/moving molecule is a group of atoms held together by an electron cloud. Electron energies can change in several ways - collision, molecular changes (ionization, oxidation), and through thermal radiation absorption and emission (EM). The probabilities of various pathways vary between molecules. CO2 is an excellent absorber of IR (a good antenna configuration for receiving, if you will), which gives it an equal chance of radiating excess energy away (transmission). This makes IR energy exchange a fairly probable pathway for CO2. O2 and N2, not so much - their molecular configuration makes them lousy antenna in the thermal IR range. -
Rob Honeycutt at 06:24 AM on 20 May 2010Has the greenhouse effect been falsified?
I just finished watching this Stephen Schneider lecture where he addresses the very same issue of climate change being falsified. He brings up several papers that claim to falsify climate change in one way or another but says all these papers do is, at best, "move the needle" of understanding ever so slightly. This is an excellent lecture that is well worth the time to watch. -
Rob Honeycutt at 06:04 AM on 20 May 2010Has the greenhouse effect been falsified?
@Monckhausen... I think the best response (I can think of as a layperson) to people who say that water vapor is the cause for most of the greenhouse warming is this: Well, how does water vapor get there? What is the mechanism? The answer is temperature. What drives the temperature? Well, obviously GHG's. If the other GHG's were not there all the water vapor in the atmosphere would freeze out and we'd have a very cold planet. So, it's the other GHG's that act as the "control knobs" (to borrow from Richard Alley) for temperature. -
Doug Bostrom at 05:51 AM on 20 May 2010Has Arctic sea ice returned to normal?
Fresh Anecdote: Martin Hartley, a member of the team, said the condition of the ice was unpleasantly bad. “We spent a couple of days walking on ice that was three or four inches thick with no other thicker ice around, which was a big surprise to us,” he told the news conference. “On more than one occasion we came across enormous areas of very thin ice, which is quite stressful to travel on. We came across open water which we had to swim across.” At one point an ice floe the team’s tent was moored on broke apart, although no one was injured. Last month explorers at the team’s ice base some 680 miles further south reported a three-minute rain shower, which they described as a freak event. Arctic team reports unusual conditions near Pole Team also reported rapid drift rates, far higher than anticipated, so perhaps we're looking at another 2007 where wind and warmth combined to make an excursion more noticeable than other years in a downward trend?
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