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The greenhouse effect and the 2nd law of thermodynamics

What the science says...

Select a level... Basic Intermediate

The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.

Climate Myth...

2nd law of thermodynamics contradicts greenhouse theory


"The atmospheric greenhouse effect, an idea that many authors trace back to the traditional works of Fourier 1824, Tyndall 1861, and Arrhenius 1896, and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system. According to the second law of thermodynamics such a planetary machine can never exist." (Gerhard Gerlich)


At a glance

Although this topic may have a highly technical feel to it, thermodynamics is a big part of all our everyday lives. So while you are reading, do remember that there are glossary entries available for all thinly underlined terms - just hover your mouse cursor over them for the entry to appear.

Thermodynamics is the branch of physics that describes how energy interacts within systems. That interaction determines, for example, how we stay cosy or freeze to death. You wear less clothing in very hot weather and layer-up or add extra blankets to your bed when it's cold because such things control how energy interacts with your own body and therefore your degree of comfort and, in extreme cases, safety.

The human body and its surroundings and energy transfer between them make up one such system with which we are all familiar. But let's go a lot bigger here and think about heat energy and its transfer between the Sun, Earth's land/ocean surfaces, the atmosphere and the cosmos.

Sunshine hits the top of our atmosphere and some of it makes it down to the surface, where it heats up the ground and the oceans alike. These in turn give off heat in the form of invisible but warming infra-red radiation. But you can see the effects of that radiation - think of the heat-shimmer you see over a tarmac road-surface on a hot sunny day.

A proportion of that radiation goes back up through the atmosphere and escapes to space. But another proportion of it is absorbed by greenhouse gas molecules, such as water vapour, carbon dioxide and methane.  Heating up themselves, those molecules then re-emit that heat energy in all directions including downwards. Due to the greenhouse effect, the total loss of that outgoing radiation is avoided and the cooling of Earth's surface is thereby inhibited. Without that extra blanket, Earth's average temperature would be more than thirty degrees Celsius cooler than is currently the case.

That's all in accordance with the laws of Thermodynamics. The First Law of Thermodynamics states that the total energy of an isolated system is constant - while energy can be transformed from one form to another it can be neither created nor destroyed. The Second Law does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. That qualifier term, 'net', is the important one here. The Earth alone is not a "closed system", but is part of a constant, net energy flow from the Sun, to Earth and back out to space. Greenhouse gases simply inhibit part of that net flow, by returning some of the outgoing energy back towards Earth's surface.

The myth that the greenhouse effect is contrary to the second law of thermodynamics is mostly based on a very long 2009 paper by two German scientists (not climate scientists), Gerlich and Tscheuschner (G&T). In its title, the paper claimed to take down the theory that heat being trapped by our atmosphere keeps us warm. That's a huge claim to make – akin to stating there is no gravity.

The G&T paper has been the subject of many detailed rebuttals over the years since its publication. That's because one thing that makes the scientific community sit up and take notice is when something making big claims is published but which is so blatantly incorrect. To fully deal with every mistake contained in the paper, this rebuttal would have to be thousands of words long. A shorter riposte, posted in a discussion on the topic at the Quora website, was as follows: “...I might add that if G&T were correct they used dozens of rambling pages to prove that blankets can’t keep you warm at night."

If the Second Law of Thermodynamics is true - something we can safely assume – then, “blankets can’t keep you warm at night”, must be false. And - as you'll know from your own experiences - that is of course the case!

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

Among the junk-science themes promoted by climate science deniers is the claim that the explanation for global warming contradicts the second law of thermodynamics. Does it? Of course not (Halpern et al. 2010), but let's explore. Firstly, we need to know how thermal energy transfer works with particular regard to Earth's atmosphere. Then, we need to know what the second law of thermodynamics is, and how it applies to global warming.

Thermal energy is transferred through systems in five main ways: conduction, convection, advection, latent heat and, last but not least, radiation. We'll take them one by one.

Conduction is important in some solids – think of how a cold metal spoon placed in a pot of boiling water can become too hot to touch. In many fluids and gases, conduction is much less important. There are a few exceptions, such as mercury, a metal whose melting point is so low it exists as a liquid above -38 degrees Celsius, making it a handy temperature-marker in thermometers. But air's thermal conductivity is so low we can more or less count it out from this discussion.



Figure 1: Severe thunderstorm developing over the Welsh countryside one evening in August 2020. This excellent example of convection had strong enough updraughts to produce hail up to 2.5 cm in diameter. (Source: John Mason)

Hot air rises – that's why hot air balloons work, because warm air is less dense than its colder surroundings, making the artificially heated air in the balloon more buoyant and thereby creating a convective current. The same principle applies in nature: convection is the upward transfer of heat in a fluid or a gas. 

Convection is highly important in Earth's atmosphere and especially in its lower part, where most of our weather goes on. On a nice day, convection may be noticed as birds soar and spiral upwards on thermals, gaining height with the help of that rising warm air-current. On other days, mass-ascent of warm, moist air can result in any type of convective weather from showers to severe thunderstorms with their attendant hazards. In the most extreme examples like supercells, that convective ascent or updraught can reach speeds getting on for a hundred miles per hour. Such powerful convective currents can keep hailstones held high in the storm-cloud for long enough to grow to golfball size or larger.


Advection is the quasi-horizontal transport of a fluid or gas with its attendant properties. Here are a couple of examples. In the Northern Hemisphere, southerly winds bring mild to warm air from the tropics northwards. During the rapid transition from a cold spell to a warm southerly over Europe in early December 2022, the temperatures over parts of the UK leapt from around -10C to +14C in one weekend, due to warm air advection. Advection can also lead to certain specific phenomena such as sea-fogs – when warm air inland is transported over the surrounding cold seas, causing rapid condensation of water vapour near the air-sea interface.


Figure 2: Advection fog completely obscures Cardigan Bay, off the west coast of Wales, on an April afternoon in 2015, Air warmed over the land was advected seawards, where its moisture promptly condensed over the much colder sea surface.

Latent heat

Latent heat is the thermal energy released or absorbed during a substance's transition from solid to liquid, liquid to vapour or vice-versa. To fuse, or melt, a solid or to boil a liquid, it is necessary to add thermal energy to a system, whereas when a vapour condenses or a liquid freezes, energy is released. The amount of energy involved varies from one substance to another: to melt iron you need a furnace but with an ice cube you only need to leave it at room-temperature for a while. Such variations from one substance to another are expressed as specific latent heats of fusion or vapourisation, measured in amount of energy (KiloJoules) per kilogram. In the case of Earth's atmosphere, the only substance of major importance with regard to latent heat is water, because at the range of temperatures present, it's the only component that is both abundant and constantly transitioning between solid, liquid and vapour phases.


Radiation is the transfer of energy as electromagnetic rays, emitted by any heated surface. Electromagnetic radiation runs from long-wave - radio waves, microwaves, infra-red (IR), through the visible-light spectrum, down to short-wave – ultra-violet (UV), x-rays and gamma-rays. Although you cannot see IR radiation, you can feel it warming you when you sit by a fire. Indeed, the visible part of the spectrum used to be called “luminous heat” and the invisible IR radiation “non-luminous heat”, back in the 1800s when such things were slowly being figured-out.

Sunshine is an example of radiation. Unlike conduction and convection, radiation has the distinction of being able to travel from its source straight through the vacuum of space. Thus, Solar radiation travels through that vacuum for some 150 million kilometres, to reach our planet at a near-constant rate. Some Solar radiation, especially short-wave UV light, is absorbed by our atmosphere. Some is reflected straight back to space by cloud-tops. The rest makes it all the way down to the ground, where it is reflected from lighter surfaces or absorbed by darker ones. That's why black tarmac road surfaces can heat up until they melt on a bright summer's day.


Figure 3: Heat haze above a warmed road-surface, Lincoln Way in San Francisco, California. May 2007. Image: Wikimedia Commons.

Energy balance

What has all of the above got to do with global warming? Well, through its radiation-flux, the Sun heats the atmosphere, the surfaces of land and oceans. The surfaces heated by solar radiation in turn emit infrared radiation, some of which can escape directly into space, but some of which is absorbed by the greenhouse gases in the atmosphere, mostly carbon dioxide, water vapour, and methane. Greenhouse gases not only slow down the loss of energy from the surface, but also re-radiate that energy, some of which is directed back down towards the surface, increasing the surface temperature and increasing how much energy is radiated from the surface. Overall, this process leads to a state where the surface is warmer than it would be in the absence of an atmosphere with greenhouse gases. On average, the amount of energy radiated back into space matches the amount of energy being received from the Sun, but there's a slight imbalance that we'll come to.

If this system was severely out of balance either way, the planet would have either frozen or overheated millions of years ago. Instead the planet's climate is (or at least was) stable, broadly speaking. Its temperatures generally stay within bounds that allow life to thrive. It's all about energy balance. Figure 4 shows the numbers.

Energy Budget AR6 WGI Figure 7_2

Figure 4: Schematic representation of the global mean energy budget of the Earth (upper panel), and its equivalent without considerations of cloud effects (lower panel). Numbers indicate best estimates for the magnitudes of the globally averaged energy balance components in W m–2 together with their uncertainty ranges in parentheses (5–95% confidence range), representing climate conditions at the beginning of the 21st century. Figure adapted for IPCC AR6 WG1 Chapter 7, from Wild et al. (2015).

While the flow in and out of our atmosphere from or to space is essentially the same, the atmosphere is inhibiting the cooling of the Earth, storing that energy mostly near its surface. If it were simply a case of sunshine straight in, infra-red straight back out, which would occur if the atmosphere was transparent to infra-red (it isn't) – or indeed if there was no atmosphere, Earth would have a similar temperature-range to the essentially airless Moon. On the Lunar equator, daytime heating can raise the temperature to a searing 120OC, but unimpeded radiative cooling means that at night, it gets down to around -130OC. No atmosphere as such, no greenhouse effect.

Clearly, the concentrations of greenhouse gases determine their energy storage capacity and therefore the greenhouse effect's strength. This is particularly the case for those gases that are non-condensing at atmospheric temperatures. Of those non-condensing gases, carbon dioxide is the most important. Because it only exists as vapour, the main way it is removed is as a weak solution of carbonic acid in rainwater – indeed the old name for carbon dioxide was 'carbonic acid gas'. That means once it's up there, it has a long 'atmospheric residency', meaning it takes a long time to be removed. 

Earth’s temperature can be stable over long periods of time, but to make that possible, incoming energy and outgoing energy have to be exactly the same, in a state of balance known as ‘radiative equilibrium’. That equilibrium can be disturbed by changing the forcing caused by any components of the system. Thus, for example, as the concentration of carbon dioxide has fluctuated over geological time, mostly on gradual time-scales but in some cases abruptly, so has the planet's energy storage capacity. Such fluctuations have in turn determined Earth's climate state, Hothouse or Icehouse – the latter defined as having Polar ice-caps present, of whatever size. Currently, Earth’s energy budget imbalance averages out at just under +1 watt per square metre - that’s global warming. 

That's all in accordance with the laws of Thermodynamics. The First Law of Thermodynamics states that the total energy of an isolated system is constant - while energy can be transformed from one component to another it can be neither created nor destroyed. Self-evidently, the "isolated" part of the law must require that the sun and the cosmos be included. They are both components of the system: without the Sun as the prime energy generator, Earth would be frozen and lifeless; with the Sun but without Earth's emitted energy dispersing out into space, the planet would cook, Just thinking about Earth's surface and atmosphere in isolation is to ignore two of this system's most important components.

The Second Law of Thermodynamics does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. To reiterate, the qualifier term, 'net', is the important one here. In the case of the Earth-Sun system, it is again necessary to consider all of the components and their interactions: the sunshine, the warmed surface giving off IR radiation into the cooler atmosphere, the greenhouse gases re-emitting that radiation in all directions and finally the radiation emitted from the top of our atmosphere, to disperse out into the cold depths of space. That energy is not destroyed – it just disperses in all directions into the cold vastness out there. Some of it even heads towards the Sun too - since infra-red radiation has no way of determining that it is heading towards a much hotter body than the Earth,

Earth’s energy budget makes sure that all portions of the system are accounted for and this is routinely done in climate models. No violations exist. Greenhouse gases return some of the energy back towards Earth's surface but the net flow is still out into space. John Tyndall, in a lecture to the Royal Institution in 1859, recognised this. He said:

Tyndall 1859

As long as carbon emissions continue to rise, so will that planetary energy imbalance. Therefore, the only way to take the situation back towards stability is to reduce those emissions.

Update June 2023:

For additional links to relevant blog posts, please look at the "Further Reading" box, below.

Last updated on 29 June 2023 by John Mason. View Archives

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Comments 1101 to 1125 out of 1393:

  1. With indulgence:
    "If in the interior of the same solid we imagine a plane M parallel to those which bound it, we see a certain quantity of heat flows across this plane during unit of time..."
    (My emphasis) Joseph Fourier, "The Analytical theory of Heat", 1878; p 105.
    "The concept of heat 'flowing' went out with the 'fluid' concept of heat i.e. caloric."
    Damorbel's theory of pedantary, 2011.
    "Did Fourier get it wrong?"
    "Title: Heat flow in the solidification of castings Author: Adams, Clyde M Advisor: Howard F. Taylor. Department: Massachusetts Institute of Technology. Dept. of Metallurgy Publisher: Massachusetts Institute of Technology Issue Date: 1953"
    "Title: Heat flow over the equatorial mid-Atlantic ridge. Author: Folinsbee, Robert Allin Advisor: Gene Simmons. Department: Massachusetts Institute of Technology. Dept. of Geology and Geophysics Publisher: Massachusetts Institute of Technology Issue Date: 1969"
    "Title: Heat flow in solidification of alloys. Author: Campagna, Alan John Advisor: Merton C. Flemings. Department: Massachusetts Institute of Technology. Dept. of Metallurgy and Materials Science Publisher: Massachusetts Institute of Technology Issue Date: 1970"
    Heat flow and material degradation during laser metal forming 1985 16.5 Steady Quasi-One-Dimensional Heat Flow in Non-Planar Geometry So not only is "heat flow" a concept used in various MIT dissertations throughout the 20th century, it is a concept used in MIT lectures on Thermodynamics in 2007.
    Response: [mc] Closed italics tag. Link to '16.5 Steady Quasi' missing.
  2. damorbel#1098: "If this 'ignorance of source temperature' on the part of photons is the basis of your science then I suggest you think again. " Please, not that again. You've already contradicted yourself on the topic of 'photon temperature' on this thread.

    [DB] Perhaps a new rule: Damorbel's Law (ala Godwin's Law).

    When someone repeats/resurrects a point already refuted on the same thread by that selfsame poster, Damorbel's Law is invoked declaring the argument forfeit and all subsequent comments by that poster on that thread may be safely ignored.

    One may safely then consider it already invoked on this thread.

  3. Thankyou mc. The link should be
  4. Must be a slow news day if everyone's willing to re-heat (ha ha) this thread. May I suggest a new article: "Heating up the Lexicon of Physics" or "HaIRNET: Heat and Infrared Radiation / Net Energy Transfer -- Could Be Important" or the new skeptical argument "GHE doesn't exist because you don't accept my definition of 'heat'."
  5. Damorbel, it turns out that your history of science is almost as bad as your science:
    By 1800, alternatives to the caloric hypothesis appeared and, in 1811, Joseph Fourier (1768-1830) published a mathematical theory of heat conduction that was entirely independent of the caloric hypothesis. Fourier's first step was to avoid speculation about "caloric." In this way, Fourier set the study of the theory of heat in the tradition of rational mechanics, basing it on differential equations that characterized the transmission of heat, equations that were independent of all physical hypotheses. In contrast to Poisson (who was, as mentioned above, a devoted Laplacian, committed to physical mechanics and to the existence of caloric), Fourier focused on heat flow, using differential equations to express how much heat diffused from a substance over time. The heat transmitted between two molecules was proportional to the difference in their temperature and a function of the distance between them, which of course varied with the nature of the intervening substance. Though formally (that is, mathematically) equivalent to Poisson's model, Fourier did not rely upon any speculation about the nature of heat. For Fourier, what was important was not what heat was, but what it did, in a given experimental setting."
    (source, emphasis added) So, Fourier made not commitment to calorific theory, for which there where alternatives at his time. What is more he directly declared his agnosticism on the issue:
    "Of the nature of heat uncertain hypotheses only could be formed, but the knowledge of the mathematical laws to which its effects are subject is independent of all hypothesis; it requires only an attentive examination of the chief facts which common observations have indicated, and which have been confirmed by exact experiments."
    (Joseph Fourier, Theory of Heat, p 26) Further, if the the independence of mathematical theory of heat flow was not independent of calorific theory, then calorific theory would be established as true, for certainly his mathematical treatment of heat flow is. As it stands, his theory is independent of calorific theory (contrary to your claims) but consistent with the metaphor of heat flow (again contrary to your claims) as is established by his use of that very metaphor. What is more, as is established by the actual practice at MIT, that metaphor is alive and well in physics today, and causes no confusion. Except, perhaps to small minded pedants.
  6. Re #1103 Tom Curtis, you give a link - This link is about heat tranfer in solids with various shapes - hollow shells, cylinders etc. under the general title "16.5 Steady Quasi-One-Dimensional Heat Flow" The explanation seems quite good to me but the title, as so ften is the case, is not really correct. What the author is describing is diffusion. Later in the article (perhaps an editor chose the title) he writes:- "The heat transfer rate per unit length is given by...." and give a formula that I can't copy here. The article is rather strange because further down it has :- "The steady-flow energy equation (no fluid flow, no work) tells us that....." Yet further it has:- "The heat transfer rate per unit length is given by... " with another formula that doesn't copy All very confusing and not really helpful for understanding the fundamental physics. You can check what Wikipedia has on this here :- Derivation in one dimension In your link the equation (16..25) corresponds to the last one in the 'one dimensional section' of the Wiki article where it adds helpfully :- "which is the heat equation. The coefficient k/(cpρ) is called thermal diffusivity and is often denoted α." You will also notice that the article refers to these equations as 'Fourier's law'.
  7. Re #1105 Tom Curtis, you cited a very nice article on Victorian Science which I intend to read fully. But it is quite clear that the author is not entirely clear about the diffusion equations that Fourier famously derived. Your citation has:- "Fourier focused on heat flow, using differential equations to express how much heat diffused from a substance over time" This is exactly the kind of confused thinking one finds today (and in history). Fourier is justly famous for his diffusion equations, I was taught them in my thermal physics course too. But his equations are about diffusion, a process found in solids not 'flow' which requires fluids. Flow is covered by Fluid dynamics which is also a relevant subject to the 2nd Law of thermodynamics but it is quite separate from diffusion.
  8. damorbel Speaking of heat flow does not necessarily imply adherence to caloric thory. One can talk metaphorically about there being a flow without the supposed existence of a fluid. For instance in information theory it is perfectly reasonable to talk of the flow of information through a channel, but information isn't carried by a fluid. It is just a metaphor.
  9. Re #1108 Dikran Marsupial, you wrote:- "Speaking of heat flow does not necessarily imply adherence to caloric thory" I know that too. But thermodynamics is rather complicated so it is essential to be quite certain of the meaning of words. There is all the difference in the world between processes involving transport of fluids and diffusion in solids. The 'flow' problem is not the only one. Frequently diagrams are drawn shoing the GHE where the authors do not distinguish betwen the reflection (as with a mirror) and the absorption/emission of radiation. These two processes are completely different, it isn't possible to even think of a CO2 GH effect unless the two processes are clearly separated.
    Response: [Dikran Marsupial] In that case, as you know that nobody in the discussion is talking about caloric theory when they speak of "flow", any further mention of "caloric" on this thread is off-topic and will be deleted, likewise any further general discussion on the meaning of the word "flow". As you apparently recognise that "flow [of heat]" is being used as a metaphor for "transfer [of energy]" this should be no hurdle to communication.
  10. 1107, damorbel, Your obsession with semantics and word choice is crippling you. The rest of us understand exactly what is meant by "diffusion," "transfer" and "flow" without the need to apply only certain terms to gases, solids or fluids... as do the learned men who wrote the referenced papers and used those terms to begin with. You have a whole lot of studying to do before you can contribute to a discussion like this. In particular, I suggest that you try to get away from what you think you know and understand (traditional thermodynamics) and begin to study more modern quantum and molecular level physics and radiative transfer (or diffusion or flow or emission/absorption for whatever term you'd like to use). Until you do, you're trying to both understand and argue from a too limited perspective. You're like one of the blind men trying to describe an elephant.
    So oft in theologic wars, The disputants, I ween, Rail on in utter ignorance Of what each other mean, And prate about an Elephant Not one of them has seen!
  11. damorbel @1109, it is rather more important to keep clear about the content of the physical laws you are appealing to, something you continually fail to do. But your just keep on plugging away drawing attention to the use of a metaphor as a substitute for actually learning the topic on which you expound so frequently.
  12. Damorbel, your attempts at distracting from your poor comprehension of the subjects on which you would pretend to comment, and even lecture, are amusing. I note that you fail to defend your IR photon thermometer/temperature of the source idea; not suprising, since it is not defensible. "thermodynamics is rather complicated" Well, it's not so bad, really. Reflect on the following long and deep and you will eliminate a lot of the confusion that has been plaguing you during this astoundingly tedious exchange: You have to play. You can't win. You can't break even. That's enough for anyone to understand thermodynamics better than what transpires from your comments.
  13. Philippe - This has been a pattern with damorbel from the beginning. When a bit of nonsense is firmly refuted, he skips to the next argument in a Gish Gallop. The original bit of nonsense will then re-emerge weeks later, perhaps to a different visitor, in a sort of never-ending zombie manner. And damorbel has shown no compunctions against contradicting himself, if it continues the argument. I've yet to see actual discussions of science with this poster - just arguments. DNFTT.
  14. I am aware of the pattern KR. To my knowledge, nobody has ever been banned from SkS. Damorbel's actions, so transparent and so consistent over time, have certainly earned him the right to set a precedent in the matter. However, considering how John has conducted this site so far, I doubt that he will do that; yet we will continue to endure the whining of pseudo-skeptics about being silenced when nonsense is called out. In thermodynamics, by respect to energy and entropy, we "can't win." It seems to be like that too in the parody of debate maintained by pseudo-skeptics.

    [DB] In the spirit of transparency, a select few have "crossed the line".  Damorbel may yet indeed set a precedent; that remains to be seen.  As an alternative, I earlier proposed "Damorbel's Law", for those who wish to consider it.

  15. Re #1108 Sphaerica, you wrote:- "Your obsession with semantics and word choice is crippling you." I don't think so. Science is not just about accurate measurement but also about clear explanation i.e. using words as precision tools to minimise misunderstanding. "The rest of us understand exactly what is meant by "diffusion," "transfer" and "flow" without the need to apply only certain terms to gases, solids or fluids..." I suggest "the rest of us" is not sufficient. I merely point to the text in a link given by Tom Curtis in #1105 which did not distinguish between 'diffusion' and 'flow', clearly not understanding Fourier's great theory. you wrote:- "as do the learned men who wrote the referenced papers and used those terms to begin with." The link was to a paper written by a historian. I do not regard historians as a reliable source, they do not generally use the scientific method.
    Response: [Dikran Marsupial] This line of discussion is off-topic. No more quibbling about terminology, damorbel has made his point, he knows what is meant by "flow of heat/energy" so there is no problem with communication, and so no reason to discuss this any further. This applies to everybody.
  16. If you look up the Second Law of Thermodynamics in Wikipedia for example you will see that it requires an "isolated physical system" which the atmosphere is not. Furthermore, one of the results of it acting is, not only that it produces uniform temperature, but also uniform pressure. Neither of these is seen between the top and bottom of the atmosphere. The pressure difference causes warmer air to rise as is well known. That said, the theory relating to the "greenhouse effect" recognises that we are not supposing that warmed air is physically being trapped and somehow warming the surface. Instead it is all about radiation. Incoming high energy radiation passes straight through GH gases, whereas low energy (low frequency infra-red) radiation which comes from a solid or liquid surface can be captured by GH gases. The photons are delayed and then others emitted. If, and only if, the ones emitted have less energy than the ones captured then the GH gas molecule will be warmed a little. This will mean that it is more likely to emit its next photon sooner, with consequent cooling, and/or it may pass on some of its heat to other air molecules. The issue is, to what extent does this happen? There are two very different sets of figures - one used by the IPCC and the other sourced from NASA. The NASA based diagram shows much more heat being transferred by conduction from the earth surface to the adjacent air, and less by radiation. When feedback calculations are applied to the NASA based one the results relating to radiation feedback are less than 30% those that the IPCC claimed. In fact, the IPCC figures indicate radiation coming down out of the air from GH gases far exceeds the radiation received from the sun. This means that, just after sunset, you should shield yourself with an umbrella to avoid feeling the heat. ( -Snip- )

    [DB] Endless self-promotion of website snipped.

  17. Doug, what are you trying to achieve here, by jumping to another thread and repeating the same assertions (that "NASA" and "IPCC" are in contradiction), when this has already been explained and referenced for you on other threads? We have measurements of DLR. Greenhouse theory predicts its magnitude and spectrum. What does your theory predict this measurement to be?
  18. scaddenp @1117, the purpose is obvious. His claims are being refuted on the other threads very convincingly. He needs to thread hop so that he can hopefully gull some naive reader who does not see the counter arguments. No matter how much he thread hops, however, he still needs to answer some questions. Why, for example, does he assert that atmospheric radiation from O2 and N2 eclipses that from CO2 even though he has seen no data to that effect, and there is data to the contrary: And why does he insist surface radiation is so low that, given the Stefan-Boltzmann law, the surface emissivity for IR radiation must be 0.18, even though the surface is known to have an emissivity greater than 0.9 in those wavelengths? Indeed, the crucial question he needs to answer is why we are required at every turn in his theory to take his mere assertion in preference to well established scientific laws, and copious empirical observations that contradict it?
  19. As the Earth heats up - it would lose more energy through radiation - except for the insulation provided by the CO2. This blanket of CO2 will result in a rise in temperature - until the energy being radiated away reaches equilibrium with the energy being received. Then our temperature will stabilize. The thicker the blanked of CO2, the warmer it gets before this equilibrium is reached. I wonder what the lag is between CO2 levels stabilizing and temperature increase ceasing.
  20. I return to this thread to present a theory of greenhouse warming which appears all over the blogs, and in some text-books, to defend a position I took in the “After McClean” thread. If we accept the Stefan-Bolzmann fourth power law of radiation, and ignore other means of heat transfer it can be done very simply. Start with a bare rock earth radiating back to the sun the incoming radiation of W watts per square meter. In order to radiate this energy back, the earth will acquire a mean temperature of 255 degrees K. Now build up an atmosphere capable of absorbing and re-radiating part of the outgoing radiation. It will radiate equal intensities, up and down. To avoid typing algebra, I will pause the analysis when the atmosphere can absorb half of the outgoing radiation.. The atmosphere will then radiate W/2 to space, and the surface (directly to space) also W/2. This means that the atmosphere must receive W from the surface (half out, half back) and the surface will receive W (from the sun) and W/2 from they atmosphere. The surface must consequently be warmed (by the sun) to radiate W + W/2. Now continue the build-up until all (100%) of the outgoing radiation is being absorbed. At that point everything reaches “goldilocks” equilibrium. The earth radiates 2W, the atmosphere receives 2W, and radiates W to space, W back to the surface. What is the ratio of the new surface temperature to the bare rock temperature? It is the fourth root of the radiant energy ratio, 2W/W. The fourth root of 2 is 1.19, so we would expect a greenhouse temperature of 1.19 x 255, or 303 degrees K. The effective radiative temperature must be 255 degrees K (goldilocks again). Why pay more?

    [DB] "Why pay more?"

    If by this you mean:

    Q.  Why have a more complex and robust model that explains fairly well everything we can observationally measure when we can opt for something far simpler that explains very little? 

    A.  Because life and physics seldom contort themselves to simple models.  Why have a faux relationship when the real thing is so much richer?.

  21. Fred Staples @1120: 1) The atmosphere will only radiate equal amounts up and down if there is no change of temperature with altitude. That is only a reasonable approximation for very thin slices of atmosphere, although it is a common simplifying assumption for unrealistic models used only to explain basic concepts. If you are trying to prove the "un-physicality" of the greenhouse effect, you are not entitled to use an un-physical model to do so. 2) Your first model state not in equilibrium. The surface is said to receive 1 W radiation from the sun, and 0.5 W radiation from the atmosphere. Therefore it should radiation 1.5 W radiation, of which half (0.75 W) is absorbed by the atmosphere. That means at the TOA the outgoing radiation is 0.5 W from the atmosphere and 0.75 W from the surface, which is 0.25 W greater than the 1 W incoming radiation. Meanwhile the atmosphere is absorbing only 0.75 W, but is radiating 1 W (0.5 W up, and the same down), making a shortfall of 0.25 W. Hence, in your model as specified, the atmosphere is rapidly loosing energy to space. These models do have equilibrium states, and they can be found, but you can't avoid the algebra if you wish to do so. 3) Your description of a perfectly absorbing, optical depth 1 atmosphere with uniform temperature is correct. The model is, of course, unphysical, and only used to explain basic concepts. Having said that, I do not know what point you are trying to make by describing it, nor by your final comment.
  22. I seem to recall noting to damborel some time ago a simpler variant of the below: The atmospheric greenhouse effect: (1) was postulated theoretically; (2) then confirmed experimentally; (3) and has since been observed empirically. Trying to argue it doesn't exist by means of the Second Law of Thermodynamics is a fool's errand.
  23. 1120, Fred, I actually think you've done a pretty good job of creating a simple model that demonstrates exactly the effect and mirrors real life (i.e. the temperature of the surface is clearly not 255K, although it's not quite 303K). As Tom pointed out, your simple model has flaws (it is, after all a simple model), so you can't expect to have used it to compute an accurate surface temperature. To elaborate a bit on what Tom said, the "half up/half down" simplification is good for a thought model but grossly flawed for a quantitative analysis. The atmosphere is more complex than that, with varying density and behavior from the surface upwards, so working with a single-slab with a half-up/half-down rule really is a gross simplification. But still, all in all, I think you have something that you can work with for understanding what is happening at a very high level. [Like Tom, I am baffled by your "why pay more?" comment. Can you explain?]
  24. Thanks for the comment, Sphaerica, but my post was intended to be a simplified version of so much that is posted about “back-radiation” theories. (You will find a complicated version in Eli Rabetts rebuttal of the original G and T paper). As such, it is not remotely realistic. There is no reason to believe that outgoing radiation will be absorbed only once. If we add another absorbing layer, radiating W to space at a temperature of 255 degrees K, we fill find that the surface temperature must rise to radiate 3W, at a temperature ratio of the fourth root of 3, or 335K. The absorption distance in the atmosphere means that there will be many such layers, and every layer will absorb the incident energy and re-emit half downwards. Repeat the calculation and you will find: One layer – Fourth root of 2 = 1.19. Tsurf = 1.19 x 255 = 303K Two Layers - Fourth root of 3 =1.315 T surf = 1.315 x 255 = 335K Three Layers - Fourth root of 4 = 1.415 Tsurf = 1.415 x 255 = 360K Four Layers - Fourth root of 5 = 1.495 Tsurf = 1.495 x 255 = 381K and so on. These results are absurd, but they are derived from the original greenhouse “explanation”. As I and several others posted here long ago,(1000) the only plausible theory of “greenhouse” warming which supports AGW is the “higher is colder” theory. The temperature difference from the surface to the 255 K effective emission level then depends on the lapse rate, which in turn depends on gravity and specific heat; it has nothing to do with radiation. AGW is then a top-of-atmosphere effect. The argument is that adding CO2 (or any other absorbing gas) will elevate the emission level to higher, and therefore colder, temperatures, so reducing the outgoing radiation, and allowing the sun to warm the entire system. We are, in fact, conducting a global experiment to test this theory. We are on course to double the CO2 content of the atmosphere. We have some evidence, satellite and radio-sonde troposphere temperatures, which we can relate to the increasing CO2 levels. In my opinion, DB, this is what is important, not more and more expensive attempts to model the heat transfer (conduction, convection, radiation, and evaporation) from the surface through the chaotic weather systems. It might be instructive to return to the McClean thread and see what can be learned from the available data.
  25. "We have some evidence..." Fred, you might want to add to that evidence, the observations from surface, aircraft and satellites of longwave radiation being scattered at GHG-specific wavelengths (some presented in the Intermediate tab). Add to that the observations of an increase in downwelling and a decrease in outgoing LW radiation at GHG-specific wavelengths observed over the past few decades. Where does the increase in downwelling radiation from GHG-specific wavelengths go?

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