By Dr. Pat Michaels at World Climate Report
A new, lower estimate of climate sensitivity
There is word circulating that a paper soon to appear in Science magazine concludes that the climate sensitivity—how much the earth’s average temperature will rise as a result of a doubling of the atmospheric concentration of carbon dioxide—likely (that is, with a 66% probability) lies in the range 1.7°C to 2.6°C, with a median value of 2.3°C. This is a sizeable contraction and reduction from the estimates of the climate sensitivity given by the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), in which the likely range is given as 2.0°C to 4.5°C, with a best estimate of 3.0°C.
Further, the results from the new analysis largely eliminate the “fat tail” of the distribution of possible values of the climate sensitivity (that the IPCC AR4 report was fond of) which included the possibility that very large climate sensitivities are a realistic possibility. In the new paper, the authors find only “vanishing probabilities” for a climate sensitivity value greater than 3.2°C and that values greater than 6.0°C are “implausible.”
Contrast that with the IPCC assessment of the literature (summarized in our Figure 1) which routinely includes studies concluding there is a greater than a 10% possibility that the true climate sensitivity exceeds 6°C and some which find that there is a greater than 5% possibility that it exceeds 10°C.
Figure 1. Climate sensitivity distributions retained (and in some cases recast) by the IPCC from their assessment of the literature. Note the “fat tail” towards the right which indicates the possibilities of the climate sensitivity having a very large positive value (that is, a huge degree of global temperature rise for a doubling of the atmospheric carbon dioxide concentration) (source: IPCC AR4).
The new paper, from a team of researchers led by Andreas Schmittner of Oregon State University, throws cold water on the IPCC’s tails. Here is its rather provocative abstract:
Assessing impacts of future anthropogenic carbon emissions is currently impeded by uncertainties in our knowledge of equilibrium climate sensitivity to atmospheric carbon dioxide doubling. Previous studies suggest 3 K as best estimate, 2–4.5 K as the 66% probability range, and non-zero probabilities for much higher values, the latter implying a small but significant chance of high-impact climate changes that would be difficult to avoid. Here, combining extensive sea and land surface temperature reconstructions from the Last Glacial Maximum with climate model simulations we estimate a lower median (2.3 K) and reduced uncertainty (1.7–2.6 K 66% probability). Assuming paleoclimatic constraints apply to the future as predicted by our model, these results imply lower probability of imminent extreme climatic change than previously thought.
Figure 2 shows the distribution of the range of the earth’s probable climate sensitivity as determined by Schmittner et al. Note the rapid drop-off in the probability that the climate sensitivity is much greater than 3°C (the IPCC “best estimate” for the sensitivity), and that the distribution falls off less slowly towards the left (towards lower sensitivity) than towards the right (higher sensitivities). The “fat right-hand tail” of the distribution is gone and the possibility that the climate sensitivity is in the 1°C to 2°C range is not minimal.
Figure 2. Distribution of the land/ocean climate sensitivity as determined by Schmittner et al. (adapted from Schmittner et al., 2011).
The Schmittner et al. results join a growing number of papers published in recent years which, by employing investigations of the earth’s paleoclimate behavior (that is, how the earth’s temperature changes in the past when subject to changing climate forcings) have come to somewhat similar conclusions, especially regarding the (lack of) evidence to support the existence of the fat right-hand tail.
For example, researchers James Annan and Julia Hargreaves published a paper in 2009 that concluded many of the assumptions underlying the possibilities of very high climate sensitivities were unjustified. They wrote:
When instead reasonable assumptions are made, much greater confidence in a moderate value for [the climate sensitivity] is easily justified, with an upper 95% probability limit for [the sensitivity] easily shown to lie close to 4°C, and certainly well below 6°C. These results also impact strongly on projected economic losses due to climate change.
Annan made repeated comments during the IPCC AR4 review process that the IPCC’s handling of climate sensitivity and its probability distributions were incorrect. His complaints largely fell upon deaf ears.
However, as there are appearing more and more examples in the literature, of which Schmittner et al. is one of them, making a convincing case that the very high climate sensitivities are not defendable, there will be growing pressure on the IPCC in its Fifth Assessment Report to greatly shrink the fat tail of the probability distribution for the true climate sensitivity. However, the climate “realists” very bad experience with the last IPCC process makes them chary. James Annan, writing at his blog in reference to the new Schmittner et al. paper had this to say as to what may result from it:
That said, [the Schmittner et al. paper] is a useful antidote to the exaggerated uncertainty estimates that have been prevalent over recent years, and I certainly applaud the intentions and effort underlying this substantial piece of work. In any case, I expect the merchants of doubt to do their worst on it when they cite it in the IPCC report.
But, as the evidence mounts against a high value for the climate sensitivity, and evidence grows for a low value (recall that the observed rate of global warming for the past several decades has fallen well below IPCC best estimates), the IPCC is going to be hard-pressed to retain the status quo in its Fifth Assessment Report, especially in light of the enhanced scrutiny that its AR4 misdeeds brought upon the process.
But, as James alludes to, perhaps we ought not be holding our breath.
And, for those keeping score out there, about 10 years ago, a couple of us here at WCR were part of a team which published a paper in the journal Climate Research in which we employed a variety of techniques to derive empirical estimates of the amount of temperature rise that we could expect by the end of this century—a rise that could pretty well be considered to be in-line with the climate sensitivity. We concluded that the expected temperature rise between 1990 and 2100 would be in the range 1.0°C to 3.0°C with our best guess being 1.8°C (in contrast to the IPCC estimates, which, at the time, were for a rise of between 1.4°C and 5.8°C).
References:
Annan, J.D., and J.C. Hargreaves, 2009. On the generation and interpretation of probabilistic estimates of climate sensitivity. Climate Change, 104, 423-436, doi:10.1007/s10584-009-9715-y, http://www.jamstec.go.jp/frsgc/research/d5/jdannan/probrevised.pdf
Michaels, P.J., P.C. Knappenberger, O.W. Frauenfeld, and R.E. Davis, 2002. Revised 21st century temperature projections. Climate Research, 23, 1-9.
Schmittner, A., et al., 2011. Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum, Science, in press*, http://www.princeton.edu/~nurban/pubs/lgm-cs-uvic.pdf
*According to the authors
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Joel, that is exactly the thread that Willis ran away from. The very same thread that motivated me to buy the equipment and do the experiment. Willis could not offer empirical evidence from a controlled experiment contradicting my claim. I doubt that you will either.
Konrad:
I’m confused. I thought you mean that as a surface is heated land and oceans behave differently because evaporation from the oceans leads too cooling whereas land warms more.
I’m also confused about your term “backscattered LWIR”. I assume LWIR means longwave infrared radiation. LW or IR radiation is not backscattered. LW radiation emitted from the surface is absorbed by molecules such as H2O and CO2 in the atmosphere. This increases their energy level (rotation and/or vibrational modes are excited). After a short time the molecule goes back into a lower energy state and emits a photon. This absorption/emission process is different from scattering, which is essentially the reflection of a photons path to a different direction. Scattering happens in the shortwave (visible and UV) and is the reason why the sky is blue.
Regarding your calculation: sorry, but it’s really wrong. You cannot divide a 1 degree average warming into 0.3 degrees over land and 0.7 over the ocean. If the land was warming 0.3 degrees and the ocean 0.7 degrees then the average warming of the planet was 0.3*AL + 0.7*AO = 0.58 degrees, where AL is the fraction of the surface area of the planet that is land and AO is the ocean fraction. So if you get simple arithmetric that wrong perhaps you shouldn’d go further in your calculations.
Joel:
I guess you’re right. But I’m trying to acknowledge that people are thinking about this and Konrad certainly is. Even if that thinking leads to a wrong conclusion, it is better than not thinking about it at all, which, I assume most people do. And I sensed some truth it his reasoning concerning evaporative cooling, but maybe I have misunderstood him.
Gottlieb,
By backscattered I am referring to IR radiation around 15 microns leaving the Earths surface, impacting CO2 and 50% of it being re-emitted back toward the surface. This long wave IR radiation does not slow the cooling of liquid water to the same extent as solid materials.
The reason for this is that 15 micro LWIR cannot penetrate even the first 10% of the 1mm evaporativly cooled skin layer of liquid water. IR photons simply trip more water molecules to their vapour state. The thermal gradient across the skin layer remains largely unchanged. The cooling rate of liquid water is not greatly effected by LWIR emitted by CO2.
Konrad,
So what is then happening to the LWIR? As Willis pointed out, the amount of energy being carried away from the earth’s surface by evaporation is well-known to be about 70 – 80 W/m^2. In order to claim that this is vastly underestimated, you would have to show that mean evaporation is vastly underestimated, which means mean precipitation is vastly underestimated (since it is a first-year physics problem to get from the mean evaporation of water to the amount of energy that this carries away to the surface). This seems rather unlikely.
Konrad: I trust over a century of accumulated physics knowledge over the probability of someone on the internet to correctly carry out and interpret an experiment, particularly when he clearly wants to get the answer to come out a certain way.
Joel Shore – indeed you may well trust over a century of accumulated physics knowledge more than someone on the internet. But as an argument that’s just an Argument From Authoriy and is absolutely worthless. To make a cogent argument it is necessary to address the actual issue. And please note that as stated, your assertion of bias applies even more strongly to the IPCC. The IPCC clearly wants to get the answer to come out a certain way, and it hasn’t even done an experiment.
Joel Shore says:
November 12, 2011 at 6:44 pm
“Konrad: I trust over a century of accumulated physics knowledge over the probability of someone on the internet to correctly carry out and interpret an experiment, particularly when he clearly wants to get the answer to come out a certain way.”
Joel, you are wise to be concerned about confirmation bias, especially with regard to climate science. I sought to circumvent this in the traditional way by designing an experiment that was repeatable by others. I have repeatedly encouraged others to replicate the experiment or design their own variant. So the question is not whether you should trust me, but rather whether you trust yourself to be able to replicate the work with sufficient care. If you do not have a link to empirical controlled lab experiments countering my claim, I would encourage you to conduct the following simple experiments.
The first one is easy –
Place a probe type digital thermometer in a tin cup full to the brim with water. Use fibreglass and foil insulation on the exposed cord. Try heating the water by applying the hot air from a paint striping heat gun to the surface of the water. Now try heating the water by pointing the gun at the side of the cup. Slight agitation of the water below the surface should be introduced by moving the probe to prevent stratification. The results are markedly different. This test does not address LWIR as the heat is only introduced conductively, however it gives an insight into the problems of trying to heat water through the evaporatively cooled skin layer.
The second is slightly more complex, instructions, some images and typical results can be found here –
http://tallbloke.wordpress.com/2011/08/25/konrad-empirical-test-of-ocean-cooling-and-back-radiation-theory/
I recommend replacing the foil reflector with a simple LWIR emitter. Use a cling film IR window and frame similar to the other side of the experiment. Use a disposable foil baking tray with its base sprayed matt black as a warm water container balanced on top of the balsa and cling film frame, ensuring a 10mm gap between the base of the tray and the cling film. Insulate the tray on the sides and top after filling with warm water. This provides a more constant LWIR source. The original foil reflector only bounces back a diminishing amount of LWIR as the sample below it cools.
The third experiment I have yet to design fully. While it appears that LWIR incident on the evaporatively cooled skin layer of liquid water may simply trip liquid molecules to their vapour state, this may not be the full story. It may be that some of the LWIR is reflected. I believe that using the human body as a LWIR source and an IR motion detector, a simple experiment could be conducted to see if liquid water could also be reflecting a small percentage of incident LWIR (unlike an ideal black body). Feel free to design and build your own variant.
Konrad: A few experiments that vaguely look at heat transfer under various circumstances do not overturn a century of understood physics. There is a large gap between what you show with your experiments, assuming that you have performed them correctly (and I am willing to believe that heating a water container from the side is more effective than heating it from the top), and claims that the energy due to the LWIR is magically transported out of the earth / atmosphere system.
The exact extent to which the LWIR causes the oceans to be warmer by direct heating vs by reducing cooling may be of some academic interest…but it doesn’t address the basic point, which is that those who think that the energy is magically transported out of the climate system aren’t able to come up with any sort of coherent explanation to how this magic actually occurs.
By the way, Konrad, you seem to assume that plastic wrap is a good transmitter of infrared radiation. Do you have data to support that assumption?
Joel Shore says:
November 13, 2011 at 7:20 am
“Konrad: A few experiments that vaguely look at heat transfer under various circumstances do not overturn a century of understood physics”
“a century of understood physics” Joel, there you go with that “call to authority” thing again 🙂
Actually it doesn’t take a few experiments, it could take just one. Further to that I am not seeking to overturn understood physics, rather I am investigating an effect that does not seem to have been previously addressed. I believe the radiation physics to be largely correct (reflection still to be checked) with regard to the emission and absorption spectra of liquid water. Climate scientists seem to have made an assumption based on known radiation physics with regard to the effect of LWIR on liquid water. However liquid water should not be treated the same as other materials as at the surface interface with the atmosphere molecules are undergoing phase change. LWIR cannot penetrate this surface layer, therefore it is important to investigate the physical behaviour of this layer to understand the effect of LWIR on liquid water. The assumptions that climate scientists are making appear to be “pointing the heat gun at the side of the cup” I am not proposing a magic transport of energy out of the atmosphere, I am claiming that CO2 does not trap as much in the oceans as assumed.
With regard to the IR properties of cling film I should add a clarification. You should use a more expensive “microwave safe” cling film as these are made of LDPE plastic (low density polyethylene). The lenses of many IR detectors are made of the same material. Al Gore should not have used glass in his “climate reality” experiment and the BBC should not have used PETG plastic bottles in theirs. Sodium chloride lenses are not transparent far enough into the longer wavelengths and like the more transparent potassium chloride salt lenses can be damaged by moisture.
I have used warm water as the LWIR source as heat lamps and other electric radiators produce too much SWIR, which may penetrate below the skin layer of liquid water.
Konrad says:
What matters at the end of the day is the energy balance at the “top of the atmosphere”, i.e., the balance between radiation received by the earth / atmosphere system and that radiated away. Trying to do backflips to come up with ways to prevent the heat from being absorbed by the oceans is not going to do any good unless you can show that you are transporting more energy out of the earth / atmosphere system as a result.
Joel Shore says:
November 15, 2011 at 5:13 pm
“What matters at the end of the day is the energy balance at the “top of the atmosphere” “
I would take issue with this on two grounds. The first is that we live in the lower troposphere and most suggested negative effects of global warming to life on Earth would require changes in this part of the atmosphere. CO2 does not warm the atmosphere by direct absorption of LWIR photons. The way CO2 can warm the troposphere is through absorbing and almost instantly re-radiating 50% of LWIR around the 15 micron band emitted by the surface back to the surface. This slows the rate at which the surface can radiativly cool. The surface can transfer heat to the lower troposphere through conduction. While release of latent heat from water vapour evaporated from a warmer surface can also warm the troposphere, this is in some part balanced by the surface cooling effect of evaporation. If CO2 has a reduced role in slowing the cooling of the surface over the oceans as I am claiming, this has significant implications for its role in warming the lower troposphere and thereby the proposed negative effects of global warming.
The second issue I would take with your statement concerns quantification of the TOA energy balance. I accept that that a radiative energy imbalance at TOA would indicate that the planet as a whole is either warming or cooling. However the quantification of this is poor. Satellites used are in low earth orbit and cannot look at the limb of the Earth. You will have noticed that much mathematical modelling for received radiation is based on reducing the energy received by a hemisphere by half to show the watts per m2 received by a flat disc of the same diameter. This will give a reasonable figure for albedo with regard to clouds but a poor figure for the reflectivity of the oceans closer to the edges of the true illuminated hemisphere. To better quantify the TOA radiation budget better remote sensing is required. The remote sensing platform required has already been built. Sadly DSCOVR is still languishing in a dry nitrogen filled box at the bottom of a gravity well, as opposed to where it should be in a lunar Lagrangian position.
The DSCOVR situation reminds me of this movie scene –
Konrad: Last things first, I agree with you on the travesty of the fact that DSCOVR has not been launched. It would be important to have it there to better quantify what is actually going on. However, in its absence, I still think we understand enough about atmospheric dynamics to determine some things.
Your post shows that you are suffering under a too-simplistic view of the greenhouse effect. Your model of the effect is a good first picture, but it ignores convection completely. A better picture is to not worry so much about the surface radiation balance, which changing purely radiative processes between the surface and the atmosphere doesn’t change very much. Rather, it is most important to worry about how increasing greenhouse gases reduces the emission of radiation into space, the top-of-the-atmosphere radiative balance that I talked about. From there, you can get the result for what happens at the surface to varying levels of approximation:
(1) In the first approximation, it is not unreasonable to assume that the tropossphere warms uniformly in altitude.
(2) A better approximation accounts for the moist adiabatic lapse rate holding in much of the tropics, which leads to faster warming at altitude than at the surface. This leads to the “lapse rate feedback”, a negative feedback in the climate models. While the magnitude of the lapse rate feedback can be fairly sensitive to assumptions and thus vary from one model to another, it turns out that this feedback and the water vapor feedback involve similar physics and are thus strongly correlated to each other, so the net result of both feedbacks is more tightly constrained than each one separately.
If you can get a hold of it, I would recommend looking at the book “Global Warming: The Hard Science” by L.D. Danny Harvey. In it, he does a calculation that shows how a change in the radiative balance between the surface and the atmosphere results in little change in surface temperature because the convection compensates for most of it. However, a change in the top-of-the-atmosphere radiative balance has a much larger effect. It is a very important point to understand.
Joel Shore (Nov. 17, 2011 at 4:22 pm):
At http://judithcurry.com/2010/11/30/physics-of-the-atmospheric-greenhouse-effect/#comment-16901, the blogger Nullius in Verba provides an account of the issue you have raised that many readers find enlightening. According to Nullius, professional climatologists confuse amateurs by ignoring convection in the descriptions of the greenhouse effect that they provide for public consumption.
Terry– I pretty much agree with what Nullius in Verba says except I would not really blame it on the climatologists. In most fields of science, it is understood that one is not really conversant on a subject once one has read only the simplest discussions and representations of it. Unfortunately, in the highly politically-charged atmosphere around climate science, people seem to think that they can read these simple explanations and then expound on the problems with the entire theory, rather than following the natural trajectory of first delving into the more complex, detailed explanations.
Joel Shore (Nov. 18,2011 at 7:33 pm):
If there is agreement that the mechanism of the purported warming effect at Earth’s surface has no relationship to the mechanism of an agricultural greenhouse, then it is high time for professional climatologists to abandon their use of the misleading phrases “greenhouse effect” and “greenhouse gases” and replace them with phrases that at the very least are not misleading. However, these phrases plus descriptions drawn from them persist in the works of professional climatologists. This persistence suggests disinclination among professional climatologists to admit and correct error.
Once, I witnessed a similar psycho-social phenomenon in a field in which I was responsible for management of a significant fraction of world research. Early in my tenure, I discovered an error that invalidated a portion of the scientific basis for belief in the safety of the nuclear power program. When I reported this error to colleagues, the reaction of 100% of them was to cover up the error. Twenty-five years later, this error persists in the fabric of nuclear power technology.
Contrary to popular belief, the peer review system is insufficient for the purposes of exposing and eliminating errors in the works of scientists. An organizational form of similar nature to that of an quality assurance organization is needed for this purpose, in my opinion.
Terry: You have a very black-and-white, two-valued view of the world. Terminology is not erroneous or correct. It is just terminology. There may be better or worse terminology, but there also tends to be inertia in terminology, so we tend to get stuck with what first develops. At any rate, it is incorrect to claim that “the purported warming effect at Earth’s surface has no relationship to the mechanism of an agricultural greenhouse”…In some respects, there is an analogous relationship; in some respects there is not. What is correct to say is that analogies are never perfect and this particular analogy is not as close as one might think.
There are many examples of terminology that may not be ideal in science. For example, the “electromagnetic force (EMF)” is not a force (and for that reason some textbooks go as far as saying that “EMF” used to stand for electromagnetic force but now doesn’t stand for anything!!!); there are other examples that I can’t think of now, but there is a fellow-instructor who rails about these various problems with terminology in physics and says “No wonder students get confused”; my personal opinion is that students are primarily confused for other reasons.
At any rate, only in the highly-politicized world surrounding climate science is such deficiencies in terminology taken to be an indictment of the entire scientific enterprise, or at least in that field.
Joel Shore (Nov. 20, 2011 at 6:16 am):
People, including policy makers, are being misled by eccentric uses of “greenhouse” and “heat” by professional climatologists into thinking that as they are relatively transparent to short wave radiation and opaque to long wave radiation, the greenhouse gases trap “heat” by shining “back radiation” on Earth’s surface. They think this addition of “heat” to Earth’s surface is the “greenhouse effect” and that the existence of this effect proves the AGW conjecture. You can satisfy yourself that this is true via a Web search on “trapping heat” and “greenhouse effect.” An example of what your Web search will turn up follows.
A Web page of the Australian parliament states that “Greenhouse gases are gases in the atmosphere that absorb and emit infrared or heat radiation, thus trapping heat in the lower atmosphere” (
http://www.aph.gov.au/library/pubs/climatechange/theBasic/greenhouse.htm ). This statement is false but the parliament that recently imposed a draconian tax upon CO2 emissions by the citizens of Australia evidently thinks it is true.
I exchanged email with a professor of climatology over a Web posted video in which the professor said greenhouse gases had an effect at Earth’s surface (the “greenhouse effect”) that was like turning on a heat lamp up in the atmosphere. I responded that while the filament of a heat lamp was at a higher temperature than the matter that was heated by it, matter up in the atmosphere was at a lower temperature than Earth’s surface. Thus, the matter in Earth’s surface could not receive radiative heat from the latter matter.
In the literature of climatology, claims that radiative “heat” flows from the relatively cold
matter in the atmosphere to the relatively hot matter in Earth’s surface is common but this usage of “heat” is inconsistent with the definition of “heat” in theremodynamics as “the energy that
crosses the boundary.”
When a word such as “heat” is used in reference to disparate ideas, consequences include deception and blockage of communication. Thus, the word “heat” should be used in reference to only one concept. For avoidance of the necessity for rewriting the literature of thermodynamics, the word “heat” should be reserved for reference to “the energy that crosses the boundary.” The term “vector irradiance” is available for use in reference to the flux of radiative energy that passes from relatively cold to relatively hot matter. The “radiative heat flux” is then the vector difference of the “vector radiosity” and the vector irradiance.
When use of the word “heat” is restricted in this way then it becomes clear to a person with a background in heat transfer and fluid mechanics that an increase in the long wave vector irradiance at Earth’s surface from an increase in the concentration of greenhouse gases will be negated by a feedback mechanism in which an the rate of convective heat transfer increases in the amount of the increase in the irradiance, maintaining the adiabatic lapse rate. Thus, the Australian parliament’s understanding of the argument for anthropogenical global warming is mistaken. The blame for the Australian parliament’s misunderstanding can be laid on the shoulders of those who insist upon eccentric uses of the words “heat” and “greenhouse” in communicating about climatology.
Terry: As near I can tell, it is you who are running yourself in circles. Whether the Australian parliament is confused about the exact mechanism of the greenhouse effect is irrelevant to what that effect will be and, in particular, you descend into nonsense with you statement:
If the lapse rate doesn’t change, when greenhouse gases increase then the entire troposphere will have to warm by an amount sufficient so that the temperature at the effective radiating level has increased to the point where incoming and outgoing radiation is again balanced. Your statement that this amounts to the increase being “negatied by a feedback mechanism…” is thus nonsense.
In reality, the lapse rate does change a little bit overall because the moist adiabatic lapse rate is a decreasing function of the temperature. This is a negative feedback effect that is included in all of the climate models…and whether the Australian Parliament understands the details of this effect are irrelevant, as long as the scientists advising them as to the potential magnitude of AGW do.
My 2c-worth :
The theory is that some of the outgoing IR is stopped (use whatever word you like best here) by CO2 in the troposphere, thus making the troposphere a bit warmer than it otherwise would be. The troposphere therefore re-radiates IR a bit more than it otherwise would, and the end effect is that the surface and the troposphere both end up a bit warmer than they otherwise would. Because the Earth’s radiative balance is affected (incoming energy vs outgoing) there is a net overall warming effect on the planet.
That’s the theory. Physically, it is nothing like a greenhouse, so is badly named. But the name doesn’t make the theory wrong.
There is never a net flow of heat (or whatever you want to call it) from a cooler object (the troposphere) to a warmer object (the surface), so no scientific laws are broken.
I think you will find that most people are comfortable with the theory, ie. they accept that it is correct.
Where people do not agree is in the magnitude of the process. CAGWers claim that together with some positive feedbacks the effect dominates everything else and will lead to an irreversible tipping point. There are multiple problems with this claim: Evidence from the troposphere shows that the effect is small enough to be undetectable. There is no evidence and no known mechanism for the positive cloud feedback, and possibly not for any other positive feedback. On the contrary, there is evidence of negative feedback although this too is disputed. Evidence of past temperatures and CO2 concentrations do not support the CAGW claim, which relied heavily on Michael Mann’s utterly incorrect hockey-stick.
All the evidence indicates that CO2 has a much smaller impact on Earth’s temperature than is claimed by the IPCC, and that natural forces are more powerful than they allow. A recent statement by the IPCC, that natural factors will outweigh CO2 for the next two or three decades, shows that CO2 is not as powerful a factor as they claimed (because their latest statement conflicts with their past predictions), and that natural factors are more powerful. Obviously – very obviouslt – what still remains to be discovered is exactly what those natural forces are, because there is nothing at all in the IPCC report which identifies or explains them.
IOW, the science is absolutely NOT settled, and the IPCC now implicitly admits it. What is absolutely inexcusable is that anyone ever claimed or allowed it to be thought that the science was settled. Had the main proponents had not bulldozed a long way outside the bounds of proper scientific process then we would not be in this very expensive mess now.
Mike Jonas: Your first few paragraphs are reasonable but then you sort of go off the rails. In particular, you say:
The “tipping point” is not a general claim…and the use of this term is somewhat problematic since it tends to be used in different ways. A more accurate statement would be that most climate scientists have concluded that positive feedbacks dominate (if one uses the terminology where the Planck response is not a feedback) and hence that the expected climate sensitivity is larger than the no-feedback value, probably around 1.5 to 4 times that value. What is also true is that there is a lot of inertia both in our society and in the climate system and, because of this, it is not easy to quickly reverse course.
This statement is simply false. For example, there is significant evidence for a positive water vapor feedback of about the expected magnitude. The paleoclimate evidence is also generally interpreted as showing a climate sensitivity in the range of what the IPCC has concluded; in fact, it is mainly on the basis of that data that such a determination has been made.
Pretty much every statement in this sentence is unsubstantiated and false in the opinion of most researchers in the field.
Where has the IPCC made such a statement? From what I can tell based on the thread here that contained this claim, it is based on a distortion of what the IPCC has said about some rather narrow issues dealing with the attribution of certain extreme events.
This is a false dichotomy. Science is never settled. The science of gravity is not settled…but that does not mean we should not make any policy decisions based on what we currently understand about gravity.
Joel Shore – “Where has the IPCC made such a statement?” [that natural factors will outweigh CO2 for the next two or three decades]
This is Richard Black’s report on “IPCC’s latest report on extreme weather” –
http://www.bbc.co.uk/news/science-environment-15698183
– and there are few stronger supporters of CAGW than RB.
““Uncertainty in the sign of projected changes in climate extremes over the coming two to three decades is relatively large because climate change signals are expected to be relatively small compared to natural climate variability“.”
Joel Shore – replying to “…There is no evidence and no known mechanism for the positive cloud feedback …” said : “This statement is simply false” and discussed only the other feedback(s). JS, if you are so certain that what I said is ‘simply false’, please explain the mechanism of positive cloud feedback and provide evidence of its actual existence.
Joel Shore – replying to “Evidence of past temperatures and CO2 concentrations do not support the CAGW claim, which relied heavily on Michael Mann’s utterly incorrect hockey-stick.” said : “Pretty much every statement in this sentence is unsubstantiated and false in the opinion of most researchers in the field.”
I don’t think I need to say anything.
Mike says:
So, like I said, “it is based on a distortion of what the IPCC has said about some rather narrow issues dealing with the attribution of certain extreme events.” You have taken one sentence, stripped of the contents of what surrounded it…and then you have left off whatever context and modifiers that are in the sentence. The IPCC was talking narrowly about attribution of extreme events, something that is notoriously more difficult to do than, say, looking at averages, and you have turned it into a much more general statement.
Actually, you stripped your own quote of the statement “and possibly not for any other positive feedback” whichI focused my reply on.
As for cloud feedback, I don’t think your statement is correct for that either…One could consider several ways in which a warmer world might lead to, say, a reduction in low clouds or an increase in high clouds, either of which would tend to lead to a positive cloud feedback. I agree with the notion that there is still a lot of uncertainty in regards to the cloud feedback and whether or not it is positive, but to simply claim that there is no known mechanism or no evidence at all to support such a positive feedback (as opposed to claiming, for example that the evidence is mixed) is going too far.
The point is that you have presented no evidence to support the claim that Mann’s hockey-stick is utterly incorrect. It is not true that evidence of past temperatures and CO2 concentrations do not support the claim of a reasonably significant climate sensitivity, and it is incorrect to claim that the claim relied particularly heavily on Mann’s hockey stick.
Joel Shore – “it is based on a distortion of what the IPCC has said”
If there was any distortion, it was by Richard Black, one of the staunchest CAGW supporters. I can’t tell because the draft report is not yet public. RB claimed to have a copy. The quote was made while discussing extreme weather events but temperature was also discussed and the quote was clearly of general application “climate change signals are expected to be relatively small compared to natural climate variability“. As an aside, it is interesting to note that “climate change” now apparently means only the man-made variety!
JS – “One could consider several ways in which a warmer world might lead to, say, a reduction in low clouds or an increase in high clouds, either of which would tend to lead to a positive cloud feedback. I agree with the notion that there is still a lot of uncertainty in regards to the cloud feedback and whether or not it is positive, but to simply claim that there is no known mechanism or no evidence at all to support such a positive feedback (as opposed to claiming, for example that the evidence is mixed) is going too far.”
Too far? Just describe the mechanism. Show me the evidence. There isn’t any. None. “One could consider several ways…” is not exactly a mechanism or evidence. “I agree with the notion that there is still a lot of uncertainty” is just a dirty great wriggle. You couldn’t even bring yourself to say “I agree that there is a lot of uncertainty”. All you needed to say was simply “I agree that there is no evidence of positive cloud feedback”.
JS – “The point is that you have presented no evidence to support the claim that Mann’s hockey-stick is utterly incorrect.”
That the hockey-stick was an atrocious piece of unscientific trickery has been so widely known for so long that I didn’t think I needed to. Oh well, ,,
http://climateaudit.org/2011/03/15/new-light-on-hide-the-decline/
http://climateaudit.org/2011/03/17/hide-the-decline-sciencemag/#more-13285
http://climateaudit.org/2011/03/21/hide-the-decline-the-other-deletion/
http://climateaudit.org/2011/03/23/13321/
http://climateaudit.org/2011/03/29/keiths-science-trick-mikes-nature-trick-and-phils-combo/
http://climateaudit.org/2011/03/29/provenance-of-the-briffa-file-in-the-jones-1998-archive/
http://climateaudit.org/2011/03/30/muir-russell-and-the-briffa-bodge/
Smokey – yes, I know. It’s funny how climate sceptics are always called on to provide evidence (which they do) and then more evidence (which they do) and then the first evidence again ….. and so on and so on ….. yet the AGWers, who actually do have the onus of providing evidence for their claims, often can’t do so because the claims are based only on unsupported computer models. Cloud feedback is a prime example. It forms a large part of AGW (its claimed impact is marginally >i>larger than that of CO2!! [AR4 8.6.2.3]) yet there is no mechanism, no evidence, and the IPCC even states that and says that the models use fiddle factors [eg. AR4 Box TS.8 “parametrizations are still used to represent unresolved physical processes such as the formation of clouds and precipitation“].
Mike Jonas,
Pay no attention to Mann’s water boy, who argues: “The point is that you have presented no evidence to support the claim that Mann’s hockey-stick is utterly incorrect. It is not true that evidence of past temperatures and CO2 concentrations do not support the claim of a reasonably significant climate sensitivity, and it is incorrect to claim that the claim relied particularly heavily on Mann’s hockey stick.” Wrong. The onus of providing evidence is entirely on the part of the alarmist crowd, and so far all their “evidence” comes from always-inaccurate computer models. But of course, that isn’t evidence at all.
CO2 has been thousands of parts per million during the great Ice Ages, and very low at times when the earth was much warmer than now. Water vapor has fifty times the effect of harmless, beneficial CO2. But governments can’t tax water vapor, so they demonize “carbon”, which can be taxed.
And the preposterous belief that Mann’s hokey stick wasn’t completely fabricated from a bogus proxy record and phony statistics is solid evidence of anti-science true belief caused by cognitive dissonance. The more we learn about climate sensitivity to CO2, the more insignificant the effects of CO2 become.
Joel Shore says:
November 17, 2011 at 4:22 pm
Joel, I do take convection into account as I indicated in a previous comment. This is how the troposphere warms, from the bottom up. The air is warmed in two ways, firstly by conduction from the surface which causes convection of warm air to higher altitude. Secondly by the release of latent heat from water vapour during condensation at altitude. A pressure gradient exists across the atmosphere and unless gravity can be cancelled, warm air and water vapour will rise , moving heat away from the Earth surface.
The problem with much of global warming theory is that it focuses too much on radiation and too little on the physical movement of gases and liquids in the atmosphere. If CO2 does not cause significant warming of the troposphere, it cannot have significant effects on life on Earth. It will effect us little if the tropopause is raised by 300m.
It is often stated that greenhouse gases keep the Earth around 33 degrees warmer on average than it would otherwise be. When compared to the surface of the Moon which is the same distance from the sun this would appear to hold true. However by looking at averages physical mechanisms are ignored. After 6 hours of sunlight the temperature of the lunar regolith is hotter than the sand in the hottest desert on Earth. Our atmosphere is actually cooling Earths surface during sunlit hours. Part of this is due to clouds, but for the most part it is through conduction, evaporation and convection that our atmosphere cools the surface. Water vapour, a greenhouse gas capable of reflecting outgoing IR, is also part of the hydrological cycle acting as a giant vapour/condensate heat pump transporting heat away from the surface.
We do not yet have the technology in place to empirically quantify the TOA radiation budget. Even if we could detect an imbalance a subtle as that likely to be caused by increases in CO2, it would not tell us what effect that would have on the lower troposphere where we live. A far better understanding of the physical behaviour of gases and liquids in our atmosphere would be required.
I have demonstrated earlier on this thread that what was assumed about the impact of 15 micron LWIR on the surface of the the oceans may be a serious error. You appear to have changed your position from claiming Willis was right to saying that it does not matter and that TOA radiation budgets are what is important. Maybe you should give Kevin Trenberth and email to tell him to stop looking for the “missing heat” in the oceans 🙂
Konrad – you say that “I do take convection into account as I indicated in a previous comment.“.
I have a question for you.
I am (casually) interested in the relative importance of the mechanisms. I have graphed the temperatures at surface, tropical TLT and tropical TMT. (Surface was global not tropical unfortunately). I did a rolling 12-month smoothing to make it easier to see what was going on on a multi-annual basis:
http://members.westnet.com.au/jonas1/TropicalTemperatureGraph_201111.jpg
It is apparent from this graph that the troposphere temperature reacts much more than the surface to ENSO – the major spikes in the graph are El Ninos, the dips are La Ninas.
It seems to me that the major mechanism on this time scale has to be convection not radiation, because I seriously doubt that changes in radiation from the ocean surface could produce such large results in the troposphere on that short time scale. On the other hand, a burst of warm air rising could do the trick (and the ending of the burst, in the other direction).
So the question is simply: Does what I’m thinking make sense? And, of course, is the mechanism well known, but since it isn’t in the climate models I suspect that it isn’t.
Mike Jonas says:
The climate models and simple basic physical arguments predict, and the data verify, that temperature fluctuations tend to get magnified as you go up in the troposphere: http://pubs.giss.nasa.gov/docs/2005/2005_Santer_etal.pdf It is due to the fact that the moist adiabatic lapse rate, which temperatures in the tropics tend to at least roughly follow, is a decreasing function of the surface temperature.
Konrad says:
If you correctly understood the role of convection, you would not be so hamstrung in your thinking that you focused so much on the surface radiative balance.
No…That is the problem with skeptics like yourself who don’t seem to understand when you have take convection into account and when you don’t. They (you) are constantly talking about the surface radiative balance, which is essentially irrelevant. Actual climate scientists understand that a better way to do things is to start with the top-of-the-atmosphere radiative balance because you truly don’t have to take convection into account there: There is no convection in the vacuum of space.
It is more than from looking at the moon. It follows from very basic physical principles like energy conservation (although technically, the statement is that it is all IR-active elements, including clouds, that contribute to this 33 C temperature difference): The earth’s surface is at a temperature where it emits ~390 W/m^2. However, the earth system as a whole can (and does) emit only about 240 W/m^2, very nearly the same amount it absorbs from the sun. The only way this is possible is if the atmosphere absorbs (or reflects) some of the 390 W/m^2 of radiation that the surface emits. In the absence of such absoprtion, the surface simply could not emit more than ~240 W/m^2 and could thus not be at a temperature higher than ~255 K. (Convection and evaporation-condensation won’t help you…in fact, will just make the discrepancy worse…unless you want to make the argument that these processes transport heat from the atmosphere to the surface…and I doubt that you do.)
This is well-understood by climate scientists…as can be seen in the Trenberth-Kiehl diagram. It also turns out that if you know the global precipitation (or evaporation) rate, you know to within a few percent how much heat is being transported from the surface into the atmosphere via the evaporation/condensation mechanism. It is simply a first-year physics problem.
We may not have the technology to measure the budget down to the tenths of a watt per m^2 that we would like to. However, we do have the technology to accurately calculate the effect of a certain increase in greenhouse gases on that budget…and it is much easier to then work your way down to figure out what is happening at the surface than to work your way up.
Convection may be complex in nature but its effect is relatively simple, which is to maintain the environmental lapse rate at something very close to the appropriate adiabatic lapse rate in the troposphere.
The fact that you can’t even convince someone like Willis of your position shows how untenable it is! Willis is not exactly disinclined toward skeptic arguments and it is rather frustrating to me to see what a very smart guy like Willis will continue to believe.
And, you are mis-characterizing my position: What I am saying is that you are not even looking at the problem correctly because you don’t understand what determines the surface temperature.
Mike: Here is one example of evidence for a positive cloud feedback – http://physicsworld.com/cws/article/news/39908 Does the evidence prove that the cloud feedback is positive? No, but I am not claiming such. I am just claiming that it is not realistic to claim there is no evidence in favor of a positive cloud feedback.
As for the evidence that you provided regarding the hockey stick by linking to many threads from Steve “Mountain out of Molehill” McIntyre, that hardly provides objective evidence that Mann’s work is “utterly incorrect”. At some point, you are going to have to get beyond your belief that all the accolades that Mann wins ( http://wattsupwiththat.com/2011/11/16/mann-gets-medal/ ) are just evidence that the entire scientific process is corrupt and entertain the fact that maybe you guys in your own little corner of the universe are wrong… Not that I am expecting that to happen very soon, given the power of cognitive dissonance and all.
Joel Shore – Evidence??? As the AGWers love to say: correlation is not causation. If the cloud cover decreases then it is not at all surprising if the sea surface warms up. That’s all they did, compare the two – less clouds = warmer sea surface, more clouds = cooler sea surface. They have no mechanism, no evidence that elevated CO2 levels cause lower cloud cover. Incidentally, I was somewhat surprised to see that of “18 leading climate models…Only two models predicted a positive feedback“. What’s going on – 16 of 18 models don’t support their findings yet the “researchers” cherry-pick one of the two that does??? Imagine the outcry from AGWers if someone drew global conclusions adverse to AGW from a short sample of data from a small fraction of the world’s oceans that contradicted 89% of their own computer models and had no known mechanism. It’s really hard to take any of this pathetic substitution for science at all seriously. And regarding the hockey stick, instead of spouting the usual ad hominems, how about addressing the actual issue? Mann cheated, he got found out. Unless, that is, you can demonstrate that McIntyre’s work was fatally flawed.