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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.

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The greenhouse effect and the 2nd law of thermodynamics

What the science says...

Select a level... Basic Intermediate

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

Climate Myth...

2nd law of thermodynamics contradicts greenhouse theory

 

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

 

At a glance

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

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

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

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

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

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

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

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

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

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


Further details

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

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

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

Convection

Convection

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

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

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

Advection

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

Advection

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

Latent heat

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

Radiation

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

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

Radiation

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

Energy balance

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

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

Energy Budget AR6 WGI Figure 7_2

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

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

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

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

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

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

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

Tyndall 1859

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


Update June 2023:

For additional links to relevant blog posts, please look at the "Further Reading" box, below.

Last updated on 29 June 2023 by John Mason. View Archives

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Comments 26 to 50 out of 1481:

  1. Here's a breakdown, h-j-m.
  2. h-j-m, you should definitely check out the post that DSL links to. Note, in particular, this graph: Courtesy Science of Doom What that shows is that there's almost no overlap between the spectral ranges of downwelling solar irradiance and upwelling terrestrial thermal IR radiance. Increasing the concentration of CO2 in the atmosphere reduces the transparency of the atmosphere to longwave radiation, but not to shortwave radiation. This is how the greenhouse effect works, in a nutshell.
  3. I don't get it! Are you saying that solar IR radiation does not heat the earth? If so, then why should visible light be able to do so? Or do you mean that incoming IR radiation does not get absorbed by green house gases? Then the diagrams both of wikipedia as well as from Science of Doom show that as well. So, what's your point guys?
  4. The point is that there pretty much is no solar IR radiation. It's minuscule compared to the visible / near-IR range. Look at the graph from SoD I posted in the previous comment. To go back to the beginning of this discussion, you said "As incoming and outgoing radiation is (more or less) equally effected by the insulation it is quite hard to see how the result could be a warming of the earth. " The point is that incoming and outgoing radiation are in completely different parts of the electromagnetic spectrum, and thus they aren't equally affected by greenhouse gases. Does that explanation help?
  5. Re #19 Daniel Bailey. Energy can only flow from a high temperature place to a lower temperature place. The surface of Earth is always hotter than the atmosphere above. As you say there is a net transfer of energy from the surface to the upper atmosphere, that is to say the upper atmosphere, which loses energy to deep space at 2.7K, is a net gainer of energy from the surface. The energy the upper atmosphere gains energy (net) from the surface preventing the (upper atmosphere) temperature from dropping to the (2.7K) temperature of deep space. The surface, as you may now realise, is a net radiater of heat to the atmosphere via longwwave IR radiation; the surface loses a lot more heat by convection of air and evaporation/condensation of water. To keep the surface temperature (more or less) stable the surface gets heat from the Sun via many different routes. The tropics are where most of the Sun's heat comes in, heating the atmosphere and sea water. This tropical heat is transported to the poles by air and water currents. Some of this heat is radiated directly from the tropics and some at intermediate distances on the way to the poles. Of course some heat also arrives from the Sun away from the tropics. The whole business of heat transport is governed by local and global temperature differences, starting with the 5780K of the Sun and finishing in deep space at 2.7K. There are a number of curiosities; it is posible using a magnifying glass or a mirror to make a local concentration of the Sun's energy on a spot but the maximum temperature you will get is 5780K. If you use an arc lamp with a temperature >5780K to boost this spot and your lens is still focussed on the Sun, the Sun will now be heated, just a little, by your lamp.
  6. h-j-m - Visible light has more energy per photon than IR does. UV has even more. There's plenty of energy in the visible portion of sunlight to heat the earth. And the atmosphere is almost totally transparent to visible light. Thermal IR, on the other hand (5-30 micrometers) does not pass through the atmosphere very well, due to greenhouse gases.
  7. damorbel - Excellent post, very correct in all respects. And at equilibrium the energy radiated to space equals the energy received from the sun. In reference to greenhouse gases - these slow the transport of energy from the surface to space. They effectively reduce the emissivity of the Earth, meaning that for the same energy radiated the Earth has to be at a higher temperature, as per the Stefan–Boltzmann law, where power radiated scales with emissivity (e) and T^4. Power = emissivity * SB constant * area * T^4
  8. More reply to h-j-m, who wrote: Are you saying that solar IR radiation does not heat the earth? If so, then why should visible light be able to do so? The very, very small amount of solar IR radiation does heat the Earth. But it's dwarfed by the much larger amount of visible light. Let's put some numbers to this. Assume we have 100 units of incoming solar radiation, distributed as follows: * 99 units of visible, near-IR, and shortwave IR * 1 unit of longwave IR Outgoing radiation from the Earth is also 100 units (because it's in balance with the incoming radiation from the sun), but distributed as follows: * 0 units of visible, near-IR, and shortwave IR * 100 units of longwave IR Now, let's say you introduce some substance into the atmosphere that absorbs longwave IR but transmits visible, near-IR, and shortwave IR. That will slightly reduce the 1 unit of downwelling solar irradiance, producing a tiny cooling effect. On the other hand, it will also reduce the 100 units of emitted terrestrial longwave radiation, producing a much larger warming effect (about 100 times larger, in fact).
  9. Re damorbel: On the cell right now, so I'll leave you with this to chew on for now: How then, when in the freezer section of a grocery store, can one see the energy from the lights coming from the cold interior of the display cases? Also, Google back radiation (Hint: Science of Doom website or over at Chris Colosse's place).
  10. Re #34 Daniel Bailey. "the energy from the lights coming from the cold interior". Nice try! What kind of lights? Oil lamps, LEDs, lasers, gas discharge, gas incandescent, electric incandescent, fluorescent, quartz halogen? You will have to be a bit more specific!
  11. Are you attempting to be funny or do you honestly think that there are some lights that you can't see because of the temperature surrounding the bulb?
  12. KR, thank you for mentioning the energy level, it just comes in handy. Ned, if you don't agree to the widely accepted definition of IR radiation then I don't know how talk to you. Now, if you look at the Science of Doom page you will find: As a proportion of total solar irradiance # Total energy from 0 – 0.75μm 54% – all energy up to infra-red # Total energy from 0 – 4μm 99% – all “shortwave” Now that leaves us 99% - 54% = 45% of total solar irradiance in the infra-red range. I would hardly call that minuscule. If you think that you can not compare radiation in this range with that of thermal infra-red then you are perfectly right. The main difference is, as KR has pointed out that the energy of a particle gets higher the shorter the wavelength. So you can figure out what's the difference between a infra-red photon at 1500 nm trapped by water vapour and one at 10000 nm trapped by CO2.
  13. Re #31 #32 KR "Thermal IR, on the other hand (5-30 micrometers) does not pass through the atmosphere very well, due to greenhouse gases." In a sense you are correct. Very little heat gets into the atmosphere by radiation from the surface because the temperature difference between the surface and the atmosphere is not very great, not only that, transfer of heat into gasses by radiation depends not only on temperature difference but the type of gas (all gasses absorb and emit some radiation) but the density is important also, more gas, more absorption and emission. Most heat gets into the atmosphere by evaporation from the sea, a lesser amount by convection over land and sea. Once in the atmosphere most heat is radiated into deep space by CO2 and H2O. Some heat is radiated directly from the surface into deep space via the 'windows' in the combined spectra of CO2 and H2O. All the heat leaving the planet goes by these 'radiation into deep space' processes, there is no other way! The temperature difference between the atmosphere of planet Earth and deep space is very large, about 200K and given that the heat tranfer is proportional to T^4 then radiation becomes very effective.
  14. Re #36 "Are you attempting to be funny?" Give the guy in #34 a break! Perhaps he is thinking of a candle in a deep freeze, you might find a candle in a deep freeze was too hard to get it lit!
  15. h-j-m, forget about the terminology, which is just confusing you. Here's what you originally wrote: "As incoming and outgoing radiation is (more or less) equally effected by the insulation it is quite hard to see how the result could be a warming of the earth. " But incoming and outgoing radiation are in completely different wavelength ranges. CO2 absorption affects one of these ranges, but not the other. Thus, your assumption that they must be "equally affected" is understandable but wrong. OK?
  16. damorbel - In regards to energy magnitudes of IR, evaporation, and convection, you are unfortunately incorrect. It's a common misconception, though. Please take a look at Trenberth 2009, "Earth's Global Energy Budget", in particular Figure 1. Surface IR runs at about 396 W/m^2, evaporation/latent heat at 80 W/m^2, thermals at 17 W/m^2, averaged over the globe. IR is the primary avenue of energy leaving the surface. Now, 333 W/m^2 comes back down from the atmosphere as backradiation, along with 161 W/m^2 from the sun, but given that all incoming energy becomes surface temperature, you can't just difference the IR flows. Currently the difference between incoming and outgoing is something like +0.9 W/m^2, hence the observed global warming.
  17. Ned, thanks, that sounds better. It is not the terminology that confuses me but your use of it. As I understand it infra-red is rather large radiation spectrum that then had been subdivided for more precise meaning (near infra-red and thermal infra-red being two of them). Of cause you are right, I should have written "If incoming and outgoing radiation is (more or less) equally effected by the insulation it is quite hard to see how the result could be a warming of the earth." But unfortunately so far I have not found any comment about the green house effect on incoming radiation. Sorry, but you are wrong, take a closer look a the solar spectrum diagrams and you will see there is an effect on incoming radiation as well for H2O and CO2. More prominent with H2O but it is there.
  18. h-j-h, see this Global Heat Flows" diagram.
  19. Can someone please remove post 43 and change the posting software so that the comment field returns blank after a post is submitted. Thanks. KR, I just saw your post stating: Currently the difference between incoming and outgoing is something like +0.9 W/m^2, hence the observed global warming. I don't know what the correct numbers would be, but don't you think that we might need some of that energy to drive the climate system (winds, ocean currents, rainfall etc.). A lot of chemical processes need energy. Last, but not least is the biosphere of this planet depending on energy. All these energies won't show up at outgoing radiation. I'm not sure but there might be even more to be added to that difference due to the entropy implied in thermodynamics.
  20. h-j-m writes: Ned, thanks, that sounds better. Thanks! It is not the terminology that confuses me but your use of it. As I understand it infra-red is rather large radiation spectrum that then had been subdivided for more precise meaning (near infra-red and thermal infra-red being two of them). Sorry, I work with this stuff every day in my job, so I may be a bit casual in how I talk about it. The term "infrared" is ambiguous, because it is used to refer to a very broad range of the EM spectrum ... but there are hugely important differences in the origins and behavior of "infrared" radiation within the Earth's atmosphere. You asked a very natural question -- if greenhouse gases warm the Earth by blocking outgoing (emitted) radiation, shouldn't they also correspondingly cool the Earth by blocking incoming (solar) radiation? The answer to that question is one of the key principles of the greenhouse effect: given the current composition of the atmosphere, adding greenhouse gases has little direct effect on the wavelengths that comprise 99% of the downwelling solar radiation (visible, near-infrared, and shortwave infrared ... i.e., everything below 3 micrometers). However, it does have a significant direct effect on the wavelength range that comprises > 99% of the outgoing emitted radiation from the Earth (longwave infrared). So, to first order, adding CO2 to the existing atmosphere directly reduces outgoing radiation but doesn't directly reduce incoming radiation. That produces the warming effect. Notice all those "directs" and "directlys" in there? That's because the indirect effects of greenhouse gases include some feedbacks (involving water vapor and changes to cloud-albedo) that do influence incoming short-wavelength irradiance. This is the largest source of uncertainty in IPCC estimates of climate sensitivity. But these feedbacks are secondary effects and are almost certainly not large enough to counter the effects of CO2 warming. See here for a discussion of water vapor and here for a comparison of the magnitude of different forcings such as CO2 vs clouds.
  21. In another comment, h-j-m also writes: A lot of chemical processes need energy. Last, but not least is the biosphere of this planet depending on energy. All these energies won't show up at outgoing radiation. Well, all the processes that you mention were occurring in the past, too. Unless there's some change that's caused the biosphere or the oceans or whatever to suddenly start storing more energy than they were able to do so before, you wouldn't expect this to have any effect on the observed energy balance of the planet. In any case, though, this isn't really relevant to the question of whether the greenhouse effect is somehow a violation of the second law of thermodynamics (it isn't) or of whether greenhouse gases must have the same effect on incoming and outgoing radiation (they don't). If some mysterious chemical or physical process were discovered to have soaked up a lot of additional energy within the climate system, it would just imply a larger planetary radiative imbalance. The observed warming of the surface and atmosphere would still be a concern ... and in fact we'd have to worry about what would happen if your mysterious process X ever stopped absorbing excess solar radiation.
  22. Damorbel wrote: "Energy can only flow from a high temperature place to a lower temperature place." Interesting. How exactly do you explain sunlight traveling from space (very cold) to the Earth (much warmer) in your world? As explained before, the greenhouse effect acts like insulation. Think of a house in winter. If you've got a heating system (the Sun) but no insulation (greenhouse gases) then the heat escapes quickly and the house (planet Earth) stays cold. If you add insulation then the heat can't escape as fast and the maximum temperature which the heating system can maintain increases even though the amount of heat it puts out hasn't changed. No violations of the laws of thermodynamics... just an every day phenomenon that we have all experienced.
  23. Damorbel wrote: "Energy can only flow from a high temperature place to a lower temperature place." One of my favorites. Ice is invisible to Damorbel. Damorbel, your post #38 suggests that you think the atmosphere is fairly uniform in temperature from surface to top. After all, no energy can move from a colder place to a hotter place. Yet instrumental observations show a cooling stratosphere and a warming troposphere. How does your physics account for this?
  24. Ugh - when I say "uniform in temperature," I mean it uniformly decreases in temp from bottom to top.
  25. When I started writing on this thread it was caused by the repulsive argument in it's lead article. It should be obvious that the main reason for any insulation to raise temperatures is due to an energy source within the insulation. Therefore the analogy is outright wrong. Which of cause leaves the lead article without any argument. Nevertheless the subject is somewhat fascinating and I started thinking about it a lot. Finally I had to come to the conclusion that greenhouse theory indeed violates the second law of thermodynamics. Now, here is why. My argument has two parts. The first part deals with infra-red radiation, heat with respect to the second law of thermodynamics. The second part rests on the assumption that the digram about global energy flows by Trenberth, K. E. and Kiehl, J. T. (at it's latest version on american meteorological society March 2009 page 4) reflects the greenhouse theory. Part 1. The second law of thermodynamics states (repeating the quote from the lead article) "Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature". Now, it should be obvious that this says nothing about directions. In essence it says that heat hitting a body that is as warm or warmer than the heat's source it can not heat up that body further. Further more, if heat hits a body at a lower temperature than it's source it will not be able to heat this body up to the exact temperature of it's source as this would constitute a perpetual motion machine which the laws of thermodynamics don't allow for. As infra-red radiation constitutes a form of heat transport the same rules have to apply here. So it needs a closer look at infra-red radiation and how it transfers heat. Now that's simple, it is absorbed by matter transferring all it's energy to it. If that higher energy level renders the absorbing matter unstable it gives the excess energy up by again emitting radiation. Part 2: Unless I screwed something horribly up in part 1 the conclusion is as follows: Due to the second law of thermodynamics infra-red radiation is bound to hit matter it can not transfer it's energy to. As it obviously cannot be destroyed there is but one alternative, it needs to be reflected. Now let us look at the mentioned diagram and look for the reflection of infra-red radiation. Sorry, I can't see any, All infra-red radiation except for the part heading to space gets absorbed and in consequence transfers energy. As for me, that clearly violates the second law of thermodynamics.

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