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The greenhouse effect and the 2nd law of thermodynamics

What the science says...

Select a level... Basic Intermediate

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

Climate Myth...

2nd law of thermodynamics contradicts greenhouse theory


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


At a glance

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

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

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

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

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

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

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

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

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

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

Further details

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

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

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



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

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

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


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


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

Latent heat

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


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

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


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

Energy balance

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

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

Energy Budget AR6 WGI Figure 7_2

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

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

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

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

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

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

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

Tyndall 1859

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

Update June 2023:

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

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

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Comments 1201 to 1225 out of 1254:

  1. I can't believe this thread now is 1200 posts! There is no violation of the second law with the Greenhouse Effect, because it's not about energy going from cold to warm through a conduction process. Does anyone actually think that a re-emitted photon cannot travel from the colder atmosphere toward the warmer surface? How do the photons from the Sun pass through the colder upper atmosphere and reach the warmer surface?
  2. I mean, I can even agree the net effect of additional CO2 could be zero or a wash, but not because of any second law violation. This is silly.
  3. RW1, you have a lot of posts on this thread and are no less culpable for its length that anyone else who has posted on it. The thread has seen little else than trolling and obfuscation, the worst example being that of Damorbel (see post #915, p. 19). Fred Staples and TOP's latest examples are not much better on substance. No need to add to it.
  4. 1201, RW1,
    Does anyone actually think that a re-emitted photon cannot travel from the colder atmosphere toward the warmer surface?
    Believe it or not, yes. Read the comments to see not only how many people believe it, but how adamant they are in sticking to their misconceptions in post after laborious post. They refuse to accept that there may be things that they misunderstand, and that they would be better served trying honestly and faithfully to find the flaws in their own understanding rather than to assume that they are correct and everyone else is wrong — including thousands and thousands of scientists and the half a dozen people here who are simply trying to help them to get things straight. Too, while the 2nd Law concepts seem basic and inarguable to you and I, climate science is rife with people who perhaps get past that hurdle, but at one point or another develop a disconnect and freeze right there, unable to get past it by learning the science well enough to see the flaws in their reasoning, correct them, and thus to understand everything far, far better and to be able to move on to the next concept. It's a curious human trait that allows such people to possess more than their fair share of intelligence and education and yet be unable to properly apply it because of some quirk of cognitive dissonance.
  5. @1200 pbjamm At some point the title of this blog got changed. Used to be about G&T's paper on the Falsification of the Greenhouse Effect. Same references. It has just been trimmed down to one quote out of that paper.
  6. TOP: "I am trying real hard to make a reasoned point" I'm not sure about that and even if it is true (one could find several different points you have tried to make, none of which is very impressive in terms of reasoning), that's part of the problem. You believe you have a point to make. I don't see that you have done the work to get to the level of understanding where that would be possible. Engage in serious study and your possible "points to make" will melt like snow under the sunshine of understanding. If I were you, sincere as you claim to be, I'd consider taking a course or two at a nearby college or even online.
  7. @1206 Philippe Well the inability to make a reasoned point goes both ways. I haven't seen a reasoned discussion of the points that G&T made regarding the fundamental physics of RGHE, but rather comments about my own less than perfect grasp of the world, the universe and why taxes go up. Perhaps you can address G&T's claim that the concept of radiative balance wrt RGHE is nonsense. (-Snip-). (-Snip-).

    [DB] Trolling snipped.

  8. TOP, G&T is a rambling diatribe of everything they could think of. I am really having a hard time finding any science in it at all. The only true science would be in section 3, but even that is mostly devoted to arguing against flaws in various greenhouse analogies (who cares?) and other things (like, as if anyone gives 2 [your-pick]s, "An Inconvenient Truth"). I had to get to page 47 before it hit any actual science, and then it did what most amateur attempts do, which is to repeat all of known science as if this is a text book, and they must walk the reader through every single foundation concept. Please help me. Find a statement -- a brief, scientific or mathematical statement, not a rambling load of arrogance -- that you believe sufficiently makes the case that the greenhouse gas effect violates the 2nd law of thermodynamics. Please note that your two quotes from this comment of yours do not represent any sort of argument, but rather just ill-considered whining. There is nothing of substance in the statements. Please identify some scientific or mathematical observation that you believe is demonstrated by G&T and which you are not on your own able to discount or untangle.
  9. 1197, TOP,
    In the Wood (1909) experiment, there was a small discrepancy in how fast the two boxes heated... So I jumped to the conclusion that if that was so...
    As has been explained, the Wood experiment is flawed. You cannot take it to be a model for anything, or make any inference from it. As far as the particular effect you describe, however, Wood himself recognized that particular problem and corrected for it (emphasis mine):
    When exposed to sunlight the temperature rose gradually to 65 oC., the enclosure covered with the salt plate keeping a little ahead of the other, owing to the fact that it transmitted the longer waves from the sun, which were stopped by the glass. In order to eliminate this action the sunlight was first passed through a glass plate. There was now scarcely a difference of one degree between the temperatures of the two enclosures.
    To clarify, all that happened here was that the glass plate blocked incoming IR, and so that box warmed more slowly. One thing Wood got wrong, though, was that the bulk of the IR that was being blocked was not coming from the sun but rather from greenhouse gases in the lower atmosphere (the same IR that you measure when you hold up your hand-held IR thermometer). So at that point it was actually the greenhouse gas effect that was interfering with his ability to prove or disprove the existence of the greenhouse gas effect!
  10. I have one question for those who think the GHE violates the second law: If downward re-emitted photons cannot travel from the colder atmosphere toward the warmer surface, how do the photons from the Sun travel through the colder upper atmosphere and reach the surface? Have any of you detractors of this ever felt the Sun's rays on your skin when you go outside?
  11. RW1: Thank you for pointing that out. It sometimes feels like it's not often that climate science skeptics will so clearly call out basic errors on the part of other skeptics.
  12. #1209 Sphaerica : "As has been explained, the Wood experiment is flawed. You cannot take it to be a model for anything, or make any inference from it." Sorry, I'v not read the all thread, but I used to read Greenhouse was not a good analogy, notably because of Wood's experiment, even here for example in France in this (rather prestigious and totally 'mainstrem') ENS popularization website for teachers and laymen. This 2009 paper seems to replicate similar results, albeit with a more complex experiment, than Wood (who is quoted on 10). (To prevent any fanciful interpretation, the authors precised: "Our results apply only to the interpretation of classroomscale demonstrations; they do not call into question the effects of anthropogenic greenhouse gases on the Earth’s climate or existing models of those phenomena.") So, finally, is there a replication / falsification of Wood's experiment in PR literature? Maybe it has been mentioned previously, but the 1200 posts are discouraging... Thanks for information.
  13. @1212, the 2009 paper is a good catch, and thanks for the h/t. However, it is possible to perform a "classroom" demonstration of the greenhouse effect. To do so you require two sealed boxes, with transparent lids. One should be transparent to IR radiation, while the other should be opaque to IR radiation. Both boxes should be evacuated (contain a vacuum) to prevent convection. Further, there should be a transparent, IR absorbing filter with a low emissivity film on the side away from the lamp to screen out IR radiation equally from both boxes. The low emissivity film is necessary because otherwise the filter will itself radiate IR, which is then not properly controlled for. It may also be necessary to evacuate the space between the "lid" and the filter to avoid convective cooling of the lids with outside air. The experiment could be performed with "lids" consisting of two IR transparent plates with the space between filled with CO2 and Argon (or Nitrogen) respectively, however, I believe the gas would need to be at substantial pressure, or the apparatus very large, to detect a significant effect in this case.
  14. There is nothing to address. G&T do not have a point. They play on words, trying to describe something for what it is not and then attack it. G&T is the ultimate strawman. That you can be fooled by it indicates that my assessment is accurate.
  15. 1212,, The Wood experiment was poorly designed, and due to its flaws it proves nothing one way or the other. SkS will have a post on it (hopefully) soon, as a matter of fact, but for the basic synopsis see my previous comment on this thread. I don't believe the falsification exists in the peer reviewed literature, just because it's so old (and the experiment itself was never peer reviewed, either). Everyone knows that it's wrong. Refuting it would be rather like writing a peer reviewed paper to refute Ptolemaic model of the solar system. It's just not necessary.
  16. @1209 Sphaerica So if what you are saying is true about the blocking of the back radiation was the true reason the glass windowed box in Wood's (1909) experiment had a lower temperature rise rate, then if the boxes were pointed at right angles to the sun, the box with the IR transparent window should also show a higher rate of temperature rise assuming that it started at a lower temperature. After all the CO2 that is radiating this back radiation is all around us. Sorry, I missed the flaw in the Wood experiment. Are you saying that it did not in fact show that real greenhouses work by blocking convection cooling and not radiation trapping? That was what was being tested in the experiment. I have half a mind to try to repeat the experiment using DOE methods. Turns out that rock salt windows are commercially available in optical grades at reasonable prices. Now you made a statement that my IR thermometer was possibly measuring the IR from the RGHE when I pointed it skyward. I did a further experiment with the IR thermometer to see if it was in fact measuring any back radiation from RGHE. It does not. The experiment was simple and I will describe it here: Using the flame of a common household propane torch as a source of IR from a visible flame composed primarily of H2O and CO2 at several thousand degrees F measure the flame temperature by pointing the IR thermometer at the flame 6 inches from the torch nozzle and slowly move the detector down the flame towards the source until the IR thermometer is pointing at the nozzle of the torch. Results: Some small temperature increase over background (75F vs 55F room background) from the flame until reaching the metal nozzle at which point the temperature reading jumped to 400F. Discussion of Results: Either the handheld IR thermometer measures a lower temperature than the actual gas temperature because the IR emitted by the high temperature gases was not in the narrow band specific to the semiconductor device or the emissivity of the high temperature gases was so low that the detector could not pick it up (this instrument not having a correction for emissivity available) and of course remembering that T&G don't believe the term emissivity can be applied to the radiation from gases at all as that applies to black body radiation which is not the radiation coming from a gas (no it isn't a different kind of photon, it is a different kind of geometry). Further refinement of the experiment: An aluminum reflector was placed behind the flame and the temperature measured increased significantly, but still nowhere near the actual flame temperature. Conclusion: The IR thermometer I have is not capable of registering any significant back radiation from the green house effect. We'll leave that to the folks who made muon's graphs. RGG emit IR in a very narrow band and require expensive instruments to detect. My IR thermometer was likely just indicating the low end of it's range when pointed at clear sky and the temperature of the moisture in the clouds when pointed at the bottoms of clouds. Note: The IR handheld did detect the correct temperature of hot water which means it should detect water droplet temperature.
  17. @1214 Philippe G&T don't have a point? Apparently they have some kind of point that needs addressing or this thread wouldn't exist. G&T made the assertion from basic physics that the concept of radiative balance is meaningless. They are well qualified to make this assertion in peer reviewed literature and have published on climate related issues on other topics. It is the assertion that they made regarding the concept of "radiative balance being bad physics" that I would like to see an answer to here. You can't just brush that off by saying they are wrong. And no, muon's graphs don't answer the assertion but are to be interpreted by the physics they assert are true. I'll have to check whether Halpern made a rebuttal to this point in his response to G&T. But I don't remember seeing it.
  18. 1216, TOP,
    Are you saying that it did not in fact show that real greenhouses work by blocking convection cooling and not radiation trapping? That was what was being tested in the experiment.
    No. That is not what was being tested. You misunderstand the experiment. I explained this to you already in comment 1175. [As an important side note, if you are going to demonstrate that you either do not read or completely ignore responses to you, then this conversation is a waste of everyone's time. The tactic of simply repeating the same thing over and over as if your points have not been refuted is common and unacceptable. If you simply missed my response I apologize, but I have no time for games.] The purpose of the experiment was to determine if infrared radiation could be "trapped" and slow the cooling process. To do this, the system attempted to control convection and all other factors so that they would be the same in both environments. The only difference in the two setups should have been the ability to emit IR (which would be blocked in one case). The setup failed in this regard. Convection and other factors were unrecognized, so that they warmed the glass plate and the rock-salt plate equally, causing it to emit IR and creating no difference . I have no idea what "RGHE" is. Please don't define your own acronyms and then use them as if they are common place.
    The IR thermometer I have is not capable of registering any significant back radiation from the green house effect.
    I don't know how in the world you get this. This is very simple. We'll work with an analogy. Everyone is in a crowded gymnasium, trying to get an autograph from someone famous at one end. Thus, most of the people are crowded at that end. There are less people milling around in the middle of the gym and almost no one at the far end. One person there is your friend, who has already gotten his autograph and is waiting for you. You are right next to the person signing autographs. The noise there from all of the people clamoring for autographs is deafening. You turn your ear in the direction of your friend to listen to see if he is calling you. What you hear is an ear-splittling cacophony. Based on your logic, you conclude that your friend is able to speak incoherently and deafeningly with several hundred voices at one time. Lets go back to GHG. The air near the surface is far more dense than the stratosphere. The number of CO2 molecules is far higher. The air near the surface is also far warmer. As such, the amount of IR being emitted by the air around you is far, far greater than the IR being emitted by the stratosphere above, and that IR in turn has layer upon layer of intercepting greenhouse gases between it and you. You have no chance of measuring the IR emissions of the stratosphere from the surface of the earth, because it will be masked by the IR emissions of the entire atmosphere, bottom to top, in between.
  19. 1216, TOP, I asked a simple question in comment 1208 and you ignored it. Again, this discussion goes no where if you simply choose to ignore things that are presented to you. I will not waste my time jumping from point to point and simple repeating the same things over and over. To repeat: G&T spend a lot of time making assertions, but do not support them. Most of their assertions and the vast bulk of their diatribe consists of pointless word games and not science. Please identify some scientific or mathematical observation that you believe is demonstrated by G&T and which you are not on your own able to discount or untangle. Please identify some way in which G&T "prove" that greenhouse gases do not work as the rest of the scientific world understands and accepts.
  20. @1215 Sphaerica I'm going to have to break the rules with the moderator's indulgence (-snip-)

    [DB] This is tedious.  Your entire agenda revolves around presumption (as defined by your repetitive use of the word seems): presumption of posts you have not read nor understood in their entirety, presumption of what other people are saying without clearly asking them, presumption of what the greenhouse effect of greenhouse gases actually is and presumption of just how much leeway you will be given in your prosecution of your agenda.

    An agenda which, in the absence of substantive points by you (and failing to answer the repeated clear questions of others) devolves to wasting everyone's time here.

    Get to the point, clearly and without dissembling, or cease.

  21. 1220, TOP,
    the point being tested in the experiment was that greenhouses function by preventing convection
    No. You misunderstand, and this is why you can't get past the Wood experiment. How in the world could GHG's "block convection"? Scientists know that convection contributes to the behavior of the atmosphere. Why would this factor be ignored? As far as the way a real greenhouse works... that's silliness. Of course GHGs don't work exactly the same way. It's an analogy! It's used to introduce a complex concept to people before getting into the nitty grity. If your issue is that the word "greenhouse" is inappropriate (as with G&T) then you are wasting everybody's time! And please stop saying "RGHE". What the heck is "RGHE?"
  22. @1218 Sphaerica You haven't answered my point. I did read 1175
    First, the purpose of the Wood experiment is not to "determine whether radiation or convection controls the temperature of the air inside the box." The purpose is to determine whether or not in a system where convection is not present radiation alone will have the capacity to control temperature in the boxes.
    In the context of both Wood and G&T the convection was with the bulk outside atmosphere. G&T also made that clear with their discussion of the warming of a car interior with closed windows. Anyone knows that convection will occur inside any closed, gas filled container with a temperature differential and gravity. Of course in such a small box, convection will soon come to a halt as the enclosed gas reaches an even temperature. Your comment is obfuscation and a lack of taking the experiment in the context in which G&T offered it. The term RGHE was not coined by me, I just contracted it from "Radiative GreenHouse Effect". It was coined on this thread by someone else and such contractions are commonly used here. If you don't read the thread as you accuse me of doing, what can I say? G&T also proposed using a different term, "atmospheric greenhouse effect", and low and behold, what do you know, it is the first that phrase that occurs in the abstract quoted as the SoD here. G&T don't support their assertions? Did you read the paper?
  23. Sphaerica, I may have misunderstood you but you appear to say that the purpose of Wood's experiment was to disprove the greenhouse effect. That is not correct. Rather, it was to show that actual greenhouses (made from glass) where warmed by preventing convection rather than by the radiative effects of the glass. As he said in his article:
    "THERE appears to be a widespread belief that the comparatively high temperature produced within a closed space covered with glass, and exposed to solar radiation, results from a transformation of wave-length, that is, that the heat waves from the sun, which are able to penetrate the glass, fall upon the walls of the enclosure and raise its temperature: the heat energy is re-emitted by the walls in the form of much longer waves, which are unable to penetrate the glass, the greenhouse acting as a radiation trap. I have always felt some doubt as to whether this action played any very large part in the elevation of temperature. It appeared much more probable that the part played by the glass was the prevention of the escape of the warm air heated by the ground within the enclosure. If we open the doors of a greenhouse on a cold and windy day, the trapping of radiation appears to lose much of its efficacy. As a matter of fact I am of the opinion that a greenhouse made of a glass transparent to waves of every possible length would show a temperature nearly, if not quite, as high as that observed in a glass house. The transparent screen allows the solar radiation to warm the ground, and the ground in turn warms the air, but only the limited amount within the enclosure. In the "open," the ground is continually brought into contact with cold air by convection currents."
    Wood's experiment does in fact demonstrate exactly this point, ie, that physical greenhouses in fact prevent convection from carrying heat away from the surface, and thereby raise the temperature. However, he goes on to say:
    "Is it therefore necessary to pay attention to trapped radiation in deducing the temperature of a planet as affected by its atmosphere? The solar rays penetrate the atmosphere, warm the ground which in turn warms the atmosphere by contact and by convection currents. The heat received is thus stored up in the atmosphere, remaining there on account of the very low radiating power of a gas. It seems to me very doubtful if the atmosphere is warmed to any great extent by absorbing the radiation from the ground, even under the most favourable conditions. I do not pretent to have gone very deeply into the matter, and publish this note merely to draw attention to the fact that trapped radiation appears to play but a very small part in the actual cases with which we are familiar."
    However, that was not the ostensible purpose of the experiment, and nor does it follow from the results he obtained. Like many a denier since, Wood has simply misinterpreted his own result. What is more, his experiment is clearly irrelevant. The greenhouse effect was deduced by an imbalance between the temperature of the Earth's surface, and the temperature the Earth' surface needed to be to balance the incoming solar energy with outgoing IR radiation. Because the effect is calculated and predicted purely from the physics of radiative transfer, the fact that convection cannot carry energy into space can in no way undermine the theory. So while it is in principle possible to falsify the greenhouse effect, it is not in principle possible to do so using Wood's experimental design, and that is exactly because it allows as a significant method of heat transfer a means (convection) which is precluded in space. (It is in principle possible to refute the greenhouse effect with a similar experiment as described in my 1213, although the performance of such an experiment would bitterly disappoint deniers everywhere.) It follows from this that all discussion of Wood's experiment is a red herring, something you already appreciate. All it shows of relevance is what everybody admits, that the "greenhouse" analogy is inexact. Finally, I understand your frustration with TOP. All he seems to do is waffle on vaguely, misrepresent the opinions of others and never get to any substantive point. I heartily recommend that further discussion of Wood's experiment be declared off topic on this thread, and that TOP be required to answer your very reasonable question at 1219. His failure to do so, I think, would be clear evidence that his only purpose here is trolling.
    Response: [muon] Indeed. This thread is about the 2nd law of thermo, not about boxes or greenhouses. Wood's experiment is off-topic.
  24. @1210 RW1 If you read G&T carefully you will find out that they do not state that IR photons or any other photons emitted by a gas do not travel in straight lines to whatever they are then stopped by. In fact they, as physicists who have published on quantum physics they have quit a nice explanation of how photons are involved in the transfer of heat both in conduction and radiation. Where they G&T disagree with you is in your definition of RGHE that, IIRC, you say requires heat to flow from the colder CO2 in the atmosphere to the ground. I believe G&T would use the term "Perpetuum Mobile of the 2nd kind" for what you are describing as your description of RGHE seems similar to one of the definitions they took exception to. Photons from the atmospheric gases (let's include all species here) can go in any direction but heat always flows from hot to cold. It is the basis for radiative heat transfer as described in G&T.
  25. TOP @1224, heat may always only travel from hot to cold, but only if you use a very specific, technical definition of heat to mean "net thermal energy". Energy, including thermal energy can travel in any direction including from cold to hot. G&T employ the former technical definition in order to refute the second possibility (as indeed you are also doing). It amounts to empty word play and has nothing to do with real science.

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