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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 501 to 525 out of 846:

  1. damorbel: How can anybody learn anything from the supposed heat transfer shown in the diagram in #491? The author who drew this failed to provide any temperature information anywhere. How can he possibly know the energy tranfers (all over the diagram in W/m^2) without indicating the temperatures? Whoever drew this diagram obviously hadn't the slightest knowledge of the 2nd Law of Thermodynamics. Who pays money for 'stuff' like this? The diagram was about the flow in energy which is expressed in units of W/m^2. That is: energy (watts) over a specific area (a square meter). Are you suggesting that it should be "degrees" per square meter? It is the appearance of dagrams like this in IPCC reports that makes one instinctively mistrust all of 'global temperature increase' figures produced by the IPCC. Why, because they used the proper of units of measure instead of the ones you suggest which make no sense whatsoever for describing the flow of energy. Also, why are you criticizing the IPCC when the diagram you are talking about is by Trenberth, Fasullo and Kiel (2009)?
    Response: [Muoncounter] Damorbel has asked the same question on prior threads. Do not try to rehash the same thing with him or it will never end.
  2. 498 Stamples -
    The questions that really elementary Physics does not ask, are these: Is it possible to use the additional energy in the gas to restore the weight to its original position? If not, why not?
    Surely 'elementary' physics asks and answers that question - although expressed more precisely - with the Carnot Cycle etc. No?
  3. Hello, Boy, this is a long thread! Can someone explain me why we are having a discussion about something that has been proved over and over again? - GW is real and it's clear as a daylight that we, humans, are driving it ...
    Response: Welcome to Skeptical Science! Please note this site's Comments Policy. Comments should be applicable to the topic at hand, and should refrain from inflammatory or insulting speech. These policies ensure that the science is communicated effectively.
  4. I happened to be a scientist as well, and claim to understand a thing or two about laws of thermodynamics and planetary energy budgets ... Satellite spectral data overwhelmingly show that earth's atmosphere absorbs strongly in the bands attributed to greenhouse gases ... what can be more proof that the greenhouse effect is real and that heat-absorbing gases are cousing it!!
  5. I've been reading through the postings on this thread, and saw some really nonsensical statements (from a physics point of view) that are backed by no evidence. I think whoever is moderating this blog (if anyone) should be more discriminating and not allow unscientific claims and statements be posted here ...
    Response: Thank you for your concern, but being wrong is not a violation of the Comments Policy. The idea is to educate by encouraging rational discussion, not shut down anyone due to a misunderstanding of the science.
  6. Thanks you! So there is a moderator after all. I totally agree with you.
    Response: There are several moderators in addition to our host John Cook.
  7. To Moderator - Yes, I agree with rational discussion, but what's rational about the crappy 'arguments' put forward by ( -Snip- )
    Response: [Daniel Bailey] Many commenters put forth crappy arguments, but the majority comply with the Comments Policy. As previously stated, dialogue is encouraged; no attempts to steer the debate or stifle free speech will be made here as long as all parties do it peacefully and respectfully. And yes, one can plainly see which are quality arguments and which are..."less so".
  8. Does anyone here agree with PhysSci, or find any credibility in those arguments?
  9. To KR 455 - You make a very good point about SB law when applied to planetary atmospheres: An increase in greenhouse gases directly decreases emissivity by absorption band deepening and widening. This drops emitted energy to space. A lot of scientists do not actually understand that indeed adding more heat-absorbing gases actually REDUCES emissivity of the atmosphere. I only know a few scientists, who realize that.
  10. With regard to the greenhouse effect - I think it works very similar to an actual greenhouse. The atmosphere does act as blanket to reduce heat loss to space and the obvious fact to support this is that we have 397 W m-2 leaving the surface and only 239-240 W m-2 exiting the atmosphere. So, the difference is actually retained by the blanket (our atmosphere). It's a no-brainer ... Also, see this recent article by prof. R. Pierrehumbert from University of Chicago, who explains very well how the greenhouse effect works making the point that the atmosphere is analogous to a house insulation in the way is prevents heat loss. Now that's real physics! http://geosci.uchicago.edu/~rtp1/papers/PhysTodayRT2011.pdf
  11. John Cook - looking through the arguments list, I dont find one for the "GHE violates the 1st Law of thermodynamics". This have been dealt with at Science of doom in some detail but perhaps a place-mark article in the arguments is needed for debate on this? Sounds like PhysSci is using this.
    Response: [Not John Cook] Concur.
  12. If think PhysSci was talking about the downward thermal radiation from the atmosphere (rather than outgoing IR from the surface) that is larger than the absorbed solar radiation. Is this really true? If so, do the arguments presented at Science of doom still hold?
  13. I suspect that there is some kind of confusion with these energy fluxes. Yes, they claim these are based on satellite observations but they also admit that the accuracy of these measurements is quite uncertain. So, I doubt that the downward IR flux is in reality larger than solar flux. That does not make much physical sense to me, unless I'm missing something.
  14. Climate_Protector @517 My understanding (and I am not an expert on Climate) is that the fact that the downward flux is greater than the Solar input is due to heat accumulated in the climate system. You can see the results of a simple spreadsheet model of the longwave component only here. The numbers don't relate to Trenbeths diagram, I picked them so the calculation would reach equilibrium fairly quickly. Column A is somewhat badly named - it should be the amount of Solar radiation absorbed and re-emitted as longwave radiation. If you wish to replicate this, the cell formulae are: Cx=Ax+Bx Dx=Cx*0.4 Ex=Cx*0.6 Bx=D(x-1) and so this represents an atmosphere that radiates 40% of its longwave radiation to space and 60% back to the ground. I hope the spreadsheet is clear, towards the end I turn the Sun off, and calculate the time taken for the planet to dissipate the accumulated heat. At the end the energy in does indeed equal the energy out - which proves that I (and OpenOffice) got the sums right and that the model conserves energy. The main point is that, in this model at least, the back-radiation does indeed grow to be greater than the incoming Solar. As I said earlier, I'm not an expert so I would welcome corrections and clarifications !
  15. Apologies I got a cell formula wrong in the previous post; Bx=E(x-1) not D(x-1)
  16. Phil 518 - Yes, this makes sense. The question now is how much energy can the real atmosphere store (accumulate). It has to be quite a bit in order for the downward IR flux to exceed the absorbed solar flux. The atmosphere is pretty deep, so maybe it could store substantial amount of energy? I'm curious what others think?
  17. Climate_Protector - The thermal mass of the atmosphere is pretty tiny; about 4-5% gets stored as warming the land mass, and about 92% goes into warming the oceans. The atmosphere is pretty much a direct in-out of the energy stored, radiating out as much energy as it receives in IR (396 W/m^2), latent heat of evaporation (80), and thermals (17). But even a simple single-layer model will show this effect of high energy in the climate system - it has to be that high in order to put 240 W/m^2 back into space. So will a zero-dimensional emissivity model - surface emissivity is about 0.98 (almost a perfect black body), and to radiate the 240 W/m^2 received back to space would be at a temperature of about -17C. The top of atmosphere (TOA) spectra integrates to an effective emissivity of ~0.612 with all the absorption dips, and to put 240 W/m^2 into space the surface needs to be at about 390 W/m^2.
  18. KR 521 - Thank you. I understand the surface fluxes and the TOA fluxes, but if the heat storage capacity of the atmosphere is tiny as you suggest, how we have such a large downward IR flux (larger than solar)? That's the part I do not quite get and that's why I suspect (personal opinion) that the proposed downward IR flux may be incorrect ...
  19. Climate_Protector @520, the atmosphere "stores" considerable heat both in the form of the kinetic energy of motion (temperature) and as the vibrational and rotational energy of molecules (specific heat). The amount stored as vibrational energy and rotational energy is always proportional to that stored as kinetic energy, ie, as temperature. The amount stored is very small, however, compared to that stored by oceans. The specific heat of dry air is 1.026 Joules per kilogram per degree Kelvin, while that of water is over four times that. Combined with the much greater mass of the ocean, this means the vast majority of thermal energy at the Earth's surface is stored in the Ocean. However, this is largely irrelevant to PhysSci's argument. The reason the atmosphere maintains a very high back radiation is because a very high energy flux into the atmosphere is maintained, both by energy transfers from the Earth (IR, convection and evapo/transpiration) and directly from the Sun. In fact, when one of those (the sun) is removed at night, the back radiation falls very rapidly unless either: 1) The surface IR flux is maintained at high levels by being over ocean; or 2) The humidity is very high (which increases the specific heat of the atmosphere) and there is a low cloud cover (which lowers significantly the average altitude from which the back radiation comes, and significantly increases the heat capacity of the source of the back radiation). Obviously, there is some regional geographic effects, with warm air over sea water at night helping maintain a higher night time back radiation on the coast than in the interior. All of this follows because the back radiation is simply the thermal (IR) emissions of the lowest kilometer or so of the atmosphere; and therefore fluctuates with the temperature of that lowest portion of the atmosphere. Because of this, back radiation can fluctuate by more than 145 watts per meter squared in a single 24 hour period (the calculated night/day variation for winter in Mount Isa, Queensland) even without major changes in weather.
    Response: This sounds like a good additional Argument for the Arguments list. John Cook, what do you think?
  20. Climate_Protecter @522, the back radiation is a direct function of the temperature of the lowest part of the atmosphere. Because the lowest part of the atmosphere is very close in temperature to the surface, and the surface is far hotter than it would be if there were no greenhouse effect, the back radiation is also very high. Absent the greenhouse effect, the surface IR radiation would equal the incoming solar radiation. The green house effect lifts that till it is much higher, and therefore the back radiation is higher. It is as simple as that.
  21. I see. So, most heat is storred in the oceans. That makes sense. It sounds like you all are telling me that there is no error in the reported intensities of back radiation, and that it is larger than the absorbed solar flux. Correct? I'm an ecologist and from working with observed met data (to drive my ecosystem models), I noticed that the diurnal variation in back radiation is much smaller than solar radiation. In fact, back radiation is nearly invariant (+- 20W m-2 or so) between day and night. This is true for sites in the NH. I'm bringing this up in response to Tom Curtis's remark that back radiation varies diurnally quite a bit. I've seen the opposite in the data sets I worked with ... Anyway, I understand that the lower atmosphere, where most of the back radiation is coming from, is heavily heated by the surface through surface-atmosphere exchange of various energies. But I'm still not clear what's making the temperature of the surface to increase beyond the black-body temperature. I guess this is the chicken-and-egg question; which is heating which?
  22. Climate_Protector @521, to evaluate your claim that back radiation at your location varies by no more than 40 w/m^2 from day to night, I would need to know the temperature range. However, two factors may be relevant. The closer you are to the coast, the smaller the diurnal temperature range, and hence diurnal range of back radiation. And the colder the climate, the smaller range in back radiation for a given range in temperatures. For instanct, a temperture range of 27 degrees (as in Mount Isa) but with the maximum equaling Mount Isa's minimum (0 degrees C) would only result in a 107 w/m^2 range in back radiation. The reported intensities in the diagram have significant margins of error (around 5% I believe), but are the best available estimates.
  23. Was the air temperature proportional to the kinetic energy of air? I think Tom Curtis said that above. So, since back radiation is also proportional to temperature (somehow I think?), then would that mean that the kinetic energy of air is proportional to back radiation? If that is the case, then the lower atmosphere must contain kinetic energy that is larger than solar radiation, IF back radiation is really larger than the absorbed solar flux. This suggests that the atmosphere must be able to somehow store significant amount of energy. So, we come again to the atmospheric heat storage question. Correct? Something here does not add up - either we have a large atmospheric heat storage or the back radiation numbers must be wrong (or I'm profoundly misunderstand something). Do you agree?
  24. To Tom Curtis 522 - I work in Colorado (far from any coast), and the climate here is relatively dry. The diurnal temperature range in the summer is about 10-13C, and the winter might be much higher or much lower depending on the frontal weather system we get.
  25. To clarify regarding the back radiation I have seen. The flux changes little between day and night ONLY if you look at any particular series of 2-3 days, but it can fluctuate more than 100 W m-2 over the coarse of a season or a year.

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