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Comments 1076 to 1100 out of 1478:

1076. Tom Curtis at 17:00 PM on 15 July, 2011
      alistair @1075: You noted that the radiative equilibrium is achieved at 5 km altitude. This is, of course, a feature of our current atmosphere because it contains gases that emit and absorb in the IR portion of the spectrum, ie, in the wavelengths of peak emissions for a black body at 255 degrees K. In the non-greenhouse case, the case with no IR absorbing or emitting gases, radiative equilibrium necessarily is achieved at the surface. That is because, with no IR radiating gases, all radiation to space from Earth must come from the surface. As all radiation comes from the surface with no green house gases, it necessarily follows that the altitude of radiative equilibrium is at the surface. It follows that the surface temperature will be the temperature that results in radiative equilibrium, ie, 255 degrees K. With no GHG, and ignoring the effect of ozone, the average temperature at 5 km will be 206 degrees K (255 - 5 * the dry adiabatic lapse rate). Heat would cease being carried from the surface by convection once the atmosphere establishes a thermal profile equal to the dry adiabatic lapse rate. Most importantly, if heat did not stop being carried away by convection, you would be invoking a violation of the first and/or second law of thermodynamics. Specifically, the heat being carried away would not be then radiated to space because there would be no IR radiating gases in the atmosphere. Therefore it would accumulate until equilibrium of heat exchange with the surface was achieved, something accomplished when the dry adiabatic lapse rate describes the heat profile of the atmosphere. Heating beyond this point would require net heat to flow from the colder to the hotter body (2nd law violation), or else the heat in the atmosphere to be dissipated without flowing back to the surface. As we have established the heat is not radiated to space because of there being no IR radiating gases, the second case requires non-conservation of energy.
1077. Rosco at 07:29 AM on 20 July, 2011
      Is anyone really saying Oxygen and Nitrogen don't become heated AND they DON'T emit infra red radiation ? If they do then they too are "greenhouse Gases". If they don't then they defy every law of physics and all our science must be completely wrong. Before you start showing me radiation absorbtion spectra charts to prove O2 and N2 don't absorb thermal radiation energy simply let me point out radiation is a very inefficient method of transferring thermal energy. Conduction is also poor but way more important on earth than radiation whilst convection is by far the most efficient and important. And you guys ignore both of these. If you don't believe it why is it that the old fashioned electric bar heaters have been replaced by fan dispersal models which heat spaces much more efficiently ? Similarly fan forced ovens. We don't rely on radiation to keep our car motors cool. A simple experiment should prove it and you don't even need to perform it - I recommend you don't - just think about it. If you put your hand near - not above - some heating element like a bar radiative heater you'll feel the radiative heat sure but you will probably be able to keep your hand near it for a long time. But would you touch the bar ? No, of course not - the heat transfer to your hand would be orders of magnitude greater than what is radiated. If radiation was such a dominant thermal transfer mechanism no child would ever scald or burn themselves on a hot stove because the radiative energy would be a clear warning - it isn't and they burn themselves - hopefully not too badly and only once. So the earth and oceans warmed by the sun heat up the whole atmosphere by conduction, the warmed air convects all over the globe moving thermal energy to the poles from the equator. The whole atmosphere radiates infra red radiation but this is only a small part of the thermal transfer mechanism. I, and everyone else, also radiate infra-red radiation and there are many more of us now than 40 years ago - perhaps that's the explanation of the temperature anomaly. This ridiculous insistence that only a miniscule proportion of the atmosphere can absorb thermal energy and radiate infra-red radiation is absolute nonsense and deserves to die and be buried.
1078. Tom Dayton at 07:35 AM on 20 July, 2011
      Rosco, a greenhouse gas is one that impedes the transfer of energy from the Earth to outer space. Convection cannot transfer energy from the Earth to outer space, because there are (effectively) no molecules in outer space for the Earth's atmospheric molecules to bump into. Radiation is the only method. By the way, your attitude could use improvement.
1079. muoncounter at 09:34 AM on 20 July, 2011
      Rosco #1077: "Is anyone really saying Oxygen and Nitrogen don't become heated AND they DON'T emit infra red radiation ?" Seems like you ought to go back several hundred comments in this thread or do some research on the vibrational modes of various gas molecules. "If radiation was such a dominant thermal transfer mechanism" Guess that bright light that appears in the eastern sky every morning doesn't use the dominant thermal mechanism? "I, and everyone else, also radiate infra-red radiation and there are many more of us now than 40 years ago" Maybe you ought to run some numbers on that; there are some great journals out there that might publish your 'global warming is people' theory. And I second Tom Dayton's final words.
1080. Tom Curtis at 10:23 AM on 20 July, 2011
      Rosco @1077: 1) Rather than ignoring the transfer of energy by collisions (conduction) modern green house theory absolutely depends on it. If it were not for that transfer, the equipartition theorem would be false, and energy could not transfer from oxygen or nitrogen to carbon dioxide, and in particular to those rotational modes of CO2 that spontaneously release their energy by emitting infrared radiation. In other words, without the transfer of energy by collisions the greenhouse effect could not work. The effects of energy transfer by collision are built into green house theory by its use of the ideal theory of gases, by its use of statistical dynamics, and by its use of quantum mechanics as it relates to molecular absorption and emission. 2) Transfer of energy by convection is essential to understanding the modern theory of the green house effect. In this case it is not essential to the effect itself, in that in principle you could have a green house effect without it. But in practice understanding the greenhouse effect cannot be divorced from understanding convection. That is because convection absolutely dominates vertical transfer of energy in the troposphere. Because of this domination, the change of temperature with altitude approximates the adiabatic lapse rate. As a result, any change in equilibrium temperature in the upper troposphere must be matched by an equivalent change at the surface. The equilibrium temperature is set by the fact that much of Earth's Outgoing Longwave Radiation comes from the mid and upper tropospheres, and that the total of the outgoing radiation from all sources must equal the total incoming radiation from the sun if the Earth's temperature is to remain constant. If CO2 levels increase, the result is that outgoing atmospheric radiation comes from slightly higher in the atmosphere. Because the vertical temperature structure of the atmosphere is set by convection, that means it comes from a slightly cooler location. As illustrated below, the result is that both the temperature at that higher altitude, and, because the vertical temperature structure is set by convection, the temperature at the surface must increase until equilibrium is reached again: Chris Colose, whose diagram I have used, provides a more detailed explanation. 3) So far we have seen that you do not understand the atmospheric greenhouse effect unless you understand the essential roles energy transfer by collision and by convection play in it. Of course, energy transfer by radiation also plays an essential role, because only by radiation can energy cross vacuums. Consequently (for practical purposes) all energy transfer from the Sun to the Earth, and all energy transfer from Earth to space is by radiation. Convection cannot vent radiation to space nor bring energy from the sun, no matter how many bad science fiction movies you have seen. As it happens the majority of energy transfer from the surface to the atmosphere is also by radiation, but that is largely irrelevant to the theory. So, our "ridiculous insistence" that only a miniscule proportion of the atmosphere accounts for nearly all radiation of energy from the atmosphere to space is based on a detailed knowledge of the physics of radiation, and on thousands of experiments mostly by the US Department of Defence undertaken with complete disregard of greenhouse theory. The DoD didn't care about global warming in the 1950's and 60's (when most of the experiments were conducted). They cared very much about which atmospheric gases absorbed IR radiation, and which didn't so that their IR heat seeking missiles, and their Forward Looking Infra Red could be effective. And our acceptance of the atmospheric green house theory is based on a sound understanding of all forms of energy transfer in the atmosphere.
1081. Composer99 at 13:00 PM on 20 July, 2011
      Tom Curtis, you have the patience and forbearance of... well, of someone with an exemplary amount of patience and forbearance. Or a saint. Take your pick. The explanations which invariably follow the appearance of a new contrarian on this thread have been very enlightening for this layman.

      ---

      I recently came across a similar discussion on how the 2nd Law of Thermodymanics is mis-used in a similar fashion by creationists to argue against evolutionary biology. You may find this comment (author's tongue firmly in cheek, I dare say) to be an amusing take on contrarian argumentation, if adapted for the climate debate.
1082. Bob Lacatena at 13:42 PM on 20 July, 2011
      1079, muoncounter,

      'global warming is people'

      That was one of the greatest moments in cinematic history, when Charlton Heston said that line in Soylent Warm. That, and when the little kid in Sixth Sense said:

      I see warming people.

1083. damorbel at 19:15 PM on 23 July, 2011
      Re #1080 Tom Curtis you write:- "2) Transfer of energy by convection is essential to understanding the modern theory of the green house effect. In this case it is not essential to the effect itself, in that in principle you could have a green house effect without it." Which is what I interpret as 'the adiabatic compression effect of gravity on the atmosphere' This is modest (55K) on Earth but severe (400K) on Venus with its x90 atmospheric mass. Are you able to distinguish between this compressive heating of the surface and the GH effect?. For me this is critical to the understanding of atmospheric physics and not often discussed. For example, in your post #1080 you have a diagram of atmospheric temperature profile with two T vs H gradients, one for 'CO2' and another for '2xCo2'. From your diagram both gradients appear to be the same i.e. the amount of CO2 does not change the gradient, only the surface temperature. From this diagram I cannot derive a clear understanding of how changes in the concentration of atmospheric CO2 influence the surface temperature.
1084. Tom Curtis at 20:13 PM on 23 July, 2011
      damorbel @1083, the diagram in 1080 shows three horizontal lines, H, H + delta H, and the Tropopause. It shows two diagonal lines, CO2 and 2*CO2. The line H represents the effective altitude of radiation with the initial CO2 concentration. The equilibrium temperature at that altitude is set by the energy balance such that the Outgoing Longwave Radiation (OLR) equals the Incoming solar radiation times the planetary albedo. The surface temperature at the normal CO2 level is set by the intersect of the lapse rate with the effective altitude of radiation at the equilibrium temperature for that altitude. If you double CO2, the effective altitude of radiation is increased. In the diagram the new effective altitude of radiation is represented by H + delta H. The equilibrium temperature at this new altitude is approximately the same as the original equilibrium temperature because incoming solar radiation and albedo have not changed (but see below). Therefore the surface temperature is still set by the intersect of the lapse rate with the new altitude of effective radiation at the equilibrium temperature. As the diagram shows, this requires that the intersect of the lapse rate with the surface shift to the right, ie, that the surface temperature increase. Of course, in real life there will be feed back effects that may change albedo, and may change the lapse rate, as well as introducing increased GHG concentrations (water vapour) to the atmosphere. These complexities do effect the final result. Indeed, in the most likely case given the evidence, they increase the change in surface temperature by a factor of 2.5. But they do not change the fundamental principles involved. Regarding the compression effect, it was once fundamental to the Earth's climate, but is no longer. To illustrate this, consider the example of pumping up a bicycle tire. As we well know, doing so raised the temperature of the air in the tire. But once we stop pumping, the extra heat dissipates even though the air remains compressed. Indeed, if we leave the bike for a few hours, the air temperature inside the tire will be the same as the ambient air temperature. The reason for this is that so long as the wall of the tire is merely holding the pressure instead of increasing it, it does no work. And because it does no work, it introduces no new energy into the air to replace any that escapes to the environment by conduction or radiation. In exactly the same manner, gravity currently holds the pressure of the atmosphere, but does not increase it. Therefore it does no work and cannot replace the energy that escapes to space by radiation. In the very distant past the Earth's gravitational field created the compression in the first place in a process astronomers call "accretion". The amount of energy released by this compression left the Earth completely molten, but as William Thompson, Lord Kelvin showed over a hundred years ago, it only takes from a hundred thousand to ten million years for all that energy to dissipate. Consequently, from long before any life evolved on Earth, almost all energy on Earth has come from the sun, and the Earth has remained molten only because of the radioactive elements in its core.
1085. damorbel at 21:42 PM on 23 July, 2011
      Re #1084 Tom Curtis you write:- "The surface temperature at the normal CO2 level is set by the intersect of the lapse rate with the effective altitude of radiation at the equilibrium temperature for that altitude." You argue here that the surface temperature is governed by the TOA temperature, the '2nd Law' argument says that the thin, cold upper atmosphere that is losing lots of radiation to deep space is quite incapable of transferring any significant quantity of thermal energy to the warm, dense surface. The simple questions are 1/ 'Where does this energy come from'? 2/ How can a cold layer with a density about a tenth of the surface value possibly raise the surface temperature by even a small amount. The laws of heat transfer say that heat energy goes only from the hot surface to the tropopause where it is further radiated into deep space. These are valid questions; if the GHE is to be accepted valid answers to theses questions are needed also. Further you write:- "In exactly the same manner, gravity currently holds the pressure of the atmosphere, but does not increase it. Therefore it does no work and cannot replace the energy that escapes to space by radiation." This isn't the whole story because the pressure increases with depth, contrary to your claim that it doesn't change. It is gravity that causes the pressure gradient. According to thermodynamic laws this temperature gradient is sustained by the pressure gradient. Your example of a bicycle tire is not valid because there is no pressure gradient in a tire. The temperature change in the tire you note dies away because the pressure gradient is supported by the tire walls and not the gas in the tire.
1086. Dikran Marsupial at 22:03 PM on 23 July, 2011
      damorbel I am astonished that this point is still being debated here, given that the questions you raise have already been answered repeatedly. The law of heat transfer says that the NET flow of energy is from hot to cold. It does not say that no energy is transfered from the colder object to the warmer, just that the flow of energy in the other direction will be larger. Thus the questions are not valid as they are based on at least one fundamental misunderstanding of thermodynamics. BTW the GHE is accepted already. The fact that you are at odds with the vast majority of scientists on this one ought to suggest to you that perhaps the problem is with your understanding of the physics rather than with the physics itself.
1087. Bob Lacatena at 22:27 PM on 23 July, 2011
      1085, damorbel, In answer to all of your questions about net heat flow, please refer to the following simplified diagram of radiation exchange between the surface of the earth, the atmosphere, and the sun. The atmosphere (blue) is transparent to visible light (yellow) from the sun. This warms the surface (+4). The surface emits (according to its temperature of 5) in wavelengths which pass through the atmosphere into space (-3), losing that heat, and in wavelengths which are absorbed by the atmosphere (2). The atmosphere emits (according to its temperature of 2) equally in all directions, which means some heads into space and some back down. Thus, the temperature of the surface is 5 (4 from the sun, plus 1 from the atmosphere). The temperature of the atmosphere is 2 (from the surface). The planet gains and loses 5 at all times. The atmosphere gains and loses 2 at all times. Space gains and loses 4 at all times. Everything nets to zero. There is no energy created or lost. The 1st Law of Thermodynamics is never violated. Every net transfer (which is the only actual restriction) is warm to cold. The 2nd Law of Thermodynamics is never violated.
1088. Bob Lacatena at 22:43 PM on 23 July, 2011
      1085, damorbel, Concerning gravity, work is only done when the pressure is changed. While it is true that the measured pressure is higher closer to the ground... it stays that way. The pressure is not changing. To increase the temperature, you must compress the gas further. This clearly is not happening. You say:

      According to thermodynamic laws this temperature gradient is sustained by the pressure gradient.

      What does this statement mean? That a gas under pressure cannot cool? Think about it. [Hint #1: There is no such statement or law in Thermodynamics, that a temperature gradient is sustained by a pressure gradient. This is an inference arrived at by misapplying the Laws of Thermodynamics.] [Hint #2: The Laws of Thermodynamics apply specifically to bodies that are in Thermodynamic Equilibrium. A non-homogeneous atmosphere with a temperature and pressure gradient is clearly not a single body in Thermodynamic Equilibrium, so the Laws simply cannot be applied in a simple, single-minded fashion.]
1089. damorbel at 23:27 PM on 23 July, 2011
      Re #1086 Dikran Marsupial you write:- "The law of heat transfer says that the NET flow of energy is from hot to cold. It does not say that no energy is transfered from the colder object to the warmer, just that the flow of energy in the other direction will be larger." I suggest that, from this argument, you would also accept that the 'net' transfer is from the warmer to the colder part of the atmosphere and thus it is the colder part that tends to be heated by the warmer surface. The logic of this is clear, CO2 in the atmosphere indeed radiates heat to deep space, cooling the planet down from the heating effect of the Sun - more CO2 makes for a greater cooling effect by re-radiating the ('net) heat transferring from the surface by convection, evaporation (and condensation) of water, surface radiation, hurricanes etc., etc. PS I would like to know what you think of the theory that the pressure gradient in the atmosphere results in a temperature gradient.
1090. damorbel at 23:42 PM on 23 July, 2011
      Re #1087 Sphaerica you write:- "In answer to all of your questions about net heat flow." I did not mention 'Net' heat flow on #1086. In thermodynamics there is no such thing as "net heat flow". Heat flow, Net or otherwise is a concept belonging to the caloric theory of heat, a theory not accepted since about 1845 following the work of James Joule on the conservation of energy. I suggest that, from this argument, you would also accept that the 'net' transfer is from the warmer to the colder part of the atmosphere and thus it is the colder part that tends to be heated by the warmer surface. The logic of this is clear, CO2 in the atmosphere indeed radiates heat to deep space, cooling the planet down from the heating effect of the Sun - more CO2 makes for a greater cooling effect by re-radiating the ('net) heat transferring from the surface by convection, evaporation (and condensation) of water, surface radiation, hurricanes etc., etc. PS I can see nothing in your diagram that shows a warming effect on the surface, thare are no temperatures to be seen, it is not possible to argue for a warming effect without atleast two temperatures.
1091. Dikran Marsupial at 23:55 PM on 23 July, 2011
      damorbel wrote: "I suggest that, from this argument, you would also accept that the 'net' transfer is from the warmer to the colder part of the atmosphere and thus it is the colder part that tends to be heated by the warmer surface." Yes, of course it is, and that is completely compatible with the commonly accepted physics of the GHE. BTW, your putting 'net' in quote strongly suggests you don't understand the reason it is there. It is a perfectly standard term, and it's meaning is key to your misunderstanding. "The logic of this is clear, CO2 in the atmosphere indeed radiates heat to deep space, cooling the planet down from the heating effect of the Sun" No, that does not follow logically. The CO2 in the amtosphere prevents heat from being radiated directly into space from the surface. Instead heat is only radiated to space from the upper trophosphere. The upper trophosphere is cooler than the surface, so there is less heat to radiate. Hence the more CO2, the higher in the trophosphere the radiating layer becomes, the colder this radiating layer is and the less heat that is radiated, not more. As for pressure gradients, I suggest we deal with the major flaw in your reasoning before getting on to more subtle points.
1092. damorbel at 00:02 AM on 24 July, 2011
      Re #1088 Sphaerica you write:- "While it is true that the measured pressure is higher closer to the ground... it stays that way. The pressure is not changing. To increase the temperature, you must compress the gas further. This clearly is not happening." As you decend through the atmosphere the pressure rises and the temperature rises. This is quite different from the bicycle pump, diesel engine etc. With the bicycle pump the ambient pressure remains the same so its temperature does not change, so the heat in the pump is tranferred into the ambient (thus the unchanging) temperature. The case of the atmosphere is quite different in that all the air at a given altitude heats up as you change that altitude, this means that the ambient temperature is changing at the same time, thus quite different from the bicycle pump example. It is a fact that, apart from wind blowing the air about a bit, the temperature gradient in the troposphere (not the absolute temperature!) is uniform over the entire globe because the force of gravity is, more or less, uniform also.
1093. Tom Curtis at 00:11 AM on 24 July, 2011
      Damorbel @1085, I did not mention energy transfer from the upper troposphere to the surface. In fact you could develop a model of the greenhouse effect in which all energy transfers within the atmosphere are convective. In that purely convective model of heat transfer within the atmosphere, there is no energy transfer from the upper troposphere to the surface. Never-the-less there is a greenhouse effect, which differs minimally from the real greenhouse effect. In such a model, the Earth's surface is warmed entirely by the Sun. But introducing more CO2 to the atmosphere temporarily slows the rate at which energy leaves the atmosphere. That creates an imbalance between incoming and outgoing energy, which must be stored somewhere and is stored as additional heat. Once enough heat is stored, the energy balance is restored, and all energy lost (or gained) is matched by energy gained (or lost) meaning the stored heat remains constant. Consider a bath tub, with a tap which lets water in, and another tap on the drain which can control the rate at which water goes out. If you turn the inlet tap on full, and the outlet tap on full, the water level of the bath will be constant. If you then half close the outlet tap, the water level in the bath will rise, even though no water flows back up the outlet pipe into the bath. This is exactly analogous to how the greenhouse effect works, and your objection is equivalent to a know-it-all on the side lines saying you can't raise the water level by closing the outlet tap. Your further claim that increasing the CO2 content of the atmosphere will increase the radiation to space assumes that energy radiated at a lower level in the atmosphere is never absorbed by CO2 at a higher level in the atmosphere. If you do not make that transparently false assumption, it becomes obvious that if you double the CO2 content, atmospheric radiation from lower in the atmosphere that formerly made it to space will be absorbed by the additional CO2 higher in the atmosphere. It will then be reradiated, but because it is reradiated by a higher and hence colder gass, it will emit less energy to space. I note that Sphaerica's and Dikran's post above more than adequately cover your other errors. As they note, you have been fully rebutted on these points many times and at length in this thread. Consequently I know there is no point in debate with you. I have responded twice now so that any late comers to this thread have a clear statement of the nature of your errors, but will not respond further. As you obviously have nothing new to add, nor any desire to learn, may I suggest you take to heart the moderator's prior direction to you.
1094. damorbel at 01:08 AM on 24 July, 2011
      Re #1093 Tom Curtis you write:- "I did not mention energy transfer from the upper troposphere to the surface." If a temperature rise is to take place, from any cause, GHE or whatever, there must be an energy source. If it is CO2 in the upper atmosphere producing 'back radiation' that warms the surface, don't you agree that the GHG-caused-back-radiation must be some sort of energy source? You also write:- "In fact you could develop a model of the greenhouse effect in which all energy transfers within the atmosphere are convective" This unlikely, gas flow surely dominates but there is plenty of gas flow that is not convective; surely surface winds play an even more important role? To restrict your analysis to convection is going rather too far I suggest; how else, apart from ocean currents, is thermal energy going to get from the tropics to the poles? You also write:- "But introducing more CO2 to the atmosphere temporarily slows the rate at which energy leaves the atmosphere". Sorry but I cannot see how this can be the case. CO2 is a powerful radiator of thermal energy and on Earth CO2 is always warmer than deep space, even Fourier when writing about heat transfer recognised that is transferred in the direction of hot to cold, so CO2 is always going to absorb heat from the warm atmosphere, both by absorbing radiation and molecular collision so that it, together with the other GHGs, cools the planet very effectively by radiating to deep space. You argue :- "if you double the CO2 content, atmospheric radiation from lower in the atmosphere that formerly made it to space will be absorbed by the additional CO2 higher in the atmosphere." Indeed the change in height does change the radiation temperature by perhaps a few degrees but this only makes a small difference because the radiation to 2.7K (deep space) is for a temperature difference of about 200K (raised to the 4th power don't forget!); the few degrees change arising from height difference will have only a tiny effect. Also the higher effective radiation level means the radiating gas has a lower density so it cannot absorb all the radiation coming from below, some radiation will pass straight through without being reabsorbed by the upper levels because the gas density is dropping.
1095. Bob Lacatena at 01:34 AM on 24 July, 2011
      damorbel, I'm not going to waste of lot of time here, because clearly many others have been down this road before, but here are a few salient points:

      In thermodynamics there is no such thing as "net heat flow".

      Yes, there is. Go study. To provide a simple example, thermodynamics does not apply on an individual molecular level. It applies in aggregate (i.e. at the macroscopic level). If a molecule emits energy in the form of a photon, the receiving molecule does not and cannot know if the emitting molecule was warmer or cooler. It does not and cannot discriminate based on the source of the photon. If that photon is of the correct frequency, then it is absorbed, no matter where it came from. To give another example, do you think that it is impossible to shine a flashlight into the sun? Of course not. The light from the flashlight (some of it) will reach the sun and be absorbed. Far more light/energy from the sun will of course reach and be absorbed by the flashlight. The net flow is from warmer (sun) to cooler (flashlight). but energy still has flowed from the flashlight to the sun.

      I can see nothing in your diagram that shows a warming effect on the surface, thare are no temperatures to be seen, it is not possible to argue for a warming effect without atleast two temperatures.

      Look again. I simplified the "temperatures" to 5 for the surface and 2 for the atmosphere, but they are clearly there. The surface temperature should be 4 (the amount coming from the sun) but it is 5. The extra "ray" is the red one, coming from the atmosphere. Take the time to actually study and understand the diagram before commenting further (although arguing without listening appears to be your modus operandi).

      As you decend through the atmosphere the pressure rises and the temperature rises.

      Wow, really? Except that the pressure is greater near the surface, but not increasing at any particular altitude. Again, no work is being done. The pressure at any altitude is constant. As such, gravity doesn't increase the temperature or artificially maintain a higher temperature. Yes, it maintains the pressure gradient, and a rising parcel of air will do work and cool. But barring that motion, and that actual expenditure of work, the atmosphere should still cool to restore the temperature differential (warm to cool, remember?). Thermodynamics does not allow gravity to violate (or suspend) the 2nd Law of Thermodynamics, any more than anything else might. [Did you even realize that when you argue that gravity maintains the temperature differential, it is in fact you who are violating the 2nd Law of Thermodynamics?] The misapplication of the laws of thermodynamics where they do not apply (i.e. a system that is not in thermodynamic equilibrium) is where people often go wrong here. That, and trying to over-simplistically apply basic theories and laws (PV=rRT, etc.) without considering all of the interactions and ramifications. In particular, the system is greatly complicated by quantum mechanics, and the fact that the substances involved may be transparent or opaque to various frequencies of radiation. The system is just far, far more complex than your simple model allows, and as such your simple model is incapable of adequately describing or bounding the system. I suggest you study the facts behind radiation (at the molecular level) in detail before proceeding further with your erroneous train of thought.
1096. Bob Lacatena at 01:41 AM on 24 July, 2011
      1094, damorbel,

      ...so CO2 is always going to absorb heat from the warm atmosphere, both by absorbing radiation and molecular collision...

      This one statement is very, very, wrong, and a major source of confusion. First, the energy is being absorbed from the surface, not the surrounding atmosphere. Thus, the surface is warming the CO2, which is in turn warming the surrounding O2/N2 in the atmosphere (it's not the atmosphere warming the contained CO2). Basically, the CO2 absorbs the radiation from the surface (or from other layers of the atmosphere, but ignore that complexity for now). Before the CO2 is able to radiate that energy away again (usually) it collides with an O2 or N2 molecule and passes the energy on that way -- freeing it to absorb more radiation from other sources. Thus, the surface warms the CO2, and the CO2 warms the O2/N2. This behavior is more pronounced near the surface, where the air is denser and collisions are more frequent. As one rises in the atmosphere, and it becomes less dense, the chance of collision is reduced, and so, too, is the time between collisions as well as the chance of receiving energy through absorbing radiation (for the CO2 molecule). As a result, CO2 higher up is more likely to gain energy through a collision, and emit it through radiation. Thus, we have a gradually changing effect, where in the denser, lower atmosphere, CO2 acts to absorb radiation and transfer it to the (otherwise transparent to IR) O2 and N2 molecules. As one rises, the balance slowly changes, until one reaches the very upper troposphere and stratosphere, where the opposite is likely to occur, and CO2 actually acts to accentuate heat loss.
1097. muoncounter at 04:41 AM on 24 July, 2011
      damorbel#1083: "distinguish between this compressive heating of the surface and the GH effect?. For me this is critical to the understanding of atmospheric physics and not often discussed." Perhaps an idea is 'not often discussed' because it is clear to most that it has little merit. You appeared as the champion of this idea as far back as comment #125 on this very thread, where the "death knell of the GHG hypothesis really is the effect of gravity on the atmosphere." Rumors of the 'death knell' of the 'GHG hypothesis' have been greatly exaggerated. This is not your personal soapbox; if you have nothing new to contribute, no one really enjoys reruns.
1098. damorbel at 06:26 AM on 24 July, 2011
      Re #1095 Sphaerica you write:- "In thermodynamics there is no such thing as "net heat flow". Yes, there is. Go study." The concept of heat 'flowing' went out with the 'fluid' concept of heat i.e. caloric. There have been many attempts to describe heat and the idea that heat is conserved was gradually replaced with the conservation of energy during the 2nd half of the 19th century. All these arguments about 'back radiation' and the like appear to be based on this idea of heat as a fluid substance and the preictions do not fit the observations. You write:- "If a molecule emits energy in the form of a photon, the receiving molecule does not and cannot know if the emitting molecule was warmer or cooler. The energy of a photon has the relationship E = hv, this is at the basis of quantum theory laid down by Max Planck and further developed by A Einstein, Werner Heisenberg etc., etc. in the early 20thC. This discussion has raised this point about 'photons not knowing the source temperature - I'm sure I have seen it before and it just isn't true! In this respect photons are no different to any other particles. If this 'ignorance of source temperature' on the part of photons is the basis of your science then I suggest you think again. How do you suppose a remote sensing infrared thermometer works if it doesn't relate the photon energy to the temperature of the emitter? Again you write:- "thermodynamics does not apply on an individual molecular level. It applies in aggregate (i.e. at the macroscopic level)." Since thermodynamics is base on the conservation of energy, not heat, it applies not only at the microscopic (molecular) level but to the sub-molecular i.e. quantum level. I suggest you are thinking of statistical mechanics which is indeed very useful for understanding ensembles of freely interacting particles. But statistical mechanics relies just as much on the conservation of energy and the conservation of momentum (both angular and linear) as does themodynamics and quantum mechanics. Further you write:- "I simplified the "temperatures" to 5 for the surface and 2 for the atmosphere, but they are clearly there. The surface temperature should be 4 (the amount coming from the sun) but it is 5. The extra "ray" is the red one, coming from the atmosphere." I am not sure of your meaning here. According to Fourier heat transfer is between two bodies according to the temperature difference you have in your diagram 2 units of heat going from the Earth at 5deg. to the atmosphere at 2 deg - quite possible. But how can you have 1 (red) unit going from the atmosphere at 2deg. to the Earth at 5deg. How so? Did Fourier get it wrong? You write:- "Thermodynamics does not allow gravity to violate (or suspend) the 2nd Law of Thermodynamics, any more than anything else might. [Did you even realize that when you argue that gravity maintains the temperature differential, it is in fact you who are violating the 2nd Law of Thermodynamics?]" What is missing from your argument is the conservation of energy, both potential and kinetic. Any object, including volumes of air, moving in a gravitational field, changes its potential and kinetic energy according to the strength of the gravitational field and the (vector) distance it moves; this is the argument that got Galileo into trouble. As for a volume of gas, it loses kinetic energy as it rises in a gravitational field, changing into potential energy therefore it cools, it is as simple as that. No need to talk about compression and expansion, gas is free to move as it likes in an atmosphere, but these movements must conform tho the conservation of momentum, potential and kinetic energy, don't you think?
1099. Bob Lacatena at 06:53 AM on 24 July, 2011
      1098, damorbel,

      All these arguments about 'back radiation' and the like appear to be based on this idea of heat as a fluid substance and the preictions do not fit the observations.

      This statement is not only wrong, but demonstrates a woefully poor understanding of the subject matter. You appear to be completely oblivious to radiative and molecular physics, and trapped in a 1960s mode. Please educate yourself.

      If this 'ignorance of source temperature' on the part of photons is the basis of your science then I suggest you think again. How do you suppose a remote sensing infrared thermometer works if it doesn't relate the photon energy to the temperature of the emitter?

      You clearly failed to comprehend anything I wrote. Please go back and reread it. At the same time, this statement also represents a complete lack of understanding of radiative physics. Again, go study.

      it applies not only at the microscopic (molecular) level but to the sub-molecular i.e. quantum level.

      No. Go study.

      But how can you have 1 (red) unit going from the atmosphere at 2deg. to the Earth at 5deg. How so? Did Fourier get it wrong?

      No, Fourier didn't, but you do. Go study.

      Any object, including volumes of air, moving in a gravitational field, changes its potential and kinetic energy according to...

      But we're not talking about moving parcels of air. We're talking about stationary air.

      ...but these movements must conform tho the conservation of momentum, potential and kinetic energy, don't you think?

      Okay, this makes it pretty clear that you're one of those people who thinks they know what they are talking about to the point that they are hopelessly lost. Hence, this is all a complete waste of time. Enjoy applying your personal version of physics to the world.
1100. Philippe Chantreau at 07:01 AM on 24 July, 2011
      Damorbel is at it again, after demonstrating how willing he was to contradict himself for the sake of argument. "How do you suppose a remote sensing infrared thermometer works if it doesn't relate the photon energy to the temperature of the emitter?" The hot plate of my stove emits IR photons. So does the Sun. No "IR thermometer" can tell whether an IR photon comes from one or the other. We've been there already. Damorbel's total confusion with Wien's law was clearly exposed on that occasion. Now the confusion is back, this time with gravity. It never ends.
      Response: (DB) Everything has an ending, including one's patience in allowing PRATT to continue to be bandied about.

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