CO2; Exactly HOW does it warm the planet?

When people with some science background first read the explanations of CO2 warming the earth due to its “greenhouse” properties, they usually start objecting on various grounds.  Actual greenhouses do something entirely different, or that breaks the laws of thermodynamics, and so on.  It takes a considerable amount of investigation (for me anyway) before one gets to the conclusion that the claims made are fundamentally correct.  It isn’t the science that is flawed (per se) it is the explanation.

The conclusions on the other hand are often flawed and sometime horrendously so.  Conclusions however, cannot be evaluated against just CO2 and how it behaves when interacting with long wave radiation.  They must be evaluated against the climate system in its entirety, and we are increasingly seeing evidence that many of the catastrophic claims are alarmism based on a massive over estimation of any number of factors that govern climate as a whole.

Yet the discussion always returns to CO2 and what it does.  The claims being fundamentally correct, but the basic explanations being flawed, there have been many attempts to arrive at an explanation simple enough for almost anyone to grasp, while at the same time being accurate enough to be useful as part of the larger discussion.  Not that easy to do, I and many others have failed and failed often.

Recently, Ira Glickstein came up with a physical analogy and posted it on WUWT where it generated a considerable amount of discussion, both pro and con. 

http://wattsupwiththat.com/2011/02/20/visualizing-the-greenhouse-effect-a-physical-analogy/

I think it is one of the best explanations I’ve ever come across that explains what is happening in the atmosphere at a basic concept level from the perspective of CO2 as a “greenhouse gas”.  But as can be seen from the comments, the model isn’t sufficient for other purposes such as understanding how CO2 behaves in a real atmosphere comprised of many other gasses.  It also generates additional questions.  Once people get the basics in their heads, they ask more in depth questions.  In the thread at WUWT, a commenter named “wayne” asked several questions and then concluded with “so, its not warming, its more like delayed cooling”.

My immediate thought was YES!  Not exactly, but close.  How could I depict the issue that wayne was trying to understand at the most basic level possible while retaining a reasonable level of accuracy?  Something I’d done during a white board discussion came to mind and this is the result.  This is my first crack at it, and feel free to be critical or ask questions, I’m looking for feedback so I understand if the messages I’m trying to encapsulate are coming through properly or not.  Then of course there is the possibility I may be wrong.  Well, to be more accurate, I AM wrong.  Models are by their very nature not reality.  They might be close, but at some level they are wrong.  Good modeling is about coming up with a model that is useful, and to the extent possible, as least wrong as can be.

So the explanation that follows is wrong on many levels.  To demonstrate how CO2 results in a warmer earth, I’ve constructed an atmosphere of sparsely populated CO2 molecules and nothing else.  I’m not trying to depict how CO2 interacts with long wave radiations in the atmosphere, I’m only trying to depict how CO2 would interact with long wave radiation if there were no other factors.  To do that, I’ve depicted it in a manner that is far out of proportion from reality.  For example, I show in the slides a photon being emitted by earth surface (LW radiation) as possibly escaping to space unimpeded.  In theory, that is possible.  In practice, highly unlikely.

The chances of any given photon not being absorbed and re-emitted thousands, perhaps millions or billions of times on the way out to space it nearly zero.  Further, when a photon is absorbed and re-emitted, it can be emitted in any possible direction.  It may zig zag up, down and sideways many times before it reaches space.  But at day’s end, the sideways moving photons cancel each other out, and the upward moving photons slightly exceed the downward moving photons.  The model presented is not to in any way to quantify the end result.  The model is only presented to provide an understanding of what the process is, why it in fact does conform to the laws of thermodynamics, that it does not “invent” new energy as many claim, and how the result is a warmer earth surface (in the absence of any other factor, which is again, not realistic)

To quickly review the theory, the sun emits Short Wave (SW) radiation that for the most part goes right through our atmosphere as if it did not exist.  That is because the molecules that make up our atmosphere cannot absorb such high energy photons.  The SW radiation as a result heats up the earth, which in turn results in the earth radiating energy back up.  But the earth is much cooler than the sun, so it radiates much lower energy photons, and we call these Long Wave (LW) radiation. 

LW photons can in fact be absorbed by CO2 molecules, which increases the energy level of that molecule.  But energy always tries to even itself out.  If the molecule absorbs a photon and as a result is at a higher energy state (warmer) than the other molecules around it, that photon will be gotten rid of.  That could happen by transferring it during a collision with another molecule, or simply emitting it so that it zips off at the speed of light in some random direction.

The model below presumes that a certain amount of energy from SW is entering the system at all times.  The number of photons of SW doesn’t matter for this part of the discussion.  What matters is that the amount of energy they carry is equal to the amount of energy of six LW photons being generated by the earth surface.  The model assumes also that even if the CO2 “atmosphere” and the earth surface change in any way due to the “greenhouse” effects of CO2, that the amount of SW absorbed still won’t change.  Again, not realistic, but the model still serves its purpose in terms of illustrating why CO2 in theory warms the earth.

And that, believe it or not, is what all the fuss is about.  The question asked on WUWT by commenter “wayne” is a reasonable way to think about it.  As a consequence of additional CO2 in the atmosphere, a new equilibrium is established in which the photons escaping to space still escape, but some number of them may be “delayed” on the way out, either existing for an extra moment in time absorbed in a CO2 molecule, or perhaps recycled back down to earth where the result is a warmer earth surface that generates photons at a higher rate to compensate.

But as for the laws of thermodynamics?  Intact. 

As for actual magnitude and actual behaviour in an actual chaotic atmosphere comprised of many different kinds of molecules and subject to many different kinds of processes?

Sorry.  I have no model for that, and my answer is I really don’t know.  That is similar to a lot of climate scientists mind you.  The difference is that they do have a model, but really don’t know.

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8 Responses to CO2; Exactly HOW does it warm the planet?

  1. wayne says:

    David, I gather this is the subject and visuals you were going to send me. Now you have my e-mail. Now I will read to see if you are paralleling my thoughts.

  2. wayne says:

    Without making a whole string of comments to kick this off I’m just going to take notes, positive and negative as I go read down this example. Wish you had put the words under each slide so the text could be read (my slipping eyesight) and would be selectable for comments.

    — One I like you simplifying to only up and down. That really is proper by physics since any horizontal component in the vectors are always cancelable by another molecule doing the same thing but in the opposite horizontal direction, that is in the case of the atmosphere about a sphere. There is a name for that ‘ignoring’ but I can’t recall it.

    — One thing you didn’t explicitly state is that whenever the ground emits a photon it cools by that amount depending on the frequency. Same for any molecule in the atmosphere, if it absorbs it warms, if it emits it cools. I which you would have kept track with the exact state of the surface for it would have added some clarity for I see a flaw later in you sequence.

    — Since your sequence of named slides go 1, 4, 2, 3, 6, 5 I will use the natural order that they are displayed instead with the slide name in parenthesis.

    Slide one (1):
    All is in a steady state so atm and surf is zero.

    Slide two (4):
    6 SW into surf – 8 LW out of surf + 2 LW in from atm = surf is 0
    4 LW into atm – 4 LW out of atm = atm is 0
    6 LW to space

    Slide three (2):
    Intermediate step since next slide has same displayed.

    Slide four (3):
    6 SW into surf – 8 LW out of surf + 2 LW in from atm = surf is 0
    4 LW into atm – 4 LW out of atm = atm is 0
    6 LW to space

    Slide five (6):
    You lost me here and here is why. Just because you add more co2 molecules does not mean they have to interact and are being affected by what the surface is doing. The incoming SW is constant. The atmosphere and the molecules ‘know’ nothing of the surface. This is the GHE where I do not agree. There would just be more co2 molecules that are not affected at all for each slide (dt) as you step one by one, slide by slide, just more blue molecules that do nothing in one given slide.

    There are plenty of co2 (h2o too) molecules that are not being affected each tick (dt). I have read it is something of 95% are just waiting for a photon of the exact frequency (not vibrationally excited) to intersect it so it can absorb. Adding more co2 will only increase that percentage that are dormant.

    You see, the AGW side would have you believe, and I mean visually see in your mind, that all of their ‘science’ that tests in close bottles in a lab show. But if you were able to take their jar and have it open on one end with near zero degrees at the open end, held by gravity, and re-run the experiment you would get a totally different result unless your LW source was so strong that you totally saturate all of the absorbers so that reverse thermalization could no longer occur, then you would see the temperature rise, that I do understand. Thermalization to O2 and N2 would still occur but the symmetric reverse would be blocked because there would be so many photons at that exact frequency that would immediately re-excite it. Thermalization would be then a more one-way street.

    Bottom line is there are so many real physics properties that are totally left out of such simple visualizations that the total picture is blurred unless further refinement is continued until the total picture is seen. David, that is why I wanted you to watch those Feynman lectures, not to learn quantum electrodynamics but to see how he took a terribly complex process and one step at a time he refined it until at the end you could have a total picture in your mind of what REALLY happens in nature. Wish we could do that here on a blog but my hopes are quickly fading. Too much noise.

    However your visualization is very close. I followed it step by step through the first few slides and there I agree. That is why I was so happy to see Ire in #3 on WUWT to show that ‘up, split, and down’ process. That by itself is correct and a start. Yours is even better though I would not put so many into play, it’s hard to go through and count each flux, a bit too busy.

    If I were you I would keep right on the track you are on and be careful making closing absolute statements such as “As a consequence of additional CO2 in the atmosphere, a new equilibrium is established” for I don’t remember trying to leave that view. I’m still not sure a need for a new equilibrium exists in reality. Miskolczi says his analysis of the radiosondes show it doesn’t exist. I’m still hang out there in space (so to speak).

    Sometimes I wish I would stop trying to say everything in one single comment. ☺

    • davidmhoffer says:

      wayne
      Thanks for the comments. The reason the logic didn’t flow is that I messed up the order of the slides. Should be fixed now, please breeze through it again.

      Re your criticism of Slide 6 or 5 or whate ever it is now
      You are correct in that just because you add some CO2 it doesn’t mean that they have to interact, and no, they don’t know what the surface is doing, they don’t even care. If you take a look, we started with 20 molecules, 4 of which “on average” absorbed a photon. Then we added 50% more. 30 molecules, 6 of which “on average” absorbed a photon. If we assume that the atmosphere stays the same size (not necessarily correct) then the density of CO2 molecules increases, and the percentage chance that any given photon on any given path will be absorbed goes up. So, if there was a 60% chance of a photon escaping to space in one leap, now it is only 40%. If “on average” a photon was absorbed and emitted 100 times before escaping, and we increase by 50%…well, now we have to figure out permutations and combinations, because the answer is NOT 150. I don’t think. I’ll ponder that and/or dig up a stats guy to ask. CO2 is known to be logarythmic, I just have to figure out how that applies in this model.

      As for the lab experiments, they are mostly hogwash and they are well known to be hogwash because they don’t scale to reality any more than my depiction above does, and the reasons are well known. Even putting aside the existance of other kinds of molecules in the atmosphere, the cylinder in the lab with CO2 in it isn’t even close. For starters, it is at pretty much the same temperature from one end to the other. In the atmosphere, temperature declines with altitude. So the frequency range of photons that can be absorbed or emitted changes with altitude. And time of day. And latitude. And season.

      PLUS, the pressure in the lab cylinder is stable. In the atmosphere, pressure declines with altitude, so while the CO2 concentration may be stable in terms of parts per million, in terms of molecules per cubic meter, it declines.

      If that hasn’t completely discredited the lab cylinder experiment yet, let me continue by adding JUST water vapour to the picture. If we were to add H2O molecules to the diagrams, unlike CO2 which is evenly distributed throughout the atmosphere, the H2O molecules would be clustered at the bottom. In the real world, the holding capacity of the air declines with temperature, so the water vapour concentration may be as high as 40,000 ppm or less than 1,000 depending on temperature. And temperature varies with…altitude, time of day, latitude, and season. So down at the bottom of our graph, at 40,000 H20 vs 390 CO2, there’s not much point even doing the math to calculate the effect from CO2, it is meaningless. But as we move in altitude, latitude, season and so on to cooler temperatures and lower levels of water vapour, CO2 becomes more and more significant.

      Sorry, not done thrashing those stupid lab cylinders yet. What else goes on in the atmosphere? Convection! As air is heated at the equator, it rises, pulling in cooler air from the temperate zones. As the hot air rises, it cools. How? By on average emitting more photons than it is absorbing. And as it cools, the wavelength of photons that is released changes… the percentage chance that an emitted photon from a rising molecule of CO2 will escape increases as the molecule gains altitude because the path to space is shorter. And the cooler air being sucked down from the poles is doing the opposite.

      Then consider all of THOSE factors in terms of what wavelength of photons are being release and what wave length are being absorbed at any given point in time based on all of those factors and map that against the atmospheric window….

      In addition to Miloscky (sp?) there’s been some more recent papers out of Russia that attempt to quantify all of those factors plus more and conclude that the net effect of CO2 is cooling. Ernst Beck sent them to me a long time ago, I’ll hunt for them and see if I still have them.

  3. wayne says:

    David, so nice to have someone listen for a bit. As for the mistakes you will find me very forgiving. In fact since I just got through listening to Feynman for hours and hours he made so many mistakes! Yeah, really. one whole lecture he is speaking of 4 and 8 where he should have been saying 8 and 16. No problem to me, he’s human and his humanity flows out and that what make listening to him so enjoyable. He always corrected himself sometime later, to be exact, and that is the way science is supposed to be. Follow the general thoughts, not the exact words or numbers.

    If you ever do find those on cooling Ernst Beck sent you, I would really like that. That is the point I was attempting to get E.M.Smith to grasp in his post on “Frostbite Falls” and why such low temperatures were being hit in Minnesota this winter.

    Can increased co2, the increase since the early 1900s, move energy faster, either direction, when out of equilibrium? That might be what those Russian scientists were addressing. I can see yes, but with little evidence but some physics intuition.

    “If we assume that the atmosphere stays the same size (not necessarily correct) then the density of CO2 molecules increases, and the percentage chance that any given photon on any given path will be absorbed goes up. So, if there was a 60% chance of a photon escaping to space in one leap, now it is only 40%.”

    Don’t think trapping, please! I need you to look at that differently. You are trying to look too globally and as Einstein pointed out, all physics is best explained locally. That increase chance is of course correct. But, think of what inter-atmosphere photons do, one leaves a molecule cooling it, and is absorbed by another molecule, normally 10-100 meters away, and warms it, back and forth, all of the time. What has happened. Nothing really without a temperature differential.

    That happens zillions of times within a parcel of atmosphere every second. If you have more co2, the photons will not travel as far but what does that change. Nothing really. Really.

    The same amount of energy will still flow across that packet if there is a temperature differential no matter how many local inter-parcel transfers are happening. See what the agw crowd want you to eat, baloney.

    That is exactly back to my point earlier. See it yet. Don’t attach ‘absorption’ with ‘heating’ without looking backwards to see what just cooled by exactly the same amount. Physics is symmetrical in almost any process you attach the word physics to. Not so for chemistry. Flowing from IPCC are well hidden thoughts that make the atmosphere and radiation transfer seem more like they are chemical reactions, one reaction then the next reaction, and it can leave you with totally wrong views of reality. Physics is better, symmetrical and continuous and always.

    One last big comment. The rest is just some thoughts of some of those missing things that are actually occurring as physics sees it. (or at least what I have come to realize over the many years I have followed physics but off of the top of my head with no Googling so you need to dig and verify if you want to make 100% sure, I would of myself)

    That brings me to address equilibrium you mentioned in your very last slide. Just remember that photons from one gas, pick co2 or h2o, will not travel far before it is absorbed and re-radiated. And I mean different photons. When I make a statement like that it is better to think of a specific unit of energy instead of photons.

    Here’s why: a photon, let’s say 15µm, leaves the surface and is absorbed. That exact photon is gone, never to exist again. Also the chance of that co2 molecule re-emitting is really small. See ‘Einstein A & B coefficients’ for co2. That is the chance of spontaneous emission per second if in excited state. Most of the time this energy is passed to surrounding molecules of any type, co2, h2o, h2, o2, Ar. So how does that increased energy that momentarily increases the tiny local temperature ever leave? By passing it, after a million transfers back and forth, to an IR active molecule which doesn’t necessarily emit but only has that same small chance to emit. And that packet of energy is not the same for it has been sliced, diced, and recombined with other sliced and diced energy pieces within the atmosphere, but we are still homing our thoughts on one 15µm worth of energy we call ‘our’ packet of energy that is going to reemit ‘somewhere very close’. To us it was all one simple action. Surface  molecule  reemit. All of the real actions are hidden but all should agree are rather ignorable in certain conversations.

    And also remember that before any absorption occurs the frequency must be exact. That’s right, not just close, exact. One adjustment is Doppler broadening that smears absorption lines, but that does not mean a photon can just be close to 15 µm, if 15 µm is the exact line of absorption. Another way to say that is if it takes exactly a 15µm photon to be absorbed and a 15.01 µm photon is rising from the surface but the co2 molecule is moving upward at 400 m/s that velocity difference will, by Doppler effect, make that very photon to appear to the molecule as an exact 15 µm photon and absorption can occur.

    So a very small percentage of absorptions are really possible at any given point, for it strictly depends on the exact frequency and the velocity of the IR active molecules near it.

    It really gets deep, for every collision of two atoms or molecules, it is really mediated by photons again. Yeah. Really. More photons interacting with the electrons. So it is best not to think too much of “this photon does this and then that photon reemits and does that” for any such statement is far from real physics.

    A big ‘however’, if you state the knowledge of all of this activity you can still draw simple drawings as you and Ira have done and still have sane conversation about the process. See, in any conversation of such depth BOTH parties have to agree on exactly what 1) is really happening by physics all of the time though not explicit and 2) what exactly is being left out of the conversation, for the effects are so tiny. Also many times you can totally ignore real effects that are really occurring but are cancelled by symmetry, as your example of only speaking of ‘up and down, not sideways’.

    I’ve written too much. If you don’t want to hear any more of more ignored factors, cry uncle. ☺
    (Just kidding, I’ll stop anyway, but I guess you get my point by now)

    If you carry this quest of understanding onward try to divide it into tiny pieces so each statement can be concretely answered true or false, when and when not, maybe a post for each, for it is so easy to get this complex conversation all tangled up and hung by the neck as seen many times before. Take the time to specify, no matter how many words are necessary, then all are on the same wavelength.

    • davidmhoffer says:

      Back to work this AM, so these will have to be brief:

      Don’t think trapping please!; You wrote a pretty detailed description of the real process, I didn’t see any holes in that as I skimmed it. Think of it as “extra delayed cooling”.

      Doppler effect; That one threw me, never thought of it that way. But one quick thought leaps to mind. You are looking at it from the relative perspective of an observer watching both the photon and the molecule. If you ARE the molecule, the photon is travelling at the speed of light as per usual. That’s as short an explanation of relativity as I’ve ever gotten to.

      Your description of photons being passed back and forth, fair. That’s what I was getting at in the early slides. Which four molecules are red doesn’t matter, it can change a billion times, there’s still only four. Until somethng changes and steady state = 5. Temp increase. So from a modeling perspective, we don’t care as much about “back and forth” as we do about escape rate at steady state and total concentration.

      I’ll look for the Russian paper. I suspect that when you add in other factors in combination is where the net effect gets reversed. For example, if you think about water vapour being very significant at low altitudes, and less at high altitudes, then you can think of CO2 as being the other way around. So the “delayed cooling” is more pronounced at higher altitudes (from CO2). Would we even notice at surface?

      But at days end I always come back to the same thought. CO2 is logarythmic. Take the IPCC worst case scenarios, accept their worst case orders of magnitude and the results are horrifying. Then calculate backwards (which they never do) exactly how much fossil fuel that is. You’ll need floating point, the number is stupendous.

  4. cptwayne says:

    I built an IR generator, 8-15 microns, which cover the adsorption bands of CO2. I fired it up to 1400 watts and flooded the room with this IR. There was not rise in air temperature for the bulk of the room. The floor did warm up 2 deg F. Then, the warmer floor caused the air above it to warm and rise a little. The convective losses were decreased by 25 %. So, this was the saved energy. In terms of Earth, CO2 does not warm the air under conditions of linear thermodynamic equilibrium (LTE). No net energy transfer. It emits the same as it adsorbs. However, at the Earth’s surface boundary, this does not occur and energy is transferred as objects are warmed up. Reradiating the warmth, these objects then heat the air. So, the lapse rate is the important parameter here and involves not just radiation, but conduction and convection. When water vapor is included, this then becomes much more complicated.

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    $25,000 Reward for the tested science proving Humans cause Climate Warming.

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  6. That’s good, that’s really good to know about External SAEF. hopefully I became impressed by read this concept. Thanks mate

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