An atmosphere’s IR activity won’t make it warmer, and so cannot be the cause of surface warming either.



A simple argument is put forth against the idea that the radiative properties of an atmosphere somehow serve as the CAUSE of elevated steady-state planetary surface temps.

  1. The presence of an atmosphere on top of a solar-heated planetary surface forces the steady-state temperature of that surface to be higher than if the atmosphere weren’t there, because it acts like a layer of thermal INSULATION interposed between the surface and its ultimate heat sink – space. The surface heat loss will simply always be lower – at any given surface temperature – with an atmosphere on top than without.

  2. Even a 100% IR-active atmosphere wouldn’t, however, be able to make any difference whatsoever to the surface temperature if the ATMOSPHERIC temperature were equal to that of space itself.

  3. In other words, it is an absolute requirement for the atmosphere in question to be capable of producing an insulating effect on the solar-heated surface at all that it be WARMER than space. What sets an atmosphere apart from the vacuum of space, after all, is its (thermal) mass, making it able to be HEATED by the surface on which it rests, thus naturally allowing it to gain a temperature much higher than that of space and therefore much closer to that of the surface itself.

  4. So for any physical property of an atmosphere, if it – on balance – helps in making it warmer than space, if it contributes positively to its net heating, then it effectively acts to promote the atmosphere’s insulating effect on the solar-heated surface below.
  5. Which leads us to the crux of this argument: An atmosphere’s RADIATIVE properties, specifically, will not on balance contribute positively to the dynamic heating/cooling budget of that atmosphere; which is to say that an atmosphere containing IR-active constituents will end up COOLER on average than an atmosphere not containing such IR-active constituents. The radiative properties of an atmosphere’s IR-active constituents simply – and quite naturally – help cool the atmosphere to a much greater extent than they help in heating it …

  6. And so, insofar as an atmosphere’s radiative properties are not contributing positively to the net heating of that atmosphere, they also cannot be CAUSING the atmosphere to exert an insulating effect on the planetary surface.

So what is the cause? The atmosphere’s TEMPERATURE is. Those particular physical properties of an atmosphere that actually help making and keeping it warmer than space, that contribute positively to its dynamic net heat budget. The ability to absorb IR photons is not such a property. Because an ability to absorb IR photons is always accompanied by an equal ability to emit IR photons. And so it takes something else, something more, to turn that inherently dual process into a non-zero-sum game and have energy starting to accumulate. Because that’s what we want, that’s what we need. The capacity for holding on to energy, storing it internally over time. Not just the catch-and-release part.

The point here is that an atmosphere is good at both catching and releasing energy in the form of radiative heat, but only good at catching energy in the form of conductive heat and evaporative heat (latent heat of vaporisation). Which means that the two latter modes of heat transfer dynamically promote the accumulation of energy within the atmosphere, while the former mode does the opposite.

In short, an atmosphere’s IR-active constituents are capable of ridding the atmosphere of excess energy in the form of heat, while its non-IR-active constituents aren’t; they are capable of capturing heat coming in, but not capable of releasing it again. For that, they need their IR-active siblings.

Let’s put some numbers to this.

Our atmosphere’s global annual heat budget looks like this (flux values from Stephens et al., 2012):

Qin(total) = QSW(from sun) + QLW(from sfc) + Qcond(from sfc) + Qevap(from sfc) → 75 W/m2 + 32.4 W/m2 + 24 W/m2 + 88 W/m2 = 219.4 W/m2

Qout(total) = QLW(to space) → [239.7 – 20 =] 219.7 W/m2

Percentage-wise:

Qin = 34.2% + 14.8% + 10.9% + 40.1% = 100%

Qout = 100%

What can we read from this?

The atmosphere can only be radiatively heated if it is significantly able to absorb radiation. Likewise, it can only radiatively cool if it is significantly able to emit radiation.

Our atmosphere on average absorbs a SW heat flux (Qin(SW)) from the Sun worth of 75 W/m2 and a LW heat flux (Qin(LW)) from the surface worth of 32.4 W/m2, totalling 107.4 W/m2, which is quite exactly equal to 49% of its entire heat gain.

At the same time, though, our atmosphere on average emits a LW heat flux (Qout(LW)) to space worth of 219.7 W/m2, which makes up 100% of its total heat loss.

In other words, our atmosphere’s radiative Qin is less than half as large as its radiative Qout. On average, it cools more than twice as effectively via radiation as it heats via radiation. The non-radiative heat transfer mechanisms, on the other hand, only heat the atmosphere. They don’t cool it at all. On average.

Which essentially means that the strictly radiative processes operating in our atmosphere aren’t working towards making it warmer at all. They’re actively and continuously working rather towards cooling it down. Specifically compensating for the exclusive heating effect resulting from the non-radiative processes going on …

And that, my friends, is basically the end of the argument 😎



 

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9 comments on “An atmosphere’s IR activity won’t make it warmer, and so cannot be the cause of surface warming either.

  1. Christopher says:

    As I see it, your argument boils down to wether or not the IR-active molecules play a zero-sum photon-game.

    AGW-proponents tend to claim that collisional de-exitation of IR-active molecules are the mechanism behind energy transfer from vibrational states of the IR-active molecules to kinetic translational or rotational motions of non-IR-active molecules, resulting in temperature increase.

    However, what they hide under the carpet is that non-IR-active molecules colliding with IR-active molecules may equally well excite as de-excite the vibrational states of the IR-active molecules.

    When excited, the vibrational states of IR-active molecules result in emission of IR-photons.

    I have asked several AGW-proponents, presumably well-skilled in particle and radiation physics, for physical evidence showing that the collision process between IR-active and non-IR-active molecules results in a net one-way transfer of energy from IR-active molecules to non-IR-active molecules. Nobody has so far presented such evidence.

    Thus, to my knowledge, your claim that the IR-active molecules play a zero-sum photon game is most probably correct.

    • okulaer says:

      Hi, Christopher.

      I think it’s rather obvious that the IR-active molecules WOULD play a zero-sum game of photon absorption/emission if it weren’t for the negative tropospheric temperature gradient. It is the fact that each level of air, as you move up from surface to tropopause, on average has a lower temperature than the one before/below that creates the APPARENT radiative “heat retention” effect, ‘apparent’ because the thermal radiation is not actually what’s CAUSING it; it is itself just an effect of it. This whole issue really boils down to a simple confusion of cause and effect in the Earth system.

  2. gbaikie says:

    “The presence of an atmosphere on top of a solar-heated planetary surface forces the steady-state temperature of that surface to be higher than if the atmosphere weren’t there, because it acts like a layer of thermal INSULATION interposed between the surface and its ultimate heat sink – space. The surface heat loss will simply always be lower – at any given surface temperature – with an atmosphere on top than without.”

    An atmosphere will increase average temperatures.
    The Moon which has essentially no atmosphere has higher surface temperature of 120 C when sun is directly above the surface.
    Earth atmosphere blocks about 300 watts of direct sunlight, with clear sky and sun is directly above the surface.

    -Even a 100% IR-active atmosphere wouldn’t, however, be able to make any difference whatsoever to the surface temperature if the ATMOSPHERIC temperature were equal to that of space itself.-

    Space is very low density of atoms [these atoms are traveling very fast], space has no air temperature because lacks “air density”. All planets with an atmosphere with have a thermosphere- it’s when density of atmosphere is very low- and like space it has no air temperature.

    Anyhow one could have CO2 only atmosphere and depending size of atmosphere such a pure CO2 atmosphere could like Earth’s atmosphere, block about 300 watts of the direct sunlight. And this result in lower surface temperature. With earth the surface could warm to about 80 C and likewise with pure CO2 which blocked 300 watts, it would only warm to about 80 C..

  3. gbaikie says:

    “Which essentially means that the strictly radiative processes operating in our atmosphere aren’t working towards making it warmer at all. They’re actively and continuously working rather towards cooling it down. Specifically compensating for the exclusive heating effect resulting from the non-radiative processes going on …

    And that, my friends, is basically the end of the argument ”

    So argument is radiant properties of greenhouse gases are a cooling effect.

    I think don’t think greenhouse gases have a cooling effect.
    And I also don’t think greenhouse gases radiant effect causes 33 K of warming of Earth- I think it’s 1/2 of 33 K [or less].
    I would say that the CO2 of Venus and Mars, doesn’t cause cooling of these planets- though I don’t think the CO2 of these planets have much of warming effect.
    With Mars I think there is mostly a warming effects of CO2 because of latent heat of CO2 when snows out of atmosphere in the poles during winter- though the radiant effect in near zero.
    With Venus, I don’t have much of opinion of how much warming effect is due the radiant effects of the CO2, though probably more than Mars, But has little to do with accounting for Venus high temperature. What seems like unknown factor for me is the CO2 at critical temperature and pressure where it’s at 72 atm or more or when CO2 in quasi liquid state. But I think main factor related to Venus high surface temperature is related to it’s clouds.

    In terms of radiant effect of greenhouse gases, I believe it occurs at low elevation. Or say when air density is about 1 kg per cubic meter or more. Mars of course doesn’t have anywhere near this density- it’s around ,02 kg per cubic meter.

    • okulaer says:

      gbaikie:

      So argument is radiant properties of greenhouse gases are a cooling effect.

      I think don’t think greenhouse gases have a cooling effect.

      You did read my post, right? The strictly radiative properties of the IR-active constituents of our atmosphere (they are NOT “greenhouse gases”!) definitely help cool the atmosphere – on balance. They ALSO aid in heating it, but their cooling effect is much stronger. As you can easily read from any Earth energy budget. Our global atmosphere is – on average – heated by a total radiative flux of [75+32.4=] 107.4 W/m^2, but is simultaneously cooled by a radiative flux of 219.7 W/m^2. Both fluxes are a direct result of our atmosphere’s distinctly radiative properties. So the radiative cooling of the atmosphere (Q_out(rad)) is more than twice as strong as the radiative heating (Q_in(rad)).

      It is very much the other way around for the surface. It is heated by a radiative flux (from the Sun) of 165 W/m^2, but is only at the same time cooled by a radiative flux (to the atmosphere and space) of a mere 52.4 W/m^2, so the radiative heating of the global surface is on average more than three times as strong as the radiative cooling.

      • gbaikie says:

        “You did read my post, right? The strictly radiative properties of the IR-active constituents of our atmosphere (they are NOT “greenhouse gases”!) definitely help cool the atmosphere – on balance”

        Well not sure about “the IR-active constituents of our atmosphere (they are NOT “greenhouse gases”!)”
        I would say CO2 counts as greenhouse gas and also is “IR-active”.
        One could say clouds are “IR-active constituents of our atmosphere ” and not gases or subset of gases which are greenhouse gases.

        I don’t think clouds or gases cool the atmosphere due to them being IR-active.
        I would say surfaces warm and cool. Though one could call clouds a surface, but Earth’s main surface is it’s ocean surface, and Earth’s land surface does most of cooling of Earth.
        Earth’s land surface provide highest temperature and highest surface air temperature, but land surfaces don’t increase earth’s global temperature, rather they decrease earth’s global temperature.
        Earth’s average land temperature is about 10 C and ocean surface temperature is about 17 C. Land surfaces have regional effect and oceans have a global effect. Even if Earth had 70% of surface being land and 30% ocean, land would cool the global temperature and ocean would warm the global temperature, of course since ocean are 70% of earth surface it warms more as compared to a planet with only 30% of surface being ocean.

        Earth oceans have global effect rather than regional like land, because ocean absorb more of the sun’s energy and prevented from having a high surface temperature, because it evaporates.

        The ocean absorbs more of energy of the sun for number of reasons, one reason which not mentioned much is that the ocean absorbs both direct and indirect sunlight. Wiki, sunlight:
        :… If the extraterrestrial solar radiation is 1367 watts per square meter (the value when the Earth–Sun distance is 1 astronomical unit), then the direct sunlight at Earth’s surface when the Sun is at the zenith is about 1050 W/m2, but the total amount (direct and indirect from the atmosphere) hitting the ground is around 1120 W/m2″
        So ocean absorbs 1120 watts and land absorbs 1050 watts at noon, sun at zenith, and a clear sky.
        And when you have clouds and sun is further from zenith, one gets a more higher ratio of indirect sunlight as compared to direct sunlight.

        And the temperature of the air above ocean is close to surface temperature [because of evaporation]. Land surface [unless there are wet] have a wider differences of temperature between ground and air above it.

        So oceans control global surface air temperature, and surface air temperature controls the temperature of air above it. [and air above controls the surface air temperature- global ocean controls air temperature above land surface air- or if you could *somehow* prevent the global air which is warmed by ocean surfaces from warming land surface air, then land surface air would be colder than it’s average of 10 C].].

        • gbaikie says:

          The model of ideal thermal conductive blackbody in a vacuum and at earth distance of the sun. absorbs on average about 340 watts and emits uniformly 340 watts. And a blackbody emitted 340 watts per square meter in a vacuum
          has temperature of about 5 C.

          Now the ideal conductive body conducts heat to night side of sphere, and it would easy not to conduct the heat to night side [the hard part of magic of ideal thermal conductive blackbody is conducting the heat to night side -and providing a uniform emission of energy, everywhere].
          If ideal thermal conductive blackbody only worked on day side of planet, it
          absorbs on average 680 watts per square meter and emits 680 watts per square meter- giving uniform day side temperature of 330.9 K [57.75 C].

          Now if didn’t have ideal conductive body, the sunlight would heat sun lit side
          where the sun is closest to zenith- noon and near equator and least near sunrise and sunset- and nearer poles [at all times].

          in terms of ideal thermal conductive blackbody, Earth day in sunlight could get quite warm, particularly in the tropics [though night side is very cold].
          Or in terms of understanding Earth’s average temperature, the question is how does nights and poles be as warm as they are. And answer is earth ocean warm these areas.

  4. RealOldOne2 says:

    Since the atmosphere’s “TEMPERATURE” is what causes the atmosphere to have it’s insulating property, that means that all of the constituents of the atmosphere which have thermal mass, ie. the N₂ & O₂ & Ar which make of 99.7% of the atmosphere’s capacity to store thermal energy, are what make the greenhouse “effect” work to keep the earth warmer than it would be without an atmosphere. The science of the atmosphere shown here: http://www.calqlata.com/Maths/Formulas_Atmosphere.html confirms this.

    All matter above absolute zero emits EM radiation:

    “Everything on Earth emits longwave radiation energy continuously.” – IPCC, http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-1.html

    The N₂ & O₂ & Ar in the atmosphere is part of that “everything on Earth”, so they also emit EMR.

    “Did you know that any object that contains any heat energy at all emits radiation? …
    All matter in the universe acts this way. …
    Any matter that is heated above absolute zero generates electromagnetic energy.” – NASA, Basics of Radio Astronomy, Chap.3, https://web.archive.org/web/20090419122219/https://www2.jpl.nasa.gov/radioastronomy/Chapter3.pdf

    The N₂ & O₂ & Ar gases in the atmosphere contain thermal energy, so they do radiate because they are at the same temperature as the CO2 molecules and because they are above absolute zero temperature.
    This thermal mass is what makes up the TEMPERATURE which acts as insulation and reduces the rate of heat loss from the surface compared to what it would be without an atmosphere. q=ϵσ(Th⁴-Tc⁴). The ~255K Tc of the atmosphere makes q lower than if Tc were ~0k without an atmosphere.

    And when the surface emit’s LWIR and that LWIR is absorbed by a radiatively active gas in the atmosphere, it transfers that absorbed energy to surrounding the surrounding N₂ & O₂ & Ar by conduction/collisions well before it can re-emit that radiation. This is confirmed by Dr. Happer, Prof. of Physics emeritus at Princeton, here: http://www.sealevel.info/Happer_UNC_2014-09-08/Another_question.html

    It’s only in the upper atmosphere when there are few surrounding N₂ & O₂ & Ar to collide with that the radiatively active gases have enough time to re-emit absorbed LWIR, and transfer heat to colder space, not to the warmer surface of the earth. That’s when the radiatively active gases do their work of cooling the planet.

    And there is no thermal energy transferred from the cold atmosphere to the warmer surface like the climate alarmist claim. This peer reviewed paper which was written expressly from the perspective of the 2nd Law of thermodynamics and the global climate system shows that: https://a.disquscdn.com/uploads/mediaembed/images/3163/2606/original.jpg There is no energy flux from the atmosphere to the surface.

  5. Perhaps you could elaborate on how the following formula is derived in the absence of bidirectional energy transfer?

    q=(σ(T2⁴-T1⁴))/(1/ϵ2+1/ϵ1-1)

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