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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 201 to 250 out of 274:

  1. Re #199 CBDunkerson you write :- "damorbel #198:Numerous people, including me, have repeatedly shown you conclusive proof... " In #198 I asked who you thought are the scientists who have moved on from Tyndall. My personal concern in this matter is not the historical side but how modern physics handles the arguments put forward by the IPCC when they are advising governments to change the basis for energy supply to much more expensive 'wild (or supposedly renewable) energy sources, all of which will have a devastating effect on the environment. Half of the IPCC thesis is that the Earths albedo reduces the surface temperature when some simple physics familiar to all shows that this simply isn't true. The other half of the IPCC thesis is that gases that emit/absorb infrared can change the heat distribution in the atmosphere. On this last I have cited the stratosphere where the temperature profile really is modified by absorption. But the planet with a very nearly pure CO2 atmosphere, Venus, does not have a stratosphere like the Earth with its characteristic temperature inversion. Surely if GHGs absorbed IR in the same way O2 absorbs UV there would be some trace of temperature inversion but I don't think you will find any.
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    Moderator Response: [muoncounter] You were asked politely in #193 to keep your politics to yourself. Yet you continue in #198, #201. Next political rant is gone -- and all the prior ones go, too.
  2. Moderator Response: [muoncounter] I am intrigued to know how contributions based on the scientific arguments presented by the IPCC or their lead authors for preventing AGW can be described as political. When geoengineering is under consideration it is essential to run the scientific arguments to their proper conclusion.
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    Moderator Response: [Daniel Bailey] This thread is on the 2nd law of thermodynamics and the greenhouse effect. Subjective remarks on the economic effects of rising CO2 or comments on geo-engineering are off-topic. Keep that in mind if comments disappear.
  3. damorbel: What does O2 absorption of Sun-sourced UV-spectrum EM radiation in the stratosphere have to do with tropospheric greenhouse gasses (CO2, CH4, H2O, &c.) absorbing surface-sourced infrared-spectrum EM radiation, or with your claim that the latter process is nonexistent on account of the 2nd Law of Thermodynamics (or at least your interpretation of it)?
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  4. Oops, I should note that contra my comment #203 greenhouse gas distribution is not exclusively limited to the troposphere. Mea culpa.
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  5. @damorbel: "I am intrigued to know how contributions based on the scientific arguments presented by the IPCC or their lead authors for preventing AGW can be described as political." Simple, it was because of your unsupported claim that any energy alternative leads to financial catastrophe (ignoring the fact that inaction will lead to much bigger financial woes. In particular, these words: "much more expensive 'wild (or supposedly renewable) energy sources, all of which will have a devastating effect on the environment." There is no evidence that alternative energy sources (solar, wind, tidal, geothermal, hydro, etc.) have "devastating effects" on the environment, especially when use of fossil fuels (oil, coal, gas, etc.) *already* has a deleterious impact on the environment. What you said was not a scientific statement, but a political one that has no basis on objective reality. Perhaps it's time for you to re-evaluate your motivations and start understanding the science rather than spout off incorrect arguments in an arrogant assault on established science.
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    Moderator Response: [muoncounter] Archiesteel - Well put!
  6. I also would like damorbel to answer the counter-arguments presented to him rather than dismiss them off-hand. So far, he has failed to make a compelling case to support his bizarre interpretation of accepted science.
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  7. damorel - the idea that text book use of heat flow (you can call it heat transfer or whatever) implies that the text book writer is confused about the historical "fluid" theory is ridiculous in the extreme. A few minutes reading the framework would dispel that notion. The standard, textbook theory of thermodynamics gives us a predictive framework. If your eccentric ideas fail to predict the outcome of an experiment and the textbook method does, then do you accept that you need to change your ideas? At the moment you are clinging to a false notion of GHE based as far as I can see on an incoherent thermodynamic framework. The argument can progress if we can discuss an experiment where your notions produce a different an answer to standard textbook ones.
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  8. CH4, H2O and CO2 are present in the stratosphere where thay absorb and radiate IR. Their radiative effects are part of the total stratospheric heat budget. Do you dispute that? Between the claims on historical elements and all the rest, it seems that your argument is that the atmosphere can not radiate any energy toward the surface because it is colder, is that what you are actually trying to defend here?
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  9. Re 208 Philippe Chantreau You wrote:- "CH4, H2O and CO2 are present in the stratosphere where thay absorb and radiate IR. Their radiative effects are part of the total stratospheric heat budget. Do you dispute that?" I suggest your question is unclear. Heat is measured by temperature, the basic rule of 2nd law of thermodynamics. A heat budget would just say that heat transfer is from the hotter location to the colder, the hard thermodynamic fact that destroys the AGW/GHE.
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  10. Since you're a stickler for words, let's kepp it tight. Heat content is what is measured by temperature. The question is very clear, let me rephrase it: do you dispute that these gases absorb and emit IR in the stratosphere and that their radiative properties affect the temperature of the stratosphere? The other question is this: Do you argue that there can be no energy (any and all kinds) transfer between the atmosphere and the surface because the atmosphere is colder than the surface?
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  11. Re 207 scaddenp You wrote:- "A few minutes reading the framework would dispel that notion" The framework has this:- "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. Trapping heat needs an insulator, material with a relatively low thermal conductivity, such as an expanded polystyrene container or a vacuum flask. This insulating material slows the rate of heat transfer in or out of the container. If your flask is made of transparent material, heat will also transfer out of (or into) the flask by radiative process. This radiative process can be reduced by coating the flask surfaces with a highly reflective material. The critical factor in this matter is that reflection 'traps' heat, not absorption/emission; GHGs do not reflect radiation to any measurable extent, certainly no more than O2 and N2. If you are interested in highly effective 'trapping' of radiation, you only have to check optical fibres used to transmit data accross oceans, some are able to contain (trap) IR radiation for 100s of kilometers before a repeater is needed.
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  12. Re #210 Philippe Chantreau You wrote:- "Since you're a stickler for words, let's kepp it tight. Heat content is what is measured by temperature" Not remotely. The tiniest particle has a temperature, its 'heat content' may be microscopic while its temperature can make it glow any colour you like. You wrote also:- "The other question is this: Do you argue that there can be no energy (any and all kinds) transfer between the atmosphere and the surface because the atmosphere is colder than the surface?" That is far too general ('any and all kinds'!) but if you confine the transfer to thermal processes (including radiation) the answer is yes, I do argue that, it's what the 2nd law is all about.
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  13. damorbel: You were asked two questions in Philippe's post #208. Both of them are quite clear - if you wanted you could answer both of them with just 'yes' or 'no'. One of them appears to be a request that you clarify your central position on this thread. You answered neither of them in your post #209. Indeed, your answer reads like a diversion rather than an attempt to address the question. As has been put to you on several previous occasions, the hard fact is that backradiation and other greenhouse-effect features can be, and have been, empirically measured. So to be frank, it appears that the issue at hand continues to be your misunderstanding of thermodynamics. All the more so since you insist (on this comment thread, at least) on arguing at a purely conceptual level, with no evidence to support your claim other than assertion. If you can provide either (A) some empirical measurements, preferably published in peer-reviewed journals, showing that the empirical measurements demonstrating a greenhouse effect are false, or (B) documents, preferably also published in peer-reviewed journals, showing that the methods used to collect the empirical measurements demonstrating a greenhouse effect are fatally flawed, then perhaps you will make some progress here.
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  14. damorbel, everyone else - Lets, just for a moment, return to the topic of this thread. Critics (exemplified by G&T, as linked in the initial topic) have argued that the atmospheric greenhouse effect violates the 2nd law of thermodynamics. They have argued this claiming that "heat cannot flow from colder to warmer" (correct, where 'heat' is the sum of energy flows), while blatantly ignoring the fact that thermal radiation from a colder atmosphere can reduce the sum energy flowing from the warmer ground/water, causing the surface to heat until it's thermal radiation once again equals the incoming visible radiation. This conflation of 'heat flow' with basic radiative dynamics is the basis of the entire "2nd law objection" error. They claim the part (thermal IR from cold to warm) is the whole (summed energy flow, or 'heat flow'), and in this they are sadly incorrect. This is the Fallacy Of Division. Greenhouse gases, by absorbing/re-radiating thermal IR at various frequencies, redirect just under 50% of that IR back to the ground (backradiation, easily measured, and quite well established over 50 years ago), which means that the amount of radiation from the surface to space is reduced at any particular temperature, as per the previous paragraph. Heat transfer (defined as sum of energy) is from the warmer ground to the atmosphere and to space. But it's less efficient when greenhouse gases are present, requiring the ground to be warmer, to radiate more, to be in equilibrium with incoming visible light. This is entirely in line with the first and second laws of thermodynamics - there is no contradiction, the greenhouse effect follows the laws of physics. damorbel - You've jumped around (intentionally or otherwise) from red herring to red herring. You too are guilty of the Fallacy Of Division. However, you have correctly noted that objects absorb photons within their absorption spectra, regardless of the source. Therefore an object (of any temperature) can receive energy from another object (of any temperature), with the 'heat flow' determined by the summation of those energies. The GHE changes the summation at the surface of the Earth, and balance can only be maintained with a higher surface temperature than would be present otherwise - it's really no more complicated than that. If you have issues with anything I have said in this post, please say so - I can point you to where each part of this has been measured and demonstrated repeatedly over the last few centuries. Note, however, that I will call out strawman arguments or red herrings.
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  15. A few minutes reading the framework would dispel that notion" The framework has this:- No it is not. You are jumping around. The framework I referred to is the way that "heat flow"/"heat transfer" is introduced in thermodynamics theory. Reading that would dispel the idea that modern thermodynamics is trapped in caloric theory. Instead of jumping around, do you that an experiment is arbitor between textbook physics and your odd ideas? There is no further point to this discussion unless you do.
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  16. "Trapping heat needs an insulator, material with a relatively low thermal conductivity, such as an expanded polystyrene container or a vacuum flask. This insulating material slows the rate of heat transfer in or out of the container. If your flask is made of transparent material, heat will also transfer out of (or into) the flask by radiative process. This radiative process can be reduced by coating the flask surfaces with a highly reflective material." More wierdness. "Insulator" in terms of GHE is more of conceptual term and I dont like it. GHGs are NOT a conductive insulator, never have been postulated to be and far as I can see, you are the only one insisting on this understanding of the word "insulator". In the more general sense of an impediment to energy transfer, then GHG are insulators but the mechanism of impediment has nothing whatsoever to do with the conductive properties of the atmosphere. But this has been explained to you before... You are persisting with idea that textbook thermodymanics postulates that GHE is due to conductive-like heat transfer from bodies of different temperatures. This is also not true. If your notions cannot explain the results of a laboratory experiment and yet textbook thermodynamics, dont you think its time to start reading?
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  17. In reference to my previous post, the Fallacy Of Division in the G&T paper is completely clear in their Figure 32, page 78, where they draw an incorrect heat transfer diagram - and claim it to disprove thermal radiation. This is both a strawman argument and a Fallacy Of Division. Completely bogus, sad to say.
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  18. @damorbel: the question was quite clear, actually. "the hard thermodynamic fact that destroys the AGW/GHE" Stop acting as if you've made that case, because you haven't. It's quite simple, really. Let's try to break it down in yes/no questions, shall we? Photons from the sun heat the surface of the Earth through thermal radiation. Do you agree with this? Assuming you agree: when object increase in temperature, they emit IR energy, as described by black body theory. Do you agree with this? Note that "the surface" as an object is a bit of an oversimplification (see sensible heat and latent heat transport), but you get the idea, right? Assuming you agree: this IR radiation is absorbed by greenhouse gas molecules, who are mostly "transparent" to visible light (i.e. they absorb photons in the IR range more than they do those in the visible light range); similarly, non-greenhouse gases such as O2 and N2 are mostly transparent to IR-range photons. Do you agree with this? Assuming you do: in order to maintain thermal equilibrium, greenhouse gas molecules re-radiates the IR energy in a random direction (i.e. in every direction, when considering large amounts of molecules). Do you agree with this? Assuming you do: some of the re-radiated IR energy will escape to space, some will get back down to the surface, and some will be captured by other greenhouse gas molecules, continuing the absorbtion/re-radiation cycle. Do you agree with this? There you go: five simple yes or no questions. Be forewarned that any attempt to circumvent the questions, divert the debate or start playing silly semantics will be met with the scorn and/or ridicule it deserves.
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  19. You could have answered the first question, I thought it was made clear enough. As for this: "The tiniest particle has a temperature, its 'heat content' may be microscopic while its temperature can make it glow any colour you like." I do not understand how that shows that temperature is not a measure of heat content. Or perhaps you'd prefer energy content? In any case, what does temperature measure then? Abut the second question, your answer is a little strange. Why only "thermal processes" (whatever that means) and IR radiation? There is a number of good questions also in post 218. Let me just add this one: If no thermal energy can be transfered by IR radiation from a cooler object to a warmer one, how does a radiant barrier work in a vacuum (they do work, and have engineering applications)?
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  20. Re #218 archiesteel You wrote:- "Photons from the sun heat.... " Yes. "Assuming.... they emit IR energy, as described by black body theory " No. Just as objects like planets do not absorb 100% of the incident radiation from the Sun because a certain % (called the albedo) is reflected, neither is 100% radiated. What you should realise is that the % 'trapped' by a radiating planet is exactly the same as the % of the incoming radiation reflected as albedo. "Assuming ....IR radiation is absorbed by greenhouse gas molecules, ... "transparent" to visible light ...similarly, non-greenhouse gases such as O2 and N2 are mostly transparent to IR-range photons. Do you agree with this?" Yes "Assuming....to maintain thermal equilibrium, greenhouse gas molecules re-radiates the IR energy in a random direction ....Do you agree with this?" Yes "some of the re-radiated IR energy will escape to space, some will get back down to the surface, and some will be captured by other greenhouse gas molecules, continuing the absorbtion/re-radiation cycle. Do you agree with this?" Yes. Now answer my questions - please. 1/You argue, correctly in my opinion, that GHGs radiate equally, on average, in all directions. Do you also accept my argument that the scattering/reflection processes that cause the albedo is completely independent of the direction of arrival of the photons that are scattered? 2/In an 'Earth' atmosphere, but of pure CO2, can you tell me, on a scale of 1 to 100, what % of photons emitted at a height of 5km will reach the surface without being reabsorbed? 3/What is in your or anyone else's writing, that explains just how the presence of GHGs change a planets surface temperature from that in the absence of GHGs?
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  21. Re #219 Philippe Chantreau You wrote:- "I do not understand how that shows that temperature is not a measure of heat content." Again it is a matter of precision. Temperature is a measure of energy density, if you double the amount of energy in a kg of material you double its absolute (K) temperature; it is a simple as that. But if you do not specify the amount of material the temperature, for a given amount of energy, is completely unspecified. 'Quantity of material' can be (almost) anything, it can be a single atom or even smaller. A single atom can vibrate in three directions and the thermal energy, which is neither more nor less than the vibrational energy of the atom. Because a single atom vibrates in three directions, called degrees of freedom, the total energy of the atom is divided into three parts, one part in each degree of freedom. The relation between temperature and vibrational energy is called the Boltzmann constant In #219 you also wrote:- "If no thermal energy can be transfered by IR radiation from a cooler object to a warmer one, how does a radiant barrier work in a vacuum (they do work, and have engineering applications)? " Radiant barriers in simplest terms reflect energy, stopping it getting where it isn't want. Reflection is quite differnt from absorption, when reflecting radiation the temperature of a mirror is not changed (or changing). There is a further consequence of this 'non-absorption' of energy by reflection; a perfect mirror cannot emit any energy at any temperature. Real objects reflect partially and emit/absorb partially Yet further in #219 you wrote:- "Abut the second question, your answer is a little strange. Why only "thermal processes" (whatever that means) and IR radiation?" Again the distinction is in the detail. Thermal processes are generally considered to be those caused by vibrations in atoms and molecules, this includes thermal radiation since thermal radiation arises from the (thermal) vibration of electric charge. An example of non-thermal transfer of energy is evaporation of water and rainfall. Both of these processes arise from thermal energy but the way they happen is rather special since it has a lot to do with intermolecular forces that are not included in thermal processes. Another non-thermal process is convection. Convection is a very important heat transfer process in the atmosphere but works by bulk change in density, not at the molecular level. Temperature and heat are still important in these processes other energy processes are at work also. Some examples may appear to break 2nd Law; the Foehn wind is one. The exact working of the Foehn process is not simple since there are a number of energy processes occurring at the same time and the importance of each will be different in different situations. I want to revisit your #210, you wrote:- "The question is very clear, let me rephrase it: do you dispute that these gases absorb and emit IR in the stratosphere and that their radiative properties affect the temperature of the stratosphere? I made it very clear that the GHGs have radiative properties in the stratosphere but, just as on the surface, they do not affect the temeprature profile there. The temperature profile in the stratosphere (e.g. temperature increasing with altitude) is determined to a considerable extent by the radiative properties of oxygen, not the GHGs.
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  22. damorbel writes: "Half of the IPCC thesis is that the Earths albedo reduces the surface temperature when some simple physics familiar to all shows that this simply isn't true." Which is, of course, pure nonsense. Black asphalt gets hotter than white cement on a sunny day. Albedo directly impacts temperature. This is something children can understand, even without knowing the big words for it. It is also simple logic. The total amount of energy coming in and going out must be the same... ergo, the amount of energy reflected plus the amount of energy absorbed and then emitted as heat must equal the amount of energy striking the object... ergo, the more energy an object reflects the less it absorbs and the less heat it emits. Which is why absorptive black asphalt gets hotter than reflective white cement. Also: "The other half of the IPCC thesis is that gases that emit/absorb infrared can change the heat distribution in the atmosphere." Actually, they've been observed doing that. Kinda like saying that there is a thesis that something will fall if you lift it up off the ground and then let go of it. Sure, that's what the thesis says... because that's what is actually happening.
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  23. damorbel @ 220: You agree with four of the questions archiesteel puts to you; where agreement would seem to indicate agreement with some sort of greenhouse effect. And yet you appear to continue to maintain that such an effect is nonexistent, if your own questions such as:
    3/What is in your or anyone else's writing, that explains just how the presence of GHGs change a planets surface temperature from that in the absence of GHGs?
    are anything to go by. I'm going to go out on a limb and suggest that the comment threads on the 2nd law of thermodynamics have for weeks been dominated by people (all of them doing a better job than I could) explaining to you just how, exactly, greenhouse gasses alter global surface temperatures (see KR's excellent summary @ 214, for example), and providing links (whether to other posts on this site or to other sites or the literature) showing how this effect can be, and is, directly observed to be taking place, and how its consequents (increase in global mean temperature, cryosphere mass balance decline, increase in ocean heat content, changes to migration patterss, animal & plant distribution, &c &c &c) are also observed to be taking place.
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  24. Damorbel: "3/What is in your or anyone else's writing, that explains just how the presence of GHGs change a planets surface temperature from that in the absence of GHGs?" You've been asked this before, I believe: do you think the temperature of the 1) Earth's surface and/or 2) lowest ten meters of the troposphere would be different in the absence of atmospheric CO2? Yes or No?
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  25. @damorbel: "No. Just as objects like planets do not absorb 100% of the incident radiation from the Sun because a certain % (called the albedo) is reflected, neither is 100% radiated." I never claimed 100% of the Energy was radiated. Stop putting words in other people's mouth in order to peddle your incorrect interpretation of physics, please. "What you should realise is that the % 'trapped' by a radiating planet is exactly the same as the % of the incoming radiation reflected as albedo." Wrong. The higher the albedo, the less energy is transferred to the surface, as the visible light is mostly reflected back into space. Are you really that misinformed, or are you indulging in disinformation? "Do you also accept my argument that the scattering/reflection processes that cause the albedo is completely independent of the direction of arrival of the photons that are scattered?" This is rather irrelevant, isn't it? Anyway, I disagree. Scattering and reflection are not equivalent, as reflection does indeed have a directional component (think of an object with 100% albedo, i.e. a mirror). "In an 'Earth' atmosphere, but of pure CO2, can you tell me, on a scale of 1 to 100, what % of photons emitted at a height of 5km will reach the surface without being reabsorbed?" No, I can't, but the exact figure is irrelevant. As I said, some IR energy will escape to space, some will warm the surface, and others will be reabsorbed and re-emitted. The time it takes for the energy to eventually reach space or the surface is inconsequential, just like the time it takes for a photon to go from the center of the sun to its surface and beyond is inconsequential to the fact it will eventually escape. Either you have a real problem with logic, or you are using this forum as a propaganda pulpit. Either way, please stop. "What is in your or anyone else's writing, that explains just how the presence of GHGs change a planets surface temperature from that in the absence of GHGs?" I just explained it to you, and you agreed on pretty much all points, except on the one about Albedo, but that's because you don't really understand the difference between reflectivity and absorbption/emmission. Again, you've been shown to be wrong on this many, many times. The fact you continue to make false statments really make me believe you're interested in pushing an agenda, not learning the truth. So, you agreed with my points, and I showed how yours are incorrect. I guess this means you have lost the argument. Sorry.
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  26. "But if you do not specify the amount of material the temperature, for a given amount of energy, is completely unspecified." What a strange way to look at things. As if it was possible to measure the temperature of something but not know what it is at all. "I measured the temperature of that object but I have no idea of its size, what it's made of and all that" How could you then measure its temperature? I mean, what would you measure the temperature of? Does one not define an object before measuring its temperature? Of course, the exact mass will never be known to the last atom but who cares? It's enough to know it to the extent necessary to have a decent idea of the heat content. Which is the all point of measuring temperature; you have not demonstrated otherwise by this weird argument, certainly not "remotely" otherwise. You are wrong on the stratosphere. It is well known that GHGs cool down the stratosphere. Line by line radiative transfer models show how much, with the altitudinal distribution. That has been verified by observation too (Iacono and Clough 1995 and later papers). In post #220 you agree that IR radiation is re-radiated to the surface. How can this happen without the surface temperature to increase if thermodynamic compliance is respected? It is a good thing that you agree on this point, however, because it has been measured too; these measurements, once again, agree quite well with MODTRAN and LBLRTM. That was confirmed by Marty et al (2003), solidifying even more the Iacono and Clough results and MODTRAN. Heck, even Judith Curry has papers showing agreement between downward IR flux at the surface and results from a wide variety of models. "In an 'Earth' atmosphere, but of pure CO2, can you tell me, on a scale of 1 to 100, what % of photons emitted at a height of 5km will reach the surface without being reabsorbed?" I would not expect any individual here to be able to answer that question. That's what MODTRAN or other models do and they take significant computing power. But their results are very, very close to the observed reality. It is probably not the best question to ask because there are photons emitted at all altitudes anyway. A lot of words, a lot of weird ideas, nothing convincing.
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  27. Incidentally, the reality of the "greenhouse" effect can be verified with a relatively simple experimental set-up. The ESPERE site describes it quite well: http://www.espere.net/Unitedkingdom/water/uk_watexpgreenhouse.htm It could be improved by taking into consideration the water vapor present in the air vessel, but the basic idea is there.
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  28. Re #223 Composer99 You wrote:- "You agree with four of the questions archiesteel puts to you; where agreement would seem to indicate agreement with some sort of greenhouse effect." I ceratinly said I didn't agree with archiesteel's first question:- "...they emit IR energy, as described by black body theory... " The idea that a body that reflects 30% or more of incident light can emit 'as described by black body theory' is completely absurd. The measuring of emissivity (e) is difficult to do directly; it is more easily done by measuring the reflectivity (r) and calculating emissivity as e = 1 - r Perhaps you do not realise that, by using the correct value for emissivity i.e. not making the false assumption of the Earth emittting 'like a black body', then the mean temperatute of the planet is 279K, not the 255K claimed in the opening argument for a GHE. You mention other contributors, I'll answer them on their own terms. Thanks for your interest.
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  29. damorbel - Did you see my post here? It was addressed to you - you've replied (in one fashion or another) to several other posts since that one.
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  30. Re #224 DSL You asked for a y/n answer to this question :- "do you think the temperature of the 1) Earth's surface and/or 2) lowest ten meters of the troposphere would be different in the absence of atmospheric CO2?" No the temperature would not be different. Your response was to my statement:- "3/What is in your or anyone else's writing, that explains just how the presence of GHGs change a planets surface temperature from that in the absence of GHGs?" The temperature profile (dT/dz) of the troposphere is fixed by the lapse rate which is a function of the specific heat of the atmospheric gases. If the GHE was serious i.e. produces a 30K rise in surface temp. there is not a lot of room for it in the lapse rate calculations. NB the lapse rate would be no different without GHGs.
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  31. With increase in GHGs: 1. Altitude of emission increases 2. Temperature at new altitude has to increase to maintain incoming/outgoing radiation balance 3. With constant lapse rate, surface must warm. You would learn a lot if you'd spend more time reading Science of Doom.
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  32. @damorbel: "I ceratinly said I didn't agree with archiesteel's first question:- "...they emit IR energy, as described by black body theory... " Actually it was my second question, and you were completely wrong in replying that. It's hard to me to qualify exactly how wrong without having this comment censored. What I said is: "When objects increase in temperature, they emit IR energy, as described by black body theory" This is easily provable. You can even do it yourself if you have IR goggles or something similar: Take a raw roastbeef and look at it with the IR goggles. It will be rather dark. Put some mustard on the roastbeef. You can insert litle pieces of garlic in it if you want. Put the roastbeef in the oven at 375F for about an hour. Take it out and look at it with IR goggles again. It will appear much brighter, because it is emitting a lot more infrared (IR) photons than it was before. Ergo, increasing the temperature of an object causes it to emit more IR photons. "The idea that a body that reflects 30% or more of incident light can emit 'as described by black body theory' is completely absurd." It's not. It's physics. Unless you're *really* arguing that black body theory is incorrect, but I can't believe someone would argue anything that stupid. "The measuring of emissivity (e) is difficult to do directly; it is more easily done by measuring the reflectivity (r) and calculating emissivity as e = 1 - r" So, according to what you just argued, an object that reflects 30% light (i.e. which has an albedo of 0.3) therefore has an emissivity of 0.7, right? Emissivity is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. A true black body would have an ε = 1 while any real object would have ε < 1. In what sense is this incompatible with Black Body theory...unless you actually believe Black Body theory is only about black bodies (it isn't). "No the temperature would not be different." And yet you have agreed to the contrary in responding to my four questions. You have just contradicted yourself, even though you tried to get out of this predicament by making a blatantly false statement (i.e. that heated objects don't produce more IR radiation).
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  33. Damorbel, I think it's clear at this point your only goal is to waste people's time by constructing deliberately complex fallacious arguments. This seems to be a favored new tactic of political skeptics, and aims at making sure intelligent people waste their time debunking the same old arguments over and over instead of doing something more constructive. That's what Ken Lambert used to do, and that is now what damorbel is doing. To everyone who has patiently been responding to damorbel, just be warned that he doesn't really want to win this debate - he knows his position is ultimately untenable. Rather, his goal is likely to make sure this dead end of a thread go as long as possible. Personally, I've done my part demolishing his bizarre argument. I don't think he'll convince anyone anyway: most skeptics, deniers and contrarians don't actively argue that AGW violates the 2nd Law of Thermodynamics (because it's too easy to demonstrate that it doesn't - one has to choose his battles, after all). I invite all of you to stop feeding this particular one...
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  34. Re #225 you wrote:- "I never claimed 100% of the Energy was radiated. Stop putting words in other people's mouth in order to peddle your incorrect interpretation of physics, please." Sory for that. but almost every other person, including the editors writing for the IPCC on the temperature calculation and all the contributions on the NASA websites, make that claim. The you cite me and comment like this:- ""What you should realise is that the % 'trapped' by a radiating planet is exactly the same as the % of the incoming radiation reflected as albedo." Wrong. The higher the albedo, the less energy is transferred to the surface, as the visible light is mostly reflected back into space" My statement is not clear, it should read like this:- The part (30%) of the radiation coming from is reflected by the Earth, this is called the albedo. The same effect happens to radiation leaving the Earth, 30% of it is reflected back and doesn't escape, it is trapped. You wrote:- "Scattering and reflection are not equivalent," I didn't say they were. What I said was that the scattering which causes the albedo is independent of the direction of arrival of a wave, that is why scattering is as effective at reducing outgoing radiation as it is at reducing incoming radiation from the Sun. You responded to a question of mine like this:- ""In an 'Earth' atmosphere, but of pure CO2, can you tell me, on a scale of 1 to 100, what % of photons emitted at a height of 5km will reach the surface without being reabsorbed?" No, I can't, but the exact figure is irrelevant. As I said, some IR energy will escape to space, some will warm the surface," Well I don't think it is irrelevant because in an atmosphere of CO2 all the molecules are absobing and emitting radiation all the time; they absorb those wavelength they emit particularly well, just where is the radiation warming the surface coming from, isn't the lapse rate warming enough?
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  35. Re #226 Philippe Chantreau you wrote:- "As if it was possible to measure the temperature of something but not know what it is at all. "I measured the temperature of that object but I have no idea of its size, what it's made of and all that" Sorry you think this way. But don't thermometers work this way all the time? After all, when you put your thermometer outside to measure the air temperature you don't have to know how much air there is 'outside', do you? You wrote :- "It is well known that GHGs cool down the stratosphere. Line by line radiative transfer models show how much, with the altitudinal distribution. That has been verified by observation too (Iacono and Clough 1995 and later papers)." I don't doubt that the stratosphere loses energy to deep space through GHGs, any satellite IR image will show that. But surely know that the temperature increases with height in the troposphere, there must be something happening in the stratosphere other than energy loss through GHGs. That 'something' is the absorption of ultraviolet energy (from the Sun) that is what causes the temperature to rise. Now in my view explanations of the GHE should also show a temperature rise (In the troposphere) if there really is a GH effect. You wrote :- "In post #220 you agree that IR radiation is re-radiated to the surface. How can this happen without the surface temperature to increase if thermodynamic compliance is respected?" I answered the question. How much reaches the surface depends on the concentration of GHGs, with very low concentrations a small amount of radiation will reach the surface, as the concentration increases effectively all of the radiation from GHGs will be reabsorbed long before it reaches the surface. As for the out going radiation, the density of GHGs (and O2, N2 etc) falls steadily to about 100km. T this point the radiation mostly escapes without being reabsorbed.
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  36. A not so minor note about albedo: Albedo is not constant across all wavelengths. As an example, a very pale friend of mine (who uses SPF 80 sunscreen) has a quite high albedo/reflectivity (or 1-absorptivity) at visible wavelengths. She has an albedo of perhaps 0.3-0.4 (just guessing) for visible light. However, the human skin at body temperature has a thermal IR emissivity/absorptivity of 0.99 regardless of visible light skin color - almost a perfect blackbody! Hence her albedo for IR is (1 - absorptivity) = 0.01. Average emissivity for the surface of the earth at IR wavelengths is ~0.96-0.97, meaning an albedo/reflectivity of only 0.03-0.04 at maximum, an order of magnitude less albedo than at visible wavelengths.
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  37. Re #227 Philippe Chantreau you wrote:- "Incidentally, the reality of the "greenhouse" effect can be verified with a relatively simple experimental set-up. The ESPERE site describes it quite well:" Philippe, what the ESPERE experiment shows is how a lamp simulating the Sun but with a temperature (probably) of 3000K (instead of 5780K) heats a box of CO2 by 30K from a starting temp. of 290K; note 290K is a lot cooler than 3000K. That is just what I would expect a heat source at 3000K to do. The GHE says that CO2 high in the atmosphere at 255K can raise a surface to 288K - not possible! The 288K surface actually send heat energy to the upper troposphere. The energy sent from the surface tends to raise the temperature of the upper troposphere but clearly has little effect.
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  38. For anyone visiting this thread - a bit of clarification on what's been discussed. - The temperature of any object, including the Earth as a whole, is determined by the amount of internal energy it has, vibrating it's molecules (reflected as temperature), forming endothermic chemical bonds (physical changes), etc. - Under the conservation of energy/mass, if there is an imbalance between incoming energy and outgoing energy, the energy in the object will change. This is generally observed as a change in temperature. The rate of change is dependent on the thermal mass of the object, dynamic equilibrium is reached when incoming = outgoing again. - Outgoing energy in a vacuum (like the Earth) is via radiation. Thermal radiation scales with emissivity and with temperature T^4, meaning that a change in temperature can change outgoing energy until it balances incoming energy. - The atmosphere is quite transparent to visible light (from the sun), hence the incoming energy is fairly constant. - Outgoing energy to space leaves the Earth as thermal IR, to which the atmosphere is partially transparent. - Greenhouse gases absorb IR, re-radiating it in all directions, including back to the ground, which re-absorbs most of what hits it. This means that less IR goes to space at any particular temperature, and the Earth has a lower effective emissivity to space due to greenhouse gases. The thermal mass of the atmosphere is irrelevant. Therefore the greenhouse effect means that the Earth must have a higher temperature than it would in the absence of the greenhouse gases in order to radiate away the energy it's receiving from sunlight. Don't be misled by convoluted side-tracking arguments. As to the "2nd law violation" skeptical argument; see the topic itself and also the post here.
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  39. damorbel at 07:45 AM I can see where you are coming from, the lapse rate and convection are important to the movement of energy out of the system, its the altitude at which energy can effectively escape however, that is responsible for the T gradient, which is necessary for the transport of energy to this altitude... So the lower atmosphere is already largely opaque to some wavelengths, but the path length shortens with altitude, so by adding more opaque molecules, it raises the height that radiation can effectively escape, so its necessary for this new altitude, to heat enough that it is emitting the incoming, and next layer down must heat enough that it is able to transport this energy up to this height, etc etc... So the radiation incident on the surface, is just a product o the atmospheric T at that altitude, but the height it can escape the troposphere, effects the T gradient.
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  40. @damorbel, your latest attempt at obfuscation won't work. You've been unmasked. "The part (30%) of the radiation coming from is reflected by the Earth, this is called the albedo. The same effect happens to radiation leaving the Earth, 30% of it is reflected back and doesn't escape, it is trapped." False. "Well I don't think it is irrelevant because in an atmosphere of CO2 all the molecules are absobing and emitting radiation all the time; they absorb those wavelength they emit particularly well, just where is the radiation warming the surface coming from, isn't the lapse rate warming enough?" Lol...are you really claiming what I think you're claiming here? That there wouldn't be room for the photons to reach the surface? In case you haven't noticed, at the temperatures we're talking about, CO2 is a gas. Now, a layer of liquid CO2 might act as an insulator, I don't know, but if you want to see what effect a dense CO2 atmosphere will have, I suggest you check out Venus, which is hotter than Mercury even though it is much farther from the sun. Seriously, it's obvious you're trying to make the debate run in circles. I mean, no one would take that much humiliation if he hadn't an ulterior motive in mind. Again, I call on other posters to ignore damorbel's fake science, which he makes as confusing and outlandish as possible in order to waste our times. Instead, just point him to KR's excelelnt post at 238, or to his own response to my questions at 220, where he basically agreed with the greenhouse effect.
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  41. "I answered the question." I don't see that. How can the surface temperature not be higher when receiving extra IR photons compared to a situation in which it would not be receiving these photons? Radiative transfer models, the Marty et al paper and many other sources indicate that the amount of IR radiation reaching the surface is not that small. "The GHE says that CO2 high in the atmosphere at 255K can raise a surface to 288K" This belongs in the category of "not even wrong." As for the stratospheric temperature profile, I don't see how it is possible for GHGs to have radiative properties there and not affect it. Are you saying that the temperature profile is identical in the stratosphere to what it would be in the absence of these gases? How can the stratosphere not be colder than it would be if these photons were not radiated to space?
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  42. "Radiative transfer models, the Marty et al paper and many other sources indicate that the amount of IR radiation reaching the surface is not that small." Damorel doesnt believe the radiative transfer equations, however how about direct measurement of DLR at the surface? Matching the spectrum and amplitude of the models no less. For life of me, I cant see how damorel explains that in his strange world.
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  43. Joe Blog writes: [...] it raises the height that radiation can effectively escape, so its necessary for this new altitude, to heat enough that it is emitting the incoming, and next layer down must heat enough [...] Yes. That's the point I was making in this comment. KR also sums the situation up nicely. I agree with archiesteel's point that damorbel has wasted too much of everybody's time on these two threads. The physics of the greenhouse effect have been explained quite well, by many people, over and over again, in different ways. Further attempts to cure damorbel's misunderstandings are not likely to be more successful than the earlier ones.
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  44. Re #238 KR - The temperature of any object,... ..(physical changes), etc. Agreed. - Under the conservation of energy... ...equilibrium is reached when incoming = outgoing again. Agreed - Outgoing energy in a vacuum ... ...a change in temperature can change outgoing energy until it balances incoming energy. Agreed "- The atmosphere is quite transparent to visible light (from the sun), hence the incoming energy is fairly constant." The incoming energy - agreed (the atmosphere is not transparent to solar infra red) "- Outgoing energy to space leaves the Earth as thermal IR, to which the atmosphere is partially transparent." Agreed (you are refering to the IR window) But what follows is unclear:- "- Greenhouse gases absorb IR, re-radiating it in all directions, including back to the ground, which re-absorbs most of what hits it." But don't GHGs also absorb the downward radiation? Surely they absorb the downward radiation from the upper atmosphere long before it gets to the ground And:- " This means that less IR goes to space at any particular temperature, and the Earth has a lower effective emissivity to space due to greenhouse gases." For me this is unclear. How does the downward radiation mean "less IR goes to space"? You said (above) "Greenhouse gases absorb IR, re-radiating it in all directions" - care to explain? You write "The thermal mass of the atmosphere is irrelevant." Not true, the atmosphere, with or without CO2 is a very important contributor to climate because it is a major distributor of heat between equator and poles. As such the mass and mean temperature are very important since they determine the thickness, from the thickness and the lapse rate you can determine the surface temperature This statement of yours is too vague:-> "Therefore the greenhouse effect means that the Earth must have a higher temperature than it would in the absence of the greenhouse gases in order to radiate away the energy it's receiving from sunlight. Don't be misled by convoluted side-tracking arguments." -> to dispute. When making claims about planetary temperature and climate change, all effects that may influence the temperature must be taken into account. Many posters here recognise that incoming radiation adds energy to a given location, few seem to recognise that, if the outgoing radiation exceeds the incoming, then the temperature cannot rise.
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  45. "But don't GHGs also absorb the downward radiation? Surely they absorb the downward radiation from the upper atmosphere long before it gets to the ground" I've seen this statement a number of times and it makes no sense to me. If the GHGs absorb the downward radiation, they would still have to re-emit some of it again, some of which would again be downward. Only if there were a layer of GHGs next to the surface that somehow magically didn't re-emit any radiation downward could this mean that none of the downward radiation reached the surface. Imagine if things worked the way you think they do, then wouldn't the same be true for the radiation going upward? All of the reflected radiation would be absorbed within a few mean free paths of the surface and never make it to the TOA, let alone into space. The layer next to the surface would become extremely hot since all the reflected IR never leaves that layer.
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  46. damorbel writes: "But don't GHGs also absorb the downward radiation? Surely they absorb the downward radiation from the upper atmosphere long before it gets to the ground" As SteveS has pointed out, this is pure nonsense. Let's say the atmosphere was 100% greenhouse gases. In such a circumstance every photon of IR in the impacted wavelengths would be absorbed immediately after leaving the ground. It would then be re-emitted... possibly back down to the ground or possibly upwards... where it would immediately be absorbed by another molecule of greenhouse gas and then re-emitted... possibly back down to the previous 'just above the surface' molecule and from there either up again or back down to the surface. Continue ad infinitum. With less than 100% atmospheric greenhouse gases the process works the same way except that most photons travel past several molecules of other types (e.g. Nitrogen) before being absorbed by another greenhouse gas molecule. Yes, the further up a photon gets the less likely it is for that energy to eventually be transmitted back to the ground... but we are talking about ridiculously large quantities of energy. Even 0.00000000001% is a tremendous amount of heat. The question also ignores everything below the "upper atmosphere"... as if photons magically teleported from the surface to the upper atmosphere without having to pass through all the space in between - with its much higher probabilities of the energy being 'bounced' back down to the surface. Also: "...few seem to recognise that, if the outgoing radiation exceeds the incoming, then the temperature cannot rise." If outgoing radiation exceeds incoming then we've violated the law of conservation of energy.
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  47. Re #245 SteveS you wrote:- "I've seen this statement a number of times and it makes no sense to me. If the GHGs absorb the downward radiation, they would still have to re-emit some of it again, some of which would again be downward. Only if there were a layer of GHGs next to the surface that somehow magically didn't re-emit any radiation downward could this mean that none of the downward radiation reached the surface." The layer just above the surface has about the same temperature as the surface so, with a very small temperture difference there is almost no radiative energy transport. By far the greatest transporter of energy from the surface to the atmosphere is the evaporation/condensation cycle of water (rainfall!) Don't forget that radiative transport is proportional to (T1^4 - T2^4) where T1 is the surface temperature and T2 is the destination temperature; whereas evaporative transport works for the order of a few degrees. BTW, when calculating radiative transport, where is the destination, so that its temperature can be known - the troposphere is very thick and has a very variable temperature?
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  48. Re #239 you wrote:- "its the altitude at which energy can effectively escape however, that is responsible for the T gradient, which is necessary for the transport of energy to this altitude... " How can this be when the temperature rises steadily in the stratosphere? So the lower atmosphere is already largely opaque to some wavelengths, but the path length shortens with altitude, so by adding more opaque molecules, it raises the height that radiation can effectively escape, so its necessary for this new altitude, to heat enough that it is emitting the incoming, and next layer down must heat enough that it is able to transport this energy up to this height, etc etc.. This would be fine if the temperature in the troposphere was a function of the radiation but it isn't. DT/dz in the troposphere is about the same over the poles as it is over the equator, this temperature gradient is called the lapse rate and it has nothing to do with radiation.
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  49. There is no logical connection between this paragraph: This would be fine if the temperature in the troposphere was a function of the radiation but it isn't. DT/dz in the troposphere is about the same over the poles as it is over the equator, this temperature gradient is called the lapse rate and it has nothing to do with radiation. and the preceding paragraph, to which it is presumably intended as a response. Nobody said that the lapse rate is determined by radiation. That is a complete red herring (something that should be no surprise to readers of this thread, or the preceding one). Raising altitude of emission (due to GHGs), and keeping the lapse rate constant (not due to GHGs), implies warming of the surface. If you're unwilling to listen to people here, and you're unwilling to read Science of Doom, and you're unwilling to look at a textbook or talk to an expert, there's probably nothing I can do that would help. But for others who might be interested, there's a very good explanation of the underlying physics of the greenhouse effect over at Chris Colose's blog. Here's a simple graphic from Chris's post, explaining how raising the height of emission while keeping the lapse rate constant (the slope of the diagonal line in this figure) implies a warming of the surface: The Y axis is altitude, the X axis is temperature. Since the temperature at the new height of emission has to increase, the constant lapse rate means that all temperatures at lower altitudes must increase, too. Here's Chris's summary:
    So…review: Because of energy balance, the planet must get rid to space as much energy as it receives from the sun. Averaged over the Earth, taking into account the albedo and geometry, this is about 240 W m-2. In the absence of an atmosphere, this flux of radiation is lost by the surface by \sigma T^{4}_{s}. With an atmosphere, this flux of radiation is allowed to emanate from upper, colder layers of the atmosphere, say on average at some altitude H. Increasing greenhouse gases increases the altitude of H, a height in the atmosphere which depends on wavelength, and characterizes a level of mean emission to space. Because the atmosphere is now emitting from colder levels of the atmosphere, the OLR has decreased, and the result is that the planet must warm to re-establish radiative equilibrium.
    I have no expectation that damorbel will learn anything from this, but others might find Chris's discussion useful. I highly recommend his blog, though he only posts very sporadically.
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  50. damorbel - By George, I think you've got it! Even if you don't recognize it. The surface of the Earth (e) radiates greenhouse gas IR bands proportionally to T(e)^4. If there were no greenhouse gases, that would go straight to space (s), which has a temperature of ~3K. Instead, we have an atmosphere (a) with greenhouse gases, which emits IR at those wavelengths proportionally to T(a)^4. Summing radiative energy transfer in those bands (as per your post): - No GHG's -> (T(e)^4 - T(s)^4), T(s) = 3K - GHG's -> (T(e)^4 - T(a)^4), T(a) = 287K Note that 287K >> 3K, and that in the GHG case much less energy leaves the surface of the Earth in those bands - lowering emissivity. The effective emissivity (proportion of energy emitted versus a black body) of the Earth has dropped, and to radiate the same incoming solar energy with a lower emissivity the temperature will go up.
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