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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 751 to 775 out of 882:

  1. For myself, Tom, I kinda like your box idea. It could be called a path lengthening device, increasing the number of photons in the system at a given time. Time is often the missing idea when considering GH effect. At equilibrium, energy in and energy out at TOA are equal. Increase IR opacity and energy out at TOA becomes less than in, until the surface temp increases to radiate enough out through the increased opacity. There is no violation of thermodynamics at all.
  2. damorbel - I didnt describe any experiment. I proposed that an experiment be designed such that normal understanding of physics and your understanding would calculate a different result. This is normal way to test scientific arguments. I asked if the experiment didn't go your way, whether you would be prepared to abandon your view and read the textbook. (ie, behave like a scientist). Got a yes/no? In fact, have you got an experiment that you think validates your views over mainstream physics?
  3. CBDunkerson750 You said: "In that both cause an area to be warmer due to redirected electromagnetic energy it isn't a matter of belief, but rather observed reality." Focusing a large radiative input to a specific point is NOT what proponents argue. Redirecting radiation is not a point of contention. What is disputed...a cold atmosphere warms the warmer earth. Google solar cooker. The principal works by redirecting radiation, (from a large area) to a small focal area. When facing the sun, the focal area (the small area) gets hot. When facing away from the sun the focal area (small area) gets cold. How can this be? Maybe you should understand what you proclaim to know.
  4. What is disputed...a cold atmosphere warms the warmer earth. No-one believes the cold atmosphere warms the warmer earth. The Greenhouse effect slows the rate at which heat escapes from the earth. Period.
  5. Just to make one thing clear. Photons from a 'hot' (5780K) source like the Sun can be refocussed at any distance (if the mirror is big enough) to recreate the surface temperature (5780K) of the source, but no higher. No amount of refocussing etc., etc., of photons from a cold (255K) source, like the upper troposphere, can produce a temperature higher than 255K... anywhere. It's the photons you see, they don't have enough energy. They may have all the power (W/m^2) you can imagine* but no amount of refocussing, adding together, accummulating in reflecting cavities etc., etc. will raise their energy. Or, in other words, increase the temperature of.... anything. That is what the 2nd law is all about. It why quantum theory holds sway. And why the 'GH' effect is not a radiation effect... from... GH gases. * Power is not energy. Power is W(atts); energy is J(oules). A surface emitting power has two options it can emit relatively few 'hot' photons to get power 'P'. Or it can emit a large number of low energy photons to get the same power 'P'. There is a lot of grief on this thread cause by contributors not distinguishing between power balance and energy balance by defining both as 'W/m^2', that is a mistake.
  6. Ryan I have read the entire thread, in case you've missed the numerous references to comments from November and December. You apparently have also missed the point about 'at the same frequency'; IR photons have considerably less energy than visible light photons. CBD's point here is quite valid, with or without the parabolic geometry (which is a mere artifact of your solar cooker analogy). You've not proved anything with it, except how much you are willing to argue for the sake of argument.
  7. Re #756 muoncounter That's exactly what #755 explains. In #750 CBD writes :- "In that both cause an area to be warmer due to redirected electromagnetic energy it isn't a matter of belief, but rather observed reality." No amount of redirecting, refocussing adding together etc.,etc., of photons can increase their energy: warmer the Earth's surface may well be but it is not a radiation effect*. *It is actually a gravity effect.
  8. CBDunkerson750 You said: "In that both cause an area to be warmer due to redirected electromagnetic energy it isn't a matter of belief, but rather observed reality." Focusing a large radiative input to a specific point is NOT what proponents argue. Redirecting radiation is not a point of contention. I say cold atmosphere radiation can not shorten terrestrial radiation, GHG proponents say otherwise. Google solar cooker. The principal works by redirecting and focusing, from a large hot area, radiation to a small target area. When facing the sun (hot),the focal area (the small area) gets very hot. When facing away from the sun (the cold atmosphere) the focal area (small area) gets cold. So the small target area looses energy via the large area to the cold atmosphere. See this process (unlike the magic box) abides the 2nd law, Hot to Cold. The atmospheric LW does NOT accumulate within the target area. The target area looses energy to the radiating atmosphere. GHG physics concludes conversely.
  9. mods - I really do think that damorbel, and particularly 755 & 757 violates the comments policy. Although not exactly an ad hominem attack, it is an attack on the work of many, many physicists through the ages. On behalf of those upon who's shoulders most of us stand - bun on who's feet damorbel seems to be stepping, I pray you, make it stop!
  10. Ugh, LJ -- not the alleged solar cooker evidence. It is proof of nothing. The reflective surface focuses incoming radiation. That radiation could be coming from the atmosphere. Your argument is that we can't differentiate between radiative transfer and conduction/convective transfer. In other words, why doesn't the solar cooker cool to near absolute zero when pointed at the open night sky? Something must be heating it. (expected response) Ok, then put it in a clear vacuum box and point it at the night sky. With no internal heat source, and no way to receive energy (according to your physical model), it should cool down at its rate of emission (and internal conduction) until it reaches near absolute zero. I'll wager that it won't, though. I'll wager that it cools more slowly, because even if we warmed it up to 50C before we put it in the box it's still receiving infrared radiation from the atmosphere. Photons can't choose their paths.
  11. Re #760 DSL you wrote:- "Ok, then put it in a clear vacuum box and point it at the night sky. With no internal heat source, and no way to receive energy (according to your physical model), it should cool down at its rate of emission (and internal conduction) until it reaches near absolute zero" There is a comparable effect known as 'clear sky' frost; the condition when surface frost appears e.g. on car windshields, even when the air teperature is not below freezing. In this situation radiation through the intervention of GHGs is exchanged with the higher levels of the troposphere which are below freezing. Some of the xchange might well be with deep space, but only a small part; which of course cannot easily be separated out.
  12. #754. Thanks Phil Glad that everyone's agreed on that one!
  13. damorbel@761 "In this situation radiation through the intervention of GHGs is exchanged with the higher levels of the troposphere which are below freezing. Some of the xchange might well be with deep space, but only a small part; which of course cannot easily be separated out." Would you please expand on this using some science? I can not make sense of what you are trying to explain.
  14. Damorbel - still havent got a yes/no to #752. Are you prepared to have nature be the arbitrator?
  15. Phil 754 "No-one believes the cold atmosphere warms the warmer earth. The Greenhouse effect slows the rate at which heat escapes from the earth. Period. " Earths blackbody temperature is 255K. This represents the theoretical maximum attainable temperature via the suns radiation. Kirchhoff's cavity experiment and subsequent law and Planks law were both derived by this pressies. So regardless of re-radiation and reflection, the atmosphere can NOT warm the warmer Earth...Period. Yet GHG proponents claim slowing the rate at which heat escapes the 255K earth some how warms the earth surface to 288K. So Phil, how does a body at 255K which is loosing heat increase it's temperature simply by slowing it's cooling....remember blackbody temperature is the theoretical maximum temp.
  16. damorbel Your lecture over the distinction between watts and Joules explains nothing; if I shine a 100 watt light bulb on your lecture notes, each second requires 100 Joules of electrical energy. If that energy is constrained from leaving the immediate environment by whatever means, the environment, including your lecture, heats up. If I direct a 125 milliWatt laser pointer on the wick of a candle in the vicinity of those notes, I can quickly set them aflame. Those applications are radiation effects. Your gravitational heating was ably dismissed on a number of occasions; the most recent by Tom C. No one is buying this brand of soap today.
  17. LJ Ryan: "regardless of re-radiation and reflection, the atmosphere can NOT warm the warmer Earth...Period." So the world you live in has an average temperature of -18C? How's that working out? Or did you forget that the blackbody 'theoretical maximum' you cling to refers to an object in equilibrium? Do you suggest that is the case for the earth? If so, do you not recall that we have an atmosphere, which traps energy that would otherwise escape? Even died-in-the-wool deniers accept that much. It is tedious to hear these repetitious 'objections' to basic physics that should be well-understood by now. Read and learn, my friend. If nothing else, the quality of your questions will improve.
  18. Tedious indeed. If you got past the idea that the atmosphere is warming the planet and bothered to learn how the GHE effects, then you would get some progress. Remember nature is the atmosphere. Your version of physics doesnt account for the observed world. The textbook version does. Is that a hint?
  19. damorbel (RE: 755), "And why the 'GH' effect is not a radiation effect... from... GH gases." OK, then what is the primary mechanism for the greenhouse effect? "No amount of refocussing etc., etc., of photons from a cold (255K) source, like the upper troposphere, can produce a temperature higher than 255K... anywhere. It's the photons you see, they don't have enough energy. They may have all the power (W/m^2) you can imagine* but no amount of refocussing, adding together, accummulating in reflecting cavities etc., etc. will raise their energy. Or, in other words, increase the temperature of.... anything. That is what the 2nd law is all about." Not really. The second law primarily states that heat can only flow from warm to cold - not the other way around. The atmosphere is largely transparent to the energy coming in from the Sun. The bottom line is the rate the incoming energy can leave the system from the surface is slower than the rate it is coming into the surface. The effect in principle is not much different than the interior of a car heating up inside on cold day from sitting out in the Sun. The Sun's energy is mostly transparent through the windows. It's then absorbed and re-radiated by the interior car components. The rate at which the energy is entering the interior is faster than the rate the re-radiated energy can leave the interior; therefore, the interior has to heat up. Ultimately, when the rate of energy entering something is faster than rate it can leave, the something has to heat up. That's the GHE.
  20. L.J. Ryan - "Earths blackbody temperature is 255K. This represents the theoretical maximum attainable temperature via the suns radiation." To be succinct - Bull - a completely unsupported statement. The surface of the Earth radiates at a temperature of 14C, or 287.15K, with an overall emissivity of 0.98. Upper layers of the troposphere (due to lapse rate) radiate at much higher altitudes, colder temperatures, rendering the planetary emissivity at ~0.612, regulating the amount of energy radiated at any temperature, and driving the surface temperature to the aforementioned 14C. Please - read some physics, get a clue. --- Folks, L.J.Ryan has shown either a complete lack of physics understanding, or a deliberate set of obfuscations. None of his objections has made sense. Damorbel is (in my opinion) a complete troll - he hasn't defended a single assertion, but keeps raising red herrings whenever pinned down, as he has done for over 4 months on this thread. He is now (as others have noted) circling back to previous disproved notions from several months ago, presented as fresh to people who have joined the thread. We are being trolled - do not feed the trolls. Moderators, John Cook - I'll join with previous posters; this cycle of denial and red herrings has gone on long enough. Are there any options in this regard? Perhaps deleting postings repeating junk from months ago? For some reason this particular thread attracts people who think that they either understand thermodynamics better than the previous 150 years of physicists, or perhaps feel that deliberate obfuscation and "common sense" arguments will draw out the discussion. 16 pages, >770 posts, with every skeptic argument repeated multiple times. Gah...
    Response:

    [DB] "We are being trolled - do not feed the trolls."

    I will join you out on that limb.  Short of a comment directly violating the Comments Policy, what we can do is this: Merely repeating a previously expressed position without adding anything new is indeed grounds for moderation.  So if anyone notices a comment being lifted from a previous one without anything new being added, bring it to the Moderator's attention. 

    700+ posts is a lot; the Mods are human & can't be expected to remember each and every post.  So help each other out:

    1. DNFTT (no matter how much you want to, Do Not Engage)
    2. Be on the watch for recycled comments by those obviously clogging up the threads
    3. Let the Mods know when you see those recycled comments

    Trolls live for attention & generating controversy; deny them the pleasure.  Those that abuse the priviledge of participating in this community may lose that priviledge.

    Thanks for your time.

  21. KR, John Cook, Tom Curtis Please explain why, seriously, why Kirchhoff's cavity experiment does not represent the theoretical BB maximum temp. I realize it doesn't explain the 33K delta but why is wrong? Maybe your superior physics can explain how BB maximums should be determined. Don't insult me or say I'm wrong without explanation of what is wrong.
  22. "how does a body at 255K which is loosing heat increase it's temperature simply by slowing it's cooling....remember blackbody temperature is the theoretical maximum temp." Considering that the body in question is continuously receiving energy at a more or less constant rate, it does not seem so difficult to imagine that its temperature will increase if the rate at which it can radiate that energy is decreased. In fact, I would have a hard time to understand if it did not warm up under these conditions.
  23. L.J. Ryan - Blackbody temperature is important as a theoretic limit. However, the Earth in the real universe is not a blackbody. The Stefan-Boltzmann relationship holds for the Earth, and the power radiated to space (which must match power coming in for dynamic equilibrium) is determined by both the temperature and the emissivity of the planet. Any body that is not a blackbody (with an emissivity < 1.0) must have a higher temperature to radiate the same power as that blackbody. The blackbody is the theoretic best case; everything else is less efficient. With an effective (surface to space) emissivity of 0.612, including clouds, GHG's, tropospheric effects, lapse rates, etc., a surface temp of ~287 radiates ~239 W/m^2 to space, almost equal to the sunlight coming in. The difference of 0.9 W/m^2 is the forcing, heating the climate and moving back towards dynamic equilibrium. So - you are incorrect because the Earth is not a blackbody. It has a limited emissivity to space, and the resulting temperature needed to radiate 240 W/m^2 is around 14-15C.
  24. L.J. Ryan - From your reference: "That a perfectly absorptive ("black") body rises to a temperature a bit higher than an actual black body that’s free to radiate to its surroundings. A theoretical blackbody thereby defines the upper limit of temperature vs radiant absorption." And there is the error. The Earth is not a black body, but is a "gray body" with ~60% the emissive efficiency of a black body. And hence a higher temperature than a perfectly efficient black body radiator. Your reference is in quite serious error to argue against the greenhouse effect in these terms - it's a rather horrid miscasting of the situation. It's only an upper limit for a black body - anything with a lower emissivity will by necessity have a higher temperature for the same power output. I would not trust that source, given the example you presented.
  25. Sorry to break this into multiple posts - it's late and I'm tired. L.J. Ryan - Incoming energy is set by spectral absorptivity, albedo, and the spectra of the sun in visible light. Greenhouse gases have little effect on that - the most important elements there are ozone absorption and Rayleigh scattering. Given a fixed input energy, the black body temperature represents a minimum temperature for the radiating gray body, the Earth. Any lowering of emissivity (such as increasing greenhouse gases) must be balanced by an increase in temperature above that of the black body case to match input power.

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