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The 2nd law of thermodynamics and the greenhouse effect

Posted on 22 October 2010 by TonyWildish

Skeptics sometimes claim that the explanation for global warming contradicts the second law of thermodynamics. But does it? To answer that, first, we need to know how global warming works. Then, we need to know what the second law of thermodynamics is, and how it applies to global warming. Global warming, in a nutshell, works like this:

The sun warms the Earth. The Earth and its atmosphere radiate heat away into space. They radiate most of the heat that is received from the sun, so the average temperature of the Earth stays more or less constant. Greenhouse gases trap some of the escaping heat closer to the Earth's surface, making it harder for it to shed that heat, so the Earth warms up in order to radiate the heat more effectively. So the greenhouse gases make the Earth warmer - like a blanket conserving body heat - and voila, you have global warming. See What is Global Warming and the Greenhouse Effect for a more detailed explanation.

The second law of thermodynamics has been stated in many ways. For us, Rudolf Clausius said it best:

"Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature."

So if you put something hot next to something cold, the hot thing won't get hotter, and the cold thing won't get colder. That's so obvious that it hardly needs a scientist to say it, we know this from our daily lives. If you put an ice-cube into your drink, the drink doesn't boil!

The skeptic tells us that, because the air, including the greenhouse gasses, is cooler than the surface of the Earth, it cannot warm the Earth. If it did, they say, that means heat would have to flow from cold to hot, in apparent violation of the second law of thermodynamics.

So have climate scientists made an elementary mistake? Of course not! The skeptic is ignoring the fact that the Earth is being warmed by the sun, which makes all the difference.

To see why, consider that blanket that keeps you warm. If your skin feels cold, wrapping yourself in a blanket can make you warmer. Why? Because your body is generating heat, and that heat is escaping from your body into the environment. When you wrap yourself in a blanket, the loss of heat is reduced, some is retained at the surface of your body, and you warm up. You get warmer because the heat that your body is generating cannot escape as fast as before.

If you put the blanket on a tailors dummy, which does not generate heat, it will have no effect. The dummy will not spontaneously get warmer. That's obvious too!

Is using a blanket an accurate model for global warming by greenhouse gases? Certainly there are differences in how the heat is created and lost, and our body can produce varying amounts of heat, unlike the near-constant heat we receive from the sun. But as far as the second law of thermodynamics goes, where we are only talking about the flow of heat, the comparison is good. The second law says nothing about how the heat is produced, only about how it flows between things.

To summarise: Heat from the sun warms the Earth, as heat from your body keeps you warm. The Earth loses heat to space, and your body loses heat to the environment. Greenhouse gases slow down the rate of heat-loss from the surface of the Earth, like a blanket that slows down the rate at which your body loses heat. The result is the same in both cases, the surface of the Earth, or of your body, gets warmer.

So global warming does not violate the second law of thermodynamics. And if someone tells you otherwise, just remember that you're a warm human being, and certainly nobody's dummy.

This post is the Basic Version (written by Tony Wildish) of the skeptic argument "The 2nd law of thermodynamics contradicts greenhouse theory".

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Comments 101 to 110 out of 110:

  1. Berényi - Keep in mind that Gerlich and Tscheuschner was not peer-reviewed. It was a multiply reworked version of their Arxiv paper that was published as a "review" article in an extremely off-topic [condensed matter???] journal, approved only by the editor.

    The paper has been thoroughly disproven. Figure 32 in their paper, pg. 78 of 115, represents the core of their 2nd law argument, and is both deceptive and incomplete; they show 'heat' flowing the wrong direction, and do not show the bi-directional energy flows. The rest of the paper is a massive collection of mis-statements, strawmen, and flat out incorrect claims.

    Perhaps the clearest refutations of G&T come from Arthur Smith, "Proof of the Atmospheric Greenhouse Effect" (well worth reading), and the Halpern et al (peer reviewed) reply.

    It's utter garbage - I would suggest reading the extensive discussions on Deltoid, Science of Doom, and Rabett Run. They're not worth rehashing here.

    Gah. I'm not going to re-argue this bit of junk science here.
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  2. The eternal story of climate "skepticism." Such nonsense as G&T does not have to be really peer-reviewed but the refutation has to be, despite the obvious nonsense. When was that double standard established? What justifies it?
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  3. #100, BP:
    "Since the measurable thermodynamic quantities of a voluminous medium, in particular the specific heat and the thermodynamic transport coefficients, naturally include the contribution from radiative interactions, we cannot expect that a change of concentration of a trace gas has any measurable effect"

    In that case, G&T would be "not expecting" wrong: change of concentration of a trace gas CAN have a measurable impact.

    I will write up a rebuttal of this error later, but briefly: The fact that the active agents of the greenhouse effect are an extreme minority of the atmosphere tells you absolutely nothing about the greenhouse efficacy of this minority. What matters is not the ratio of the number of greenhouse molecules to the total number of gas molecules, but the number of greenhouse molecules to the number of IR photons that are being blocked.

    As long as you have enough greenhouse molecules to catch the number of IR photons, you will have a greenhouse effect - pretty much regardless of the non-greenhouse molecules, which are incapable of interacting with the IR photons.

    In fact, to 1st order, if you increased the number of non-greenhouse gases by a factor of 10, so the trace GHG becomes 10 times "tracier", it would have NO EFFECT on the greenhouse capability of this minority.

    To 2nd order: the increase in the total amount of gas would increase the pressure of the atmosphere 10 times, resulting in pressure broadening of the IR absorption lines of the GHGs. So in fact, the GHGs would become even more efficacious, even as their relative concentration was reduced by 10.

    An analogy: You have a population of 10,000 people in a walled city, which is afflicted by invasions of kangaroos. So you hire 10 hunters to discourage the kangaroos.

    Do you ask, "10 hunters out of 10,000 people? That's only 0.1% ! How can 0.1% of the population protect against the kangaroos?" No, you don't, because the question is silly: What matters is not how many hunters there are relative to the population, but how many hunters there are relative to the number of kangaroos (and possibly, to the circumference of the walls). If there are 2 kangaroo intrusions per night, 10 hunters might be more than enough; if there are 100 kangaroo intrusions per night, probably not. In any case, it has NOTHING to do with the whether the population is 10,000 or 10,000,000.

    It would be an issue if we were talking about policemen trying to control crime among the populace: In that case, there would be an important difference between having 10 policemen for 10,000 people and 10 policemen for 10,000,000. But that is because policemen have to influence the populace, so their relative concentration is important.

    But the GHG molecules don't have to influence the non-GHG molecules: They just have to go after the IR photons. So the correct analogy is to the kangaroo hunters, and it doesn't matter how small a minority they are in the atmosphere.
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  4. @nealjking: a brilliant explanation, thank you!

    I want more kangaroo-related metaphors.
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  5. #101 KR at 03:46 AM on 28 October, 2010
    Perhaps the clearest refutations of G&T come from Arthur Smith, "Proof of the Atmospheric Greenhouse Effect" (well worth reading)

    If we delve into arXiv.org, it should be read along with its counterpart.

    arXiv.org > physics > arXiv:0904.2767
    Physics > Atmospheric and Oceanic Physics (physics.ao-ph)
    Cite as: arXiv:0904.2767v3 [physics.ao-ph]
    Comments on the "Proof of the atmospheric greenhouse effect" by Arthur P. Smith, arXiv:0802.4324
    Gerhard Kramm, Ralph Dlugi & Michael Zelger

    "Smith's discussion of the infrared absorption in the atmosphere was scrutinized and evaluated. It was shown that his attempt to refute the criticism of Gerlich and Tscheuschner (2007, 2009) on the so-called greenhouse effect is rather fruitless."
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  6. I admit that the sentence in the quotation marks in my comment shown as #96, "greenhouse effect contradicts the 2nd law of thermodynamics", is not a quote from Gerlich and Tscheuschner. I consider that the main subject of this thread is to discuss such a notion that may be expressed by the sentence I showed in the quotation marks. I think it is rather irrelevant whether it comes from Gerlich and Tscheuschner or not.
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  7. BP, I'm curious. Is it your personal opinion that the atmospheric greenhouse effect has been falsified indeed, as G&T or Kramm seem to argue?
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  8. @nealjking

    In no way am i saying the greenhouse effect is a contradiction of the second law... but i think the example of the net flow of heat being from hotter to colder, should be seen as a result of the second law, not the second law... Entropy increases or stays the same, is the second law. And its simply stating the behavior of energy. That chaos increases, a body with a high T has confined chaos, and it will increase, the hotter the body, the more confined the chaos, the more efficiently that chaos increases. It behaves the opposite to matter/gravity basically.

    So as a result of this, a hotter object will have greater increasing chaos than a colder object, put simply. To test if the earth has decreasing entropy, switch off the sun, if it heats, its in violation o the second law;-) And energy locked in chemical bonds entropy stays the same... till yah burn it, then its chaos increases. Decreasing entropy implies the clumping together of energy from lower to higher concentrations.
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  9. The line "greenhouse effect contradicts the 2nd law of thermodynamics" is indeed not from G&T.

    The quote this is based upon, from the introduction of their paper, is:

    "The atmospheric greenhouse e ffect, 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.

    While much shorter, I think the abbreviated line accurately conveys the meaning of G&T's quoted words, although the shorthand line skips major portions of G&T's strawman argument.

    Berényi - do you indeed feel that the greenhouse effect does not exist?
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  10. #107 Philippe Chantreau at 07:40 AM on 28 October, 2010
    BP, I'm curious. Is it your personal opinion that the atmospheric greenhouse effect has been falsified indeed, as G&T or Kramm seem to argue?

    No, it is not falsified and at the present level of discussion never will be (as it belongs to the "not even wrong" category). Therefore the very title of that infamous paper is misleading.

    Gerlich and Tscheuschner in their reply to Halpern at al. say:

    "In other words, we analyze the rationale and the inner contradiction of derivations of the atmospheric greenhouse effects communicated in the standard climate literature from the viewpoint of a physicist. In part, we are arguing within the context of the standard assumptions put forward by mainstream global climatologists. Nowhere we offer our own model, and we never will."

    And it is exactly that's what they do. Current formulations of the atmospheric greenhouse effect fail to meet standards of theoretical physics. It is as simple as that.

    The correct response of course is not to debunk the messenger, but to understand the message and having completed that task to present such a clear definition of the concept, that makes sense even for theoretical physicists. This job is not done so far.

    Of course I would never deny atmospheric emissivity in thermal IR has a role in maintaining quasi-adiabatic thermal structure in the troposphere. Without it (in a pure N2 - Ar atmosphere for example) vertical thermal profile would be much closer to an isothermal model.

    It may even be interesting to analyze the effect of adding some more IR emitter to an already saturated narrow emission band, but analyzing its effect on what?

    Let's consider the problem of average temperatures. It is often stated with no atmospheric greenhouse effect "equilibrium temperature" would be 255 K (-18°C). In fact it is the approximate effective temperature of Earth as it is. However, as you can see, geographic distribution of outgoing thermal IR radiation at TOA (Top of Atmosphere) is very uneven.



    Effective temperature of an object is defined as the actual temperature of an isothermal perfect black body with the same surface area and same radiative power output. For the Earth this temperature does not depend on its IR emissivity, neither on the IR emissivity of any atmospheric ingredient. It is perfectly determined by ASR (Absorbed Shortwave Radiation), that is, short wave (visible & near IR) albedo and incoming solar radiation flux.

    Outgoing longwave radiation is not only uneven, but neither it is thermalized perfectly, because at such low temperatures no material approximates a black body and due to the semitransparent nature of atmosphere radiation escaping to space originates in different layers with vastly different temperatures. Therefore it is a tricky business to assign (radiative) temperature to each and every point of the globe.

    Nevertheless it can be done. If it's useful or not, is another matter entirely.

    If the surface of the globe is divided up into a grid, having measured the distribution of OLR (Outgoing Logwave Radiation), effective temperature can be calculated for each gridcell, then one can take the (area weighted) average of these temperatures. As <T>4 ≤ <T4>, the finer the grid the smaller this average will be. A decreasing series bounded from below is convergent, therefore with a fine enough grid we can calculate a well defined unique average temperature for the globe as it is seen from the outside.

    This temperature is much smaller than the oft quoted -18°C, it is certainly somewhere below -30°C. In defining the atmospheric greenhouse effect it also has the advantage of having a chance to be the correct choice to compare average surface temperature against, because comparing average temperatures to an effective temperature hardly makes sense in the first place (like apples to oranges).

    Is the atmospheric greenhouse effect more than 45°C then (instead of 33°C)?

    One also wonders what is the correct choice for surface? I know we live at the bottom of the atmosphere, so the special surface separating it from the rest of the globe is important for us. However, at least from the 16th century on we are moving away from an anthropocentric viewpoint, not by pure chance, but it has turned out the Universe is not centered around mankind after all, at least not in any trivial sense.

    So the correct question to ask is "Which surface is the important one for the climate system?"

    The question put this way has a unique straightforward answer: the upper surface of crust. The interface between the atmosphere and ocean is a busy one, both material and heat flows are several orders of magnitude higher there than those between the crust and atmosphere/hydrosphere combined. The whole AGW issue is started by the realization of a small, but in a geological sense still fast flow of the element carbon from crust to atmosphere effected by industry. It can be considered a "forcing" precisely because this interface is usually much more "closed" than the one between air and ocean.

    So when talking about "average surface temperature" we'd better compute it along a true boundary surface of the climate system, that is, along the surface of land and bottom of ocean. This average would be less than 7°C and much more stable than the usual one.

    In this case is the atmospheric greenhouse effect 25°C? or 37°C?

    I have no idea if average temperature of the globe as it is seen from space is increasing, decreasing or just fluctuating around some value. Neither do I know if among the several possible definitions of atmospheric greenhouse effect which one has a trend and in what direction. But it would certainly be interesting to know.

    Average temperature is probably not as important as some say. Entropy fluxes could be calculated in a similar, although slightly more complicated manner (one would need spectral resolution as well) and that would be way more informative than average temperature at an arbitrary interface.
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  11. Much ado about nothing. You're picking on words. I do not believe it matters that much how the problem is sliced, as long as all the meat is still there. I see no evidence that climatologists lost or added any. Picking on the wording used to communicate the ideas to a larger public is just rethoric.

    I have not followed the back and forth exchanges, in which it appears that G&T somewhat recant on the language quoted by KR above. That quote is pretty clear and indeed well summarized by the punch line used to sell the original G&T "paper" to skeptics. I have only so much time and will certainly not spend it on G&T's wirtings subsequent to their first paper, when I could play with my daughter or practice my trumpet instead (that choice is a no brainer).

    This is not worth anywhere near that much attention. I'm done here.
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  12. BP #110

    Been following the discussion with great interest. As a humble applied scientist (Engineer) with a passable knowledge of thermodynamics, my interest has been in the purported imbalance of about +0.9W/sq.m oft quoted by Dr Trenberth, Hansen et al..which is adding energy to the 'Earth system' - atmosphere, land, oceans etc. This is the much feared AGW.

    I have been trying to piece together a complete set of forcings from NASA GISS data and IPCC AR4 - which includes S-B radiative cooling.

    Dr Trenberth - a leading scientist (of travesty fame) uses a figure for positive feedback of +2.1 W/sq.m (Water Vapor + Ice Albedo), and a Figure of -2.8W/sq.m for S-B radiative cooling derived from the assumption of a 0.75 degK surface temperature rise since AD1750 which is importantly assumed to be approximately the same as the increase in the Earth's radiating temperature since AD1750.

    These are the climate responses added to the net of all the forcings (+1.6W/sq.m) from Fig2.4 of AR4. (ie +1.6 + 2.1 - 2.8 = +0.9W/sq.m imbalance)

    Assuming an average of about 240W/sq.m incoming solar radiation (TSI of 340 minus 100 Reflected), and a current radiating temp for the Earth of 255 degK the sum is simply:

    (T2/T1)^4 x 240 viz: (255/254.25)^4 x 240 = 242.8W/sq.m, hence a increase of 2.8W/sq.m in outgoing IR or a forcing of -2.8W/sq.m.

    This implies that there is no 'insulating' effect of the atmospheric column in the Trenberth calculation which equates the surface and Earth radiating temperature increase to 0.75degK (AD1750 to AD2005).

    The positive feedback term of +2.1W/sq.m from Water Vapour and Ice Albedo implies a higher surface temp increase than the radiating Earth temp increase - which is the proposed 'enhanced greenhouse effect of CO2GHG interacting with Water Vapour' - I presume.

    It seems that the two are inconsistent. Would anyone care to comment on this?
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  13. Ken Lambert - Have you been accounting for the varying T^4 temperature relationship with radiated energy since AD1750? And was 1750 truly at equilibrium? (My opinion is that it would not, being near the end of the LIA, including the 1650, 1770, and 1850 Northern European minima with warming between them)

    Given the known inaccuracies of TOA radiation, PDO and other cyclic ocean heat sequestrations, etc., I don't believe you can do absolute imbalance calculations over 160 years like that.
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  14. Energy is not always moves from warmer to colder places because there are different forms of energy in space and time leading to the advantage of the accumulation of heat over its dissipation - entropy - it is "cliché" but "cliché" is and (here), significantly.
    Where does most of the "imbalance" of energy in the atmosphere of the Earth (or Earth is more heated, and loses less energy - the primary side effect of the discussion here) the interesting tries to explain: „Earth and Ocean Science”- A 1st order global energy model based on observed TOA radiant flux and ocean and atmosphere heat data - cloud changes in the satellite era. Comparing the changes in OLR and RSW (2000 - 2010), comes to the conclusion that far outweighs "heating" (decreasing RSW) ocean (accumulating heat) by the SW, it’s have advantage over retention of heat (decreasing OLR) through the atmosphere:
    “CERES data since 2000 clearly show SW changes – this drove the ocean heat content increase measured in ARGO. Most of recent warming is driven by changes in reflected SW. SW changes imply changes in global cloud cover over the period.”

    Regarding this point: 'enhanced greenhouse effect of CO2GHG interacting with Water Vapour', again had to go to the discussion of the reaction - sensitivity, of the system: Earth - the atmosphere. An interesting critique of messages posted on the SkS on this topic is
    here.
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  15. KR #113

    Yes, I have making the same assumption as Dr Trenberth. ie. the surface temperature increase is the same as the increase in Earth's radiating temperature.

    The approx numbers are:

    Date / Temp Increase / S-B Cooling Forcing (W/sq.m)

    1750 / 0.0 / 0.0
    1800 / 0.0 / 0.0
    1850 / 0.03 / -0.11
    1900 / 0.03 / -0.11
    1950 / 0.15 / -0.57
    1975 / 0.25 / -0.94
    2000 / 0.72 / -2.70
    2005 / 0.75 / -2.80

    It could be done in smaller increments but the point is that S-B cooling is rising rapidly with the 4th power.
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  16. Ken: It appears to me that you do not understand the terms in the equation you are trying to use. I have not loked at this equation carefully before and have only your description to go on. It seems to me that the equation follows the heat and not the temperature. You calculate the change due to the measured increase in temperature as 2.8 w/m2. The 2.1 w/m2 is the measured increase in water backradiation and lowered surface albeido. The other atmospheric forcings are estimated at 1.6 w/m2. It adds up to a net forcing of 0.9 w/m2. Your interpretation of no insulating effect of the atmosphere seems to me to disregard the water backradiation and the other forcings. Trenberth has separated the insulation effect from the radiation effect for the purposes of calculation. It appears to me that your calculation confirms Trenberths. You need to show that Trenberths 2.1 w/m2 or the 1.6 w/m2 are in error to show that heat is not accumulating. Since they have large error bars (especially the other forcings) they might be higher or lower.

    Since the S-B cooling rises with the 4th power it will ultimately limit the temperature rise. The rise depends on how much CO2 is added to the atmosphere.
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  17. michael sweet #116

    I can't find an equation for the 'WV and Ice Albedo feedback' which is stated for AD2005 at +2.1W/sq.m. I could make an estimate that it is linear back to zero back 255 years to AD1750 - or some other relationship (logarithmic? inverse square?) Please advise if you know this relationship.

    Read this again:

    "Dr Trenberth - a leading scientist (of travesty fame) uses a figure for positive feedback of +2.1 W/sq.m (Water Vapor + Ice Albedo), and a Figure of -2.8W/sq.m for S-B radiative cooling derived from the assumption of a 0.75 degK surface temperature rise since AD1750 which is importantly assumed to be approximately the same as the increase in the Earth's radiating temperature since AD1750." and

    "The positive feedback term of +2.1W/sq.m from Water Vapour and Ice Albedo implies a higher surface temp increase than the radiating Earth temp increase - which is the proposed 'enhanced greenhouse effect of CO2GHG interacting with Water Vapour' - I presume.

    It seems that the two are inconsistent. Would anyone care to comment on this?"

    I think I have covered the point. How can it be assumed that the S-B temperature increase around the Temp which the Earth radiates (assumed at 255 degK) is the same as the surface Temp increase (both 0.75 degK), if the enhanced greenhouse effect is already operative and producing a differential across the atmospheric column?

    If there is a WV + Ice albedo feedback of +2.1 W/sq.m then the surface temp increase of 0.75 degK should be significantly greater than the S-B radiating temp increase, should it not?

    Does not the enhanced CO2GHG theory state that for a doubling of CO2 we should see an approx 3degK surface temp increase for a 1 degK increase in the S-B radiating temperature.

    Now we have not had a doubling of CO2 at AD2005 wrt AD1750, but if there is a WV - CO2 feedback working then the surface temperature increase should be larger than the S-B radiating temp incease right now.
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  18. @ leading post
    The explanation of the greenhouse effect with the blanket works well and don't contradict at all the second law of thermodynamics as in this case the energy (heat) flows from higher temperature (ground) to lower temperature (atmosphere) and the ground has to rise its temperature for winning the thermal resistance of the blanket, as in the conduction through a wall.
    There exists also the explanation of “back radiation” that is mostly supported too.
    Well, it is, really, the back radiation that contradicts the second law assuming that the energy (heat) flows from lower temperature (atmosphere) to higher temperature (ground).
    Then, what’s the matter?
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  19. Michele, your writing is a bit unclear, probably due to language issues.

    Well, it is, really, the back radiation that contradicts the second law assuming that the energy (heat) flows from lower temperature (atmosphere) to higher temperature (ground).

    There is a net heat flow from the warmer surface to the cooler atmosphere. But the presence of the (GHG-laden) atmosphere keeps the surface warmer than it would be in the absence of greenhouse gases. There's no contradiction of the 2nd law.

    As it happens, there is a nice discussion of this right now over at Science of Doom.
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  20. Michele,

    back-radiation from cooler air to warmer earth is perfectly valid. Radiation from a cool object can be absorbed by a warmer one. Example, take a glow-in-the-dark haloween mask, put it in the fridge for a few minutes, then take it out. Can you see it glowing? If so, that means that your warm eyes are absorbing radiation emitted by a cooler object, which is exactly what back-radiation is about.

    So the idea of back-radiation does not contradict the second law of thermodynamics.
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  21. I would remind something about what occurs when two waves traveling in opposite direction interfere between each other, taking into account the simplest case 1-D.
    1- The sum of two counter - propagating waves (of equal amplitude and frequency) creates a standing wave and there isn’t propagation of energy. In other words, using the principle of superposition, the resulting wave may be written as:
    R = Asin(kx+wt) + Asin(kx-wt) = 2Asin(kx)cos(wt)
    that is no longer a travelling wave because the position and time dependence have been separated.
    2 – If the two waves haven’t equal amplitude, then the global effect is:
    R = (A + B)sin(kx+wt) + Asin(kx-wt) = 2Asin(kx)cos(wt) + Bsin(kx+wt)
    that corresponds to a standing wave 2Asin(kx)cos(wt) plus a traveling wave Bsin(kx+wt) which has the propagating sense of (A+B). In other words, the strong wave (A+B) blocks on the way the weak wave (A) and there rests acting only the difference between the two waves.
    That’s, the traveling effect of counter wave Asin(kx-wt) (for us, the back radiation) vanishes on the way and there’s a reduced traveling effect of stronger wave (A+B). Of course, the energy that don’t travels isn’t destroyed but simply turned into potential energy of the stationary wave.
    There is nothing strange. In all phenomena of nature only the strongest survive and it always stifles the weaker, that however isn’t suppressed but only captured because Nature always selects for to operate the most elegant and economic way.
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  22. #121: "The sum of two counter - propagating waves (of equal amplitude and frequency) creates a standing wave"

    That's true when there are requisite boundary conditions (such as a pair of reflecting or nonreflecting surfaces). If this is the atmosphere, what boundary conditions are you suggesting?
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  23. Michele - I've seen this constructive/destructive interference argument before. However, this kind of interference does not destroy any energy, merely displaces it at most a half-wavelength of the beat frequency. And it only occurs with coherent light and the boundary conditions muoncounter pointed out, neither of which applies in atmospheric IR.

    Constructive/destructive interference is a red herring. It's simply not relevant to Earth climate energies.
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  24. Michele, a similar argument about wave interference was made by another commenter a while ago on another thread. I posted links to explanations and animations that help illustrate the responses by muoncounter and KR. See these comments on that other thread: 206, 207, and 208. See also Riccardo's comment there.
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  25. I don't tend to divert the attention from the talking point, but the waves superposition is more relevant to energy exchange at Hearth’s surface.
    Indeed, at any point of the surface there are acting (and traveling opposite each other) at least two EM waves along any direction. The energy flux (Watt/m2) coming in/out at that point is the amplitude of Poynting vector, the cross product of resultant electric field and resultant magnetic field, both obtained applying the superposition principle (notice, there’s a quadratic relationship between resultant field and flux that doesn’t allow to sum the fluxes of component fields because the flux quadruples as the field doubles).
    Thus, for any frequency, at any point of surface exists only a resultant electric field, only a resultant magnetic field, only an energy flux. Moreover, the standing wave that reduces the flux coming out induces the temperature increase of surface to restore the energy balance at surface.
    Thus both the energy transfer problem and the GH effect are simply and definitively explained by vector kinematics. The thermodynamics isn’t needed because it muddles up our ideas instead of making them clear.

    Yet I want to point that the 2th law of thermodynamics doesn’t refer only to the heat flow between two objects; it have an overall meaning that concerns the flow of every energy form, induced by its density gradient.
    The thermal radiation density, given by Planck’s relationship B(T), is a monotonically increasing function of the absolute temperature. In the empirical relationship between temperature and pressure of a gas, at constant volume, p = const*T, both the terms depict an energy density and are monotonically increasing functions of absolute temperature and pressure.
    For an energy exchange is needed an energy flow and that occurs only if there’s a not-zero grad(T) or a not-zero grad(p) and the flow happens along the decreasing T or p.
    If were true to assume that the thermal radiation energy can flow along increasing T, then also heat and the other form of energy could flow along increasing pressure/temperature. In other words it would be (almost sometimes) normal for an adrift boat to sail upstream the river, or for the outlet flow of a water turbine to return spontaneously into the higher feeding reservoir, and again, for a gas escaped by a cylinder to re-enter it naturally.
    All the cases are obviously absurd because all they contradict the second law of thermodynamics.
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  26. Michele - EM wave superimposition doesn't create or destroy energy, it just moves it around a little. Waves pass through each other unchanged - surface energies may be redistributed by interference.

    Given incoherent IR (the very definition of thermal radiation involves incoherent emission scaled by object spectra and temperature), wave superimposition really has no effect whatsoever on the greenhouse effect. This is a complete red herring argument.

    As to the 2nd law of thermodynamics, a cold object (yet warmer than absolute zero) can keep a nearby warm object warmer than it would be without the cold object, simply by not being as much of a heat sink as empty space. See Yes, Virginia, Cooler Objects Can Make Warmer Objects Even Warmer Still and In Defense of the Greenhouse Effect, by Dr. Roy Spencer (self described skeptic).

    Energy flows in all directions. The sum of energy flows is what is described by the 2nd law of thermodynamics. Consider a warm object (internally heated with 100 watts) radiating 100 watts to empty space, it's at equilibrium. If a nearby cold object radiates 20 watts to the warm object, the total outgoing energy is only 80 watts - and the warm object will increase in temperature until it's radiating 100 watts again.
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  27. Michele - I may have misinterpreted your post here. Are you agreeing with this article by Tony Wildish or disagreeing? It's not clear to me from your comments.
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  28. In comments 65 and Berényi Péter refer to papers by R. Dewar.

    A new comment on two of Dewars papers is online. The comment apparently show that results of two his papers are based on an physical unrealistic assumption.
    The comment discuss the following papers by Dewar:

    Information theory explanation of the fluctuation theorem, maximum entropy production and self-organized criticality in non-equilibrium stationary states [R. Dewar, J. Phys. A:
    Math. Gen. 36 (2003), 631–641]

    Maximum entropy production and the fluctuation theorem
    [R. Dewar, J. Phys. A: Math. Gen. 38 (2005), L371–L381].
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  29. A blanket adds a sheet to composite multilayer system that protects our epidermis by surrounding cold air increasing/decreasing its thermal resistance/conductance and so requiring a higher skin temperature to dispose of the same metabolic heat.
    The GH effect explained with the idea of a blanket works well and doesn’t contradict the 2^ law because the energy flows always along the straight and narrow path towards decreasing temperatures. I think an EM blanket (a standing wave that captures and stores back radiation together part of forward radiation without destroying anything, operating upon homogenous physical properties) that cuts down the radiative conductance of atmosphere, brings to surface temperature increase and doesn’t contradict the 2^ law.
    The problem arises when the blanket working is explained whit a sort of walking back and forth of the energy carried by radiation because all that seems unreal. A radiating molecule can naturally emit its photon but it isn’t able to excite itself .
    I notice that the radiative transfer theory, agreeing to heating of hotter body produced by back radiation, is the one physical theory that is characterized by a sort of omnipotence since both Planck’s and SB’s relationships assume an absolute (rather than relative) significance since any body radiates, always and however, regardless of environmental conditions. Not at all. That doesn’t make much sense. The radiative flux is physically analogous to any other flux induced within a transport phenomenon that’s always founded on the gradient of the driving physical property (pressure, temperature, altitude, electric potential, etc.), not on its absolute value.
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  30. Michele - The outgoing thermal flux from an object is strictly a property of the object emission spectra and temperature, not a gradient.

    Changes in temperature, on the other hand, are due to the differences between outgoing energy and incoming energy, and that incoming energy differs depending on surroundings, which is where relative positioning and nearby objects matter.
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  31. KR, Yes, if the emitting body is alone in the vacuum, No if it isn’t more alone because it feels the presence of the other bodies and it changes his behavior that’s tied to resultant EM at any point of its surface.

    The temperature change occurs only if the integral(resultant_flux*dt) isn’t zero. You aren’t allowed to add two or more fluxes of components waves because the energy carried is proportional to square of field. Doing so the energy would be destroyed as is always (SumEi)^2 > Sum(Ei^2).
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  32. Michele, one body "feels the presence" of the other body? Halloween has passed already....
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  33. Michele - Your statement "it feels the presence of the other bodies and it changes his behavior" is incorrect. Outgoing thermal radiation is only dependent upon the object temperature (scaling as T^4), emission spectra, and the size and shape of the object. There is no neighbor effect, and no surface EM interference that affects the thermal radiation.

    Please read the Wiki Thermal Radiation page for a good overview.
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  34. Michele - To be more specific, the thermal radiation from an object is:

    P = e * s * A * T^4

    Where:

    P: Power
    e: Emissivity (fractional power relative to a theoretic black body)
    s: Stefan–Boltzmann constant
    A: Object Area
    T: Temperature Kelvin

    There is no neighbor term, no incoming radiation term in this relationship.
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  35. KR, sorry I cannot agree with you because the concept of flow implies the contemporary presence of both the supplier and the receiver. There is no flow if either of them misses or neither of them exists. In other words, something exists only if there’s something else that feels its presence. Really, the idea of *absolute* doesn't belong to Physics and perhaps it not even belongs to Metaphysics since *God created the world because He felt lonely*.
    Conversely, the exact formula of power flux is:
    P = e*s*A12*(T1^4-T2^4)
    = (e*s*(T1+T2)*(T1^2+T2^2))*A12*(T1-T2)
    = K*A12*(T1-T2)
    formally identical to the others well known expressions of thermal flow.
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  36. Michele, you have unusual ideas about "contemporary presence." In this universe, all "things" are in the presence of all other "things." It is the universe itself as a whole that you need to apply your "unless something else feels its presence" philosophy to. All "things" radiate if they are above 0K, whether the next nearest "thing" is ten miles away and is a bowling ball or 10 million parsecs away and is a hydrogen atom in "deep" space.

    It sounds like you're saying that a "thing" uses some extraphysical means of "sensing" the presence of other "things."

    I'm saying "things" because there is actually only one thing, and that's the universe. All "things" within the universe are connected in various ways, even if we can only sense a narrow range of these connections (or not "see" them at all).
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  37. Michele, you have just confirmed what I said here.

    The amount of thermal IR coming from an object is dependent solely on it's area, emissivity, and temperature. The integrated energy over time (the flux, as you put it), is dependent on the neighborhood, and that determines temperature changes of those objects.

    There are no standing wave effects.
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  38. I try to write my thought in other way.
    Energy is a scalar physical property that acts in different forms, all equivalent between them. If not confined (potential energy form) it spreads in order to be shared with surrounding, flowing according to the gradient of its density that’s a vector.
    In other words the energy flow field is a vectorial field and it’s well known that the lines of a vectorial field never intersect, i.e. at any point of such a field exists only one vector (the resultant of whatever number of presumable components) tangent to such a line and the effect caused at that point (the effect of the resultant vector, not the resultant of the effects of component vectors, that are different between each other if there isn’t a linear relationship tying causes and effects) is only one: the vector, if not zero, solely operates in a direction or in the opposite direction.
    At the Earth’s surface the energy flows as sensible and/or latent heat and as EMR. There will occur only a single sensible heat flow, only a single latent heat flow, and, for any frequency into the whole spectrum, only a single EMR flow that, in not zeros, are directed or upward or downward.
    Then, the feedback radiation isn’t possible because in this case the vector of energy flux doesn’t comply with the vectorial field line uniqueness rule and it would be in contrast to its gradient and hence to the second law of thermodynamics, that has a general value for any form of energy, not only for the heat. Otherwise we have to come back to 19th century’s *caloric theory*.
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  39. Michele - Your statement "the feedback radiation isn’t possible" is quite simply incorrect. This is a measured value, observable everywhere on Earth. Your statement contradicts both physics and observations.

    The sum of upwards and downwards energies is (at equilibrium conditions) zero. Heat flow from incoming solar photons warms the earth, the atmosphere, oceans, etc., and then goes upwards out to space. The greenhouse backradiation (which is always less than the upward IR) slows the cooling of the earth, limits the outgoing radiation, and causes the Earth to stabilize at a much higher temperature than it would have otherwise.

    Please read the links I provided here. Heat flow requires an inequality in energy flows, not a uni-directional energy flow.

    Basics:
    An object has 100 watts of energy coming, warming it until it radiates 100 watts. If you then place a nearby cooler object that (back) radiates 25 watts to the object, it has 125 watts coming in, but is only radiating 100. It will heat up until it's thermal radiation matches incoming energy at 125 watts. Multiple vectors, Michele, not a uni-directional flow.
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  40. KR, “Multiple vector”. A fluid dynamics example.
    A gas at rest is only macroscopically at rest as the molecules keep on their fluctuations around the center of mass of the particle that includes them. Indeed, the vectorial sum of the all velocities relative to the center of mass of the particle, is statistically zero because the velocities, also if chaotic, are really isotropic. The agitation motion of molecules only causes the local equipartition of macroscopic characteristics as pressure, density, temperature (in practice of energy density) within the particle, and it don’t cause any transfer of energy or of mass. The macroscopic transfer of mass (mechanic energy) occurs only if the pressures between two different parcel of the gas are different. With different temperatures there’s always a transfer of thermal energy and at given conditions also of mass. This transfer is measurable (and indeed exists for real world that we feel) only at macroscopic scale.
    You cannot lump microscopic an macroscopic things together.
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  41. Michele - Sorry if I was not clear in this posting. Multiple EM waves in both directions (not canceling, not unidirectional) between warm and cold bodies, with heat flow (total energy transfer) determined by the difference in magnitudes. I'm speaking of EM first, the heat flow is the result of those emissions.

    The principle of superimposition means just that - EM emissions are superimposed on each other, which (in the very limited case of coherent light) can give rise to standing patterns of constructive/destructive interference thus displacing energy along the pattern, but never destroying energy. And coherence is absolutely not a factor in thermal emission, which is incoherent - individual molecules giving up energy are not synchronized.
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  42. KR,
    I agree with you the GH gases cause the increase of planetary surface temperature.
    I cannot agree with your explanation of its mechanism. In any transfer phenomenon the driving physical property arises upstream if the induced flow encounters downstream a higher resistance. The counter flow that acts simultaneously is for me an unphysical idea.
    My last attempt.
    The spontaneous heat exchange between two bodies increases the entropy of the system.
    If the first body emits a specific power P1=s*T1^4 and the second P2=s*T2^4 then the increase rate of system entropy is R1=s*(T1^3+T2^3).
    Conversely, if T1>T2 and the unidirectional exchanged specific power is P=s*(T1^4-T2^4) then the entropy increase rate is R=s*(T1^3-T2^4/T1), clearly more and more less than R1.
    A higher entropy increase rate means to put forward the end of world because as higher is entropy as lower is the probability for energy exchanging and a world without energy exchanging is a dead world.
    As far as I know Nature uses its own energy with the highest degree of efficiency and doesn’t waste it for nothing.
    By the way, the energy never is destroyed but always conveyed towards its spontaneously unusable ground level.
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  43. Michele - Greenhouse gases absorb some of the outgoing surface IR (which warms the atmosphere to some degree). Based upon atmospheric temperatures, greenhouse gases incoherently and uniformly emit IR in all directions, and roughly half of this IR heads back to the ground (Figure 1, where absorption notches are clearly seen). The effect is a reduction of outgoing IR, reducing the emissivity of the planet, and meaning that in order to emit all the energy received by the sun the Earth has to be at a higher temperature than it would be without greenhouse gases (at a higher emissivity).

    That is the mechanism, measured, well established, and matching theory. And the measured convection and evaporative effects total only 1/4th the energy of that IR in the lower atmosphere.
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  44. KR,
    I suggest the following draft http://www.csc.kth.se/~cgjoh/ambsblack.pdf
    Claes Johnson, relating to classical harmonic oscillator with radiation and dissipation, forced by an incoming wave, shows in a straightforward manner that the energy is transferred only from warmer to cooler and the back radiation isn’t able to heat the planetary surface.
    Up to now, I didn’t know this very fine detail!
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  45. Michele - There is a quote from Carl Sagan, that "Extraordinary claims require extraordinary evidence".

    Your article (by a Claes Johnson) attempts to overturn Planck, the Stephen-Boltzmann law, and quantum effects on radiation, returning to classical wave mechanics by arguing for finite precision math and small scale diffusion effects. And without proposing any experimental differences between these two interpretations that could be used as a test.

    If this is the case, and your author is correct, by all means, he should submit to Science and everywhere else. But he's going to have to have rather extraordinary evidence to throw out the last 100 years of quantum physics.

    I consider it much more likely that Claes Johnson is completely wrong, and is in fact indulging in wishful thinking. Until and unless Johnson proves his amazing theories, I'm going with the greenhouse effect. As should you.
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  46. Michele
    I wouldn't venture to disprove (ignore?) statistical mechanics and quantum mechanics in one shot. This is what that paper does.
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  47. I think that a physicist doesn't put his own trust in a theory;
    he has to show it is a true theory.
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  48. Re #143 KR you write:-
    "Greenhouse gases absorb some of the outgoing surface IR"

    This leads to question 1/ Do GHGs emit out going radiation?

    question 2/ Do GHGs absorb radiation emitted by GHGs?

    question 3/ What calculation of emission and absorption by GHGs do you use to decide whether the temperature of a particular quantity of gas will increase or deacrease?
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  49. @Michele: that's your rebuttal? Ouch. I think you need to learn more about the actual science before trying to present such arguments here. This isn't WUWT - most people commenting here actually know what they're talking about.

    @damorbel: I can answer the first two points.

    1) Yes, I believe that's the whole point of the greenhouse effect: GHG molecules absorb IR and re-release it in a random direction.

    2) Sure. Radiation is radiation. How would a CO2 molecule know where the IR is coming from?

    3) I don't understand your question. I think you're confusing the "greenhouse" effect of GHGs with the capacity that every molecule has to be heated by an influx of radiated energy.

    Seriously, for someone who barged in here claiming the GHE violated the 2nd law of thermodynamics, you seem to understand very little about the actual physics involved.
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  50. Re #149 archiesteel you wrote:-

    "I don't understand your question. I think you're confusing the "greenhouse" effect of GHGs with the capacity that every molecule has to be heated by an influx of radiated energy."

    Surely the important characteristic of GHGs is that they absorb (and emit) photons (EM energy) much more readily than other molecules such as O2 & N2?

    GHGs are uniformly mixed in the atmosphere until about 80km up, except for water. The point being, if GHGs absorb and emit radiation they will do that with local GHG molecules first, rather than travel all the way to the Earth's surface to add energy there.

    GHGs are at the same temperature as (local) O2 & N2; any warming effect of surface radiation heats the whole atmosphere at the height where it is absorbed.

    Further gases tend to have a uniform temperature because the molecules exchange energy by collision. In the atmosphere, at atmospheric temperatures, this energy exchange by collision exceeds the exchange by photons, simply because the mechanical momentum of a molecule exceeds the photon momentum by far.

    Also the density of atmospheric gases (including GHGs) gets smaller with altitude thus the energy density, even if the temperature did not fall with height, gets progressively lower with altitude; is there really going to be enough energy at altitude to raise the temperature of gases at the surface by the claimed 33C?
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