Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


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

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

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

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

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

Prev  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  Next

Comments 626 to 650 out of 895:

  1. L.J.Ryan, I forgot in my post 615 to mention the equalities only apply in the equilibrium condition. To explore the non-equilibrium condition, let us assume time steps equal to the average time it takes light to cross the depth of the box once. We use the average time because the photons may be at different angles, and hence have different path lengths. Let us also assume that 100 photons enter the box in each time step. We set the initial time step,0, to the time photons first start entering the box, but before they strike the back wall of the box. In that case, the number of photons in each of A, B, C, and D for progressive time steps are: Following Phil's suggestion, I have modeled this on a spreadsheet, using the following formulars: Column B2 and subsequent: 100, column C2: 0, Column C3 and subsequent is the sum of columns B and D for the preceding row. Column's D and E2: 0; and for columns D and E3 and subsequent, 0.5 times the value of column C in the preceding row. The first twelve steps show as follows: STEP A B C D 0 100 0 0 0 1 100 100 0 0 2 100 100 50 50 3 100 150 50 50 4 100 150 75 75 5 100 175 75 75 6 100 175 87.5 87.5 7 100 187.5 87.5 87.5 8 100 187.5 93.75 93.75 9 100 193.75 93.75 93.75 10 100 193.75 96.875 96.875 11 100 196.875 96.875 96.875 12 100 196.875 98.4375 98.4375 Clearly there is a problem for the spreadsheet that it allows fractional photons. What would happen in the real case is that occasionally 99 photons would leave the box, and occasionally 101, but typically 100 would leave the box. Furthermore, the mean value of photons leaving the box once the equilibrium state is reached would be 100. So, ignoring the quirk of fractional values, it is plain the system quickly approaches the state described in my 615. Do you have any problems with that?
  2. C Truth @627, the ideal gas law is included in atmospheric physics in calculating the lapse rate, as shown in this university lecture, and as explained by me very briefly in 563 above. It is also included in analysis of convection, but as convection in the atmosphere is what establishes (on average) the lapse rate, that is saying the same thing. It follows that any explanation of the green house effect that incorporates the environmental lapse rate already incorporates the gas law. As previously discussed in this thread, the standard theory of the greenhouse effect incorporates the lapse rate as an essential element of the theory. So, yes, understanding the gas law can provide insights into the greenhouse effect, and those insights were discovered decades ago, and are the basis of the modern understanding of the greenhouse effect.
  3. Tom Curtis @626 "Do you have any problems with that?" As I said A=C, so with that we agree. However, energy can NOT accumulate within the box, B can not equal 2A, no way can't happen. Your scenario is a light/energy doubler. If you change your filter to reflect 75% what happens? Take it further, enclose a flashlight within a completely and perfectly reflective box, at what point is there infinite energy therein?
  4. Tom Curtis (RE: 615), "By simplifying the situation, ie, by getting rid of any concerns about convection and light absorbed by the atmosphere etc, we should be able to raise any issues you have with the consistency of the GHE with the laws of thermodynamics without getting hung up on trivia. Do you agree?" No, I don't agree that it is trivia. Understanding the energy flows relative to the radiative balance is absolutely fundamental to the entire GHE and ultimately surface temperatures (i.e. how much surface emitted radiation is coming back from the atmosphere and how much is passing through). All I'm saying is latent heat and thermals are just redistributing energy around the thermal mass of the system - mostly from the tropics to the higher latitudes. The bulk of this energy condenses to form clouds, weather systems and returns as precipitation. Any amount of it that ends up radiated out to space is equally offset at the surface by a lesser amount returning, which cools the surface. All the energy flows are constant, thus this effect is already accounted for in the 396 W/m^2 emitted at the surface.
  5. LJ@629>However, energy can NOT accumulate within the box, This is not correct. Don't forget that the flashlight is continuously outputting radiative energy (converted from energy stored in batteries). If the energy cannot escape, then yes of course the radiative energy accumulates in the box. Otherwise you would violate conservation of energy, because if the flashlight is outputting energy and it does not escape and it does not accumulate, then it must have been destroyed. It would of course stop accumulating after the flashlight runs out of battery or shuts off. Fortunately in the earth system analogy our "flashlight" will not run out of juice for a very long time.
  6. e @631 Let's assume the flashlight radiates with a 1W bulb for 100 hrs. How much energy is contained within the box at the end of a 100 hrs? How long to accumulate a gigawatt?
  7. 1J/s for 100 hours, thats 360kJ accumulated. Of course your torch also absorbs energy so guess that is going melt at some point. RW1 - this lightbox example is simple demo of how not to make inappropriate inference about energy from energy flux through different surfaces. Do you agree with light box as TC has set it up?
  8. Keep in mind, everyone, that the gain of the box is 0.5, less than one, and hence a run-away feedback is not possible. Please see Does positive feedback necessarily mean runaway warming for details. Tom Curtis, I like your example. I did much the same thing on this thread earlier, except adding a value (which could be a column) of emissivity (0.612 for Earth, as measured), where your "C" was (1.0 - emissivity) * B, and "D" was emissivity * B. If you do that with 240 as input, the results are quite interesting, as per Trenberth 2009.
  9. RW1 @630, as it is difficult to carry on two discussions at once on the same thread, do you mind holding of on the discussion of the relevance of the light box until we have settled that it does not violate any law of thermodynamics? And to that end, do you agree that the light box does not violate any law of thermodynamics?
  10. scaddenp @633 360kJ is at minimum expended by the batteries. Surely you would accumulate more then 360kJ within the box. After all, the claim is reflected light (B from Tom Curtis's diagram) is twice the input. Why the discrepancy? So lets step it back, if your box was fully enclosed such all surfaces are reflective save two small aperture. One aperture to receive light the second to radiate light. Close the output while receiving 1W at the input. The energy accumulated within the box after 100 hrs is what, 360kj? If the first aperture is then closed does the box now contain 360kj of light?
  11. L.J.Ryan @629, let us consider this step by step: 1) Consider the box as described, but without any lid. In this case all the light will reflect of the wall of the box and exit through the aperture where the lid was. Is that correct? 2) Now consider the case in which we place the lid on the box, but at an angle so that all light reflected of the lid will leave the box through some other aperture. In this case, the amount of light leaving the box through the lid will be half of that which enters, while the amount that is reflected by the lid and leaves through the other aperture will also be half of that which enters the box. Is that correct? Do either of these scenarios violate any law of thermodynamics?
  12. 636 Ryan "One aperture to receive light the second to radiate light" Ah, some more thermodynamics... ... have you met Maxwells Demon?
  13. CTruth @627 said I agree with RW1 and a few others that observational data seem to indicate the availability of a significant kinetic energy content in the lower troposphere than cannot be accounted for by the solar input alone. CTruth, my position (and if I may be so bold to suggest, I think the position of Tom Curtis, KR, scaddenp et al) is this; ... that observational data indicates the availability of a significant energy content in the lower troposphere than cannot be accounted for by the solar input alone but is accounted for by an exchange of heat between the surface and the atmosphere. This heat has accumulated in the planetary system in the distant past in the process of reaching (approximate) thermal equilibrium If you tried the spreadsheet model I suggested earlier (and Tom Curtis improved @626), one thing you can discover from it is that at the time P(in) = P(out) then ΣTP(in) - ΣTP(out) is at its maximum and is equal to the capacity of the system to hold P (so as to conserve energy or matter) These statements hold true for Tom's half-mirrored box (where P is photons), KR's rivers running in and out of a reservoir (where P is water) and the earths energy budget (where P is heat). T is time, of course, and - heads up to les @623 - yes of course the summations should really be integrals !
  14. Phil, interesting point @639. I have included two new columns in my spreadsheet. One, titled Gain, is Bx-Dx for each row, x. The second, titled "Stored" is the sum of the values in the Gain column from row 2 to row x, for each row, x. The exact formula is "=SUM(G$2:G2)" where G is the column for Gain. As expected, with each progressive iteration, Gain falls to 0 while Stored increases to 400 when the number of photons exiting the box matches the number entering the box. When the incoming photons are reduced to zero, the Gain immediately becomes -100 before slowly increasing to zero, which it reaches approximately as Stored reaches zero and photons leaving the box reaches zero.
  15. Tom @640 Cool - thats shows it nicely - but hey I don't need convincing :-( Kudos has to go to KR, who first alerted me to the idea of using spreadsheets to do these sort of simple iterative demonstrations. On a more general note I wonder if the SkpSci team have considered trying to let contributers share "live" spreadsheets via "cloud" providers like GoogleDocs. It would need to protect the documents from abuse and hide users email addresses, but it might be a useful additional resource if it could be made to work.
  16. LJ >After all, the claim is reflected light (B from Tom Curtis's diagram) is twice the input. Why the discrepancy? Amount reflected off a surface is not the same as accumulated energy in the box. If a single photon "bounces" back and forth from one wall to another, then you are going to count multiple reflections even though the energy content is still a single photon. The amount reflected tells us how many times photons have bounced off the walls, while the accumulated energy tells us how many photons are in the box. Do you see the distinction?
  17. Re #580 RickG You wrote "The diagram is not about temperature. Its about incoming solar radiation expressed in W/m^2 and how it is distributed throughout the Earth's climate system, which is the proper unit of measure for that particular type of energy (Incoming Solar Radiation)." The thread is about 2nd Law of Thermodynamics which states the direction energy is transferred WRT temperature. Trenberth's diagram is all about energy transfer (W/m^2) without any reference to temperature anywhere, thus it says absolutely nothing about atmospheric thermodynamics or the possibility of CO2 having any influence on climate in any way. You write further:- "Why would Ternberth or anyone for that matter want to use 12 year old data when more up to date data is available? And again, the diagram is about the distribution of energy, not temperature." The age of the data has no relevance, Trenberth's diagram does not present any useful information for any discussion on climate change (anthropogenic global warming - AGW) because it is completely deficient in temperature information, the driving parameter in the 2nd law of thermodynamics.
  18. 643 damorbel - "Trenberth's ... is completely deficient in temperature information" Someone might correct me; but, seems to me, the diagram includes "surface radiation", "back radiation" from GHGs, "Emitted by Atmosphere" ... all of which are temperature dependent.
  19. Tom Curtis@637 You are avoiding questions posed @636. If your box was fully enclosed such that all surfaces are reflective save two small aperture. One aperture to receive light the second to radiate light. Close the output while receiving 1W at the input. The light source occludes the reflected light from "leaking" out the input. The energy "accumulated" within the box after 100 hrs is what, 360kj? If the first aperture is then closed, does the box now contain 360kj of light? Asked otherwise, can the "accumulated" energy in the box be captured?
  20. e@642 You asked: "The amount reflected tells us how many times photons have bounced off the walls, while the accumulated energy tells us how many photons are in the box. Do you see the distinction? " Using Tom Curtis 615, what is the value of each at equilibrium i.e. 1. accumulated energy 2. reflected energy..if you can quantify it
  21. LJRyan @645, in an ideal fully mirrored box, the accumulated energy would be 360 kilojoules. Of course, in practise you would not have perfectly reflecting walls, and given the high speed of light, and consequent very large number of reflections in a short period, the light would decay to zero very quickly. Likewise, again because of the high speed, the light would escape the aperture before you could close it. But practical difficulties do not prevent us from exploring theoretical possibilities in ideal cases. @646, let the time interval be the time it takes a photon to travel from the lid to the back wall. Then 1) the accumulated photons at equilibrium is 4 times the number of photons that enter the light box at each time interval (see 640); and 2) at equilibrium the number of photons reflected in each time interval is 3 times the number that enter the light box in each time interval. Of those, 2 times that number are reflected of the back wall, and a number of photons equal to the number that enter are reflected of the lid. This ignores reflections of the side walls which are irrelevant to the overall issue. The answer has to be in terms of photon numbers, not energy because the wavelength of the photons has not been specified. If we specify that all photons have the same wavelength, then the multipliers for photons in the answers above can be used for energy. Now, can you answer my questions @637
  22. Re #644 les you write:- "... all of which are temperature dependent." Too true, I couldn't agree with you more. So do you not think, to make a useful contribution to a discussion on temperature change, the temperatures should be mentioned? Also, the emitting materials do not all have the same emissivity; Trenberth should have inserted the emissivity that applies.
  23. damorbel 648 - fine. We agree on so much including, it would seem, that the diagram is not "completely deficient in temperature information". Why don't people say what is apparent without exaggeration? The diagram doesn't explicitly mention temperatures and piles of other information. Indeed it's a cartoon. It clearly does "present ... useful information for any discussion on climate change (anthropogenic global warming - AGW) ". Why the hysteria, then? Same with LJRyan, giles et al. If you guys where half the scientist scientists you'd have be to participate in tgis discussing, you'd be far more easy with the shorthand notations, use of approximations, anstract models,partial perspectives and all the other tool we use on a daily basis to understand things. Take a chill pill.
  24. damorbel @ 643, I'm well aware of the title of the thread. However, my original comment was about Trenberth's diagram and what you said about it. For what Trenberth is demonstrating temperature is neither necessary or relevant in that diagram. I have no problem understanding the diagram myself. Trenberth has a presentation in which that diagram is described here on pages 13 & 14. Other diagrams with "temperature" are described in the presentation as well, in their appropriate place. If you still have a problem with the diagram, then perhaps you should contact him personally and take the matter up with him at the National Center for Atmospheric Research (NCAR).. I'm sure he is open to new ideas and wants to be sure his diagrams convey the proper information and documentation.
    Response: [Muoncounter] damorbel has been given this suggestion a number of times to little if any effect. Instead, we have more pointless repetition of the same tedious argument, which we may surmise is damorbel's actual intent.
  25. Tom Curtis@647 "accumulated energy would be 360 kilojoules" So the accumulated "boxed" light would radiate 1W for a 100 hrs, once the second aperture is opened? "the light would decay to zero very quickly" Sounds like a violation of the 1st law...remember perfectly reflective walls. Sounds as if you don't believe your own answer. "The answer has to be in terms of photon numbers, not energy because the wavelength of the photons has not been specified. If we specify that all photons have the same wavelength, then the multipliers for photons in the answers above can be used for energy." ok lets assign three wavelengths and redo @646 1. 11364 nm 2. 10062 nm 3. 2898 nm @637 questions 1) Consider the box as described, but without any lid. In this case all the light will reflect of the wall of the box and exit through the aperture where the lid was. Is that correct? 1a)I not sure I understand your question...if the lid included the aperture wouldn't it also be removed with the lid...? 2) Now consider the case in which we place the lid on the box, but at an angle so that all light reflected of the lid will leave the box through some other aperture. In this case, the amount of light leaving the box through the lid will be half of that which enters, while the amount that is reflected by the lid and leaves through the other aperture will also be half of that which enters the box. Is that correct? 2a)Again, I'm not sure I understand your question. Is the box partially open? How open?

Prev  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  Next

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page



The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2022 John Cook
Home | Translations | About Us | Privacy | Contact Us