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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)

 

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

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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 1001 to 1025 out of 1393:

  1. Fred, congratulations on post No. 1000 - although it may as well be 1000 mod 1. No amount of the written word, nor bean counting, can substitute for some good solid physics. No one has yet given the equations which demonstrates that the introduction of a some particular gas, when placed between two radiating bodies at different temperatures, can cause the 2nd law of thermodynamic to brake down. On the other hand, we have perfectly good illustrative physics models of the target system showing the 2nd law in good shape. Equally we have perfectly good physics models showing how the above arrangement of certain gases can reduce the rate of cooling of body at the lower temperatures. Thus far, the thesis of this blog post holds good. IMHO 1001 posts is more than adequate to establish that!
  2. Fred> The most fundamental point is that you cannot consider the out and back long wave energy transfers in isolation. Tom @ 995 demonstrated the entropy calculations including surface radiation, back radiation, and radiation to space. Entropy was indeed reduced, therefore the 2nd law is not violated. Do you have some actual math to match your bare assertions?
  3. Fred >As to the “higher is colder” mechanism, 978,it has nothing to do with back-radiation ... If increasing CO2 concentration elevates the emission point (for the sake of the argument) outgoing radiation will be reduced. Since the temperature of the surface and troposphere isn't reduced with this mechanism, the total amount of energy radiated must be the same (per Stefan-Boltzmann). If the total energy radiated stays the same, but the amount radiating upwards from the atmosphere into space is reduced, what do you think happens to the energy that used to radiate upwards? If it's no longer radiating upwards, in what other directions do you suppose it's going?
  4. Tom Curtis 998 I don't agree with your simplified Entropy calculations/equations. However, more problematic is your “equilibrium” condition from which you start. That is, prior to radiating 480W/m^2 the earth is limited by SW input. It is how temperature is increased beyond the solar input which is at question. As I was trying to explain with my Teqreference, 240 W/m^2 SW absorbed by the earths surface results in surface radiation of 240 W/m^2 LW. Because the atmosphere in your example is a blackbody, all 240 W/m^2 of terrestrial radiation is absorbed...atmosphere flux 240W/m^2 equates to 255K. Now as you said, “ with an atmosphere at 255 K, it will radiate 240 w/m^2 to space and 240 w/m^2 towards the surface. It follows that there is no violation of conservation of energy, and I did not double count.” Ok Tom, if you didn’t double count, and the system is in equilibrium, then back radiation is not physical. GHG physics can not have it both ways either: 1) the simple slab model atmosphere absorbs all terrestrial radiation and is therefore the overall system is at equilibrium when terrestrial emission reaches 240 W/m^2 OR 2) the simple slab model atmosphere transmits half the terrestrial emissions and absorbs half. The slab then re-radiates up and down...surface temperature increases until total outgoing radiation is equal to 240 W/m^2...surface temp 255K.
  5. e 999 You said: “Nothing is changing if input and output are the same. Using your terms, you are looking for the point in time when AU = I.” See 1004. You said: “These two models are describing the system in very different ways, and cannot be mixed and matched in the simple fashion you are attempting.” Maybe, but only to the detriment of the GHG physics. The slab model only works with ε= 1, ok then what good is the model? If effective emissivity is not demonstrable then what good is it? If ee is only to be plugged Stefan-Boltzmann law, it is only conjecture. As I mentioned to KR, a semi- transparent filter with ε=.612 will not function GHG physics proclaims. That is, will 240 W/m^2 incident on filter with ε=.612 will increase the incident to 390 W/m2 while radiating 240 W/m^2 originally incident...NO.
  6. LJRyan @1005: you are now circling back over ground we have already covered. Specifically, you are assuming that Atmdn is not absorbed by the surface. If it were absorbed by the surface, then at equilibrium (when Atmup= S = 240 Watts/m^2), Surf = S plus Atmdn = 240 + 240 Watts/m^2 = 480 Watts/m^2. It follows that you have conservation of energy at equilibrium and, as shown a net gain in entropy. Only by ignoring Atmdn, or assuming that it is not absorbed by the surface can you escape this conclusion. However, rather than fruitlessly attack this point directly, and just rehashing old ground, I ask that you answer the following questions (and some follow ons) and we'll see if we cannot get a better understanding obliquely: Imagine you have to plates, both having an emissivity of 0 on the backside, and on the edges, but having an emissivity of 1 on the front side. The first plate (plate A) has a surface area with emissivity 1 of 1 square meter, while the second plate has a surface area with emissivity 1 of 2 square meters. Both plates are perfectly conductive, except for a high resistance wire (heating element) embedded in the plate. A 480 Watt current is fed through the heating element. Assuming no losses due to resistance outside of the heating element: 1) What will be the temperature of the two plates? 2) Is there any contradiction of the laws of thermodynamics in this arrangement?
  7. Tom Curtis 1006 1) Assuming the constraints as outlined, the temperature for both plates is solely based on heating element. Your heating element description is a bit muddled. That is, power = current^2 x resistance...so "480 W current" is a bit confusing. Does the wire run the entire length of each plate? Or is the element the same for both, only the plate dimensions different. Going with the identical heating element scenario, and assuming plate surroundings are of lower temp then plates both plates radiate 480W/m^2...303K. 2) No violation, other then the fantastic assumptions. You said: "Specifically, you are assuming that Atmdn is not absorbed by the surface. If it were absorbed by the surface, then at equilibrium (when Atmup= S = 240 Watts/m^2), Surf = S plus Atmdn = 240 + 240 Watts/m^2 = 480 Watts/m^2." Then what would stop the surface from absorbing the next cycle of re-radiation and increase emissions further? Why does it stop at 480 and not 720 or 960 etc.? You said: "It follows that you have conservation of energy at equilibrium and, as shown a net gain in entropy. Only by ignoring Atmdn, or assuming that it is not absorbed by the surface can you escape this conclusion." But Tom, back radiation need not be absorbed for equilibrium. Nor for entropy to increase. As I demonstrated in 1004, system equilibrium is reached without back radiation. Let me try a different approach, do you agree with Idealized greenhouse model?
  8. LJRyan @1007, I apologize for my description being confusing. Just to make sure we are on the same page: The plates are perfect thermal conductors, so therefore position and length of the heating elements is irrelevant; The heating elements are such that, plugged into mains power, each draws 480 Watts of power, and with no losses else where, ie, each receives 480 Watts heating (and please note, that is 480 Watts, not 480 Watts/meter^2). Given these clarifications, does your answer change, and if yes, to what? You asked why Surface radiation stops at 480 rather than a higher value. The simple answer is that if Surface radiation goes above 2*S, or AtmUp, or AtmDn goes above S, then the system losses more energy than it gains, and therefore cools. The easiest way to see this is with the spread sheet models discussed some 400 posts backs. Rather than try to find that discussion again, I have done up another spread sheet. Column A is the Step; Column B is S (energy in); Column C is Surf; Column D is AtmUp (energy out); and Column E is AtmDn (recirculated energy). Row three contains the initial values, which for S(Column B) is always 240 in three "experiments" that I conducted. In my three experiments, the initial value for Surf (Column C) was 0 for the first two experiments, and 1000 for the third. The initial values of AtmUp and AtmDn (Columns D and E) where 0 for the first and third experiments, and 500 for the second. The formulas for each of steps 2 to 100 where: In column B: =the value in column B for step minus 1 (=B3) In column C: = the value for column B and the value for column E for step minus 1 (=B3+E3) In column D: = (the value in column C in step minus 1)/2 (=C3/2) In column E: = the value in column D in the current step (=D5) The values in brackets are the actual formulas from my spread sheet for row 4 (the second step). The results for each of the three experiments above on step 60: Column A (Step) : 60 Column B (S) : 240 Column C (Surf) : 480 Column D (AtmUp): 240 Column E (AtmDn): 240 So, regardless of the initial conditions of the Surface or Atmosphere, in this model after a short number of steps the outgoing energy will equal the back radiation will equal the incoming energy; and the surface radiation will equal 2 times the incoming energy. You said equilibrium will be reached without back radiation being absorbed. Well, first note that in this model there must be back radiation because the "atmosphere" has an emissivity of 1 in IR wavelengths. Second, the back radiation must be absorbed because the surface has a blackbody. But even if the surface has an emissivity of less than 1 in the IR spectrum, the radiation from the surface to the atmosphere will be equal to the incoming solar radiation plus emissivity times the back radiation plus (1-emissivity) times the back radiation. That is, the radiation from the surface will equal the solar radiation plus the absorbed back radiation plus the reflected back radiation, which is to say the equilibrium point will be identical, although we may wish to relabel some components of the model. Of course, this result obtains only so long as the emissivity of the surface is not so low that the spectrum of its radiation is not forced into the range of the spectrum to which the atmosphere is transparent. Also obviously, the surface temperature will be higher with emissivity < 1. With respect to the idealized greenhouse model it is the next step in complexity of atmospheric models from a simple grey slab model. It is still inaccurate as a representation of reality, but useful for exploring concepts. I have not yet checked the maths on the Wiki page, and will comment on it as need in the discussion.
  9. Re #998 Tom Curtis you wrote:- "Because thermal radiation is the same in all directions" At the molecular level - yes. But the atmosphere is denser at lower levels so there are more molecules emitting. Also the lower levels are warmer so they emit more intensely. This should not be a surprise since it corresponds with the visible part of the spectrum, there is a net output of radiation, it is the reason why stars shine. Further you wrote:- "if the atmosphere were 303 K, then it would radiate 480 w/m^2 up, and the same down. That would violate conservation of energy." If you accept that the exchange of energy between layers of the atmosphere can be characterised in W/m^2 then "480 w/m^2 up, and the same down" merely makes the case for constant density and temperature. These conditions do not exist in the atmosphere so it makes for a rather pointless discussion. There is no point in arguing about 'violation of conservation of energy' unless you account for all energy, assuming constant density (or temperature) in a gravitationally bound system automatically excludes 'conservation of energy'.
  10. Damorbel @1009: Yes, the radiation up is less than the radiation down from the atmosphere because the atmosphere is thicker and warmer closer to the Earth than near the tropopause. But we are discussing an idealized system kept deliberately simple for clarity of discussion. Use of such simplified models is standard in physics, whether it be with gravitational equations from point masses, or the use of frictionless surfaces. There is no principled objection to using such simplified models, and in the simplified model, AtmUp = AtmDn. It follows that your point is a mere distraction rather than a contribution.
  11. Re #1010 Tom Curtis you wrote:- "But we are discussing an idealized system kept deliberately simple for clarity of discussion." Surely that is the whole point? That is why I offered the constant temperature/density by way of comparison. Simplified models are indeed very useful to help clarify the basics but they only work if they include the major parameters. Leaving out the gravitational force {- snip -}
    Response: [muoncounter] Gravitational lapse rate was declared off topic at #972. It's been demonstrated repeatedly that this idea is irrelevant here.
  12. damorbel @1011, where I discussing the mechanisms of the greenhouse effect I would agree with you. As it happens, however, I am discussing the claim by some deniers that the GHE violates the second law of thermodynamics because the Surface radiation is greater than the incoming Solar radiation and/or because the back radiation is absorbed by the surface, which is warmer than the atmosphere. Neither of those claims is based on the density/temperature profile of the atmosphere, and therefore a simplified model for discussing those objections need not include those profiles. Now if you have a more subtle 2nd law objection to the GHE, just state for the record that your objection is not based either on S < Surf, and the surface absorbing AtmDn; and that the model described above does not violate any laws of thermodynamics and then we can proceed on to your more subtle objections. On the other hand, if you do not have a second law objection, may I remind you of the topic, and that the Moderators have already told you:
    "The claim that lapse rate or gravitational compression is responsible for the GHE is not directly relevant to this thread, as has already been addressed in multiple links provided. Please take this particular point of discussion elsewhere."
    Consequently if you are not explicitly discussing 2nd law issues, may I suggest you take your discussion elsewhere.
  13. Tom Curtis 1008 You asked: Given these clarifications, does your answer change, and if yes, to what? Unless I'm missing something, and assuming the constraints as outlined, the temperature for both plates is solely based on heating element....303K You said: The simple answer is that if Surface radiation goes above 2*S, or AtmUp, or AtmDn goes above S, then the system losses more energy than it gains, and therefore cools. I suspect we're arguing semantics, but how is that gaining energy cools? If Atm_up and Atm _dn are components of the an equally divided surface radiation, there is no cooling nor a decrease in entropy. The challenge for the alarmist is to find any partition of the system such that conservation of energy is maintained for that partition, and such that the Entropy decreases for that partition. That is, the partition must show an energy flow from E1 to E2 such that E1 = E2, but such that the Entropy of E1 is greater than that of E2. As an example, we have: 1) Insolation + Back radiation => surface radiation I said you said: You said equilibrium will be reached without back radiation being absorbed. Well, first note that in this model there must be back radiation because the "atmosphere" has an emissivity of 1 in IR wavelengths. Tom, do you agree equilibrium is reached WITHOUT back radiation? That is, with surface emission = 240 W/m^2 and only 240 W/m^2 (no additional back radiation) will system equilibrium be reached? Notice I'm not arguing the validity of forcing, at this point, but rather is equilibrium less forcing. So again, do you agree equilibrium is reached WITHOUT back radiation? You said: “With respect to the idealized greenhouse model it is the next step in complexity of atmospheric models from a simple grey slab model. It is still inaccurate...” Can you point me to the least flawed model. Not flippant or snide, but seriously...what is the best (least flawed) atmospheric model?
  14. Re #1012 Tom Curtis you wrote:- "Consequently if you are not explicitly discussing 2nd law issues, may I suggest you take your discussion elsewhere." The argument I put is that adding gases that radiate (and absorb) are to the mixture comprising the atmosphere in the zone known as the troposphere, cannot change the equilibrium temperature of the surface because this region is almost always colder than the surface. The argument is based on the 2nd Law of thermodynamics which is that energy transfer (which is required for temperature change) cannot result in an increase (i.e. net increase) of the surface energy which would be required for a rise in surface temperature, because the temperature of the troposphere is, in general, lower than the surface. This fact is known because with a few exceptions known as inversions, the gradient of temperature against altitude is negative, meaning that the troposphere is almost always colder than the surface. It may be thought relevant why the Troposphere is always colder than the surface, I suggest this is a relevant matter.
  15. In order to discuss the “higher is colder” theory, which most contributors to this thread endorse as the only plausible explanation of AGW, we have to leave the comfortable certainties of thermodynamics, (and G and T) and move on to the more controversial arguments of climate science. A good debate on the basic Physics can be found at “Climateclash.com”, which includes the basic spectroscopy as well as “higher is colder”, presented in a long paper by Ray Pierrehumbert (Infrared radiation and planetary temperature) and numerous posts from Leonard Weinstein. The theory suggests that doubling the CO2 in the atmosphere moves the boundary between the optically thick region below, and the optically thin region above, where radiation to space is relatively unimpeded. Since this region is colder, outgoing radiation falls, and the sun warms the entire system, shifting the lapse rate to the right. To some extent this must be true, but it is reasonable to ask if effect is detectable. It is almost never quantified (an obscure calculation at P 113 of Taylor gives an elevation of 3kms, and a temperature increase of 18 degrees C). With a lapse rate of 6.5 degrees C per 1000 meters, we are looking for an elevation of the effective radiation level of just 154 meters for an increase in temperature everywhere of 1 degree C. Since the transition from thick to thin must be gradual, and different for different frequencies of radiation, there is no possibility of detecting such a change directly. Then there is the role of water vapour. At sea level, the H2O concentration about 12000 ppm, or more than 30 times CO2. Over the troposphere as a whole it is 20 times CO2, and at 5 kms (the region of effective radiation) it is still 4 times greater. Doubling CO2 to 600 ppm will still leave H2O as the dominant greenhouse gas. Thereafter, it falls away rapidly, to create the optically thin region, but it is will still mask the effect of any increase in CO2 absorption at the effective emission point. The only mechanism by which doubling the CO2 concentration can elevate the emission level is absorption, with atmospheric warming (via kinetic energy) and subsequent emission (and consequential cooling). To measure that effect we would expect to find experiments. The usual suspects (Woods and Angstrom) are a century old, and hotly disputed (usually without the tedium of repetition). One experiment reported on the net is at espere.net/united kingdom/water/uk_overview.htm. It is an attempt to demonstrate the greenhouse effect, they pass short wave radiation through gas-filled containers, with long wave radiation filtered out. Back-warming of the gasses is from black cardboard (which absorbed the incoming radiation)in the base of the containers. They compare air (at atmospheric pressure) with 100% CO2, a greater concentration than on Venus. Anyone expecting a dramatic difference will be disappointed. Initially, the CO2 warms rather faster. After 5 minutes the increases are : 100% Co2 15 degrees C Air 10 degrees C In the next 15 minutes additional warming was as follows: 100% Co2 13 degrees C Air 12 degrees C Sadly, the experiment stopped (before equilibrium) just when it was becoming interesting. For those with long lives ahead, the earth’s AGW experiment will go on long enough to resolve doubts and errors, and reach a conclusion.
  16. Re #1015 Fred Staples you wrote:- "The theory suggests that doubling the CO2 in the atmosphere moves the boundary between the optically thick region below, and the optically thin region above, where radiation to space is relatively unimpeded. Since this region is colder, outgoing radiation falls, and the sun warms the entire system, shifting the lapse rate to the right." This hypothesis has many weaknesses. One of Tyndall's most important discoveries was that GHGs were the perfect absorbers of their own emissions. This has the important consequence that, if two samples are irradiating each other, heat energy only goes to the cooler from the hotter, (tending to raise it temperature) thoroughly in accord with the 2nd law. The same is true for density, the denser emits more radiation than the less dense, assuming the two samples have the same temperature. Of course in the atmosphere both effects (density and temperature difference) are to be observed, so there is considerable energy transfer, but only upwards. Without energy transfer 'downwards' there will be no heating of the surface by adding GHGs.
    Response: [muoncounter] This is not a forum for endless repetition of your prior comments (see #143 on this thread and its rebuttal here). If you can only recycle your prior words, perhaps you really have nothing further to contribute.
  17. Of some interest: Jo Nova has posted a thread by a guest poster that states quite clearly that the radiative greenhouse effect does not violate thermodynamics. There's still a lot of arguing that the effect is small, that feedbacks are negative - but I find it very interesting that a major skeptic website has posted this. It takes a lot of effort at times, but it is possible to convince the skeptical of the validity of physics sometimes. The thread is currently >230 comments after a couple of days... many of the regulars there are quite displeased.
    Response: Link here
  18. RSVP @ 182 or 181? . Igloo do not make you warmer, they slow your loss. Igloos are not ovens. The contents, be it Eskimos or lamps, must have it's own power source. To further your parallel resistance analogy. If your circuit is powered with a 240 W sources, how many resistors, any arrangement of your choosing, are required to increase the supply power to 390 W?
  19. Jigoro Kano @1018, your analogy is inaccurate and fails to understand the greenhouse effect. 1) It is inaccurate because it models temperature with power measured in Watts. Temperature, however, is not power, ie, energy over time. Rather it is (in a gas) the mean kinetic energy of the particles of the gas. As such, it is analogous to Voltage in electronic systems, ie, the energy per unit charge. So, you challenge should be,
    What electronic circuit will, when powered by a 240 watt source, raise the voltage? 2) It fails to understand the greenhouse effect because in the greenhouse effect, at equilibrium energy in equals out so that over time, power (Watts) in equals power (Watts) out. You are probably aware that the surface radiation is greater than the incoming solar radiation averaged overtime (and after albedo losses). But this is compensated for by the fact that the back radiation very nearly equals the surface radiation. As a result the net upward energy flow from the surface (516 Joules per second averaged over a year and the Earth's surface) very nearly equals the downward energy flow at the Earth's surface (517 Joules per second averaged globally and annually). The very slight difference is the reason for global warming, and will be balanced out once equilibrium is reached. Likewise at the Top Of the Atmosphere, energy in (341.3 Joules per second globally and annually averaged) very nearly equals energy out (340.4 Joules per second globally and annually averaged). (The slight difference between TOA balance and surface balance is due to measurement error). What is more, although it is not shown on the diagram, at every level of the atmosphere, energy in equals energy out except when that level is warming or cooling. Note, although there is more power flowing from surface to atmosphere than from the sun to the surface, that does not indicate an increase in power in the circuit. It merely indicates that the circuit doubles back on itself. Treating it as the circuit increasing the power is like considering only the bottom half of the Villard Cascade (above) and concluding that the circuit has increased the power threefold because there are three connections (Ds, D2, and D4) each carrying the initial power to the lower half of the circuit. It should be noted that climate models all have the feature that for each distinguished layer, energy in equals energy out if temperature is constant. Indeed, if a model of the atmosphere includes greenhouse gasses, it can only avoid a greenhouse effect by not having this feature.
  20. Re #1019 Tom Curtis, you write:- "Jigoro Kano @1018, your analogy is inaccurate" I suggest your analogy is little better. What do you mean "...the surface radiation is greater than the incoming solar radiation averaged overtime"? Greater power? Higher temperature? The analogy of temperature and voltage has some merit but the voltage multiplier (VM) circuit you show does not increase the overall power. With 100% efficiency the output power is the same as the input power. The VM bears fair comparison with the atmosphere where the specific energy at the bottom of the atmosphere is the same as at a greater altitude. The temperature at the surface is higher than at altitude but the specific energy (J/mol) (or J/kg) remains the same. Yes the temperature cganges with altitude but it changes for all gases with or without GHGs.
  21. damorbel @1020: 1) First you contradict yourself by claiming that my "analogy is little better" than that of Jigaro Kano, but then stating "The analogy of temperature and voltage has some merit". As the analogy of temperature to voltage was my only analogy, if it has merit, then it is better than that of Jigaro Kano. Kano wanted to analogise the increased greenhouse effect to an increase of power in a circuit. As the greenhouse effect is an increase of temperature, he is therefore analogising temperature to power, which is invalid. 2) The voltage multiplier circuit is not an analogue of the greenhouse effect, and nor is it intended as such. It merely demonstrates that circuits can increase voltage, and do not violate any law of thermodynamics in doing so. Therefore if Kano's analogy is adapted so that analogues are analogised with analogues, it provides no argument against the greenhouse effect. 3) The electrical circuit analogy breaks down because any circuit involves a small number of non-overlapping paths while energy transfer in the atmosphere involves an infinite number of overlapping paths. Consequently individual surfaces or sections of the atmosphere may have more power entering and leaving them than enters or leave the top of the atmosphere, but this is a consequence only of overlapping energy paths and does not represent a creation of energy or destruction of entropy. We know this because the net energy transfer is the same for the TOA, and for each level of the atmosphere below that, including the surface/atmosphere interface. 3a) The overlapping of paths is analogous to a laser striking a mirror in a dark room, then striking another mirror at right angles to the reflected beam so that the beam retraces its path. In such a scenario twice the output power of the laser strikes the first mirror, and is reflected from it, which is purely a function of that mirror being struck twice by the beam. No violation of the laws of thermodynamics is involved. This situation is exactly analogous to what happens in the atmosphere except that in the atmosphere and at the surface, energy is often absorbed and reradiated, and is often reradiated after being transferred to other molecules by collisions, and (as previously noted) there is no one path for energy in the atmosphere. 4) The issue of temperature change with altitude is very important for understanding the greenhouse effect, but irrelevant to the topic here, ie,whether the greenhouse effect violates the laws of thermodynamics. Unless you wish to argue that the adiabatic lapse rate violates the laws of thermodynamics, or against some other denier who on this thread has argued that, it is therefore of topic (as the moderators have repeatedly informed you).
  22. Tom Curtis @ 1019 No Tom, I an not comparing circuit watts to atmospheric temperature, or the increase thereof. Rather I'm comparing input watts to a circuit to input watts to the Earths surface. But to your circuit. If radiation is analogues to voltage not power, does that make GHG the analogues capacitors? You seem to contradict your own analogy at 2) when referencing input/output watts. The diagram is a itself is perplexing. The title alone Global Energy Flows W/m^2 is wrong. Shouldn't it be titled Power Distribution or Flux Allotment or something more accurate. The diagram shows 161 W/m^2 shortwave incident on the surface, while the texts say 240 W/m^2. Using radiavite transfers equations, and starting text value of 240 W/m^2 solar input how you get to 390 W/m^2?
    Response:

    [DB] Sorry, L.J., we've all been down this road before.

  23. Jigoro Kano (RE: 1022), The diagram shows 161 W/m^2 shortwave incident on the surface, while the texts say 240 W/m^2. Using radiavite transfers equations, and starting text value of 240 W/m^2 solar input how you get to 390 W/m^2?" Good luck trying to convince anyone here of this, even though - as you say, the text of paper on page 6 clearly says the "Net Down" radiation equals the full post albedo (or at least to within 1 W/m^2). I've tried and have given up. Apparently, Tom Curtis and everyone here thinks they can create an additional 121 W/m^2 out thin air to justify that diagram (517 - 396 = 121) and that the surface can be receiving a net flux of 493 W/m^2 when it's only emitting 396 W/m^2. No one seems to be able to deduce that the incoming 78 W/m^2 from the Sun designated as "absorbed by the atmosphere" must get to the surface one way or another because the atmosphere cannot create any energy of its own and the Sun is the only source of energy in the system. Now, it doesn't all have to get there in the form of downward emitted LW radiation - some of it could get to the surface kinetically in the form of latent heat via precipitation, for example, but this just offsets energy that what would otherwise be radiated to the surface.
  24. "Good luck trying to convince anyone here of this, even though" Correct, it would appear most of the rest us bothered to learn physics.
  25. Jigoro Kano @1022 1) If you intended only an analogy with regard to power transfers, the analogy fails because electrical circuits have limited, non-overlapping paths, while the atmosphere has infinitely many, overlapping energy paths. Put more simply, the analogy fails because atmospheres don't short out. 2) I did not make an analogy between the GHG and any electrical circuit or component for the reasons given in (1) above (and in (3) of my 1021). I did point out that counting the total energy input into the surface (sunlight plus back radiation) as a gain in power is a fallacy equivalent to counting the total energy input into the lower half of the Villard Cascade as a gain in power. The laser/mirror analogy is better for this purpose (3) in 1021, but you where talking about circuits. 3) We divide the diagram into three parts, Space, the Atmosphere and the Surface: a) Total energy entering space = Reflected Solar Radiation + Outgoing Longwave Radation = 101.9 + 238.5 = 340.4 =~= 341.3 = Incoming Solar Radiation = Total energy leaving space. b) Total energy incident on the surface = ISR Reflected by Surface + ISR Absorbed by Surface + BackRadiation = 23 + 161 + 333 = 517 =~= 23 + 17 + 80 + 396 = ISR Reflected by Surface + Thermals + Evapo/Transpiration + Surface Radiation = 516 = Total energy leaving the surface. c) Total energy entering and interacting with the atmosphere (ie, excluding energy that merely transits without being reflected or absorbed) = ISR Reflected by Clouds and Atmosphere + ISR Absorbed by Atmosphere + (Surface Radiation - Atmospheric Window) + Thermals + Evapo/Transpiration = 79 + 78 + (396-40) + 17 + 80 = 610 =~= 79 + (239 - 40) + 333 = 611 = ISR Reflected by Clouds and Atmosphere + (Outgoing Longwave Radiation - Amospheric Window) + Back Radiation = Total energy leaving the atmosphere. All units in Watts/m^2, the slight discrepancies being due to measurement error and the fact that due to the enhanced Greenhouse effect, the Earth is not currently in radiative equilibrium. You appear to want to join RW1 as one of those deniers who believe the greenhouse effect does not exist because they cannot add. For the record, the 240 W/m^2 is the solar radiation less reflected radiation, and so obviously includes radiation absorbed at the surface and in the atmosphere = 161 + 78 = 239 which is rounded to 240 for convenience. For RW1 convenience (and for the umpteenth time) there is no guarantee that energy absorbed by the atmosphere will make its way to the surface, and as most of it is absorbed in the stratosphere, most of it doesn't. In fact, most of it is radiated to space. 4) (3a) in my 1021 clearly explains how you can get twice the input power incident on a surface using a laser and two mirrors. A similar thing happens in the climate system. Solar energy is absorbed by the Earth's surface then reradiated as IR radiation, or carried to the atmosphere by thermals or evapotranspiration. Nearly 90% of that is absorbed in the atmosphere, which in turn radiates IR radiation so that some of it (58%) returns to the Earth's surface. The energy returned to the surface is again reradiated (or carried by thermals or evapotranspiration) so that only a small fraction escapes to space and so through astronomically many iterations. The large number of iterations is relatively unimportant as the sum of the downward component of all these iterations, the back radiation, quickly converges on a stable value. Calculating the converged value including energy absorbed in the atmosphere from sunlight, and using a slab atmosphere shows an expected back radiation of around 281 Watts/m^2. That is an underestimate on reality because of the flaws in using a slab atmosphere, but it clearly demonstrates that the back radiation can exceed the incoming solar radiation without violating any law of thermodynamics. Most importantly, the average 333 Watts/m^2 is not only that which has been calculated using Line by Line and Atmosphere-Ocean Global Circulation Models, it is the back radiation that has actually been observed. Any theory that does not predict it, in other words, is falsified by observation. Of course only greenhouse theories predict that back radiation, or at least they are the only ones that do so without violating the laws of thermodynamics. So and denier of green house theories is left to explain how there can be an average 333 Watts/m^2 back radiation given a 240 Watts/m^2 input energy from the sun, and without the absorption and reradiation of energy by green house gasses.

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