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Climate Hustle

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)

 

Skeptics sometimes claim that the explanation for global warming contradicts the second law of thermodynamics. But does it? To answer that, first, we need to know how global warming works. Then, we need to know what the second law of thermodynamics is, and how it applies to global warming. Global warming, in a nutshell, works like this:

The sun warms the Earth. The Earth and its atmosphere radiate heat away into space. They radiate most of the heat that is received from the sun, so the average temperature of the Earth stays more or less constant. Greenhouse gases trap some of the escaping heat closer to the Earth's surface, making it harder for it to shed that heat, so the Earth warms up in order to radiate the heat more effectively. So the greenhouse gases make the Earth warmer - like a blanket conserving body heat - and voila, you have global warming. See What is Global Warming and the Greenhouse Effect for a more detailed explanation.

The second law of thermodynamics has been stated in many ways. For us, Rudolf Clausius said it best:

"Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature."

So if you put something hot next to something cold, the hot thing won't get hotter, and the cold thing won't get colder. That's so obvious that it hardly needs a scientist to say it, we know this from our daily lives. If you put an ice-cube into your drink, the drink doesn't boil!

The skeptic tells us that, because the air, including the greenhouse gasses, is cooler than the surface of the Earth, it cannot warm the Earth. If it did, they say, that means heat would have to flow from cold to hot, in apparent violation of the second law of thermodynamics.

So have climate scientists made an elementary mistake? Of course not! The skeptic is ignoring the fact that the Earth is being warmed by the sun, which makes all the difference.

To see why, consider that blanket that keeps you warm. If your skin feels cold, wrapping yourself in a blanket can make you warmer. Why? Because your body is generating heat, and that heat is escaping from your body into the environment. When you wrap yourself in a blanket, the loss of heat is reduced, some is retained at the surface of your body, and you warm up. You get warmer because the heat that your body is generating cannot escape as fast as before.

If you put the blanket on a tailors dummy, which does not generate heat, it will have no effect. The dummy will not spontaneously get warmer. That's obvious too!

Is using a blanket an accurate model for global warming by greenhouse gases? Certainly there are differences in how the heat is created and lost, and our body can produce varying amounts of heat, unlike the near-constant heat we receive from the sun. But as far as the second law of thermodynamics goes, where we are only talking about the flow of heat, the comparison is good. The second law says nothing about how the heat is produced, only about how it flows between things.

To summarise: Heat from the sun warms the Earth, as heat from your body keeps you warm. The Earth loses heat to space, and your body loses heat to the environment. Greenhouse gases slow down the rate of heat-loss from the surface of the Earth, like a blanket that slows down the rate at which your body loses heat. The result is the same in both cases, the surface of the Earth, or of your body, gets warmer.

So global warming does not violate the second law of thermodynamics. And if someone tells you otherwise, just remember that you're a warm human being, and certainly nobody's dummy.

Basic rebuttal written by Tony Wildish


Update July 2015:

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial

 


Update October 2017:

Here is a walk-through explanation of the Greenhouse Effect for bunnies, by none other than Eli, over at Rabbit Run.

Last updated on 7 October 2017 by skeptickev. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Related Arguments

Further reading

  • Most textbooks on climate or atmospheric physics describe the greenhouse effect, and you can easily find these in a university library. Some examples include:
  • The Greenhouse Effect, part of a module on "Cycles of the Earth and Atmosphere" provided for teachers by the University Corporation for Atmospheric Research (UCAR).
  • What is the greenhouse effect?, part of a FAQ provided by the European Environment Agency.

References

Comments

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Comments 151 to 200 out of 1494:

  1. That spectral chart is a visual example of what I said - incoming solar energy is primarily in the form of visible & UV light.

    For your other question, about what makes greenhouse gases so special, you could read the 150 year old research report by Tyndall that I linked to earlier. I apologize for not relinking as this is being tapped out from my phone.
  2. Ah, h-j-m's point (I think) could be stated as follows

    Since GHG's absorb in the visible (as well as the infra-red), doesn't increasing the concentration mean that the earth receives less energy because the subsequent emission of that radiation scatters some of it into space - back radiation on incoming EM which thus goes into space.

    Assuming I've understood h-j-m's issue correctly let me offer the following rebutals

    1. Absorption of EM radiation, either visible incoming or IR outgoing does not result in all the radiation being emitted, some will be converted into vibrational, rotational and translational energy. Thus increasing absorption of visible incoming EM will, in certain extent warm the upper atmosphere as well as decrease slightly the EM hitting the surface.

    2. The areas of the incoming EM spectrum in which H2O (primarily) absorb are not near the peak of frequencies and are at the longer wavelength(lower energy) end. Thus they do not absorb proportional as much as the outgoing earth-light.

    3. The Greenhouse effect is measured empirically by comparing the temperature at the top of atmosphere with the ground. The commonly quoted 33deg is therefore the nett effect of IR absorption of Earthlight coming out - Visible absorption of Sunlight coming in. I seem to remember seeing 50deg as a figure for the 1st, but I'll be damned if I can remember where ...


    Thats quite a long response to a point that I may have misunderstood, and is getting increasingly off-topic for this particular thread... :-(
  3. Re #144 archiesteel You write:
    "To say they do is either to misunderstand the science, or to disingenuously misrepresent what climatologists believe."
    Lets look at Trenberth's diagram:-

    You write:-
    "The point is not that all of the absorbed photons will go back down. The photon re-emission by GHG molecules happens in a random direction."

    Trenberth's diagram shows 165Wm^2 going out from the atmosphere, 30Wm^2 from clouds 360Wm^2 going up from the ground and 324Wm^2 back radiation going down.

    The problem is both the back radiation and the ground radiation. First they are both greater than the input from the Sun, second they are not reflected by the ground or the clouds whereas the Sun's input is reflected by both the clouds and the ground. Third the Suns input is absorbed (67Wm^2) by the atmosphere, why isn't the '324Wm^2 back radiation' similarly absorbed?

    Since 'back radiation' is emitted by GHGs it does not have a short wave component like sunlight, so a bigger % of the 324Wm^2 is going to be reabsorbed by GHGs.

    All I was doing in my post #143 was drawing attention to Eli Rabbet's recognition that this IPCC diagram does not represent anything real.

    Using Eli's explanation there is no substantial downward radiation because the photons emitted by GHGs are largely absorbed locally and certainly never get to the ground at a level comparable to the Sun's input.

    Likewise Earth's 390Wm^2 surface emission cannot be well over double the 168Wm^2 arriving there from the Sun.

    The IPCC claims that the GHGs warm the surface by about 33C but there are no numbers on this diagram showing how this happens, even though the various places are shown emitting and absorbing radiation, there are no temperatures showing the basis for explaining the greenhouse effect. Is this the way we plan to change the World fuel economy?
  4. Composer99, the wikipedia diagram as well as a similar diagram (unfortunately only black and white) on the mentioned Science of Doom page show clearly that incoming radiation gets absorbed (by water vapour mostly). The Trenberth et al. diagram I have included in my post #50 shows ~ 20% of incoming energy absorbed by atmosphere. I doubt you could justify neglecting it. Nevertheless I completely failed to find any credible further information on that subject.

    The rest of your post urges me to some provocative questions.
    How does the earth measure the incoming radiation?
    How does the earth measure the outgoing radiation?
    How can it tell the difference?
    But if it can do this.
    Who told the earth that there should be a balance?
    How can he force the earth to respond?
    Consider these questions answered.
    How can the earth know what to do?
    Does the earth have the means to do what needs to be done?

    Sorry, somehow that sounds rather non scientific, but I could not help writing it anyway.
  5. Damorbel @ 153 - The problem is both the back radiation and the ground radiation. First they are both greater than the input from the Sun

    Well, yes both surface and back radiation occur night and day, whereas incoming solar radiation doesn't.
  6. damorbel - "... there is no substantial downward radiation because the photons emitted by GHGs are largely absorbed locally and certainly never get to the ground at a level comparable to the Sun's input."

    Nuh. Any molecule that can absorb radiation must, by definition, emit radiation. The fact that radiation is absorbed, emitted, absorbed again, emitted again multiple times within the atmosphere before striking the surface (again) or eventually escaping at TOA is what the "greenhouse effect" consists of.

    All this bouncing around is the evidence of energy staying in the system. When there are more GHGs in the atmosphere, more energy stays in the system longer.
  7. You are aware that backradiation etc is MEASURED? (Look for DLR stations). If your understanding mismatches experimental observations, then your understanding is wrong. As to balance - Planck radiation is the "balancing mechanism". First Law of thermodynamics - that you cant destroy energy - is why you have balance. If a body absorbs energy its temperature rises - temperature is expression of average molecular kinetic and potential energy in the body. It emits radiation in proportion to its temperature. When radiation outgoing matches incoming energy temperature stays constant. Its simple physical law, readily demonstrated a lab. A body "knows" what do in accordance Stefan-Boltzmann, derivable from QM theory - a moving charged particle must irradiate. Incoming and outgoing radiation are measured at TOA by atmosphere. There is problem with the measurements in they have good precision but poor accuracy.
  8. @damobel: the graph simplifies how the heat exchange mechanisms work. You can't look at such a graph and claim it is supposed to accurately represent the path of each photon.

    Others have explained this clearly. If you still can't understand it at this point, then one of two things must be true: a) this is beyond your intellectual capacity, or b) you're not debating in good faith. There are a lot of trolls and astroturfers here, please don't join their ranks and make a serious effort to read the material on this site before repeating the debunked junk peddled by professional climate deniers...
  9. Bibliovermis wrote: "That spectral chart is a visual example of what I said - incoming solar energy is primarily in the form of visible & UV light."
    So far so true if you define primarily to be more than 50%. But I would not dare to call 45% negligible. Further you stated that incoming solar radiation is not effected by green house gases but the chart clearly shows the opposite.
  10. Re #158 archiesteel you wrote@

    "the graph simplifies how the heat exchange mechanisms work. You can't look at such a graph and claim it is supposed to accurately represent the path of each photon."

    I take it you mean the diagram in #153? I am not arguing that there aren't better explanations for the GH effect but this diagram is what is used by the IPCC in its Assessment Reports and its Summaries for Policymakers. This is what is used by government agencies like the Met Office when they are advising on energy source policies.

    The diagram is a principle feature of the IPCC AGW science, it appears in volumes of the various IPCC Assessment Reports called "The Scientific Basis". In thess volumes it is stated that the GHE warms the surface (on average) from 255K to 288K i.e. 33K.

    If the diagram were improved it would show just how this 33K comes about. As it stands there are no temperatures at all reported on it, this should be possible using themal models of the atmosphere such as the US Standard Atmosphere (which does not recognise the GHE), then perhaps the arguments of the IPCC will become more clear.
  11. Phil, first you say as Bibliovermis did, that incoming solar radiation is not effected by green house gases.

    Now you state otherwise, but now you claim that the effect on outgoing radiation is greater though you don't say how much as well as to provide any evidence.

    OK, again that leaves all the work for me.
    Then I will try evaluate the effects. If I am not mistaken then usually differences between TOA and the earth surface are taken as a measurement of the green house effect. Seems quite reasonable, let me try. I suppose all can agree that I use the numbers provided by the Trenberth et al. diagram I have included in my post #50.

    It says incoming at TOA 341, reflected 102 and absorbed at surface 161. As the reflected part is not affected by the green house effect it has to be taken out (subtracted from the TOA value) which leaves us with an effective TOA value of 239.
    So the relation is 239 / 161 = 1.48

    Now we have surface radiation 396 Radiation leaving the atmosphere is at 239. Here the relation is 396 / 239 = 1.65.

    So, yes you are right, the green house house effect is stronger on outgoing radiation though I hardly assume the magnitude of the difference satisfied your strong wording.

    As to your comment about this being rather off topic I have to disagree for the reason that the whole argument of the lead article rests on the green house effect. So any discussion on this is quite on topic.
  12. Concerning my post #148:
    Seemingly no one contradicted my postulations concerning the behaviour of gases. So I can surely say that the emitting of radiation as a result of absorbing energy can be attributed to all gases. This of cause leaves the green house gases off the hook when subjects like back-radiation are concerned, as it should be clear that the whole atmosphere plays a part in that game.

    That of cause, as Bibliovermis has correctly pointed out when he referred to Tyndall, points to the green house gasses speciality being able to trap (meaning store) heat and this way delay its further transmission. But considering this the most significant data with respect to global warming should be the specific thermal capacity of green house gases and I wonder why I can not recall it being mentioned.

    Someone willing to offer further information on this?
  13. h-j-m
    "Seemingly no one contradicted my postulations concerning the behaviour of gases. So I can surely say that the emitting of radiation as a result of absorbing energy can be attributed to all gases"
    I can see one more possibility, people gave up trying to explain if you don't even bother to check this two century old physics.
  14. #162: "So I can surely say that the emitting of radiation as a result of absorbing energy can be attributed to all gases."

    You can say whatever you like; whether what you say is correct or not might matter to some. Look at these lecture notes for some further basics, including a model of how gas molecules absorb energy.
  15. #160: "If the diagram were improved it would show just how this 33K comes about."

    That would be called reinventing the wheel. Look here, particularly the paragraph beginning "If an ideal thermally conductive blackbody was the same distance from the Sun as the Earth,"
  16. @damorbel: the graph serves its purpose. It is not misleading to anyone with any kind of base scientific knowledge.

    I'm sorry, but it really sound as if you're grasping at straws, here. The greenhouse effect is real, a fact the majority of climate change skeptics recognize.

    Heck, I even had skeptics here assure me that "no one disputes the greenhouse effect"...yet it seems that this is exactly what you're (unsuccessfully) attempting here. Is this really a wise tactic on your part?
  17. RE#148 h-j-m.

    Drawing on these texts [**] I’m going to attempt to answer this question:
    Why is CO2 a greenhouse gas?

    Introduction...
    Gas molecules whether they be CO2, N2, O2, CH4, CO, H2, He, Ar etc will all interact with light at specific frequencies.

    So for example if a single photon is absorbed by one of these gas molecules the absorption or emission of a photon will be accompanied by a change in the internal energy state of the molecule. This is a consequence of Quantum Mechanics that a molecule can only take on values drawn from a finite set of possible energy states. The distribution of which is determined by the structure of the molecule.

    The energy states involved in infrared absorption and emission are connected with displacement
    of the nuclei in the molecule, and take the form of vibrations or rotations.

    So how does the number of atoms in a molecule and its geometry effect this?

    The noble gases like He, and Ar are have one atom (monatomic) and have only electron transitions, so are not active in the infrared. And indeed QM calculations and lab experiments verify this.


    A molecule with two atoms (a diatomic molecule) eg CO, O2, N2 amongst others has a set of energy levels associated with the oscillation caused by pulling the nuclei apart and allowing them to spring back and forth.

    Now triatomic molecules (like CO2 or H2O) have an even richer set of vibrations and rotations, especially if their equilibrium state is bent rather than linear.

    What specifically then, makes one type of gas molecule more infrared active than another...

    For a molecule to be a good infrared absorber and emitter, it is not enough that it have transitions whose energy corresponds to the infrared spectrum. In order for a photon to be absorbed or emitted, the associated molecular motions must also couple strongly to the electromagnetic field.

    You can classically think of the infrared light as providing a large scale fluctuating electromagnetic field which alters the environment in which the molecule finds itself in, and, exerts a force on the constituent parts of the molecule. This force displaces the nuclei and electron cloud, and excites vibration or rotation.

    The strongest interaction that will happen between an electromagnetic field and a particle is one where the particle has a net charge. A charged particle will experience a net force when subjected to an electric field, which will cause the particle to accelerate.

    In relation to Earth's atmosphere...

    Ions are extremely rare in the atmosphere. Thus molecules involved in determining a planet’s energy balance are almost invariably electrically neutral.

    So where does this leave us?

    Ok we have now elimated charged particles…so what’s the next best physical property of a molecule that will make it a strong infrared active one?

    Why molecules that have a dipole moment!
    (This is when we have a disproportionate part of a molecule’s negatively charged electron cloud bunched up on one side, while a compensating excess of positive charged nuclei are at the other side.)

    Does our atmosphere have a molecule that fits this criteria?

    Yes! Good old CO2!

    CO2 is a linear molecule with the two oxygens symmetrically lying about the central
    carbon. Whilst a uniform stretch of such a molecule does not create a dipole moment, a vibrational mode which displaces the central atom from one side to the other does.

    Addionally, the bending modes of CO2 have a fluctuating dipole moment, which can in turn be further influenced by rotation. Modes of this sort make CO2 a very good greenhouse gas.

    Here you might ask, but the atmosphere is full of O2 and N2 and there is only ppm concentrations of CO2?

    Many common atmospheric molecules have no dipole moment in their unperturbed equilibrium state. Such nonpolar molecules can nonetheless couple strongly to the electromagnetic field. They do so because vibration and rotation can lead to a dipole moment through distortion of the equilibrium positions of the electron cloud and the nucleii. Diatomic molecules made of two identical atoms, do not acquire a dipole moment under the action of either rotation or stretching. Symmetric diatomic molecules, such as N2, O2 and H2 in fact have plenty of rotational and vibrational transitions that are in the infrared range. However, because the associated molecular distortions have no dipole moment, these gases are essentially transparent to infrared unless they are strongly perturbed by frequent collisions. This is why N2 and O2, the most common gases in Earth’s atmosphere do not contribute to Earth’s greenhouse effect.

    However, it is important to recognize that situations exist in which diatomic molecules become good greenhouse gases are in fact quite common in planetary atmospheres. When there are frequent collisions, such as on planets with high density atmospheres like Titan and on all the giant planets, diatomic molecules will acquire enough of a dipole moment during the time collisions that are taking place ,and the electromagnetic field can indeed interact with their transitions quite strongly. This makes N2 and H2 the most important greenhouse gases on Titan, and H2 a very important greenhouse gas on all the gas giant planets.

    I don't think I even scratched the surface, but hooray for physics!

    [**]

    Principles of Planetary Climate, R. T. Pierrehumbert

    Molecular Quantum Mechanics P. W. Atkins (Author), R. S. Friedman

    An Introduction to Statistical Thermodynamics. T. Hill
  18. Wow, yocta, that was the best explanation I've ever read! Thanks!
  19. addendum to yocta @167

    Its also true that the asymmetric isotopic variants of O2 and N2 absorb ever-so slightly in the IR: N14-N15 for example. This is because the stretching vibration becomes ever so slightly asymmetric because of the differing weights of the two nuclei. Because the dipole moment change is so small, and the proportion of isotopes so small, and the frequencies at which these vibrations occur is outside the range of "earthlight" their contribution to the GHE is effectively zero. Nevertheless there was one contributor to this site trying to argue the case a few months back :-(
  20. "Wow, yocta" Double-plus good job! Here are some illustrations of the CO2 molecule's vibrational modes.
  21. h-j-m @161

    Your calculations are not correct because they assume that scattering of incoming UV-visible EM and outgoing IR are done by the same molecules in the atmosphere. The largest contributor to scattering UV-visible light is, in fact, Ozone (O3) which is contributing a substantial proportion of your 1.48 figure. You are, in effect, comparing apples with oranges.
  22. yocta, in my post #148 my question was "what specifically makes green house gases so special".

    Which means:

    What effects do green house gases produce that other gases don't?

    I am sorry and apologize if my initial phrasing led to any misunderstanding.

    When you state at the beginning of your post you are going to answer the question "Why is CO2 a greenhouse gas?" clearly indicates some sort of misunderstanding must have taken place.
  23. Phil, my calculations assume nothing except what I wrote they assume which is 1. the assumption that differences between TOA and surface provide a measurement for the green house effect and
    2. that the numbers from Trenberth's diagram are reliably correct.

    Following your argument the first assumption should be incorrect but then I am the wrong man to point your critique at.
  24. h-j-m, greenhouse gases absorb 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.
  25. h-j-m @173

    Your original point was, as I paraphrased at @152:
    Since GHG's absorb in the visible (as well as the infra-red), doesn't increasing the concentration mean that the earth receives less energy because the subsequent emission of that radiation scatters some of it into space - back radiation on incoming EM which thus goes into space.

    To answer to this in @161 you derived two numbers that measured the total visible absorption by the atmosphere of incoming EM by all gases in the atmosphere and the absorption of outgoing IR radiation by only GHGs. Since the numbers the first number was slightly smaller than the first, you then concluded that the magnitude of the difference was small:

    [Quote from @161]
    So, yes you are right, the green house house effect is stronger on outgoing radiation though I hardly assume the magnitude of the difference satisfied your strong wording.

    But the "magnitude of the difference" is not valid because you are not comparing like for like.
  26. 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.
  27. Just an afterthought. My explanation will no way predict a tropospheric hot spot so you can cease looking for it.
  28. 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)
  29. 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
  30. 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.
  31. 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?
  32. 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.
  33. 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.
  34. #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.
  35. 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.
  36. 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!
  37. 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.
  38. 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.
  39. 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.
  40. 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.
  41. "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.
  42. 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?
  43. 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.
  44. @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...
  45. 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.
  46. 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?
  47. 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.
  48. 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.
  49. 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.
  50. 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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