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The greenhouse effect and the 2nd law of thermodynamics

What the science says...

Select a level... Basic Intermediate

The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.

Climate Myth...

2nd law of thermodynamics contradicts greenhouse theory

 

"The atmospheric greenhouse effect, an idea that many authors trace back to the traditional works of Fourier 1824, Tyndall 1861, and Arrhenius 1896, and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system. According to the second law of thermodynamics such a planetary machine can never exist." (Gerhard Gerlich)

 

At a glance

Although this topic may have a highly technical feel to it, thermodynamics is a big part of all our everyday lives. So while you are reading, do remember that there are glossary entries available for all thinly underlined terms - just hover your mouse cursor over them for the entry to appear.

Thermodynamics is the branch of physics that describes how energy interacts within systems. That interaction determines, for example, how we stay cosy or freeze to death. You wear less clothing in very hot weather and layer-up or add extra blankets to your bed when it's cold because such things control how energy interacts with your own body and therefore your degree of comfort and, in extreme cases, safety.

The human body and its surroundings and energy transfer between them make up one such system with which we are all familiar. But let's go a lot bigger here and think about heat energy and its transfer between the Sun, Earth's land/ocean surfaces, the atmosphere and the cosmos.

Sunshine hits the top of our atmosphere and some of it makes it down to the surface, where it heats up the ground and the oceans alike. These in turn give off heat in the form of invisible but warming infra-red radiation. But you can see the effects of that radiation - think of the heat-shimmer you see over a tarmac road-surface on a hot sunny day.

A proportion of that radiation goes back up through the atmosphere and escapes to space. But another proportion of it is absorbed by greenhouse gas molecules, such as water vapour, carbon dioxide and methane.  Heating up themselves, those molecules then re-emit that heat energy in all directions including downwards. Due to the greenhouse effect, the total loss of that outgoing radiation is avoided and the cooling of Earth's surface is thereby inhibited. Without that extra blanket, Earth's average temperature would be more than thirty degrees Celsius cooler than is currently the case.

That's all in accordance with the laws of Thermodynamics. The First Law of Thermodynamics states that the total energy of an isolated system is constant - while energy can be transformed from one form to another it can be neither created nor destroyed. The Second Law does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. That qualifier term, 'net', is the important one here. The Earth alone is not a "closed system", but is part of a constant, net energy flow from the Sun, to Earth and back out to space. Greenhouse gases simply inhibit part of that net flow, by returning some of the outgoing energy back towards Earth's surface.

The myth that the greenhouse effect is contrary to the second law of thermodynamics is mostly based on a very long 2009 paper by two German scientists (not climate scientists), Gerlich and Tscheuschner (G&T). In its title, the paper claimed to take down the theory that heat being trapped by our atmosphere keeps us warm. That's a huge claim to make – akin to stating there is no gravity.

The G&T paper has been the subject of many detailed rebuttals over the years since its publication. That's because one thing that makes the scientific community sit up and take notice is when something making big claims is published but which is so blatantly incorrect. To fully deal with every mistake contained in the paper, this rebuttal would have to be thousands of words long. A shorter riposte, posted in a discussion on the topic at the Quora website, was as follows: “...I might add that if G&T were correct they used dozens of rambling pages to prove that blankets can’t keep you warm at night."

If the Second Law of Thermodynamics is true - something we can safely assume – then, “blankets can’t keep you warm at night”, must be false. And - as you'll know from your own experiences - that is of course the case!

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


Further details

Among the junk-science themes promoted by climate science deniers is the claim that the explanation for global warming contradicts the second law of thermodynamics. Does it? Of course not (Halpern et al. 2010), but let's explore. Firstly, we need to know how thermal energy transfer works with particular regard to Earth's atmosphere. Then, we need to know what the second law of thermodynamics is, and how it applies to global warming.

Thermal energy is transferred through systems in five main ways: conduction, convection, advection, latent heat and, last but not least, radiation. We'll take them one by one.

Conduction is important in some solids – think of how a cold metal spoon placed in a pot of boiling water can become too hot to touch. In many fluids and gases, conduction is much less important. There are a few exceptions, such as mercury, a metal whose melting point is so low it exists as a liquid above -38 degrees Celsius, making it a handy temperature-marker in thermometers. But air's thermal conductivity is so low we can more or less count it out from this discussion.

Convection

Convection

Figure 1: Severe thunderstorm developing over the Welsh countryside one evening in August 2020. This excellent example of convection had strong enough updraughts to produce hail up to 2.5 cm in diameter. (Source: John Mason)

Hot air rises – that's why hot air balloons work, because warm air is less dense than its colder surroundings, making the artificially heated air in the balloon more buoyant and thereby creating a convective current. The same principle applies in nature: convection is the upward transfer of heat in a fluid or a gas. 

Convection is highly important in Earth's atmosphere and especially in its lower part, where most of our weather goes on. On a nice day, convection may be noticed as birds soar and spiral upwards on thermals, gaining height with the help of that rising warm air-current. On other days, mass-ascent of warm, moist air can result in any type of convective weather from showers to severe thunderstorms with their attendant hazards. In the most extreme examples like supercells, that convective ascent or updraught can reach speeds getting on for a hundred miles per hour. Such powerful convective currents can keep hailstones held high in the storm-cloud for long enough to grow to golfball size or larger.

Advection

Advection is the quasi-horizontal transport of a fluid or gas with its attendant properties. Here are a couple of examples. In the Northern Hemisphere, southerly winds bring mild to warm air from the tropics northwards. During the rapid transition from a cold spell to a warm southerly over Europe in early December 2022, the temperatures over parts of the UK leapt from around -10C to +14C in one weekend, due to warm air advection. Advection can also lead to certain specific phenomena such as sea-fogs – when warm air inland is transported over the surrounding cold seas, causing rapid condensation of water vapour near the air-sea interface.

Advection

Figure 2: Advection fog completely obscures Cardigan Bay, off the west coast of Wales, on an April afternoon in 2015, Air warmed over the land was advected seawards, where its moisture promptly condensed over the much colder sea surface.

Latent heat

Latent heat is the thermal energy released or absorbed during a substance's transition from solid to liquid, liquid to vapour or vice-versa. To fuse, or melt, a solid or to boil a liquid, it is necessary to add thermal energy to a system, whereas when a vapour condenses or a liquid freezes, energy is released. The amount of energy involved varies from one substance to another: to melt iron you need a furnace but with an ice cube you only need to leave it at room-temperature for a while. Such variations from one substance to another are expressed as specific latent heats of fusion or vapourisation, measured in amount of energy (KiloJoules) per kilogram. In the case of Earth's atmosphere, the only substance of major importance with regard to latent heat is water, because at the range of temperatures present, it's the only component that is both abundant and constantly transitioning between solid, liquid and vapour phases.

Radiation

Radiation is the transfer of energy as electromagnetic rays, emitted by any heated surface. Electromagnetic radiation runs from long-wave - radio waves, microwaves, infra-red (IR), through the visible-light spectrum, down to short-wave – ultra-violet (UV), x-rays and gamma-rays. Although you cannot see IR radiation, you can feel it warming you when you sit by a fire. Indeed, the visible part of the spectrum used to be called “luminous heat” and the invisible IR radiation “non-luminous heat”, back in the 1800s when such things were slowly being figured-out.

Sunshine is an example of radiation. Unlike conduction and convection, radiation has the distinction of being able to travel from its source straight through the vacuum of space. Thus, Solar radiation travels through that vacuum for some 150 million kilometres, to reach our planet at a near-constant rate. Some Solar radiation, especially short-wave UV light, is absorbed by our atmosphere. Some is reflected straight back to space by cloud-tops. The rest makes it all the way down to the ground, where it is reflected from lighter surfaces or absorbed by darker ones. That's why black tarmac road surfaces can heat up until they melt on a bright summer's day.

Radiation

Figure 3: Heat haze above a warmed road-surface, Lincoln Way in San Francisco, California. May 2007. Image: Wikimedia Commons.

Energy balance

What has all of the above got to do with global warming? Well, through its radiation-flux, the Sun heats the atmosphere, the surfaces of land and oceans. The surfaces heated by solar radiation in turn emit infrared radiation, some of which can escape directly into space, but some of which is absorbed by the greenhouse gases in the atmosphere, mostly carbon dioxide, water vapour, and methane. Greenhouse gases not only slow down the loss of energy from the surface, but also re-radiate that energy, some of which is directed back down towards the surface, increasing the surface temperature and increasing how much energy is radiated from the surface. Overall, this process leads to a state where the surface is warmer than it would be in the absence of an atmosphere with greenhouse gases. On average, the amount of energy radiated back into space matches the amount of energy being received from the Sun, but there's a slight imbalance that we'll come to.

If this system was severely out of balance either way, the planet would have either frozen or overheated millions of years ago. Instead the planet's climate is (or at least was) stable, broadly speaking. Its temperatures generally stay within bounds that allow life to thrive. It's all about energy balance. Figure 4 shows the numbers.

Energy Budget AR6 WGI Figure 7_2

Figure 4: Schematic representation of the global mean energy budget of the Earth (upper panel), and its equivalent without considerations of cloud effects (lower panel). Numbers indicate best estimates for the magnitudes of the globally averaged energy balance components in W m–2 together with their uncertainty ranges in parentheses (5–95% confidence range), representing climate conditions at the beginning of the 21st century. Figure adapted for IPCC AR6 WG1 Chapter 7, from Wild et al. (2015).

While the flow in and out of our atmosphere from or to space is essentially the same, the atmosphere is inhibiting the cooling of the Earth, storing that energy mostly near its surface. If it were simply a case of sunshine straight in, infra-red straight back out, which would occur if the atmosphere was transparent to infra-red (it isn't) – or indeed if there was no atmosphere, Earth would have a similar temperature-range to the essentially airless Moon. On the Lunar equator, daytime heating can raise the temperature to a searing 120OC, but unimpeded radiative cooling means that at night, it gets down to around -130OC. No atmosphere as such, no greenhouse effect.

Clearly, the concentrations of greenhouse gases determine their energy storage capacity and therefore the greenhouse effect's strength. This is particularly the case for those gases that are non-condensing at atmospheric temperatures. Of those non-condensing gases, carbon dioxide is the most important. Because it only exists as vapour, the main way it is removed is as a weak solution of carbonic acid in rainwater – indeed the old name for carbon dioxide was 'carbonic acid gas'. That means once it's up there, it has a long 'atmospheric residency', meaning it takes a long time to be removed. 

Earth’s temperature can be stable over long periods of time, but to make that possible, incoming energy and outgoing energy have to be exactly the same, in a state of balance known as ‘radiative equilibrium’. That equilibrium can be disturbed by changing the forcing caused by any components of the system. Thus, for example, as the concentration of carbon dioxide has fluctuated over geological time, mostly on gradual time-scales but in some cases abruptly, so has the planet's energy storage capacity. Such fluctuations have in turn determined Earth's climate state, Hothouse or Icehouse – the latter defined as having Polar ice-caps present, of whatever size. Currently, Earth’s energy budget imbalance averages out at just under +1 watt per square metre - that’s global warming. 

That's all in accordance with the laws of Thermodynamics. The First Law of Thermodynamics states that the total energy of an isolated system is constant - while energy can be transformed from one component to another it can be neither created nor destroyed. Self-evidently, the "isolated" part of the law must require that the sun and the cosmos be included. They are both components of the system: without the Sun as the prime energy generator, Earth would be frozen and lifeless; with the Sun but without Earth's emitted energy dispersing out into space, the planet would cook, Just thinking about Earth's surface and atmosphere in isolation is to ignore two of this system's most important components.

The Second Law of Thermodynamics does not state that the only flow of energy is from hot to cold - but instead that the net sum of the energy flows will be from hot to cold. To reiterate, the qualifier term, 'net', is the important one here. In the case of the Earth-Sun system, it is again necessary to consider all of the components and their interactions: the sunshine, the warmed surface giving off IR radiation into the cooler atmosphere, the greenhouse gases re-emitting that radiation in all directions and finally the radiation emitted from the top of our atmosphere, to disperse out into the cold depths of space. That energy is not destroyed – it just disperses in all directions into the cold vastness out there. Some of it even heads towards the Sun too - since infra-red radiation has no way of determining that it is heading towards a much hotter body than the Earth,

Earth’s energy budget makes sure that all portions of the system are accounted for and this is routinely done in climate models. No violations exist. Greenhouse gases return some of the energy back towards Earth's surface but the net flow is still out into space. John Tyndall, in a lecture to the Royal Institution in 1859, recognised this. He said:

Tyndall 1859

As long as carbon emissions continue to rise, so will that planetary energy imbalance. Therefore, the only way to take the situation back towards stability is to reduce those emissions.


Update 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 14 February 2023 by John Mason. 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

Denial101x video

Comments

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Comments 301 to 325 out of 1516:

  1. Re #299 Ned you wrote:- "Damorbel, did you ever read the last paragraph of this comment? Did you understand it?" Is this from your paragraph:- "If the albedo of the earth increased, it will receive less short-wavelength radiation (visible, near-infrared). But this doesn't imply an immediate, corresponding reduction in outgoing long-wavelength radiation"? How so? Isn't the outgoing radiation scattered by the same material that scatters the incoming radiation to give the albedo? And further you wrote:- "I'd also note that damorbel has still not explained why he/she approvingly cites an explanation at wikipedia that explicitly relies on the exact same mechanism that he/she thinks violates the 2nd law of thermodynamics." Which is just a multilayer metalised thermal blanket. Thermal blankets don't break any laws of themodynamics because it doesn't matter which way the radiation comes or on its wavelength. They work by reflecting radiation in both directions; a metalised themal blanket doesn't have to be 100% opaque, it could be 30%; reflecting just 30%, same as the Earth. The Earth reflects back 30% of the radiation coming from the Sun, isn't 30% of the radiation coming from the Earth going to get reflected back in the same way? The Earth is not equipped with a one-way mirror that reflects 30% of the Sunlight but transmits its own radiation 100% (making it behave like a black body); no way does that happen in real physics.
  2. @damorbel: "The Earth reflects back 30% of the radiation coming from the Sun, isn't 30% of the radiation coming from the Earth going to get reflected back in the same way?" You seem to believe that albedo is solely determined by atmospheric (i.e. "above-ground") conditions, but a lot of the actual albedo is determined by the actual reflectiveness of the Earth's surface (water, rock, vegetation, deserts, polar caps, etc.). In that sense, a significant portion of the energy reflected to space cannot be reflected back to the ground, because the ground itself is what's reflecting it.
  3. No, damorbel, multilayer thermal blankets do not operate solely by reflection. Apparently you really did not read the article you linked to. Go read it. Really, read it. Notice the explanation of the non-reflective mechanism by which it operates.
  4. damorbel, reflection (scattering) does depend on frequency. That's why the sky is blue.
  5. Re #303 Tom Dayton you wrote:- "apparently you really did not read the article you linked to. Go read it. Really, read it. Notice the explanation of the non-reflective mechanism by which it operates." You are right. But the article, which says :- "the principle behind MLI is radiation balance. To see why it works, start with a concrete example - imagine a square meter of a surface in outer space, at 300 K, with an emissivity of 1, facing away from the sun or other heat sources. From the Stefan-Boltzmann law, this surface will radiate 460 watts. Now imagine we place a thin (but opaque) layer 1 cm away from the plate, thermally insulated from it, and also with an emissivity of 1. This new layer will cool until it is radiating 230 watts from each side, at which point everything is in balance." is wrong; it says (5lines down) "and also with an emissivity of 1. This new layer will cool until it is radiating 230 watts." The whole principle of reflective insulation is using material with low emissivity. Initially satellites used gold plating as a barier against heat tranfer. Gold has an emissivity <0.05, depending on the finish. Also the well known silver teapot (emissivity = 0.02 - 0.03) has only one emitting surface, it keeps the tea hot better than any other material. Further, the vacuum flask the vacuum flask has only two layers and achieves far greater insulation than the explanation given in the 'Multi Layer article. When you write :- "Notice the explanation of the non-reflective mechanism by which it operates." I do not know what you mean. These materials work best in a vacuum which is the case for Sun/Earth heat transfer. In #304 you write:- "reflection (scattering) does depend on frequency. That's why the sky is blue." This wavelength dependence of scattering has no effect on total transfer of heat when at the equilibrium temperature, if it did there could be no equilibrium.
  6. Re #302 archiesteel you wrote:- "You seem to believe that albedo is solely determined by atmospheric (i.e. "above-ground") conditions, but a lot of the actual albedo is determined by the actual reflectiveness of the Earth's surface (water, rock, vegetation, deserts, polar caps, etc.)." The albedo is the radiation reflected by an object in space, it is the average over the surface.
  7. damorbel, multilayer insulation works even when its surfaces are not coated with reflective material. Read that article again--carefully this time. Oh, wait, you've now decided the article you yourself first pointed to as support is wrong, now that we have forced you to actually read it. In fact, you believe everyone on the planet but you is wrong--everything that everyone has told you, and everything that we've told you to read, and now something that you told the rest of us to read. Do you really believe you are the lone genius on Earth who truly understands the second law of thermodynamics?
  8. @damorbel: it is averaged to obtain the entire planet's albedo, sure, but that doesn't mean this accurately describes the actual reflection at any given location on the globe. Anyway, that's besides the point. You seem not to understand the fact that we are talking about two different types of radiation, i.e. short-wave (visible light, ultraviolet, etc.) and long-wave radiation (infrared). CO2 and greenhouse gases absorb and re-emit the latter, not the former. That is the so-called greenhouse effect. A higher albedo means less of the energy is converted from short-wave to long-wave by the surface, i.e. the latter's temperature doesn't increase as much; therefore a higher albedo value usually means colder temperature.
  9. damorbel, you completely missed the point archiesteel made. He was countering your claim that reflection of radiation incoming to the Earth must be matched by reflection of radiation outgoing from the Earth. A large part of the reflection of the incoming radiation is by things on the ground. Since the radiation outgoing from the Earth is headed away from things on the ground, the things on the ground cannot reflect it. So the reflection of outgoing cannot automatically be the same as the reflection of incoming, since the reflectors in the two cases are different.
  10. Tom Dayton wrote : "Do you really believe you are the lone genius on Earth who truly understands the second law of thermodynamics?" I think the answer to this, in damorbel's mind, is 'yes'. I'm not being insulting but I think everyone should look at this Wikipedia page, which seems to be the same damorbel going through the same arguments, with others attempting what you are all trying to explain here. What is the point and why should anyone be allowed to do this here ?
  11. Tom, I came to that conclusion about damorbel many posts ago. If you believe that your own version of physics is right and all textbooks are wrong and you determine not to learn otherwise, then noone can teach you. We are wasting time. I sure hope the person that taught him physics isnt still in a job.
  12. Thanks for digging up damorbel's rap sheet. I'm going to ignore him or her from now on.
  13. Same here. Damorbel is clearly not interested in learning the science, but rather in pushing his own unsupported theories. When someone is consistently being shown wrong and he/she refuses to acknowledge it, then that persons is likely a troll looking for attention. I'll ingore him/her as well.
  14. I've been following damorbel's arguments, and the counter arguments which seem weak and highly tortuous. Doesn't the complexity and stretching of the 2nd law of thermodynamics send any alarm bells ringing? Damorbel is certainly not alone and has my support and that of Claes Johnson(Prof Appl Maths,Stockholm), Alan Siddons, and Piers Corbyn, weatherman extraordinaire, latter-day Druid.In fact, he is probably the only pundit that is doing what scientists,as latter-day druids are supposed to do....making predictions that turn out to be correct.....unlike the agw believers. The layman will judge you, as he has done over millenia, by the accuracy of your predictions. Get it right and you'll be respected as gods. Get it wrong and you may be outlawed...or worse. Piers is anti-AGW, yet his predictions have been miles more accurate than the British Met Office....who have actually opted out of giving long-range forecasts.
  15. AWoL, let's see. (1) The counterarguments are perfectly straightforward. (2) AGW gets along fine with the 2nd law of thermodynamics; there's no stretching at all. (3) Piers Corbyn has a very poor predictive record, which is unsurprising given his unscientific methods. Aside from that, your comment is right on!
  16. AWoL, the claim of "weak" needs to be supported. There's very little that's "weak" about AGW. There are a few unknowns, but the basic physics is straightforward. The claim of "highly tortuous" is relative and therefore unarguable, since the reader/thinker making the claim may be unable to process the concepts involved. If so, this is hardly proof that the theory is in any way weak or flawed, and is more likely a sign that the reader/thinker needs to spend more time developing a comprehensive understanding rather than parroting those who have a more comforting but less physically consistent message. The layman will judge, as you say, but the layman will also believe in--and in fact kill in defense of--2000 year old theories that are still unsupported by any sort of evidence at all. If you're a strong believer in ethical behavior and integrity, think about what happens if you get it wrong and end up partially responsible for a great deal of suffering. As for Corbyn, I'll second Ned.
  17. Re #307 Tom Dayton you wrote:- "multilayer insulation works even when its surfaces are not coated with reflective material." All material reflects, or more accurately, scatters radiation; mirror type reflection or indeed refraction, is called coherent scattering because the phase relationship of the incoming radiation is (largely) preserved. Coherent or not, scattering reduces the transmission of radiation through a given aperture (the Earth's disk?) This reduction is independent of the direction of the source. This means that, if the Sun's incoming radiation is reduced by factor called the Albedo, then the outgoing thermal radiation will be reduced by the same amount. The magnitude of the scattering function may well be subtantially independent of wavelength as with transparent materials such as water but that doesn't mean the radiation is not redirected away from absorption/emission. For example clouds (water) contribute substantially to the albedo because the droplets are very small, whereas the oceans (water) which appears dark in images of the Earth appears to make a much smaller contribution to the albedo. Liquid water (70% of Earth's surface) having a relatively smooth surface, allows sunlight to get to depths far greater than its wavelength where it gets gradually absorbed. Only a limited % of the radiation penetrating the water surface remerges because of the phenomenon of total internal reflection, an example of coherent scattering. This total internal reflection phenomenon applies equally to radiation originating (thermally) under the water surface, it means that thermal radiation is, to a certain extent, trapped there, reducing its emissivity in proportion and thus water (70% of... remember?) cannot radiate like the black body central to GH effect theory.
  18. Re #315 Ned you wrote:- "2) AGW gets along fine with the 2nd law of thermodynamics; there's no stretching at all" The original argument for AGW is that "Earth radiates like a black body", that is how a supposed equilibrium temperature (without GHE) of 255K is calculated. It is this 'never justified assumption' (check p3 for a 'list of assumptions') that means the AGW 'science' breaks the 2nd Law of Thermodynamics. The fact that Earth manifestly is not a black body (because it has an albedo) destroys the GHE temperature calculation completely. Trying to sustain this by observations about a wavelength function do not account for the fact that the wavelength function of Earth's albedo alone is irrelevant because it doesn't include the magnitude (wavelength independent part) of the albedo. It is the magnitude of the albedo, not the wavelength function, that governs energy transfer, as explained in #317.
  19. damorbel writes: the wavelength function of Earth's albedo alone is irrelevant because it doesn't include the magnitude (wavelength independent part) of the albedo. It is the magnitude of the albedo, not the wavelength function, that governs energy transfer More anti-mathematical gibberish. AWoL, is this really the person you want to be following? "Albedo" is just the average spectral reflectance across a broad range of the spectrum. That's all that it is. Whether a particular photon is absorbed or reflected by a surface depends on the spectral reflectance of the surface at that particular photon's wavelength. It doesn't depend on the generalized average reflectance of the surface across a wide range of wavelengths (albedo).
  20. damorbel & AWoL, the simple fact is that the stuff damorbel is saying is on the level of 'the earth is flat', 'the sun orbits the earth', and 'the earth is only 6000 years old'. It is completely at odds with science that has been considered established fact, based on hundreds of lines of evidence, for over a century. If you believe otherwise you are either a nutjob or a revolutionary genius. However, if you want to prove that you are a genius, and not a nutjob, ranting on the internet does not seem the most effective approach. If you think you've found some amazing and clear evidence which disproves the greenhouse effect (which mainstream science considers to have been proven by Tyndall in 1858) what you should be doing is publishing your findings in science journals. Trying to argue it out here, while the textbooks still contradict you, just leads people to the 'nutjob' conclusion.
  21. AWoL wrote : "I've been following damorbel's arguments, and the counter arguments which seem weak and highly tortuous." Could you list what darmobel's arguments are and which particular "counter arguments" are "weak and higly tortuous" ? Can you give more detail ? AWoL also wrote : "Doesn't the complexity and stretching of the 2nd law of thermodynamics send any alarm bells ringing?" Again, can you give more details of the "stretching" ? As to this all being complex : well, you don't say ! That doesn't mean that anything in particular, involving the 2nd Law or AGW, is wrong, does it ? Or can you point out what you believe is wrong ? AWoL then wrote : "Damorbel is certainly not alone and has my support and that of Claes Johnson(Prof Appl Maths,Stockholm), Alan Siddons, and Piers Corbyn, weatherman extraordinaire, latter-day Druid." The usual so-called skeptical reliance on lone voices, especially weathermen ! Tell me : how can you tell when those lone voices are so far out there that they are beyond rational science ? Does that ever bother you, or do you accept the creationist view of life on earth too - i.e. the lone voices ? As for your use of the word "Druid", that suggests to me that you have a religious basis for your beliefs, so maybe creationism IS your favoured view of life on earth ? AWoL also wrote : "In fact, he is probably the only pundit that is doing what scientists,as latter-day druids are supposed to do....making predictions that turn out to be correct.....unlike the agw believers." Uh oh, that religious angle again. You would be better looking for scientists who are NOT "latter-day druids" (whatever you believe that means), and stick to scientists who work in the fields in which they are pronouncing. AWoL wrote : "The layman will judge you, as he has done over millenia, by the accuracy of your predictions. Get it right and you'll be respected as gods. Get it wrong and you may be outlawed...or worse." Love the implied threath there : "or worse". Why don't you reveal what will happen to anyone who uses the scientific method without being able to get 100% results, i.e. just about every scientist in any field you care to mention. And, once again, try to leave religion out of this, please. AWoL finally wrote : "Piers is anti-AGW, yet his predictions have been miles more accurate than the British Met Office....who have actually opted out of giving long-range forecasts." Do you have any evidence of the predictions of this druid of yours, so we can see how good he is at crystal-gazing ? By the way, the Met Office no longer do seasonal forecasts, as they recognise the difficulty of predictions for this time-period, and they know that any wrong word will be taken out of context and abused by the denialosphere.
  22. Re #319 Ned you wrote:- ""Albedo" is just the average spectral reflectance across a broad range of the spectrum. That's all that it is." And you cited my #318:- "It is the magnitude of the albedo, not the wavelength function, that governs energy transfer" Did it occur to you that these may be the same thing? We seem to be in agreement. So do you also agree that the albedo is not a 'one way' effect? That the material making the reflections that produce the albedo, water, ice, desert sand, clouds etc., also can reflect back some of the Earth's thermal radiation, in the manner of total internal reflection, as I described in #317? Or do you subscribe to the idea that radiation from Earth is completely unhindered, just like that of a theoretical black body?
  23. damorbel, re: your belief that the temperature of a planet is independent of its albedo: ---------------------- (1) Almost all incident solar radiation on the planet is shortwave (visible/near-infrared). (2) An increase [or decrease] in the planet's albedo causes it to absorb less [or more] energy from the sun. (3) This causes the planet to cool down [or heat up]. (4) As the planet cools down [or heats up], it emits less [or more] longwave radiation, because of the T4 term in the Stefan-Bolzmann equation. Eventually, the planet reaches a new equilibrium whereby incoming and outgoing radiation are once again balanced, but with the planet at a lower [or higher] mean temperature. ---------------------- None of that has much to do with the greenhouse effect -- it would all be true even on a planet with no atmosphere at all. The only connection seems to be that your confusion about planetary radiation balance is deeper and more fundamental than just the parts relating to greenhouse gases. OK, so what about the subject of this thread? Re: your belief that the greenhouse effect violates the second law of thermodynamics: ---------------------- (A) The planet is heated by absorbing shortwave radiation from the sun. (B) The planet loses heat by emitting longwave radiation to space. (C) Greenhouse gases in the atmosphere will reduce the flux of outgoing longwave radiation within their absorption bands. (D) This reduction in OLR causes the planet's temperature to rise. (E) As the temperature rises, more OLR is emitted outside the greenhouse gas absorption bands. (F) Eventually, the total emitted radiation once again balances the incoming solar radiation, but with a proportionately lower amount in the absorption bands, a higher amount outside the absorption bands, and a higher mean temperature of the planet. ---------------------- It's all perfectly straightforward, and there's no violation of the second law of thermodynamics anywhere in there. So where does this mistaken idea about violation of the 2LOT come from? As far as I can tell, it's within step (D). It's pretty clear how this process warms the atmosphere. But how can it warm the surface? After all, the surface is warmer than the atmosphere, and the net transfer of energy should be from the warmer surface to the cooler atmosphere. This is the line of reasoning used by most of the 2LOT-skeptics. But that line of reasoning is mistaken, and the greenhouse effect is perfectly capable of warming the surface without violating any laws: ---------------------- (D.1) In accordance with the Stefan-Bolzmann law, the atmosphere emits longwave radiation. (D.2) Some of this radiation goes outward to space, and is lost to the planet's system. Some of it goes inward towards the surface. (D.3) This downwelling longwave radiation from the atmosphere is absorbed by the planet's surface. (D.4) The absorption of this downwelling radiation reduces the magnitude of the net flux of longwave radiation leaving the surface, making the surface warmer than it would have been if it were not surrounded by an atmosphere that includes greenhouse gases. ---------------------- That's a bit more complicated than the previous two descriptions, but there's still no violation of the second law (or any other law). The net heat flux is from the surface to the atmosphere; it's just a smaller flux than it would have been if the atmosphere weren't there (or didn't contain greenhouse gases). What gets really convoluted are the attempts to force this description into something that would violate the second law, by those who are convinced that it must do so. Generally, these involve asserting that the second law doesn't just mean that the net flow of radiation has to be from the surface to the atmosphere, but that there can be no radiation at all flowing in the opposite direction. When people claim this, they think they're preserving the second law, but they're actually going far beyond what the second law says, and breaking some other part of physics in the process (perhaps the Stefan-Bolzmann law, perhaps the first law of thermodynamics, or perhaps something else). This is all completely uncontroversial among physicists, earth and planetary scientists, and others who deal with radiation balances in their work. There is no fertile ground for AGW-skepticism here. A rational AGW-skeptic will accept this, and ground her or his skepticism in some other part of the landscape (climate sensitivity is low, the impacts won't be negative overall, the costs of mitigating AGW would be higher than the costs of adapting to it, or whatever).
  24. Wow, Ned. That was extremely well done. Congrats.
  25. Re #323 Ned you wrote: "Generally, these involve asserting that the second law doesn't just mean that the net flow of radiation has to be from the surface to the atmosphere," In particular:- "but that there can be no radiation at all flowing in the opposite direction." I don't assert what you write, nor have I seen it in any serious text on thermodynamics. The idea is completely absurd; but it has often been said by those, like yourself, defending the concepts of AGW/GHE. Further you write:- "When people claim this, they think they're preserving the second law." That is what you say, do you have a link I can follow? And futher you write:- "but they're actually going far beyond what the second law says, and breaking some other part of physics in the process (perhaps the Stefan-Bolzmann law, perhaps the first law of thermodynamics, or perhaps something else)." Now I would like to think you are not just asserting some kind of ignorance on my part by describing my arguments in such an absurd way, this of course would a classical 'straw man' argument. I would like to discuss the matter properly, I suggest that is the intention of the founders of www.skepticalscience.com but surely trying to make my contributions look absurd is not the best way forward.

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