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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 176 to 200 out of 352:

  1. Phil, my original point was that the mentioned isolation (blanket) analogy is no way valid to explain the facts. How you rephrased this is of no concern to me. Now let me try to give my view on the green house effect which indeed leads to the conclusion that the green house effect does not interfere with the second law of thermodynamics, but for reasons that so far have just been mentioned here but not explained. In my posts #148 and #162 I tried to show that green house gases differ from other gases in their ability to store (trap) heat (falsely hoping nobody would object to that) at a significant higher rate than other gases. From here the argument is simple. Higher concentrations of green house gases in the the atmosphere will allow the more energy to be stored in the atmosphere. Due to the chemical composition of green house gases the bulk of that energy has to be drawn from surface emissions. As a result the energy content of the atmosphere is higher than before. In consequence incoming radiation will be less able to heat the atmosphere and more of it will reach and heat the surface. That in turn may cause more green house gases to be released. This explanation does not rely on back-radiation to heat the surface and therefore does not contradict the second law of thermodynamics.
  2. Just an afterthought. My explanation will no way predict a tropospheric hot spot so you can cease looking for it.
  3. h-j-m, You have successfully described the greenhouse effect. One point of note: That in turn may cause more green house gases to be released. Yes, that is how it happened historically. An initial forcing factor, such as a solar irradiance increase caused by an orbital change (Milankovitch cycles), caused a temperature increase. This temperature increase caused the release of CO2 from the oceans which increased the temperature further and caused more oceanic CO2 release. That isn't what is happening currently. The oceans & terrestrial biomes have been net CO2 absorbers during this recent warming. CO2 is coming from the ocean (argument #87)
  4. Re: h-j-m (177) "My explanation will no way predict a tropospheric hot spot so you can cease looking for it." That's OK, it's already been found here and has been confirmed more recently here (source study here). The Yooper
  5. Bibliovermis, can you please explain how in hell can I can come up with a correct description when everything that led to it was wrong, misinterpreted and misunderstood as far as any comment to it told. By the way, I was deliberately using the term green house gases for not referring to CO2. I had more H2O in mind as well as these semi solid hydrocarbons in the oceans just kept in their state due to a delicate balance of pressure and temperature.
  6. 180: "how ... can I can come up with a correct description" Check back a hundred or so comments. You've basically retold the same story; with or without any of the so-called 'back radiation' you find so distasteful, the result is the same (and we won't let anyone know you're now a believer). "semi solid hydrocarbons in the oceans just kept in their state " Can you explain what that means, where you heard about it and what it has to do with the (now verified) Greenhouse Effect?
  7. muoncounter, yes you are right I don't change arguments (stories) as long as I find them sufficiently backed by facts. But of course, I will never be a believer. I thought this is rather to be a matter of science, not belief. As to hydrocarbons in the oceans I might have meant this.
  8. h-j-m, if you are trying to find a correct description which somehow misses a measurable phenomena like back-radition, then good luck. How do you account for what DLR pyrgeometers actually detect then? People have pointed you at many good resources for getting a correct description - you appear to have rejected all because they dont conform to your incorrect understanding of physics. I suggest that you go to the textbook and read it from there, correcting your misinterpretations of science as you go. eg "Fundamentals of Heat and Mass Transfer, Incropera and DeWitt (2007)". And as for methane - hydrate release would be a disastrous feedback but not likely. We can tell from isotopic composition that bulk of methane going into atmosphere is not from fossil/hydrate sources. I do agree that that "insulator" analogy is poor because most people think in terms of a conductive insulator and its easy to jump to the wrong conclusions. I dont like "heat storage" in atmosphere because the convention use of the term does not strictly apply. This is all about the physics of radiative heat transfer and better understood in those terms rather than by analogy.
  9. #182: "I thought this is rather to be a matter of science," One believes what the science says. As opposed to refusing to believe it, no matter how many times it is demonstrated, referenced, explained, etc. The New Scientist article you cite refers to methane from melting permafrost bubbling out into the Arctic Oceans. There do not appear to be 'semi-solid hydrocarbons' in the oceans, unless you are applying that designation to methane hydrates, colloquially known as 'ice that burns'. The discovery will rekindle fears that global warming might be on the verge of unlocking billions of tonnes of methane from beneath the oceans, which could trigger runaway climate change. ... The team located more than 100 hotspots where methane is leaking from seabed permafrost. Most of the water in the region had methane concentrations more than eight times the normal amount in the Arctic Ocean, and concentrations of the gas in the air above averaged four times the Arctic norm. Yes, methane is a GHG, but this is clearly a response to warming that is already underway. This added methane will indeed make things worse; whether it is 'runaway climate change' or not remains to be seen. Let's hope it's not. The headlines 'Arctic Ocean catches fire' will be too hard for even Watt$ to spin. The problem is now that your argument will break down if you are OK with water vapor as a GHG, but refuse to accept CO2. As yocta explained earlier, they are both molecules with the vibrational modes needed to capture IR radiation from the surface. You can't believe that one is a GHG and the other isn't; that just wouldn't be scientific.
  10. Again I am getting accused of denying the existence of back-radiation, saying CO2 is no green house gas and for my incorrect understanding of physics as well as refusing to accept science. I thought of having gained some patience during 60 years, but now it is wearing really thin. So far I have taken on any concrete counter argument and refuted it with evidence. So far I did not recognize that someone offered evidence for his counter arguments which makes the whole event somewhat lopsided. Nevertheless I tried and hopefully managed to keep calm and polite. But having to deal any other reply with, as it meanwhile seems, wilfully misreadings or misinterpretations of what I wrote is getting at my nerves. Then there are explanations like that of yocta, really helpful. It is as if you go to your car mechanic and ask him why the cylinder-head of your vehicle broke and he answers with a detailed description on the metallurgic composition of the cylinder-head. I'm too old for this crap. Good bye.
  11. Re #167 yocta you explain that CO2 etc, the greenhouse gases (GHGs) absorb radiation in the IR band. I have never heard this disputed, do you think that those who question the GH effect actually question this? I certainly don't. Do you know that GHGs also radiate IR? The most common explanation for the GH effect is that this radiation causes the surface to get warmer somehow; this thread is about how GHGs which are between cold and very cold (-50C) in the upper atmosphere can warm Earth's surface which is normally between +30C and -30C. It is rather like claiming that if you are cold (+10C) you can get warm by taking your clothes off and hugging a snowman at -3C but much, much worse! The snowman hugger gets cold because his body heat, at 10C transfers to the colder (-3C) snowman, melting part of the snowman meanwhile making the hugger quite a few degrees colder. This is what the 2nd Law of Thermodynamics is all about. The explanations of the IPCC claim that GHGs in the troposphere warm Earth's surface at 255K by 33K to 288K, that's a lot of warming!
  12. damorbel - IR at greenhouse frequencies gets absorbed and re-emitted within about 100 meters. That means the surface is facing an atmospheric IR emitter at 14C, not -50C. The -50C is reached through atmospheric lapse rate temperature drop, until the altitude where lowering pressure reduces IR absorption enough to radiate to space. Now, realize that without the GHG absorption and emission at 14C we would instead be radiating those bands directly from the surface to space, which is (if you include microwave background radiation) at -269C? I suggest you think about sitting (a) in a room at 14C, then try (b) sitting in a cryo-fridge at -269C, and consider what kind of body temperature you could maintain in those two circumstances. Wear warm socks.
  13. Re #166 archiesteel you wrote :- "@damorbel: the graph serves its purpose. It is not misleading to anyone with any kind of base scientific knowledge." A diagram without any temperatures? Telling us that the surface is warmed? This is not scientific, the thread is about the 2nd Law of themodynamics which is about how heat moves between places with different temperatures; I am curious to know how you find a diagram without any temperatures on it AT ALL "serves a [useful] purpose" in this regard.
  14. Re #174 Tom Dayton you wrote :- "wavelengths of radiation that are plentifully emitted by the Earth but only weakly emitted by the Sun, thereby acting as a partially closed valve that traps energy below the top of the atmosphere" A (partially) closed valve? The absorbed insolation is converted to heat, it warms the soil, water, atmosphere etc. A (partially) closed valve is not an idea that applies to radiation, even the IPCC doesn't mention this idea! Now this soil, water, atmosphere etc. only emits radiation when it is above 0K, whereas it absorbs radiation regardless of its temperature. For example Earth can absorb microwave radiation very efficiently but the whole point of microwave ovens is that their radiation does not have thermal properties, it is "monochromatic" with a wavelength many orders of magnitude longer than IR. Starting from 0K the temperature of material receiving radiation (of any sort) can only rise and as it rises it starts to emit radiation, eventually reaching a temperatures at which it emits as much radiation as it absorbs - it has nothing to do with the wavelength of the incoming radiation. However if you want to assign a temperature to your source then you must choose a source with a thermal spectrum, a spectrum that follows Planck's radiation law; it must not be monochromatic like a laser, a microwave oven or any other non-Planckian spectrum, only then can you speak of a temperature.
  15. damorbel "It is rather like claiming that if you are cold (+10C) you can get warm by taking your clothes off and hugging a snowman at -3C but much, much worse!" No, it's rather like claiming that 10 °C is better than -3 °C. Your clothes are colder than your body on average, at almost the same temperature inside and colder outside. But they reduce the heat fluxes due to both conduction and convection and you feel warmer. The point here is that whatever reduces heat dispersion (heat flux) makes you feel "warmer", even if it is colder than yourself. And even if the prevailing mechanism is radiative instead of conductive or convective. Please note the flux from the atmosphere to the surface is not a heat flux but an energy flux, the former being the net energy flux at the surface. So, the heat flux does not revert upon increasing the greenhouse effect as required by the 2nd law of thermodynamics.
  16. "It is rather like claiming that if you are cold (+10C) you can get warm by taking your clothes off and hugging a snowman at -3C but much, much worse!" Good grief, damorbel: you really don't get it, do you? Warmer objects can indeed absorb radiation from cooler objects. If you shine a steady UV light on a spinning steel ball, the ball will eventually reach a specific temperature. True? If you then place another steel ball nearby--a steel ball below the temp of the first one but above 0K--then I'll bet you lunch that the first steel ball's surface temperature will increase slightly until it once again reaches an "equilibrium" temp. Allow this to take place in an atmosphere that does not support convection or conduction--only radiation. The total incoming radiation for the first ball will have increased due to the second (cooler) ball's radiation (and subsequent re-radiation of the first ball's radiation). In your model, does the radiation from the second ball just "bounce off" the first ball? Or does the second ball magically know not to radiate toward the first ball? Your snowman example is not good, because A) you're working primarily with conduction and convection and B) the naked person has an internal engine. There is still radiative transfer, though, between the snowman and the naked person.
  17. damorbel wrote: "Do you know that GHGs also radiate IR? The most common explanation for the GH effect is that this radiation causes the surface to get warmer somehow" So, you accept that GHGs absorb and then re-emit IR. Yet you insist that this re-emitted radiation can't possibly warm the planet. So... what exactly do you think happens to it? It somehow 'knows' the relative temperatures of the matter it was emitted from and the matter it is about to impact and 'changes course' to avoid any matter which is warmer than the previous? How do you imagine microwave ovens work? After all, as the food gets warmer the microwave photons can't possibly travel from the cool walls of the microwave to the warm food... they must be repulsed away from anything warmer. Therefor, a frozen dinner might be warmed up to room temperature, but a microwave oven could never make anything warmer than room temperature because the radiation can only travel into colder objects. Ditto sunlight, lasers, radio and television broadcasts, remote controls, and dozens of other aspects of everyday life. All of which demonstrate that your position is gibberish. Seriously. How can you not see that you are spouting completely ludicrous nonsense?
  18. damorbel wrote: "Now this soil, water, atmosphere etc. only emits radiation when it is above 0K, whereas it absorbs radiation regardless of its temperature." BTW... it should be pointed out that 0K has never been observed. It's a theoretical minimum. Nothing that cold is actually known to exist. Therefor your contrast between one thing which 'only' happens above 0K and another which happens regardless of temperature is really two things which happen regardless of temperature.
  19. @damorbel: "A diagram without any temperatures?" Yes. It's a diagram about energy flow. it serves its purpose, no matter how much *you* misunderstand it. "I am curious to know how you find a diagram without any temperatures on it AT ALL "serves a [useful] purpose" in this regard." Because it shows energy transfers. What's your problem with it, apart from the fact that you don't understand what it's used for? It seems that, like many deniers here, you are consciously trying to muddy the waters and create confusion about AGW science. Too bad (for you) the level of knowledge on this site is so high...
  20. h-j-m, well patience of both is tried. Your "evidence" and "counter-examples" simply revealed a flawed understanding of the physics. People have responded by trying to help you understand the physics.
  21. damorbel - continuing to talk about what happens and how the 2nd law works in conductive energy transfer is not helping you understand how it works in radiative energy transfer. People are trying to help you understand this. As a matter of interest what do understand the relationship of temperature to energy to be?
  22. Re #187 KR you wrote :- "IR at greenhouse frequencies gets absorbed and re-emitted within about 100 meters. That means the surface is facing an atmospheric IR emitter at 14C, not -50C. The -50C is reached through atmospheric lapse rate temperature drop, until the altitude where lowering pressure reduces IR absorption enough to radiate to space" To a considerable extent you are correct. On Earth the density of atmospheric GHGs is very low and low level absorption of IR is a very small % of the thermal input to the atmosphere. Much more atmospheric energy comes from the evaporation of water, water heated by the direct input of the Sun's radiation. The atmosphere is also heated by direct convection from the surface. Water evaporation becomes spectacular in hurricanes, violent air convection is the corresponding phenomenon over land, sometimes called tornados; neither extreme form is required for convection to take place. You then wrote:- "Now, realize that without the GHG absorption and emission at 14C we would instead be radiating those bands directly from the surface to space, which is (if you include microwave background radiation) at -269C?" Well? Is this going to change the average temperature? The answer depends on how thick the atmosphere is. Atmospheres are held in place by gravity, the effect of this is to make a temperature profile that increases (at the "lapse rate") with depth. Such an increase gets very high with the very deep atmospheres of planets like Jupiter; relly massive gas objects like stars reach nuclear fusion temperatures in their core, that is where their energy comes from. Earth has a surface pressure of 1 bar and its surface temperature is not much above the equilibrium temperature of 279K. Venus has a much higher surface pressure about 92bar and a surface temperature of 735K. You wrote:- "without the GHG absorption and emission at 14C we would instead be radiating those bands directly from the surface to space, which is (if you include microwave background radiation) at -269C? " Erm. no you wouldn't, you'd be in a warm bath of air at 14C, 1/2 surrounded by radiation from the ground at 14C; 1/2 from deep space at 2.7K. The thing that would finish you off would be the complete absence of H2O, you would be dead before you knew. With water and no CO2 you would only die of hunger because without CO2 nothing would grow, there would be no plant life.
  23. damorbel - And once more, you miss the point in several respects. You've been pointed to Trenberth 2009 several times. Convection and evaporation together represent only 1/4 the energy involved in IR from the ground. The backradiation at 333 W/m^2 is twice the energy of incoming sunlight. The greenhouse effect does not heat the Earth; it slows cooling, by providing a warmer background than outer space, reducing the ability of Earth to dump the energy from incoming sunlight. This is basic radiative energy balance - the Earth radiates to space with P = e*s*A*T^4, and when greenhouse gases decrease emissivity 'e', as per The greenhouse effect and the 2nd law of thermodynamics (intermediate), with an emission spectra like this: Notches in graph A show greenhouse gas bands, where IR is sent back to the ground, as seen in graph B then there is an energy imbalance (more coming in than going out), and the temperature will rise until 'P', the energy radiated to space, equals the sunlight coming in. At this point, damorbel, I'm coming to the conclusion that you are deliberately misunderstanding the point. You've ignored repeated pointers to the physics involved, and brought up multiple straw-man arguments. I don't believe it's worth debating with you unless you are willing to engage in an actual discussion of the science.
  24. Re #191 DSL you wrote :- "Warmer objects can indeed absorb radiation from cooler objects." Look at it this way. Emitted power is proportional to T^4, thus the warmer object emits most power. Both objects absorb power indpendent of temperature thus the warm object cools down and the cool one warms up, they are in thermal contact as if they were touching each other if the two objects are isolated they will slowly arrive at the same temperature, somewhere between the two original temperatures. Further you wrote:- "If you shine a steady UV light... ... once again reaches an "equilibrium" temp." Let us assume these balls are planets and the UV source is a star. Wavelength is unimportant. The balls will slowly approach a temperature dependent only on the distance of and the power emitted by your UV source. The temperature they reach is not dependent on how shiny they are, that only affects the rate they approach this 'equlibrium' temperature You wrote:- "Your snowman example is not good, because A) you're working primarily with conduction and convection and B) the naked person has an internal engine. There is still radiative transfer, though, between the snowman and the naked person." Temperature rules in all thermal tranfers, be it conduction radiation or convection. Convection is a bit special because it won't work 'downwards' but both radiation and conduction will tend to equalise the temperature in an isolated convective (e.g. gravitational) system. Radiative transfer is not influenced by gravity.
  25. Re #192 CBDunkerson you wrote :- "Warmer objects can indeed absorb radiation from cooler objectsYet you insist that this re-emitted radiation can't possibly warm the planet." If it is cooler than the planet, yes. Then you wrote :- "So... what exactly do you think happens to it? It somehow 'knows' the relative temperatures of the matter it was emitted from and the matter it is about to impact and 'changes course' to avoid any matter which is warmer than the previous?" In #200 I wrote:- "Look at it this way. Emitted power is proportional to T^4, thus the warmer object emits most power. Both objects absorb power indpendent of temperature thus the warm object cools down and the cool one warms up, they are in thermal contact as if they were touching each other if the two objects are isolated they will slowly arrive at the same temperature, somewhere between the two original temperatures." Which explains why the cold troposphere cannot raise the temperature of the Earth's surface. You wrote :- "How do you imagine microwave ovens work?" Read #189 3rd para. Microwaves are not 'thermal' like a grill; they have a magnetron inside wich makes single frequency (monochromatic) radiofrequency (RF) power at about 2450MHz, this power is absorbed by water molecules which get hot in consequence. This is quite different from a 'thermal' oven which uses thermal radiation to grill and hot air to bake. In #193 you wrote: "it should be pointed out that 0K has never been observed. It's a theoretical minimum. Nothing that cold is actually known to exist. Therefor your contrast between one thing which 'only' happens above 0K and another which happens regardless of temperature is really two things which happen regardless of temperature." Oh alright then, not 0K, lets put 0.00000000001K.

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