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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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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.

Convection

Convection

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

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.

Advection

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

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.

Radiation

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 376 to 400 out of 765:

  1. Re 375 Dikran Marsupial you wrote:- "how does the first body know that it is radiating to 0K". It doesn't 'know' that. A body radiates only according to its temperature. What is does 'know' (if you can talk of bodies 'knowing' anything) is how many photons it receives. Your example of a body 'surrounded by a black shell at 272K 1mm away' means that the inside body receives almost as much energy from the shell as it loses. This imbalance means the inner body cools slowly to 272K. You wrote:- "and know to emit fewer photons?" The first body doesn't emit 'fewer photons'; the photons it emits get progressively less enegetic as it cools, according to the formula for photon energy 'E', E = hv where 'h' is Planck's constant and 'v' is the frequency. The number of photons remains the same.
  2. damorbel@376 O.K. so you agree that heat energy can flow from a cooler body to a warmer object? In this case heat energy does flow from the cooler shell to the warmer inner body, although there is a greater flow of heat in the other direction, and so the second law of thermodynamics isn't broken. Now put an identical heater in both bodies, each supplying the same amount of heat energy - just sufficient for the first body to maintain its temperature. What happens to the temperature of the inner body within the shell?
  3. DM, You should be aware that friend damorbel is on record against heat flow: "first off heat doesn't flow'; only fluids flow." A couple of hundred comments later comes "I have made a number of relevant arguments about the direction of heat transfer (hotter to colder)". Are you willing to spend another hundred or more comments re-drawing the distinction between 'flow' vs. 'transfer'?
  4. Re #377 Dikran Marsupial You wrote:- "so you agree that heat energy can flow from a cooler body to a warmer object?" Flow in this connection is an outdated concept, it went out with the caloric theory of heat in the early 1800s. I admit to using the term sometimes but it is a mistake because energy is frequently transformed during thermodynamic interactions. Now look at it this way; I give you a $100 bill, you give me 9 $10 bills by way of change; which way is the money transfer? Who has the increased financial liquidity? Would the transfer have been significantly different had I just given you a $10 bill in the first place? The analogy is good because the money transaction can have different formats such as bank transfer. The similarity is remarkable because energy transfers can also have different formats e.g. compresing gas in a cylinder with a piston heats the gas because work is done on the gas by the piston; energy is transferred to the gas via the piston.
  5. Re #378 muoncounter You wrote:- "Are you willing to spend another hundred or more comments re-drawing the distinction between 'flow' vs. 'transfer'?" As I noted above 'heat flowing' is an outdated concept belonging to the caloric theory of heat. It is outdated because it was discovered that it didn't explain experimental results, so a better theory of heat was developed called thermodynamics. The attractions of the 'heat flowing' concept are very great, I fall for them myself occasionally but none the less lead to erronius results. My advice is to avoid the term to maintain scientific credibility.
  6. Damobel@379 Rather than engaging in pedantry, please answer the question. You can call it transfer instead of flow if you like, it makes no difference to the argument, I;ll reword it for you: "O.K. so you agree that heat energy can be transferred from a cooler body to a warmer object? In this case heat energy is transferred from the cooler shell to the warmer inner body, although there is a greater transfer of heat in the other direction, and so the second law of thermodynamics isn't broken." Your financial analogy is incorrect, money is transferred in both directions. The net transfer would have been the same if you had just given me the $10 instead, but to understand the physics of the greenhouse effect the individual transfers are relevant, not just the net effect. To continue the analogy, consider two companies that trade with eachother, one buys $1M of services from the other, which then buys $999,999 of services from the first. If you are the IRS, would you accept the argument that the first company had only given the second $1? No, becuase in finance, just as in physics, the individual fluxes matter, not just the net flux.
  7. Re #381 Dikran Marsupial you wrote:- "it makes no difference to the argument" I'm afraid it does make a difference. Between atoms and molecules heat energy is transferred by processes which result in the exchange of momentum. This is most obvious with gases in which case the momentum exchange is by inelastic collision; here the billiard ball analogy is very helpful for many people but for solids and liquids it is intermolecular forces that do the same job. For a gas one may imagine a surface accross which you wish to measure the heat transfer, the temperature is different on either side of the surface, thus the mean velocity of the molecules on the hot side is higher than the mean velocity on the cooler side. The velocities of the molecules on both sides have a wide range which is described by the Maxwell-Boltzmann distribution; when referring to the 'mean velocity' (above) it is the mean of the velocities in the Maxwell-Boltzmann distribution. So when there is a temperature difference accross a surface the molecules on both sides of the surface exchange momentum by colliding with each other but on average the hotter molecules lose momentum and the cooler ones gain momentum; this is the basic theory behind the 2nd law of thermodynamics. Since there is momentum exchange in both directions but the energy transfer is only in one direction you should thus be able to grasp the physics behind the 2nd law. Energy transfer by photons is no different except the 'collisions' are purely electromagnetic. Photons tranfer energy by momentum exchange also; Einstein wrote a very good paper about this in 1917. Between two adjacent bodies of nearly equal temperature there is a very large exchange of photons but only a small exchange of energy. With photons the energy follows the Planck distribution; Einstein showed in his paper how it is equivalent to the Maxwell-Boltzmann distribution.
  8. Damorbel@382 O.K. I can see you are unwilling to discuss the science and want to bog the discussion down with pointless pedantry after I had already altered my terminology to suit you (from "flow" to "transfer"). Suit yourself, it is a tacit admission that your position is indefensible - if it weren't you would have the confidence to engage in the thought-experiment.
  9. damorbel @382 said Photons transfer energy by momentum exchange also This statement is incorrect.
  10. Re #384 Phil you wrote:- "This statement is incorrect." You can find out about photons and momentum here:- Physical properties of photons
  11. Re #383 Dikran Marsupial You wrote:- " I can see you are unwilling to discuss the science" Um, do you think my #382 is not discussing the science? Momentum transfer? Maxwell-Boltzmann statistics? The relation between momentum and energy? These are the fundamentals of kinetic theory, the scientific basis of the 2nd Law of thermodynamics. If I haven't done your 'thought experiment' properly I am really interested to know what I have missed. Please help.
  12. damobel@386 the science in post #382 appears to be merely a continuation of the pedantry regarding "flow" versus "transfer", which is a distraction from discussion of the substantive issue. Back to the thought experiment: Do you agree that heat energy can be transferred from a cooler body to a warmer object? In this case heat energy is transferred from the cooler shell to the warmer inner body, although there is a greater transfer of heat in the other direction, and so the second law of thermodynamics isn't broken as the net transfer is from warmer to cooler body. from 377: Now put an identical heater in both bodies, each supplying the same amount of heat energy - just sufficient for the first body to maintain its temperature. What happens to the temperature of the inner body within the shell?
  13. Re #383 Dikran Marsupial You wrote:- " I can see you are unwilling to discuss the science and want to bog the discussion down with pointless pedantry after I had already altered my terminology to suit you (from "flow" to "transfer"). Suit yourself" I would like to suit you so perhaps you could explain what part of #382 is 'pointless pedantry'? Your comment is rather dismissive of what is necessarily short on detail. Re #387 Dikran Marsupial You wrote:- "Do you agree that heat energy can be transferred from a cooler body to a warmer object? " My #382 explains about how heat energy is tranferred and how it happens. You appear to have a problem with #382, could you make it just a little clearer what it is? Re #377 You wrote:- "Now put an identical heater in both bodies, each supplying the same amount of heat energy - just sufficient for the first body to maintain its temperature. What happens to the temperature of the inner body within the shell? " The 'body in the shell' is the 2nd body - right? In #373 you wrote "The shell is maintained at 272 degrees Kelvin" - You ask "What happens to the temperature of the inner body within the shell?" When you put the same heater (in the 2nd...) as gives - what? You say 'just sufficient for the first body to maintain its temperature'. But how does it do this (keep the first body at 273K)? Is it 1/a constant temperature heater, regulating its output to maintain 273K? or 2/does it deliver the same power to the 2nd body as the 1st? The two cases are very different. The matter is complicated because you said (in #373) "The shell [tound the 2nd body] is maintained at 272 degrees Kelvin." The simplest case is /2 because the shell temperature is defined at 272K. In this case the temperature of the body inside the shell would rise somewhat according to the thermal resistance of the 1mm gap, which is something I am leaving to you. I am really interested as to why you put this problem together, as yet I cannot see why. I am waiting for your explanation.
  14. Damorbel I asked: "Do you agree that heat energy can be transferred from a cooler body to a warmer object? " Instead of giving a direct answer (yes or no would be a good start), you wrote: "My #382 explains about how heat energy is tranferred and how it happens. You appear to have a problem with #382, could you make it just a little clearer what it is?" which doesn't actually answer the question. I don't have a particular problem with what you had written, other than that it was avoiding giving a direct answer to a direct question. "You say 'just sufficient for the first body to maintain its temperature'. But how does it do this (keep the first body at 273K)?" If the heater is producing heat at the rate that the black body 273K radiates heat, it will stay at the same temperature as energy in = energy out. It doesn't need a regulator to achieve that. So can you just give a direct answer to the question, what will happen to the body in the shell if it is heated by a heater providing the same amount of energy required to keep the first body at a constant temperature.
  15. Re #389 Dikran Marsupial You wrote:- "Do you agree that heat energy can be transferred from a cooler body to a warmer object? " I wrote in #382:- " Since there is momentum exchange in both directions but the energy transfer is only in one direction you should thus be able to grasp the physics behind the 2nd law." And that is the complete answer to your question. Perhaps I can expand it. The Kinetic theory of heat replaced the Caloric theory in the 2nd 1/4 of the 1800s. This theory is that, above 0K all molecules are in a continuous state of vibration with momentum proportional to temperature. Momentum and energy are closely related momentum p = mv; it is a vector quantity because v (velocity) is a vector. The energy of moving particles is E = 1/2mv^2 which is not a vector quantity because v^2 is not a vector. Since heat transfer has a direction, it needs some kind of vector (you can use energy gradient but it is clumsy) to define the direction of heat transfer; momentum is much more handy. So heat energy tranfer goes from the high momentum/high temperature place to the cold/low momentum place but there is all the time (unless the cold side is at 0K) a tranfer of momentum in both directions but the average is fron the hot side to the cold side. You ask me:- "Do you agree that heat energy can be transferred from a cooler body to a warmer object? " Don't you see that the answer must be no? The mechanism of transfer (as well as all observations) make it impossible.
  16. " Since there is momentum exchange in both directions but the energy transfer is only in one direction you should thus be able to grasp the physics behind the 2nd law." That is obviously incorrect, every photon that is emitted by the shell and is absorbed by the body within has transferred energy from the cooler shell to the warmer body. You still haven't given a clear answer to what happens to the second body within the shell when it is heated. Keep it simple, does it (a) get warmer (b) stay the same temperature or(c) get cooler?
  17. damorbel - One last quixotic attempt: The surface of the Earth receives energy 'A' from the sun. If there were no other elements involved, the Earth would have to be at an equilibrium temperature sufficient to thermally radiate 'A' to space. Otherwise it would warm or cool until the incoming radiation power matches the outgoing. Now we introduce an object cooler than the Earth (at some temperature above absolute zero) that radiates 'B' to the Earth. It doesn't matter what power level 'B' is - other than it is > 0. The Earth now receives 'A + B' power, where 'A + B > A'. The Earth must now radiate a power 'A + B' in order to regain equilibrium. Since power radiated scales with T^4, this means that the Earth when radiating 'A + B' must be warmer than when radiating 'A'. Cool objects add energy to all nearby objects, even warmer ones, and cause them to be warmer than they would be in the absence of those cooler objects. Otherwise you would be violating the first law of thermodynamics - conservation of energy. The atmosphere is cooler than the Earth, but still warms it accordingly to a higher temperature than it would be without a greenhouse gas containing atmosphere. Do you disagree with this post? And if so, how do you justify it?
  18. "Do you disagree with this post?" Let me make a prediction: 'Yes, because a cold body cant warm a warmer body because its a violation of 2nd law thermodynamics". On and on like a broken record. Let me pose another question for damorbel. If you do an experiment and it results can be explained by the real 2nd law of thermodynamics but not by you imaginary version, then will you abandon your imaginary version?
  19. Re #393 scaddenp you wrote:- "If you do an experiment and it results can be explained by the real 2nd law of thermodynamics but not by you imaginary version" I am most interested in what you write but two lines is just a bit too little to give me a proper grasp of your point. I would very much like to hear how you see 'the real 2nd law of thermodynamics' and how it differs from my 'imaginary version'. Make this clear and I'll happily agree with you.
  20. Re #392 KR you wrote:- "Now we introduce an object cooler than the Earth (at some temperature above absolute zero) that radiates 'B' to the Earth. It doesn't matter what power level 'B' is - other than it is > 0." How does this 'object' get introduced? The troposphere is only 10 - 15 km thick and in close contact with a surface of 510,072,000 km2 which means they are closely coupled thermally and will quickly come into thermal equilibrium. Any object that is relatively cold will quickly be warmed up to a temperature related to the Earth's surface. Let us suppose the cold object was at 0K (you say it isn't but it could be) such an object would be producing no thermal radiation so it would have no effect on the surface temperature but it would still be warmed from the surface. Do you see a point where this cold object, as its temperature rises, it would begin to warm the surface by radiation?
  21. Looks like SoD has some suggestions for people confused on this issue, and who want to get a proper grasp of the maths... Find Stuff Out and Book Reviews
  22. Re #396 les you wrote:- "Looks like SoD has some suggestions for people confused on this issue," Would you like to reccommend some passage?
  23. damorbel - The purpose of my example is to demonstrate that a cool object can add energy to a warmer object, making it warmer still. The surface and atmosphere are in dynamic equilibrium, as described by the Trenberth 2009 energy budgets; the surface receives sunlight and back radiation (input), emits IR, convection, and latent heat, flow and sum flow of energy going sun->surface->atmosphere/space. The atmosphere receives sunlight, various inputs from the surface, and radiates that energy away, flows going sun/earth->atmosphere->earth/space, sum flow sun/earth->atmosphere->space with the energy flow to the surface considerably less than the energy flow from the surface to the atmosphere (thus satisfying the 2nd law of thermodynamics), while still adding some energy to the surface - and hence raising it's temperature to a higher level than it would have without the GHG containing atmosphere. Of course, we've covered this ever so repeatedly before...
  24. scaddenp - Actually, the response I expected to my post was a combination of over-interpretation, nit-picking, and red herrings, while ignoring the actual point. If only I was as accurate with the lottery...
  25. Re #398 KR in #392 you wrote:- "The purpose of my example is to demonstrate that a cool object can add energy to a warmer object, making it warmer still." It seems from your #398, where you wrote :- "The surface and atmosphere are in dynamic equilibrium, as described by..." that you didn't really mean an 'cool object' but a gassy atmosphere. You really should be more clear because thermally speaking 'objects' and gas are very different. The really serious difference is that gases are compressible and their temperature changes when compressed. Also the Earth's gravity compresses the atmosphere while holding it on the planet. Trenberth doesn't consider this at all; none of his diagrams have any mention of temperature, it really is not at all easy to understand his explanations, perhaps you can help.

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