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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? -
Riccardo at 05:42 AM on 20 May 2010Has Arctic sea ice returned to normal?
Eric, indeed they show the comparison with ICEsat for 2003-2007 here. -
Stephen Baines at 05:36 AM on 20 May 2010The significance of the CO2 lag
@ Frogstar "A review of biospheric feedbacks on temperature suggests that the effect may be small on a time-scale of years (about 3 ppmv CO2 /0C), and moderate at millennium time-scales (about 13 ppmv CO2 /0C), but large at a scale of centuries (about 20 ppmv CO2 /0C)" ? This sequence of scales refers to effects of soil microbial and plant physiological responses to temp (short term: years to decades), changes in soil and terrestrial plant carbon inventories (medium term: centuries), and deep ocean turnover, glacial loss and (perhaps) vegetation expansion (long term: centuries-millenia). Different mechanisms working on different time scales may have opposite effects on the relationship between temp and CO2. Unfortunately, most of the ones working in the short-medium scales seem to exacerbate the problems facing us. Of course, I'm mostly interested in getting through the next couple centuries...unless Monckton has a cure for old age as well as AIDs, that is. -
actually thoughtful at 05:35 AM on 20 May 2010Has Arctic sea ice returned to normal?
Today the ice extent, which was reported in late March at various skeptic sites to be completely recovered, compared to the 30 year average, intersected the 2007 (lowest recorded year) line. And it intersected it at a steep slope. Compared to 2007, the 2007 extent was limited the whole time and followed the curve pattern of the 30 year average. This year, the decline is much steeper than the 30 year curve. How shall we hide THIS decline? http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png (usual caveats about weather is not climate apply, and of course I am just eye-balling the graph. For those who complain that 30 years isn't long enough – here is a graph that incorporates data back to 1900. http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg -
Riccardo at 05:32 AM on 20 May 2010There's no empirical evidence
PaulK, my bad, not willing to be bothered by the constants i screwed up everything, or better, i didn't notice that the two constants c and b were the same. For the sake of this retraction, below I'll re-formulate the equations. Strange enough, I'm kind of happy that I did this error because before finding it I could not resolve some inconsistencies of the model results. :) As for the problem at hand, i'd like first to point out what the value of the response time τ should be. In the heat balance model, it is defined as the ratio of the relevant heat capacity (of the oceans, mainly) and the climate sensitivity. The oceans do not have a single response time for sure so we're forced to admit that it is the one relevant to the time span considered. In the Schwartz 2007 paper quoted above he gives numbers between 5 and 16 years based on two different approaches. The former looks definitely too small and is probably due to some error. So, in a time span of a some decades and in the presence of a linear forcing one would exepect a essentially zero OLR slope. A positive OLR slope indicates a negative change the in slope of the radiative forcing and viceversa. Looking at the radiative forcings provided by GISS, there has been a slowing down of the GHG forcing around 1990 which could have produce an increasing OLR. But the OLR data are in my opinion too noisy for any definitive assessment (see for example the annual global averages here). In any case, GHGs can still be (and in fact are) the primary (not the only!) forcing but some other effect may just have slowed down the overall forcing. ======== Correct equations from my comment #56 the temperature change is as before ΔT(t) = β*((t-τ )+τ *exp(-t/τ ))/λ OLR(t) = β *((t-τ)+τ*exp(-t/τ))-β*t for t > > τ : OLR(t) ~ -β*τ d OLR/dt = β*(1-exp(t/τ))-β = -β*exp(-t/τ) -
monckhausen at 04:52 AM on 20 May 2010Has the greenhouse effect been falsified?
Stephen Baines # 25: Thanks! I knew it must have been something really simple that had been overlooked. -
Stephen Baines at 04:28 AM on 20 May 2010The significance of the CO2 lag
@ fydijkstra #29 Your analysis is not correct on several levels. Some clarification. First, it makes no sense to subtract out the effect of feedbacks from the direct effects of CO2 on climate. Just because they are indirect effects doesn't mean they won't respond add to the direct effects of increasing CO2. You're basically assuming the feedbacks that amplify the effects of CO2 on climate will magically cease to apply to the next century. Second, the feedbacks you are talking about are not the ones discussed in this paper. There are fast feedback mechanisms -- like water vapor, clouds, lapse rate -- that are involved in the response of our current climate to CO2. These sorts of feedbacks are included in typical climate sensitivity estimates based on modern models and empirical measurements. The paper here is addressing SLOW feedback mechanisms. These are not included in typical climate sensitivity measurements because they take a long time (often a century or more) to be manifest. They often include complex processes that are hard to predict. One example includes the feedback of temperature on albedo through ice sheets, sea ice extent and sea level. The topic of this paper -- changes to the carbon cycle in response to temperature -- reflect changes in the processes that store C in the oceans and land and take centuries to adjust to new temperature regimes. Time scales are governed by lifetimes of soil carbon, vegetational shifts and lags in ocean temp and deep water circulation. Given the complexity and the slow development of these feedbacks, it makes sense to look back in time to see how the system as a whole responded, so as to calibrate our expectations for the future. Because these feedbacks have not had time to manifest, they add to the sensitivity we estimate based on the direct effects of CO2 and the fast feedbacks. Moreover, because they are slower and have not been manifested yet, they actually mean the climate is more sensitive to CO2 that we think based on the fast feedback mechanisms we can observe over short time scales and in the models. -
chris at 04:21 AM on 20 May 2010Has the greenhouse effect been falsified?
The Ville, the CO2 molecule doesn't stop vibrating. A CO2 molecule is constantly undergoing translation, rotational and bond vibrational motions according to the thermal energy (temperature) of its surrounds. Absorption of a photon of LWIR of appropriate energy excites a specific bond vibrational mode promoting the molecule to an excited "high energy" state. The equilibrium state appropriate to the local temperature is a lower energy (ground state) and the relaxation back to this ground state is achieved either by re-emitting a photon, or by transmitting the energy to local molecules (which need not be IR absorbing; e.g. O2 or N2) by molecular collisions (thus raising the temperature of the gas a tiny amount). -
Paul D at 03:59 AM on 20 May 2010Has the greenhouse effect been falsified?
Interesting! My introduction to Kirchoff was as a teenager in electrical engineering! http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws Now he turns up in climate science. OK. I understand Kirchoffs law, applied to large bodies. But I don't really understand how at the quantum level a CO2 molecule stops vibrating and suddenly re-emits the IR electromagnetic wave. What makes this happen. I can understand the absorption, but not so clear on the emission. -
John Russell at 03:33 AM on 20 May 2010Has the greenhouse effect been falsified?
KR: I can't remember reading yours before but it looks like we both came up with exactly the same analogy independently, right down to humans raising the sides; so I guess it must be a good one but I'm happy to acknowledge you were first. I arrived at it as a re-think of the 'bucket with the hole analogy' where naturally-produced CO2 (the tap) is balanced by the same amount of CO2 being locked-up by natural processes (leaking through the hole), thus keeping atmospheric CO2 in equilibrium -- before a small but steady amount of human-produced CO2 causes the level to slowly rise and the bucket to overflow. But that's off topic and I guess will probably hit the cutting room floor. I agree; analogies are very useful. -
Stephen Baines at 03:31 AM on 20 May 2010Has the greenhouse effect been falsified?
Monckhausen at #23 Besides the fact that they start by understating the direct contribution of CO2 to the GH effect (more likely 15-25% depending on whether you include clouds), they are ignoring the feedback that increased temperatures due to higher CO2 have on water vapor in the troposphere. That water vapor amplifies the effect of CO2 on the GH effect substantially. Water vapor is the most powerful greenhouse gas This seems to be a common "mistake." -
thpritch at 03:19 AM on 20 May 2010The significance of the CO2 lag
It should be noted that while increases in the CO2 concentrations measured in Antarctic cores lag observed increases in calculated temperatures obtained from isotope ratios from those same cores and from Southern ocean sediment cores, that same lag is not seen in mid-latitude core samples. In the March 14, 2003 issue of Science, page 1730, Caillon et. al. state the following: "We follow Petit et al. (1) in assuming that CH4 can be used as a time marker of the glacial- interglacial warming in the Northern Hemisphere. The CH4 increase at 2810 m, which occurred when _40Ar reached its first maxima, would thus signal a first warming in the North leading to some equivalent of the Bølling-Allerød interval. We point here to the existence of a cold reversal at the start of termination III (1), now firmly identified in both our detailed deuterium and _40Ar Vostok profiles. The sudden increase of 150 ppbv practically coeval with the _40Ar maximum would be linked to the main deglaciation, thus indicating that Vostok temperature began warming _6000 years (Fig. 3) before the associated warming in the Northern Hemisphere (1)" (Their reference 1 is 1. J. R. Petit et al., Nature 399, 429 (1999).) In other words, while changes in the Earth's orbit relative to the Sun may have been the driving force for the warming of the Southern Ocean and Antarctica, the elevated CO2 concentrations from the outgassing of the Southern Ocean was likely a major, if not the major, driver in the warming and deglaceration of the Northern Hemisphere. -
Doug Bostrom at 03:18 AM on 20 May 2010Has the greenhouse effect been falsified?
I don't think it's too off-topic to contrast G&T's kamikaze attack on climate science w/the National Academies of Science release today of three reports regarding climate change. This NAS effort excellently illustrates just how far off track G&T have wandered with their thought experiment. Follow this link to get to the NAS materials: Strong Evidence on Climate Change Underscores Need For Actions to Reduce Emissions and Begin Adapting to Impacts For us amateurs and bystanders including G&T, here's the significant nut of the entire rather overwhelming set of three reports: 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. That's the NAS speaking, not known for its rhetorical liberality. In this arena G&T are no better or worse or more importantly useful to the advancement of understanding than most of us other odd ducks who natter away on climate. We offer our best interpretations and guesses regarding a topic that we can't actually attack in a serious way because we're innocently too ignorant of the specialized information and practice needed. Like most of us, G&T's perspective, level of information and specific skills on the topic of climate change are not sufficient to produce useful contributions. -
monckhausen at 03:08 AM on 20 May 2010Has the greenhouse effect been falsified?
In a Geocanada 2010 talk last week, the presenter claims that the greenhouse effect is 34.5C and that CO2 is responsible for 10% of it, which is 3.45C. From this he concludes that a doubling of the current CO2 concentration in the atmosphere adds only 0.345C to global temperatures. Can anybody explain, how someone can arrive at these numbers? The talk was recorded as an mp3 and is found here. -
chudiburg at 02:29 AM on 20 May 2010It's cooling
We have just experienced the warmest January-April period on record when considering the combined land and ocean temps. Here is the link. http://www.ncdc.noaa.gov/sotc/index.php#global_highlights -
Albatross at 01:36 AM on 20 May 2010Has the greenhouse effect been falsified?
"Has the greenhouse effect been falsified?" No it has not. IMO, G&T should have never gone to press and represents yet another attempt by the contrarians to create the impression of debate based on sub par science (and some might argue that that description is too generous) and sow doubt amongst lay people. Steve Carson also does an excellent (and thorough) debunking of G&T. That all said, the terminology "greenhouse effect" is clearly a misnomer and as such remains problematic and confusing to some. Anyhow, congratulations (and a big thanks) to Halpern et al. for making the effort and taking the time to soundly refute G&T. -
sylas at 01:12 AM on 20 May 2010Has the greenhouse effect been falsified?
HumanityRules, I am open to clearer ways to express this! On the other hand, there will always be a need to explain it further, and that's ok. The current two sentences to which you refer are: 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. The surface of the Earth is around about 15C, or 288K. If you take a uniform temperature and high emissivity you get about 390 W/m2 emitted. The real value is a few W/m2 higher mainly because temperatures are not uniform, which gives slightly higher total emission thanks to a 4th power relation from temperature to emission. But the energy we actually absorb from the Sun, in total, is about 240 W/m2, which is what you get from a sphere at a temperature of about 255K, or -18C. What the Earth radiates into space is about 240 W/m2, in total. This is huge difference between what is radiated at the surface and what gets out to space. This is only possible because surface radiation mostly never gets out to space, but is absorbed in the atmosphere. What eventually gets out to space is mostly emitted within the atmosphere, where it is colder. You also ask: Do you know if there has been a change over time for the past couple of decades to the results seen in Fig 1? I just noticed the other day, as I was browsing this site, a nice discussion of the changes from 1970 to 1996. It's described, with some good illustrations, at Empirical evidence that humans are causing global warming. Note that you get different emission spectra at different seasons, times of day, and locations. So changes actually refer to a global mean, and not the specific observations on a particular day, and a certain place, which I am using here to show direct observations of the greenhouse effect at work. I think we are best to continue to focus on the existence of the greenhouse effect in this page, rather than how it may be changing. As for the absorption spectrum of water; it is intrinsically complex in any case, with a large number of distinct absorption bands. On top of that it is not well mixed in the atmosphere. And to finish things off, you get the differences associated with phase changes, which apsmith is speaking of. -
KR at 01:11 AM on 20 May 2010Has the greenhouse effect been falsified?
Hey! The tap/bucket analogy was mine! LOL... I'm certain that I'm far from the only person who has come up with this comparison - I first used it years ago when discussing evolution with some people who thought that it violated entropy/thermodynamics. I think it's a useful mental image for GHG warming, and I've found it helpful in explaining these concepts to a number of people. One nice thing about it is that you can directly see in it that energy is flowing in the correct direction. But as sylas said, it's much better to actually understand the system itself, rather than analogies. -
Eric (skeptic) at 00:53 AM on 20 May 2010Has Arctic sea ice returned to normal?
Riccardo, thanks for the reply. The PIOMAS seemed to be used for projection in the paper, namely 7 experiments to test the predictive skill of the model. I was hoping for a followup paper here: http://psc.apl.washington.edu/publications/publications.php?year=2009 but there was only a Jan 2009 paper talking about the model, but not the predictions made in the previous paper or the success of those predictions. Direct independent measurements would seem appropriate and they are at least partly available for 2008 to compare to the predictions. -
HumanityRules at 00:46 AM on 20 May 2010Has the greenhouse effect been falsified?
18.sylas Thanks I sort of guessed that somebody was going to tell me that all that energy in the ocean was irrelevant to this. I'm not sure those two sentances go well together. I think something is wrong with the wording in the first, it doesn't seem to make sense. Do you know if there has been a change over time for the past couple of decades to the results seen in Fig 1? Also you make the following point "Water vapor has complex absorption spectrum". I thought water as a vapour has a discrete absorption spectrum. Isn't it condensed water droplets that's more complex? (So says apsmith on your forum) -
PaulK at 00:23 AM on 20 May 2010There's no empirical evidence
Riccardo, Just a couple of points: 1) I have never had a problem accepting the possibility of OLR increasing (even if CO2 is having some warming effect at the same time). If you re-read my first post again, you will see that my argument is that you cannot have CO2 as the PRIMARY driver of heating from the 70s, and have the OLR response which is critical to that heating overwhelmed by thermal emissions derived from some other unspecified source of heating - unless, that is, some other basic assumptions are wrong. 2) You wrote: "Even assuming its validity, for example, the position of the minimum in the OLR critically depends on the choice of the parameters involved, not just the actual time response of the system. There's no point in pushing a model beyond its limits." I disagree strongly with this statement. For a geometric growth in CO2, the minimum (perturbation) in OLR is always achieved at exactly the equilibration time. This is completely independent of the choice of any other parameters. Small variations away from the geometric model, provided they are fitted to the actual data, will always yield a minimum very close to the equilibration time. This is dictated by simple mathematics and requires only two assumptions: (a) CO2 does not cause planetary cooling at some stage in its affect on the system (but it can be multimodal in its affects) (b) Equilibrium temperature change is linearly proportional to the total heat energy gained/lost by the system (i.e. constant specific heat capacity). If the issue here is that I did not adequately explain the maths behind this, then please let me know and I will be happy to provide a more formal proof of this. -
sylas at 00:15 AM on 20 May 2010Has the greenhouse effect been falsified?
Humanity rules, the sentence you quoted speaks of "this" radiation, which in the context of the preceding sentence, means the thermal radiation emitted from the surface. Most of this radiation is indeed absorbed in the atmosphere. -
sylas at 00:10 AM on 20 May 2010Has the greenhouse effect been falsified?
Followup to Berényi's correction. How's this. I propose to get rid of some technical terms not used in the rest of the essay anyway. I have suggested the incorrect phrase be replaced to read: In some frequencies, thermal radiation is blocked very efficiently, and the backradiation shows the temperature of the warm air right near the surface. Thanks again -- sylas -
sylas at 00:03 AM on 20 May 2010Has the greenhouse effect been falsified?
Thank you Berényi, you are quite correct! I have emailed John to get that fixed. Much appreciated! -- sylas
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