Why 33 deg. C for the Earth’s Greenhouse Effect is Misleading

September 13th, 2010 by Roy W. Spencer, Ph. D.

In my previous post I argued, using commonly cited numbers, that the greenhouse effect enhancement of adding carbon dioxide to the atmosphere would be about 3% for a doubling of CO2 (“2XCO2”).

The 3% enhancement is based upon 2 commonly quoted numbers: (1) 33 deg. C global-average surface warming for the natural greenhouse effect, and (2) about 1 deg. C additional surface warming from 2XCO2, without feedbacks. (Interestingly, these numbers can only be computed from theory, which always requires a variety of assumptions.)

The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and the estimated surface temperature if there was no atmosphere.


I explained that the 3% statistic is the one we should be dealing with conceptually, rather than what some people seem to be interested in, which is what portion of the Earth’s greenhouse effect is due to CO2. I argued that the answer to that question, which has been recently addressed in a new paper by Schmidt et al., really tells us very little regarding the impact of adding more CO2 to the atmosphere.

But what many people don’t realize is that the 33 deg. C of surface warming is not actually a measure of the greenhouse warming – it represents the balance between TWO competing effects: a greenhouse warming effect of about 60 deg. C (the so-called “pure radiative equilibrium” case), and a convective cooling effect of about 30 deg. C. When these two are combined, we get the real-world observed “radiative-convective equilibrium” case.

This has been known since at least 1964 (Manabe and Strickler, 1964). It was also discussed in Dick Lindzen’s 1990 paper, Some Coolness Regarding Global Warming, which is when I became aware of its significance.

Why is this Important?

When global warming is discussed, the warming effect of greenhouse gases is obviously of prime interest. But it is seldom if ever mentioned that about 50% of the surface warming influence of greenhouse gases has been short-circuited by the cooling effects of weather, as just discussed.

When Danny Braswell and I did similar calculations in 1997 to better understand the physics, we found that 1 deg. C of surface warming was true even for the pure radiative equilibrium case (no convective cooling by weather processes). This would mean that the REAL enhancement of the greenhouse effect with 2XCO2 is really only about 1.5%, not 3%, since the natural greenhouse effect is trying to warm the surface by over 60 deg. C, not by 33 deg. C.

Is this Simple Evidence of Negative Feedback?

These climate basics, which have been known since the 1960s, also raises an intriguing question: If the surface warming effect of 2XCO2 before surface cooling by convection is 1 deg. C, and (as even the IPCC knows) 50% of that natural greenhouse warming is then short-circuited by convection, might this then tell us that negative feedbacks in the climate system can be expected to reduce anthropogenic global warming to only 0.5 deg. C?

I believe this is entirely possible.

How could this happen, since there is so much evidence that water vapor feedback is positive? Because, even if water vapor feedback is positive, an increase in the solar shading effect of clouds (negative cloud feedback) could more than overwhelm the positive water vapor feedback, leading to little net warming.

The IPCC already admits feedbacks due to low clouds are the least understood. Indeed, the evidence presented in Spencer and Braswell (2010), at face value, would suggest this could happen.

We already know that the net effect of clouds is to cool the climate system in response to solar heating. Are we to believe that cloud changes turn into a warming influence when temperatures get a little bit higher? Well, that’s what all of the IPCC coupled climate models do now.

The Importance of Convective Cooling Versus Greenhouse Warming

I sometimes get e-mails asking why I don’t mention convection as a cooling mechanism in the context of global warming. Folks, I used to be virtually the only one speaking out on the subject. For years I harped on this issue.

The reason why I have been recently defending the basic physics of the greenhouse effect is because I think the credibility of those who claim that the greenhouse effect of the atmosphere cannot be increased (or doesn’t even exist) is compromised when they object to something that – as far as I have seen – has no alternative explanation.

I’m always upon open to new theories, but as I have said before, until someone puts their alternative physics into an energy-conserving model of the vertical temperature profile of the atmosphere, which then produces the present-day temperature profile as current models do, it is little more than hand-waving.

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57 Responses to “Why 33 deg. C for the Earth’s Greenhouse Effect is Misleading”

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  1. Jacob C says:

    Interesting.
    From this, it seems clear that perhaps there is some intended purpose for those in the Warmist cult to conveniently forget to mention convective cooling in almost every single description of the greenhouse effect out there.
    Quick question: how many atmospheric layers are there in the 60C calculation? I know that with one layer, you get about 50C in warming in an RC model, but with two you get about 80C. How are these layers chosen – arbitrarily or due to some parameter like pressure, and how high is this layer? I know, a lot of in depth stuff, but I can’t seem to glean it from the papers or other blog posts on the subject.
    Help? :-)

  2. I think we used 59 layers in our model, corresponding to the levels in the average AFGL atmospheric profiles. This included 39 layers from the surface to 100 mb, then 20 layers above that up to 0.1 mb.

  3. Jim Cripwell says:

    You write “(Interestingly, these numbers can only be computed from theory, which always requires a variety of assumptions.)”

    I wish this statement could be emblazoned somewhere so everyone who is interested in AGW realizes that it is true. But I would go further. I believe some of the “variety of assumptions” are just plain wrong. Further, any number that it is theoretically impossible to measure is an anathema in physics. (This is as opposed to numbers which are impractical to measure). And the 1 C rise in global temperatures, without feedback, is just such a number. It ought never to be allowed in any discussion of proper physics. It is perfectly acceptable as an interim number to estimate the rise in temperature with feedbacks, but on it’s own it is just plain nonsense.

    • Anonymous says:

      Perhaps a niyon my part.
      Sort of understand the thrust of your post. But the conclusions seem a bit extreme — theoretical physics? I would go to the extent of expressing caution in such situations

      • not sure which conclusion you view as extreme.

      • Anonymous says:

        I am considering how one goes from change of radiative forcing to change in global temperature. From what I can gather, this is done using the Stefan Boltzmann 4th power law. That is, it only considers radiation transfer of energy within the atmosphere. So we arrive at 1 C rise for a doubling of CO2, without considering conduction, convection or latent heat. I find it impossible to believe that this is sound physics.

        I suspect that there is an inherent assumption that all the energy that is radiated into space, comes from the surface of the earth. If so, then this is wrong. One should apply Stefan Boltzmann to those places from where the energy is being radiatied into space (eg the TOA), and then estimate what difference this makes to surface temperatures. The touble is, no-one knows how to do this.

  4. kuhnkat says:

    Dr. Spencer,

    In your theoretical computations you seem to only include pure radiative effects and convection for the 33c number. Where are the effects from conduction ala the Moon Greenhouse effect. I realize that “paper” had problems, but, that does not discredit the actual physical attributes of a system.

    How is the slower cooling and heating caused by conduction to and from deeper layers of both the ground and oceans included in these theoretical computations?

    • Conduction is ignored, since it is assumed to only impact how long it takes for equilibrium to be reached. Yes, it is an assumption.

      • kuhnkat says:

        This is troubling. As the effect of back radiation is alledgedly most apparent at night, wouldn’t it be necessary to separate out this other cause for the slower cooling of the surface before assigning a value to CO2 and back radiation?

  5. Juraj V. says:

    Dr Spencer, this 33 deg C is calculated for theoretical planet without atmosphere, but with present albedo, created mostly by clouds and frozen water. Without clouds, it should be close to 15C. And still the heat capacity of ground, atmosphere and ocean creates big and unquantified part of our warm nights, which can not be solely attributed to “greenhouse effect”, whatever its real effect is.

    • yes, I believe I alluded to the fact that “assumptions” are necessary to make these theoretical computations. I didn’t want to get into the details, like how one can meaningfully calculate a pure radiative equilibrium surface temperature when there is no convection, since convection acts to cause clouds (and thereby increase albedo, thus a cooling effect) and increase water vapor (and thereby increase the natural GE, a warming effect).

      It is true that these theoretically-computed quantities involve assumptions that we know are unrealistic.

      • Anonymous says:

        Dr Spencer,
        The most unsatisfactory aspect of climate science to this layman is the propensity of scientists to knowingly make unrealistic assumptions to facilitate theoretical computations which they nevertheless claim to be reliable.

        The 33 degrees C of net natural greenhouse effect assumes the climate system radiates as an idealised entity known as a black body which occurs nowhere in the real world. Within the climate system, the earth’s surface may approximate the ideal but, according to the global mean surface energy budget (K&T 1997) less than 20% of radiation to space originates at the surface.

        Since the bulk of the heat loss to space originates in the atmosphere, the emissivity of air determines the theoretical effective radiating temperature of the atmosphere. Swinbank in the 1960s showed air emissivity to vary directly with the square of temperature giving rise to values of 0.76 and 0.45 at the surface and tropopause, respectively. This implies a much higher radiating temperature than the 255K from which the 33 degrees C natural greenhouse effect is calculated and, therefore, a much lower natural greenhouse effect. In turn that would imply a much reduced enhanced greenhouse effect due to man. Intriguingly, if these numbers are reliable, a negative greenhouse effect, ie a refrigerator effect, seems physically feasible. De-carbonising world economies would warm the planet??

  6. Christopher Game says:

    Christopher Game commenting on the Schmidt Ruedy Miller Lacis 2010 draft cited by Dr Spencer.

    These authors write in the cited draft: “The global mean greenhouse effect can be defined as the difference between the planetary blackbody emitting temperature (in balance with the absorbed solar irradiance) and the global mean surface temperature.”

    It is a pity these people define the greenhouse effect in terms of temperature. As Dr Spencer makes clear in his article, the definition in terms of temperature is heavily theory-laden, and perhaps ambiguous or hypothetical, for example “if there was no atmosphere”:

    “(Interestingly, these numbers can only be computed from theory, which always requires a variety of assumptions.)

    The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and the estimated surface temperature if there was no atmosphere.”

    Surely it is better to define the greenhouse effect quantitatively as proposed by Inamdar and Ramanathan (1997) ‘On monitoring the atmospheric greenhouse effect from space’, Tellus 49B: 216-230, and by Stephens, Slingo, and Webb (1993) ‘On measuring the greenhouse effect of Earth’, NATO ASI Series, vol. 19, pages 395-417?

    I&R97 define the greenhouse effect G by G = Sg – OLR, where Sg denotes the upwards thermal radiation flux density entering the atmosphere from the ground (land-sea body).

    SS&W93 define it by G` = Sg / OLR.

    These definitions are directly in terms of radiation, which is really the focus of interest in the term. For example, SRM&L2010 write: “The key issues relate to the spectral overlaps between absorbers and, potentially, the spatial and temporal distribution of absorbers.”

    In practice SRM&L2010 actually use the same definition as I&R97 cited above: “We quantify the impact of each individual absorber in the total effect by examining the net amount of long-wave radiation absorbed in the atmosphere (G, global annual mean surface upwelling LW minus the TOA LW upwelling flux) [Raval and Ramanathan, 1989; Stephens and Greenwald, 1991].”

    Temperatures have various well known drawbacks for this kind of work. For example, they are not specifically diagnostic of radiative transfer. I think perhaps people may use the temperature definition to make the subject palatable to non-scientists?

  7. Buzz Belleville says:

    I’m still on clouds … trying to thoroughly grasp some of the finer points of Dr. Spencer’s theories. He writes:
    “We already know that the net effect of clouds is to cool the climate system in response to solar heating. Are we to believe that cloud changes turn into a warming influence when temperatures get a little bit higher? Well, that’s what all of the IPCC coupled climate models do now.”

    Is someone (the IPCC or any reputed scientist from the AGW camp) really arguing that the net effect of clouds will be to warm the climate system? Because that’s certainly not the position I have understood from the IPCC or elsewhere. The position I have seen from some models is that the greenhouse effect of clouds will be increased, but never that it would surpass the cloud albedo effect such that clouds as a whole are a net negative forcing. In other words, they argue that the clouds will absorb and reradiate more infrared radiation emitted from the planet (because there is more being emitted), but I’ve never seen anyone argue that clouds will suddenly be absorbing more than the 45 or 50 W/m2 (whatever the number) of direct solar radiation that is reflected by clouds in the first place. We can expect more infrared radiation from the surface, but not more (or less) direct energy from the sun. Maybe I’m missing something.

    I also continue to be confused by the assertion that all of the IPCC models show a warming effect from clouds. Roughly half of the IPCC models show a negative radiative forcing from clouds, and about half predicting a positive forcing. (Figure 8.15 and section 8.6.3.2.). (And, to square that with my first point, these are not depicting the net effect of clouds on the climate system, but the net change in the energy balance ratio between cloud albedo and greenhouse effect).

    Finally, I understood that our paleoclimatic history had shown that, during glacial periods, a tropical lessening of clouds (due to cooler waters) would have amplified the global cooling and the glaciation. Is there any empirical evidence yet (I know the real data on the topic is scattered, incomplete and/or in its infancy) showing that cloud albedo increases in response to either the PDO or some other cycle, or in response to a greenfouse-nduced warming? Or is this just all theory at this point?

    Thanks to any who can continue to enlighten me.

    • Anonymous says:

      Buzz, I think you have discovered one of the wonderful symmetries in cyberspace. Once you have done an adequate job of convincing your audience that some statement made by some source is not true, it is very easy to convince them that the source also made another untrue statement, even if they didn’t. After all, if the source were thorough enough, they would have covered all the untrue statements. It is actually only through the laziness of the source that they didn’t get around to making the untrue statement you attribute to them.

    • Buzz, you are confusing the *average* effect of clouds on the climate system with cloud feedbacks, which is how their influence *changes with warming or cooling* away from the average state.

      For instance, Fig. 8.15 from IPCC AR4 you mention refers to the fact that, in the *tropics*, in roughly half the models the average effect of clouds is to cool, while in the other half the average effect is to warm. This paper by Soden and Held shows that the net, global cloud feedbacks in all models are positive.

  8. Buzz Belleville says:

    One more question (sorry, just trying to learn). While convection as a negative feedback to AGW makes theoretical sense to me, would the cooling effects have to await the new equilibrium before they will be felt. In other words, as long as more “hot” energy is being forced into the troposphere from the greenhouse effect, would the expected convection cycle (of hot replacing cool up high and cooler thus replacing hotter down low) happen? I know I’ve worded that poorly. To borrow from Dr. Spencer’s boiling pot analogy, the water down low in the pot gets warmer due to conduction … as it gets warmer the molecules spread (up and out) … and then the colder fluid at the top is ultimately displaced and it replaces the warmer fluid at the bottom. Does this whole cycle happen while conduction is still occurring (the stove is still turned on directly warming the metal pot)? Back to the climate, as long as there is a greenhouse effect which is causing the warmer air near the surface, will cooler air from higher up displace the warmer surface air? Is this answerable by a physics equation, or ‘only’ by modelling?

    • what you are asking about is how events unfold during the transition to a new equilibrium state. This is something that is not thought about much. It is definitely not the case that a new equilibrium temperature state is achieved before feedbacks kick in. I would say that as soon as the temperature departs from the average state, feedbacks come into play. But this sort of required by our definition of feedback.

  9. jeff id says:

    The greenhouse effect is not possible to dispute. I’ve done several posts on it to various peoples chagrin. I work in optics and have for 20 years now. The basics are real, it is the feedback that is complex. It is impossible to dispute the basic effect though from not just these less obscure points but rather from the physics based gas absorption argument.

    For the feedback to be even potentially negative is a huge point in an era where discussions of $100 billion per year are commonplace.

    As far as the convection, there are moisture condensation based convection effects which aren’t even close to being correctly quantified in models. I think Anastassia Makarievea’s paper on condensation driven hurricanes makes the point rather nicely

    http://noconsensus.wordpress.com/2010/02/02/the-power-behind-hurricanes-and-tornadoes/

    Really nice post again. BTW, I’m very unimpressed so far with the lack of reaction to your feedback paper. I mentioned it in a WUWT thread. This year two papers have been more effective critiques of the IPCC climate change outlook MMH10 and yours. They both should be more startling than climategate ever was but it’s all quiet at this point.

    • kuhnkat says:

      Intelligent people, when caught cooking the books, shut up and get their lawyers!!!

    • kuhnkat says:

      Jeff,

      you make much of your experience with radiative optics. Could you please provide us with experimental data showing how much CO2 reduces the cooling of the surface irradiating it??

      Also, data on how much the CO2 warms the gasses surrounding it would be of help also.

  10. Brego says:

    Why 33 deg. C for the Earth’s Greenhouse Effect is Misleading

    Dr. Spencer, I applaud your effort to address this issue, but I’m afraid that you have gotten off on the wrong foot from the git-go.

    There is no such thing as a “greenhouse effect” that keeps our planet’s surface temperature warmer than it would be otherwise, as I will explain.

    Imagine a planet whose atmosphere is transparent to IR, and incapable of absorbing or emitting IR energy. That planet’s atmosphere would still be warmed via conduction with the planet’s surface, but it would not possess any means of ever cooling. That planet’s atmosphere would be very hot, night and day, for as long as that planet and it’s atmosphere existed.

    Fortunately, on our planet, we have a different situation. The net result of our planet’s atmosphere possessing components that are capable of absorbing and emitting IR energy is to keep tropospheric and surface temperatures cooler than they would be otherwise, not warmer. That is backwards.

    We have to remember, that at any layer of the troposphere, half of the emissions are upwards and outwards, and lesser in total than the layer below. That is what keeps tropospheric and surface temperatures cooler than they would be otherwise.

    Our planet’s atmosphere radiates a great deal of energy to space, and makes life as we know it possible on our planet. Rather than condemning it, we should be appreciative of it.

    • Anonymous says:

      You are missing an important point. EVERYTHING emits blackbody radiation based on its temperature. Even with no GHG’s the earth, ocean and atmosphere would be radiating IR.

    • Anonymous says:

      John Millett commenting on Brego
      September 13, 2010 at 4:13 PM

      I think the conditions you posit would result in an isothermal atmosphere at about 390K, the effective temperature of the solar flux at TOA. As you say, the presence of matter in the atmosphere capable of radiating to space avoids this result.

      However, if that capability is restricted to trace gases, the so-called GHGs, the question arises as to how heat is transported from the 99% non-radiating component of the atmosphere to the GHGs. This would have to be by non-radiative means, probably through molecular collisions, the probability of which would seem to be low and variable directly with the concentration of GHGs. That is, while GHGs choke the transport of heat to space from the surface they facilitate it from the atmosphere. In other words GHGs simultaneously warm and cool the planet.

      Alternatively, why restrict radiating capability to the trace gases? Recall that over 80% of radiation to space originates in the atmosphere. As another comment has it, all matter relevant to climate science radiates according to its absolute temperature (and to its emissivity). However, scientists say that Kirchoff’s Law, which equates absorptivity and emissivity (given wavelength) precludes this – nitrogen and oxygen molecules can’t absorb radiation therefore they can’t emit it. I would very much appreciate resolution of this apparent conflict in thermodynamic theory.

  11. Transport by Zepelin says:

    Dr spencer;
    Quote

    “How could this happen, since there is so much evidence that water vapor feedback is positive?”

    I understand that, in a warming atmosphere the rate of evaporation would increase, but this would not necessarily result in a net increase in atmospheric water vapor (positive feedback), a greenhouse gas, leading to an increase in forcing.

    Dr Spencer, are you specifically saying that there has been an increase in atmospheric water vapor? If so, what is the evidence you’re refering too that supports this?

    I consider this surprising, specially considering the fact that the modelled expectation of the ‘Hot Spot’ never eventuated & papers that have tried to support this have been bumpkin.

    • I always get myself into trouble on this point. I guess I need to devote a blog post to water vapor feedback, since there are so many things involved. For instance (as a teaser) it is possible that water vapor can increase, but for water vapor feedback to be negative. We, among others, have published this elsewhere.

  12. jeff id says:

    Comment is stuck in moderation.

  13. Baa Humbug says:

    Thankyou for another informative post Dr S.
    I for one would like to see the isolation of H2O from other GHG’s in research and discussions.

    H2O does not physically behave like a GHG gas in our atmosphere. We ask “what if there were no GHG’s?”
    We should also ask “what if there was no H2O?”

  14. steveta_uk says:

    Brgeo says:

    “That planet’s atmosphere would still be warmed via conduction with the planet’s surface, but it would not possess any means of ever cooling.”

    That’s simply illogical. Conduction works both ways, so the atmosphere has no reason to be hotter than the surface. Since the surface temperature is regulated by IR emissions directly to space (in your IR-transparent atmosphere) there is no reason to expect high atmospheric temps.

  15. Jim Cripwell says:

    I seem to have messed things up a bit. On the part of my original comment, my reply is attributed to Anonymous. Sorry about that.

  16. Mike Edwards says:

    Dr Spencer,

    As always, an excellent and lucid discussion of a truly complex system.

    The changing behaviour of the Earth’s atmosphere under varing conditions is not easy to model and understand, for sure. Your studies of the relative aridity of the atmosphere in the tropical high pressure zones and the sensitivity of these zones to changes in humidity with respect to infrared emissions hint at the difficulties of building good models.

    It is intriguing to consider the behaviour of some of these zones in the past, with clear indications of considerably higher humidities across areas of the Sahara and Arabian Peninsula at the Holocene maximum and in previous interglacials. This suggests an entirely different mode of atmospheric circulation, perhaps associated with higher overall global temperatures, as indicated in the ice core data.

    Is this perhaps an indication of natural oscillations on longer timescales that dwarf the PDO and NAO that we see in our present?

  17. Kevin says:

    Dr Spencer, I do find your posts enlightening in that they do increase my understanding of the approach taken by the climate science community. I am still trying to “translate” between my engineering understandings of the processes of heat transfer to better align with the understandings of the climate science community. However I am still “Speaking Greek” while you are “Speaking French”, (no offense intended, please select sample languages (perhaps dead languages) that do not offend anyone).

    So, I still see this defense of the Radiative Transfer Equations, i.e. a Blackbody SURFACE emits an amount of energy that can be precisely calculated and it causes a new “equilibrium temperature” to be reached as the FATAL flaw in the “Greenhouse Effect Theory”. This to me is still the “crux” of the problem, as an electrical engineer I do not believe that an “equilibrium temperature” ever exists! I believe that different compositions of gases (and of course Water Vapor) in the atmosphere of the Earth cause changes in the “frequency response “of the total system.

    We in the electrical engineering field rarely talk of “a system in equilibrium”, we tend by training and experience to think and talk of systems with respect to the frequency response of the system. When we create a “Direct Current” power supply we worry about the noise content and the response to transient demands due to load changes. So we attempt to create an “ideal system in equilibrium” when we specify a Direct Current power supply. Of course we never ever really create an ideal system.

    Just one example of how we are speaking different languages, I have seen you write about how dew condenses on the hood of your car because of “infrared radiation” from the hood of your car that makes it cooler than the moist air. I hope I paraphrased that accurately. From my perspective this is much more a demonstration of the “speed of heat” than a demonstration of any unique heat transfer function performed by the emission of infrared radiation. Due mostly to the higher “speed of heat” in the metal your car hood is constructed of the temperature of your car hood falls faster (i.e. the frequency response) than the temperature of the atmosphere interfacing with your car hood.

    I suggest a simple empirical experiment; take two slabs of material, copper and polystyrene one foot square. Adjust the relative thicknesses so that each sample exhibits the same total thermal capacity (probably a half inch of copper versus several inches of plastic). Next, paint these samples with equally reflective gray paint (over most of the visible spectrum) to establish equal albedo characteristics. Now place them out in the sun and monitor the temperature of the sun exposed surface for 24 hours. I predict that that the copper sample will reach a higher temperature at its surface than the polystyrene sample. Why ? Equal Albedo, Equal Thermal Capacity, Equal Influence from “greenhouse gases”, Why the difference ? Because of the higher “speed of heat” in the copper slab more Joules (BTU’s, KCalories, etc.) are transported DEEPER into the material while the joules are present at the surface (i.e. 12 out of 24 hours).

    A simpler empirical experiment, place a plastic pool toy out in the sunlight, and also place a metal monkey wrench out into the same sunlight. After a few hours pick each one up, which one causes you to winch and drop the object ?

    Cheers, Kevin

    • Anonymous says:

      The reason you drop the wrench is not that it is warmer but that the stored amount of energy is higher. When you touch the plastic the surface cools so fast by conduction to your hand that you dont feel the heat. The wrench on the other hand does not cool so fast because it has stored more energy such that the temperature does not drop so fast. You are also completely wrong with your polystyrene vs. copper example for the same reason as explained above. You might be an excelent electrical engineer but thermodynamics is not you strong side. I work with thermodynamics on a daily basis as an engineer.

      • Anonymous says:

        Anonymous wrote;

        “The reason you drop the wrench is not that it is warmer but that the stored amount of energy is higher.”

        Respectfully I must disagree, the reasons you drop the wrench is because (1) the amount of energy stored in the wrench is higher AND (2) the speed of heat in the metal comprising the wrench is MUCH faster than the speed of heat in the human tissue. This means that the metal wrench can deliver much more power (heat) in less time (i.e. more energy) into the tissue of your hand. The electrical analogy would be discharging a capacitor, it happens much faster without a series resistor in the circuit.

        Anonymous wrote;

        “When you touch the plastic the surface cools so fast by conduction to your hand that you dont feel the heat.”

        Again I respectfully disagree, YES the energy at the surface (a.k.a. the interface) quickly moves into the tissue of your hand, BUT the energy below the surface SLOWLY moves towards your hand, thus making the (electrical analogy here) capacitor discharge more slowly. How is it a material (polystyrene with VERY LOW thermal conductivity, i.e. that’s why it’s a very popular THERMAL INSULATOR) can “cool so fast” that the final effect is that “you don’t feel the heat” ?

        Anonymous wrote;

        “You are also completely wrong with your polystyrene vs. copper example for the same reason as explained above.”
        Ok, fair enough, do the empirical experiment suggested (I constructed it as simply as possible) and report your results, Please ?

        Anonymous wrote;

        “You might be an excelent (sic excellent) electrical engineer but thermodynamics is not you (sic your) strong side”

        Ok, fair enough, but at this moment in time there are several satellites orbiting the Earth and exceeding their predicted performance regarding actual temperatures at actual locations within the satellite. The analyses behind these predicted temperatures was reviewed and approved by myself as a systems engineer in the aerospace industry. So if thermodynamics is not my strong side, there are a bunch of thermal analysts that fooled the heck out of me and a bunch of satellites must be overheating right about now.

        Cheers, Kevin.

        • Anonymous says:

          You are ofcause completely right that the speed of conduction is faster in the wrench and that this is also the reason why the wrench feels hotter I never argued against that, actualy I completely agree with your arguments in the second post but I still maintain the position that the wrench and the plastic has the same surface temperature after being heated in the sun for a long time. Actualy the plastic will have a higher surface temperature at the beginning because the heat is not conducted away from the surface with the same speed as with the wrench. but when thermal equilibrium is reached the two surfaces will have the same surface temperature, ofcause with the asumption that no heat is lost on the backside. In real life the wrench will actualy be cooler on the surface because the heat is conducted away from the frontside and then lost on the dark backside.

          Peter H. Sorensen

          • Anonymous says:

            Mr. Sorensen;

            You wrote: ”I still maintain the position that the wrench and the plastic has the same surface temperature after being heated in the sun for a long time.” I fully agree, my basic point is that the definition of “a long time” is indeed critical to this debate. I maintain the position that at some point in time the surface temperature of the wrench is higher than that of the plastic object. Additionally, at some other point in time (i.e. after the sun sets) the surface temperature of the wrench is lower than that of the plastic object. Empirical evidence suggested here, ever pick up a monkey wrench that you left out overnight in January in Upstate New York? I strongly suggest the use of gloves.

            My empirical evidence;

            1) In my climate (upstate New York) we often get light snowfalls that cover all types of surfaces; car hoods, concrete sidewalks, roof shingles, lawns, etc. When I’m not leaving early for my place of employment I sometimes get to enjoy a warm coffee and observe which surfaces lose their snow cover first. I have observed a clear correlation between the thermal diffusivity of the materials and the rate at which the snow melts. The snow melts from the metal surfaces first, and in fact I sometimes return from work to find a snow free driveway while the grass lawn is still covered with snow. I believe that this demonstrates that in a dynamic system the thermal diffusivity (i.e. the speed of heat) within the materials involved does indeed matter.

            2) We also have the classic example of dew on the hood of your automobile in the late evening and early morning. I suggest an empirical experiment using two gray car hoods, one made of steel and one made of fiberglass. Let’s measure the amount of dew that each experiences during the same weather conditions. Perhaps I can get a grant to build an advanced imaging system that will continuously measure the area of each car hood that is covered by dew ?

            Just to clarify my position;

            1 I do not dispute the existence of “backradiation”; EVERY SURFACE emits radiation commensurate with its temperature. Due to the selective molecule sizes inherent to gases (as opposed to the random mix of molecule sizes in a rock) the gases emit (and also absorb) at specific wavelengths (or multiples of wavelengths). In fact if you ever get around to investigating radio astrometry I believe you will find that VERY COLD objects (stars in this case) also emit radio frequency radiation based on Planck’s Law (look up the Physical units of Janskey’s just for fun).

            2 I also admit that in a STATIC system the nearby presence of anything that slows the flow of heat/energy will cause the energy (as expressed by the temperature) at a warmer (i.e. more energetic) location to equilibrate to a higher temperature.

            3)I postulate that the climate of the Earth is NOT A STATIC system and it is imperative to consider the “speed of heat” within the materials that are present in the system. Since my original training is as an electrical engineer (a.k.a. A “SPARKY”) my instinct is to characterize the climate of the Earth as an “AC Coupled” system. Therefore my instincts immediately cause me to question the “response time”, “frequency response”, “rise/fall time”, “delay time” of the system. I know from experience that many things maybe happening at frequencies above my observational abilities. This is why I find the assumption that we can accurately characterize the “temperature” of the Earth based on a few daily measurements at limited locations to be a major limitation.

            Maybe I’m crazy, but I am still of the opinion that increases in “Greenhouse Gases” actually cause more heat/energy to flow through the climate system of the Earth at the speed of light (quite speedy) versus the speed of heat (comparatively slower). I also postulate that the final effect of this is that the gases in the atmosphere warm up slightly faster after sunrise and cool down slightly faster after sunset. I also postulate that these effects are so small that we probably could not spend enough money to measure them.

            Cheers, Kevin.

    • Kevin, I think you might be misinterpreting something here, and I suspect others are as well. If there is an energy imbalance for the global climate system, it will *tend toward* equilibrium, with a change in temperature and any resulting feedbacks. Now, this doesn’t mean the system ever *achieves* equilibrium, which I think is your point. It’s like a pot of water warming on the stove…if the energy lost does not equal the energy gained, then the temperature will change in a direction that restores balance. It’s just conservation of energy.

      • Anonymous says:

        Dr. Spencer,

        I don’t believe that I have any misunderstanding about the climate system. As postulated by the proponents of the “Greenhouse Effect” the existence of “backradiation” (please insert other appropriate terms here) causes the climate to “assume” a new higher equilibrium temperature, thereby causing all kinds of evil results. If I have paraphrased the alleged results of the “Greenhouse Effect” incorrectly please correct me.

        As an alternative, I postulate that the existence of “backradiation” only affects the response time of the climate (what you call “feedbacks” both positive and negative). And due to the relative thermal capacities of the materials involved (oceans (huge), rocks (big) and gases (tiny)) I alternatively postulate that the changes to the response time of the climate (i.e. how fast the gases warm up after sunrise) are so small that we probably could not spend enough money to measure them.

        I really don’t see a misunderstanding here, just two vastly different interpretations of the Science.

        Keep up the excellent work.

        Cheers, Kevin.

        • Anonymous says:

          Slight correction please,

          In the second paragraph please replace;

          “I alternatively postulate”

          with;

          “I additionally postulate”

          Thanks, Kevin.

  18. Ed says:

    Thank you Dr Spencer for your common sense approach in the midst of the religious name calling.

    I would value your view if this very simple layman’s view is about right

    The FUTILITY of Mankind trying to Control Climate

    http://www.youtube.com/watch?v=Wy0_SNSM8kg

    On average world temperature is +15 deg C. This is sustained by the atmospheric Greenhouse Effect 33 deg C. Without the Greenhouse Effect the planet would be un-inhabitable at -18 deg C. The Biosphere and Mankind need the Greenhouse Effect.

    Just running the numbers by translating the agents causing the Greenhouse Effect into degrees centigrade:
    • Greenhouse Effect = 33.00 deg C
    • Water Vapour accounts for about 95% of the Greenhouse Effect = + 31.35 deg C
    • Other Greenhouse Gases GHGs account for 5% = ~1.65 deg C
    • CO2 is 75% of the effect of all accounting fort the enhanced effects of Methane and Nitrous Oxide GHGs = ~1.24 deg C
    • Most CO2 in the atmosphere is natural, more than 93%
    • Man-made CO2 is less than 7% of total atmospheric CO2 = 0.087 deg C
    • the UK contribution to CO2 is 2% equals = 1740 millionths deg C

    As closing carbon economies of the Whole World could only ever achieve a virtually undetectable less than 0.01deg C. How can the Green movement and their supporting politicians think that their remedial actions can limit warming to only + 2.00 deg C?

    So the probability is that any current global warming is not man-made and in any case such warming could be not be influenced by any remedial action taken by mankind however drastic.

    As this is so, the prospect should be greeted with Unmitigated Joy:
    • concern over CO2 as a man-made pollutant can be discounted.
    • it is not necessary to damage the world’s economy to no purpose.
    • if warming were happening, it would lead to a more benign and healthy climate for all mankind.
    • any extra CO2 is already increasing the fertility and reducing water needs of all plant life and thus enhancing world food production.
    • a warmer climate, within natural variation, would provide a future of greater opportunity and prosperity for human development. This has been well proven in the past and would now especially benefit the third world.

    Nonetheless, this is not to say that the world should not be seeking more efficient ways of generating its energy, conserving its energy use and stopping damaging its environments. And there is a real need to wean the world off the continued use of fossil fuels simply on the grounds of:
    • security of supply
    • increasing scarcity
    • rising costs
    • their use as the feedstock for industry rather than simply burning them.

    The French long-term energy strategy with its massive commitment to nuclear power is impressive, (85% of electricity generation). Even if one is concerned about CO2, Nuclear Energy pays off, French CO2 emissions / head are the lowest in the developed world.

    However in the light of the state of the current solar cycle, it seems that there is a real prospect of damaging cooling occurring in the near future for several decades. And as Green policies are closing productive power stations the lights may well go out in the winter 2016.

    All because CO2 based Man-made Global Warming has become a state sponsored religion.

  19. Alexander Davidson says:

    Time for reductio ad absurdum. To cover up systemic over-prediction, AR4 included entirely imaginary ‘cloud albedo effect’ cooling. It’s 44% of 1.6 W/m^2 AGW forcing. [Figure 2.4, http://www.ipcc.ch/publications_and_data/ar4/syr/en/mains2-2.html ].

    If you take off the 44% then scale by 33/60: you get 0.5 W/m^2. But the models exclude natural heating, recently estimated at 60% of post-1970 temperature rise[ http://arxiv.org/abs/1005.4639 ]. You could get 0.2 W/m^2.

    But even that is under threat because real cloud optical physics means the ‘cloud albedo effect’ may heat instead of cool. So CO2 AGW could be zero with the real warming above natural being from clouds!

    • Anonymous says:

      Christopher Game replying to Alexander Davidson’s post of September 15, 2010 at 2:17 AM.

      Alexander writes: “So CO2 AGW could be zero with the real warming above natural being from clouds!”

      Christopher replies: yes !!!

  20. Mike Blackadder says:

    “When Danny Braswell and I did similar calculations in 1997 to better understand the physics, we found that 1 deg. C of surface warming was true even for the pure radiative equilibrium case (no convective cooling by weather processes). ”

    I’m not certain that halving the 1 deg C due to convection follows from this argument. Like you say, convection basically short-circuits the greenhouse warming. But this happens near the earth’s surface where greenhouse gas concentrations are very high.

    I would think that in teh purely radiative case that doubling CO2 would have only a weak effect on the lapse rate near the Earth’s surface, since we are already saturated with greenhouse gases in this area. Therefore, temperature increases (ie. negative change lapse rate) due to higher CO2 would occur in upper atmosphere and would not get shorted out by convection.

  21. coldlynx says:

    It seems that most of basic radiative calculations miss the real and basic circumstance that the lapse rate decide possible temperature gradient with altitude. With higher temperature gradient as in M&S 64 pure radiative equilibrium, is the atmosphere not stable. Heated air rise and we have convection. that cools the surface but heat higher altitudes.
    With lower = real conditions temperature gradient, is radiative heat transfer capacity within atmosphere slabs reduced.
    There is less or nearly no net energy transported between atmospheric slabs in humid atmosphere with low lapse rate.
    IR is blocked by the lapse rate temperature differences for the optical depth common.
    The wapor content decide the lapse rate, and also the optical depth in IR band.
    This reality are the cause that show us that temperature in the atmosphere is NOT in radiative equilibrium balance.
    Energy are distributed by the lapse rate and by vapor content from the surface to higher altitude. Not by radiation but by density differences.
    Condensing vapor are a strong feedback for this altitude heating.
    In short more vapor reduce lapse rate and that lift more energy into the atmosphere by increased convection.
    That cool the earth surface becasue the surface is where the energy are lifted from.
    A negative forcing of surface temperatures. But not on higher altitude temperatures. That is why I suspect the near surface channel at AMSU-A measure above the pivot point of convetion/lapse balance shown in M&S 64. At 14.000 feet may the atmosphere be heated by reduced lapse rate but that cool down the surface.

  22. Re: “Why 33 deg. C for the Earth’s Greenhouse Effect is Misleading”

    Dear Roy, you wrote:

    “The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and the estimated surface temperature if there was no atmosphere.

    (…) the 33 deg. C of surface warming is not actually a measure of the greenhouse warming – it represents the balance between TWO competing effects: a greenhouse warming effect of about 60 deg. C (the so-called “pure radiative equilibrium” case), and a convective cooling effect of about 30 deg. C. When these two are combined, we get the real-world observed “radiative-convective equilibrium” case.”

    (End of quote)

    Let me denote by Fo here the incoming available SW ( =total incoming shortwave minus reflected; =OLR), and by F the portion of SW absorbed by the atmosphere.

    You suggest a new definition instead of Ramanathan’s G=Sg-OLR :

    G’ = Sg – (Fo-F) = “Back Radiation – Convective cooling”

    Let me denote “Back Radiation” by Ed (Emitted downward LW by the atmosphere), and “Convective cooling” by K.

    Then, in your case, we simple have:

    G’ = Sg – (OLR – F) = Ed – K .

    From this, we get in one step for the old G:

    G = Sg – OLR = Ed – Eu = Ed – (K+F)

    (I introduced here Eu as the upward emitted atmospheric LW.)

    That is, from YOUR G’ we get for Eu in the OLD G :

    Eu = K + F,

    which is artihmetically equivalent to :

    Aa = Ed .

    Miklos

  23. Dear Roy,
    You wrote further:

    “The reason why I have been recently defending the basic physics of the greenhouse effect is because I think the credibility of those who claim that the greenhouse effect of the atmosphere cannot be increased (or doesn’t even exist) is compromised when they object to something that – as far as I have seen – has no alternative explanation.”

    I think in this blog you have just successfully pointed out the evidence of the first relationship (from three) on which the claim that the greenhouse effect of our atmosphere cannot be increased stably rests.

    Miklos

    • Anonymous says:

      Christopher Game replying to Miklos Zagoni’s posts of September 21, 2010 at 2:51 AM and 3:43 AM.

      Dear Miklos,

      Surely you are playing with words here. You are trying to put words into Dr Spencer’s mouth. I don’t think that will work.

      Dr Spencer very reasonably objects to the claim that Aa = Ed on the theoretical ground that it seems to mean that while there is on average a temperature lapse rate in the troposphere, Aa = Ed would seem to mean that there is no within-atmosphere radiative transfer down that average temperature gradient. I think you will not persuade Dr Spencer by the reasoning which you offer, which does not directly respond to his theoretical objection, and hardly seems to respond to it indirectly.

      I think that the proper response to Dr Spencer’s objection is to look more closely at the empirical data, referring not to the average lapse rate, but referring rather to the temperature inversions that are measured in individual radio-soundings, though averaged out in ‘average’ atmospheres, and referring to the proper emissivity of the land-sea body and the reflectivity of the land-sea/atmosphere interface. I am saying that I think that the proper response to Dr Spencer’s objection is to look more closely in the direction of empirical observation, not in the direction of abstract theory.

      Dr Spencer’s objection to the Aa ~ Ed claim is one of quantity. He thinks that the difference Aa – Ed will always be positive. His questions are just by how much positive, and only on average, or in every radio-sounding?

      Yours sincerely,

      Christopher

  24. Dear Christopher,

    I think I have simply pointed out above that there is no room in basic physics of the greenhouse effect for a positive (or even negative) X-factor in the equation Aa-Ed=X if Dr. Spencer’s given argumentation is correct. I am not trying to put words into Dr Spencer’s mouth, just tried to quantify the consequences of his notes. You are right, this should be proved also in empirical data.

    Miklos

    • Anonymous says:

      Christopher Game replying to Miklos Zagoni’s post of September 22, 2010 at 12:31 AM.

      Dear Miklos,

      Please state explicitly what you mean by the phrase “Dr Spencer’s given argumentation”. The phrase as it stands in your post is an unresolved grammatical anaphora on a grand scale.

      Yours sincerely,

      Christopher

  25. Kevin says:

    Dr. Spencer, just one more comment if I might be allowed;

    You Wrote:

    “The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and the estimated surface temperature if there was no atmosphere.”

    If I might be so bold I would like to edit this slightly:

    “The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and ONE estimated surface temperature if there was no atmosphere.”

    I know this is swimming quite a bit upstream, but what if the “estimated surface temperature if there was no atmosphere” (i.e. 33 deg. C) is wrong ?

    As an engineer I must accord the following order of consideration to measurements of any kind (temperature in this case, which by the way is not the correct measurement to apply when assessing HEAT ENERGY content in any system, but that’s a totally different argument);

    1) Actual Empirical Measurements based on traceable standards (i.e. calibrated and traceable to NIST or one of the other international equivalents)

    2) Actual Empirical Measurements made with well understood uncertainties (i.e. uncalibrated measurements made with high quality instruments)

    3) Actual Empirical Measurements with unknown or postulated uncertainties (i.e. uncalibrated measurements made with poor quality instruments based on well accepted principals)

    4) Predicted Measurements based on well accepted first order laws/theories (i.e. Ohm’s Law)

    5) Predicted Measurements based on ”verified” computer models (i.e. Thermal models, SPICE models, Optical Ray Tracing Models, etc.)

    6) Predicted Measurements based on computer models (or equations) that were originally constructed to “prove” a theory

    I’m afraid that I must assign the 33 degree Celsius estimated temperature rise from the “greenhouse effect” to the last category.

    Again, and I’m sure you are sick of hearing this but we have a saying: “If your hardware does not perform as predicted by your model you MUST improve your model”.

    I have tried to be open to the perspectives of the climate science community, but I have to give up. I see that finally some in the climate science community are finally having a discussion about assessing the heat content of the oceans instead of the temperature of the air (a smart thing to do when assessing the energy content of a system). I’m afraid it’s too late, you have lost almost all of the engineers I know, and they are pretty darn smart.

    Cheers, Kevin.

  26. Dear Christopher:

    In his statement I quoted first Roy calls our attention that

    “the 33 deg. C of surface warming is not actually a measure of the greenhouse warming – it represents the balance between TWO competing effects: a greenhouse warming effect of about 60 deg. C (the so-called “pure radiative equilibrium” case), and a convective cooling effect of about 30 deg. C.”

    As he is talking about TWO effects here, a radiative warming and a convective cooling (Ed-K at the surface; or Ed-Eu for the whole atmosphere), these two effects define the equations I wrote down. There is no room for a third one, an “X-factor”, in the definition of the greenhouse effect. I think if Dr Spencer was really an “X-ist”, he would show us his equations that introduce the physical content and mechanism of X.

    Miklos

  27. Christopher Game says:

    Christopher Game replying to Miklos Zagoni’s posts of September 22, 2010 at 11:08 PM and of September 21, 2010 at 2:51 AM.

    Dear Miklos,

    Thank you for making this explicit.

    You quote Dr Spencer as writing: “(…) the 33 deg. C of surface warming is not actually a measure of the greenhouse warming”

    This looks to me like a statement by Dr Spencer that he does not define the 33 deg. C as his “new definition” or measure of greenhouse warming.

    You write: “You suggest a new definition instead of Ramanathan’s G=Sg-OLR :”

    This looks to me like a statement by you that Dr Spencer is offering new definition of the measurement of the greenhouse warming, contradicting his saying he does not.

    You write: “Let me denote by Fo here the incoming available SW ( =total incoming shortwave minus reflected; =OLR), and by F the portion of SW absorbed by the atmosphere.”

    As I read this it means that you intend to use the steady-state condition Fo = OLR.

    You then write as what you are attributing to Dr Spencer:
    “G’ = Sg – (Fo-F) = “Back Radiation – Convective cooling””.

    Without prejudice, looking at the second equality:
    Sg – (Fo-F) = “Back Radiation – Convective cooling”
    we may infer that it is true if and only if
    Sg + Convective cooling = Fo – F + Back radiation.
    This looks true to me, because it means that at the steady state the ground cooling is balanced by the ground warming, but does not seem to contain anything new from Dr Spencer; definitions for the measurement of the greenhouse effect don’t come into it.

    Rewriting this second equality we have
    Sg – (Fo-F) = Ed – K, and using Fo = OLR, thence we have
    Sg – Fo + F
    = Sg – OLR + F = Ed – K, and thence
    Sg – OLR = Ed – (K+F).

    You write:
    “From this, we get in one step for the old G:
    G = Sg – OLR = Ed – Eu = Ed – (K+F)
    (I introduced here Eu as the upward emitted atmospheric LW.)”

    This looks to me like one of the always wonderfully valuable products of saving time by being quick and efficient. Your “one step” is an elliptical anaphora that seems to be resolved only by relying on the proposition that Aa = Ed. As I read your “one step”, you mean the reader to supply the propositions that
    OLR = St + Eu
    and Su = Aa + St
    and thence
    Sg – OLR = Aa + St – St – Eu
    = Aa – Eu, and thence, relying on Aa = Ed,
    = Ed – Eu.
    But I thought your were trying to prove that Aa = Ed, not to show its consequences.

    This is a detailed explication of my comment “Surely you are playing with words here.” That comment of mine was obvious at a glance at your post of September 21, 2010 at 2:51 AM: you can’t prove a physical fact just by introducing a definition. But it took me some time to work through your time-saving argumentation to pinpoint the problem. Your time saved at the cost of my time.

    I don’t have the leisure to discuss your further remark: “As he is talking about TWO effects here, a radiative warming and a convective cooling (Ed-K at the surface; or Ed-Eu for the whole atmosphere), these two effects define the equations I wrote down. There is no room for a third one, an “X-factor”, in the definition of the greenhouse effect. I think if Dr Spencer was really an “X-ist”, he would show us his equations that introduce the physical content and mechanism of X.”

    Yours sincerely,

    Christopher

  28. Dear Christopher,

    Thank you for your detailed reply.

    If G = Sg – OLR (the old, Ramanathan’s definition of G, describing the extra heating of the atmosphere from the presence of IR-active gases) was not equal to Dr. Spencer’s “Radiative heating minus Convective cooling” at the surface, Ed – Eu, then something not-radiative-and-not-convective energy, “an X quantity of the third kind”, SHOULD HAVE REMAINED IN the atmosphere — what Dr. Spencer in his notes, correctly, did not mention.

    Again, of course, this is not a “proof” of Aa=Ed, only an indication that Dr. Spencer’s basic physics point to (or, at least, does not excluse) Aa=Ed.

    I think Dr Roy’s is a better position then the one I have read from another acknowledged and experienced close-to-mainstream climatologist:

    “The empirical finding that Aa = Ed I find surprising. I have no arguments that they are of near equal value…”

    Miklos

  29. JAE says:

    Perhaps the REAL reason for the 33 C “greenhouse effect:”

    http://hockeyschtick.blogspot.com/2010/09/shattering-greenhouse-effect.html

    If this is wrong, I would sure like to see a clear exposition of why….

  30. RW says:

    Maybe someone can help me out here. I’m just a lay person that has been researching this issue for about a year. Maybe I’m missing something obvious, but as best I can tell, the whole CO2 forcing theory seems to be one big “the emperor has no clothes.” There are many things that just don’t seem to add up.

    Firstly, I don’t quite understand how the so-called “intrinsic” effect from a doubling of CO2 results in about a 1 degree C increase of the surface temperature. Is this assuming no other substance in the atmosphere? No convection either? Wouldn’t about half of this effect be radiated out to space (half goes up, half goes down to the surface)? Also, doesn’t water vapor overlap the main CO2 absorbing LW bands (around 15u) and exist in much higher concentrations than CO2? I mean it seems to me that even without factoring in clouds (and their potential feedbacks), it seems extremely unlikely to me that a doubling of CO2 would even cause any increase in the surface temperature – let alone the 1 degree C that is supposed to cause all the warming via positive water wapor and cloud feedbacks (according to the IPCC models).

    I mean isn’t this the crux of the whole thing? I mean without the 1 degree of warming, there can’t be any amplified warming from positive water vapor and cloud feedbacks, right? Wrong?

    I also see that according to the geological evidence, CO2 levels have no causal relationship to temperature going back thousands, even hundreds of millions of years. Even when CO2 levels were like 10+ times higher than present, we had colder temperatures than now. In addition, we have more recent history like the Roman Warming and the Medieval Warming – both likely warmer globally than now. If the current CO2 AGW theory says that that the little increase above current temperatures from a doubling of CO2 is supposed to trigger runaway warming via positive water vapor and cloud feedbacks, why didn’t that happen during the Medieval or Roman warmings? Instead the exact opposite occurred – it got colder. How can these things be ignored?

    Maybe I’m wrong, but it looks highly probable to me that this whole thing is a fairytale. The evidence to this layman strongly suggests the effect of increasing CO2 is – if not infinitesimal, extremely small. Or am I wrong?