CO2 As A Coolant

The greenhouse effect near the surface is completely dominated by water vapor, but in the upper atmosphere there is little water vapor – so the greenhouse effect is dominated by CO2, which radiates out into space and cools the planet.

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72 Responses to CO2 As A Coolant

  1. Now you’re cooking!!!

    • I am blogging science here, like I have always done. The fact that some people like to pick and choose which facts they believe doesn’t impress me.

      • Scottish Sceptic 2011: “CO2 the cooling gas. The simple fact is that CO2 is a cooling gas. It tends to cool the atmosphere where the CO2 is warmer than the surrounding environment … which high in the atmosphere is the cold of space.”

        • CO2 warms the lower atmosphere.

        • AZ1971 says:

          What relevance does knowing that CO2 warms at the lower atmosphere levels and cools higher up, when compared to water vapor which is much more abundant and broad-spectrum? We live on the surface of the planet, not 100km up. What’s relevant is what’s going on here at the surface, and water vapor is the 800-pound gorilla in the room.

        • Andy Oz says:

          They can’t tax water vapour. They can easily implement a global tax on carbon, via a WTO tax on coal, oil and gas. “Climate science” is the magicians left hand distracting the observer, while the right hand implements the tax. Panicking the punters with End of the World stories, means the implementation of the C Tax is demanded by the sheeple.

          By the way, how come the USA dropped all the u’s in all words ending with “our”?
          Is it a French thing?

        • Andy all the spelling rules in the US were invented by Noah Webster. Ask him.

      • CO2 warms lower – in a static atmosphere you are certainly right. Once we start considering convection I’m not so sure. It traps more heat in the lower atmosphere but that could be offset by higher emissivity in the upper atmosphere.

        And when we add clouds in … argghhhh!!

        It’s like one of those black and white bladed things in a near vacuum. One theory says the black emits more than the white, another says the black absorbs. Another says the black is hotter so the gas hitting it is expelled. All I know is that it rotates one way and I would have to see one to know which way it is.

      • davidswuk says:

        Science is the art of constructing theories which explain the observable facts and not just listing them.
        What we do not know (yet) is whether co2 is a net warmer or cooler 24/7 but what we do is that it does not have the tools to warm complex substances by way of LW radiation or anything already warmer than itself and,in ant case, is but a bit player in a very big Ballgame.
        For Co2 to be an active Stratospheric coolant the Troposphere would have to near transparent to it and so I see it as just another gas radiating some heat back into Space
        whilst, down below, Mother belches off all She doesn`t need.

  2. Password protected says:

    Wasn’t that long wave radiation in the upper atmosphere on its way to space anyways?

  3. nielszoo says:

    It doesn’t really make much difference what the gas composition is at the very low pressures at the top of the atmosphere. Different gases just radiate energy at different wavelengths so they all act to radiatively cool at pressures below ~100 mbar. CO2 cools us a bit less than most due to it’s predominately LWIR emission spectra that emits lower energy photons than the other gasses… and the fact that there ain’t a heck of a lot of it anyway.

    • Gases either absorb or they do not. So, they are either opaque and absorb or emit electromagnetic energy (depending on temperature) or they allow light to pass through.

      So if we look down on the earth the electro-magnetic spectrum we see will consist of the highest IR interactive molecules OR the surface.

      So, more CO2 will mean that there is more chance of “seeing” a molecule interacting at the wavelengths that CO2 emits/absorbs. But it doesn’t change the chance of seeing wavelengths at which CO2 is transparent.

    • Robert Austin says:

      Mono-atomic (argon) and diatomic (O2 & N2) gases have no significant excitation states in the long wave spectra so they do not radiate in upper troposphere. Greenhouse gases and aerosols do radiate in the long wave spectra, hence their importance to our atmospheric structure. That being said, the system is almost certainly extremely insensitive to changes in CO2 concentration above 20-50 ppm. In other words, the modern increase in CO2 concentration theoretically will raise the earth’s surface temperature, but to paraphrase Richard Lintzen, the effect is trivial.

      • nielszoo says:

        All we’re trying to do is get rid of energy, whether UV, Visible or the IR gamut. Both Nitrogen and Oxygen have excitation bands in the 1 to 5 micron range and will dump energy to a place with higher entropy… space. Earth, like most planets is a broadband emitter. Whether it is water, CO2, Nitrogen, the Oxygens or Argon rising in the column and then radiating at its specific λ’s it’s still moving energy out to space in order to get back to equilibrium.

    • Gail Combs says:

      Scottish Sceptic,
      I am afraid that Niel is correct. That is why the thermospherehas a temperature range from about 500° C (932° F) to 2,000° C (3,632° F) or higher.

      Everyone forgets we have incoming and outgoing energy at a wide range of wavelengths from EUV to IR. The atmosphere gases don’t care where the energy is coming from they only care whether or not the wavelength is correct.

      You can see H2O emitting at just below the tropopause and O3 and CO2 emitting in the stratosphere just above the tropopause.

      • It depends what you mean by “top”. By “top” I meant above the bulk of the atmosphere which is about 10-20km so much cooler than the surface. Looking at your posts you are using “top” to mean …. I presume some random distance – which is neither the top in terms of volume nor top in terms of distance (nowhere near the 500km at which we still find traces of the atmosphere) … obviously by “top” you mean “the warmer 80% (by distance) above 100km”.

        • Gail Combs says:

          The temperature decreases with height in the troposphere, increases in the stratosphere, decreases in the mesosphere and again increases in the thermosphere.

          Water is dumping energy at the tropopause ~10KM and according to Dr. Happer CO2 (barely) starts dumping energy at 11KM. Ozone is most active between 20KM and 30 KM.

        • nielszoo says:

          Gases are lousy emitters at “normal” pressures and do all of their energy transfer via mechanical means… ie molecules bumping into one another. (When we want them to radiate we dump enough energy in to turn them into plasmas.) I don’t think any gas radiates at atmospheric pressures and temperatures normally found on Earth below the stratosphere as we’re pretty close to equilibrium and conduction and convection does the energy transfer. At the temperature ranges in our atmosphere you’re talking about <100mb or 15km+ in altitude before the molecules get scarce enough that they keep energy long enough to have to drop to ground state to get rid of it, which results in radiating a photon at a characteristic wavelength.

        • The bullshit level here is going off scale

        • Gail – interesting graphic that “spectral cooling rates for the Mid-Latitude summer atmosphere”. I make it 2K cooling at 100mb, 20k at 10mb and ~200k at 1mb, which I guess makes the rate of heat energy loss fairly constant from the top of the troposphere. Would love to see the original paper – but it’s behind a paywall.

      • Janice Moore says:


        Thanks to Stewart Pid and rah who graciously replied to my “where’s Gail Combs I miss her” post, here:, I found you!


        I miss you (not that I’m at WUWT all that often… still looking for work…grr). Did you get that legal research I tried to have forwarded to you? Sure hope you found it helpful!

        Your old WUWT pal,

        Janice Moore

        {Dear mo-der-ator — please forgive this off-topic aside — I’ve been concerned about Gail for quite some time, now. Thanks for your patience with me here.}

  4. Sorry to disappoint but most of the cooling from Earth into space happens from the tropopause (water vapor) and black body radiation from cloud tops (water droplets) and radiation from the terrestrial surface which gets out through the N-band window. CO2 has very little to do with anything at the top of the atmosphere. It’s all about the water vapor and N band.

    You see, the 15 micron band is a low emitter. Look at this and ponder why there is so little emissivity in the 15 micron region.

    It’s because CO2 doesn’t amount to a hill of shizzle.

    • Morgan, any chance you happen to have some quantitative data on the relative emissions of IR from a cloudy and cloudless sky?

      • Gail Combs says:

        Dr. Happer may have the info. You can ask via David Burton who sometimes comments here. He has Dr Happer’s e-mail.

      • nielszoo says:

        I have a new thermal camera on order (for work) and that’s one of the things I intend to look at some weekend when the weather cooperates… as a comparison between the two ONLY. Its sensitivity is right across the LWIR range of H2O and CO2 but since I don’t have any MW or LWIR bandpass filters I can’t isolate anything specific wavelength wise.

        • Nielzoo, I am so envious!! A few years ago I begged and begged everyone I could think of to get hold of a camera. Nothing at all to do with climate, but something equally as interesting relating to archaeology.

          Drew a complete blank and if you live anywhere in the UK ….

          I will post anything you produce as an article, but I notice you’ve started/got a blog.

        • nielszoo says:

          SS, I’m in rural Central Florida so there’s a bit of water between us. I got a bit of side work a while back and bit the bullet and added one to my test gear suite. I had visible and SW~MW IR covered (I don’t do any UV work) but had to farm out LW thermal testing the last time I needed it.

          My other application will be veterinary with our passel of “special needs” rescue animals. (FYI the blog is a placeholder. I wanted to comment on a site the other day and it wouldn’t take my regular WordPress log on, it expected a valid URL as well. I may use it as an online archive of links to exceptional posts on sites like Steven’s.)

        • nielszoo – I’ve a few vets in the family so I’d be interested to know how you intend using the IR camera (a friend of mine is also looking at using IR for medical use).

    • Latitude says:

      CO2 has very little to do with anything at the top of the atmosphere…..

      exactly….and CO2 has very little to do with anything at the bottom either

      …and that’s the point, CO2 is just not that strong of a player

    • RoscoRosco says:

      That graph shows clearly how little effect GHG’s actually have on the direct emissions to space.

      The plot is approximately equal to a 295 K emission curve from ~8 to ~13 microns. Virtually all the radiation from these wavelengths escapes directly from the surface with the exception being the “bit” taken out by Ozone.

      Below 8 microns there is little radiation from the Earth anyway as the surface temperatures are never hot enough to cause significant emission in these wavelengths – 8 microns represents the peak emission from something that is almost 90 degrees C and there are few natural surfaces at that temperature – NASA says 70.7 is the maximum they’ve measured.

      This area of the curve does not represent absorption by GHGs unlike the other areas.

      Above 18 the emissions again show little effect from GHGs although the curve approaches a 260 K curve. 18 microns represents the peak emission from something that is almost minus 112 degrees C.

      If you sum the areas under the curve it is apparent that significantly more than 50 % of the surface radiation escapes freely to space – even if you approximate to a 300 K curve.

      The area under a Planck curve represents sigma T^4 after all.

      It is also instructive to see these curves using a different variable such as wavelength rather than wave number.

  5. davidswuk says:

    “The bullshit level here is going off scale”

    If you ever might mean “Bulls-Hit” I reckon you couldn`t even hit the board matey……..otherwise I`d go with the above summary describing that it is quantified by use of the Bushel dwarfing “Hills”.quantum.due to its extra-ordinary size.

  6. Salient point . Plant food is indeed a COOLING agent. Grade 9 science use to teach this.

  7. Ben Vorlich says:

    You recently posted this

    PV = nRT
    Posted on December 1, 2014 by stevengoddard

    If P, V and n remain the same, T has to remain the same as well.

    P and n are fixed in the troposphere, so the only degrees of freedom in the Ideal Gas Law equation are V and T.

    PV = nRT and can also be written PV = NkT
    k = Boltzmann constant
    N = number of molecules
    In converting O2 into CO2 the number of molecules remains the same.

    CO2 content of the atmosphere has increased (according to the data) by ~50% since the industrial revolution.

    CO2 is a denser gas than O2 therefore the mass of the atmosphere has increased and therefore, if nothing else changes, the P in the equation changes (increases) therefore as N and k are constant the T must also increase. Now you’re going to say

    1. Other things have changed
    2. The increase in P and therefore T are miniscule.

    I don’t have the data to hand but USHCN say that US has increased by 1’F, which is 0.5’K give or take a smidgeon. This is about 0.15% of T in the equation for earth. My rough estimate is that the mass of the atmosphere* has increased by a similar percentage in the same time.

    * Not counting water vapour.

  8. SMS says:

    According to the CAGW theory, the middle/upper troposphere is suppose to warm at an accelerated rate compared to the surface of the Earth. It’s been awhile since I’ve seen an update but the last information I remember reading showed that neither UAH or RSS have found any difference in the rate of warming/cooling between the two levels; which is another invalidation of the CAGW theory.

  9. higley7 says:

    During the day, CO2 and water vapor are emitting and radiating IR with only a tiny bit of energy converted to heat, but equally able to convert heat into IR. It’s a two way street. So, during the day, the radiative gases are a wash and have no effect. Any downward directed IR is reflected by the surface, which is always hotter than the IR source gases in the atmosphere. It is not possible for a cold gas to heat a hotter surface.

    It is during the night when there is no outside energy input, that these radiative gases convert heat energy to IR, which is either radiated upward and lost to space or radiated downward, reflected by the surface, and sent back upward and out to space. That is why the air cools down so rapidly after sundown and why breezes pick up so fast in the shade of clouds on a partly cloudy day. It takes seconds for the air to cool in the shadow of a cloud, creating pressure differences and these breezes.

  10. Centinel2012 says:

    Reblogged this on Centinel2012 and commented:
    I have saved up a series of Climate posts to re-post and they are all good and should be read. I will be putting this same message in all of them to save time.

  11. johnosullivan says:

    Steve and others,

    Once you accept CO2 cools upper atmosphere and warms the lower, you are in the business of defining what you mean by global warming and average temperature. The net depends on how you average, an arbitrary procedure. See below

    CO2 can’t cause warming because CO2 emits IR as fast as it absorbs. Greenhouse effect believers need to write the energy conservation law for a CO2 molecule they describe, with clear definitions and correct parameters. At steady-state, when dT/dt = 0, I assure you the rate of absorption equal rate of emission, no matter what the body is.

    CO2 cools, not warms the atmosphere. No empirical evidence has been adduced to show otherwise.

    Adding CO2 to the atmosphere has no effect because the CO2 absorption bands are already 100% opaque. When you see S-B intensities like NASA AIRS CO2 retrievals how do you determine whether it is caused by changes in T or emissivity? So what is the actual effect of adding CO2?

    Lower atmospheric warmth is due to the lapse rate/adiabatic compression.

    Warming causes CO2 to rise, not the other way around. Yes, human emissions from hydrocarbon combustion adds CO2 to atmosphere. Solubility of CO2 in water (ocean) decreases with water T, high school chemistry for Champagne drinkers. The lag is known to be about 800 years.

    The IPCC’s ‘theory’ is pure junk science. As the 1,000+ scientists at Principia Scientific International will attest, there are ‘Almost as Many Greenhouse Gas Theories as Clueless Climate Scientists.’
    So much for “settled science.”

    • Curt says:

      John: You say “CO2 can’t cause warming because CO2 emits IR as fast as it absorbs.”

      By that logic, a solid substance on the earth’s surface — let’s say a black asphalt parking lot — emits visible light as fast as it absorbs.

      Of course, we know that’s nonsense. Why doesn’t it happen — if emissivity equals absorptivity at any wavelength? Because the asphalt parking lot, even if at 50C (323K) is far colder than the sun at 5700K.

      Absorptivity and emissivity — the numbers that are equal — are fractions of the magnitude of the blackbody Planck curve for that wavelength at any temperature. The magnitude of the Planck curve increases with temperature at all wavelengths.

      Therefore, a substance absorbing a certain fraction of radiation at a certain wavelength from a hotter body, even though it emits the same fraction for that wavelength as a blackbody at its own temperature would, is emitting less than it absorbs.

      • davidswuk says:

        I didn`t see a black band in the last rainbow I saw and would therefore suggest that black asphlat radiates in the IR rimariiy.
        As to heat exchange though much of its emission would be by weather condition controlled convection and so it must follow that its heat loss by way of radiation would be considerably less than its gain.

  12. PetterT says:

    Don’t tell the “warmists”, cause when global cooling starts after the present hiatus, they will blame cooling on CO2 and ban all heating by fossil fuel so we will freeze to death (instead of being cooked according to “the oceans will boil” Dr. (!) James Hansen)

  13. northernont says:

    Ahhh..CO2 the magical molecule. Responsible for all sorts of planetary ailments, from being the cause of sinking the Titanic to altering the croaking of frogs to a higher pitch, or alternatively making them squeal like a pig. As the warmist (insert your favourite opportunist here) CO2 creed goes…Never was so much owed by so many to so few molecules.

  14. nickreality65 says:

    Steve/Andrew S.
    “LWIR is at the lower energy end of the E.M. spectrum (true) while Radar and Microwaves are higher energy much shorter wavelengths (not true).”

    Not so. Lower energy = longer wave lengths.

    High energy/short waves to Low energy/long waves
    Gamma/X rays – UV – Visible – IR – Radar/microwave – radio waves.

    I trust Wiki copied the table correctly.

    4 Types of radiation 4.1 Boundaries
    4.2 Regions of the spectrum
    4.3 Radio frequency (Lowest energy & longest waves)
    4.4 Microwaves
    4.5 Terahertz radiation
    4.6 Infrared radiation
    4.7 Visible radiation (light)
    4.8 Ultraviolet radiation
    4.9 X-rays
    4.10 Gamma rays (Highest energy and shortest waves)

    • Andrew S says:

      nickreality65, I corrected my comments with the added comment to “disregard, I was wrong.” Faulty memory of e.m. spectrum, then I looked, thought aww crap. “Now… I know.”

    • Andrew S says:

      I suppose I confused the Radio Spectrum with the visible light (and fringes) spectrum. When it’s all part of the one e.m. spectrum. :/

  15. Gail Combs says:

    higley7 says:
    The runaway anything idea is bogus. Why does everything have to runaway? …
    You are correct. As Dr Brown has stated repeatedly at WUWT the climate is a bistable chaotic system. But it is fun to jerk the chains of the warmists with ‘Snow Ball Earth’

    You do however have jumps from stable state to stable state like Dansgaard-Oeschger oscillations, Bond events and Heinrich events that cause global temps to change 8C to 16C in dramatically short times and NASA and everyone else hasn’t the foggiest idea of why.

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