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Is the CO2 effect saturated?

What the science says...

Select a level... Basic Intermediate Advanced

The notion that the CO2 effect is 'saturated' is based on a misunderstanding of how the greenhouse effect works.

Climate Myth...

CO2 effect is saturated

"Each unit of CO2 you put into the atmosphere has less and less of a warming impact. Once the atmosphere reaches a saturation point, additional input of CO2 will not really have any major impact. It's like putting insulation in your attic. They give a recommended amount and after that you can stack the insulation up to the roof and it's going to have no impact." (Marc Morano, as quoted by Steve Eliot)

The mistaken idea that the Greenhouse Effect is 'saturated', that adding more CO2 will have virtually no effect, is based on a simple misunderstanding of how the Greenhouse Effect works.

The myth goes something like this:

  • CO2 absorbs nearly all the Infrared (heat) radiation leaving the Earth's surface that it can absorb. True!
  • Therefore adding more CO2 won't absorb much more IR radiation at the surface. True!
  • Therefore adding more CO2 can't cause more warming. FALSE!!!

Here's why; it ignores the very simplest arithmetic.

If the air is only absorbing heat from the surface then the air should just keep getting hotter and hotter. By now the Earth should be a cinder from all that absorbed heat. But not too surprisingly, it isn't! What are we missing?

The air doesn't just absorb heat, it also loses it as well! The atmosphere isn't just absorbing IR Radiation (heat) from the surface. It is also radiating IR Radiation (heat) to Space. If these two heat flows are in balance, the atmosphere doesn't warm or cool - it stays the same.

Lets think about a simple analogy:

We have a water tank. A pump is adding water to the tank at, perhaps, 100 litres per minute. And an outlet pipe is letting water drain out of the tank at 100 litres per minute. What is happening to the water level in the tank? It is remaining steady because the flows into and out of the tank are the same. In our analogy the pump adding water is the absorption of heat by the atmosphere; the water flowing from the outlet pipe is the heat being radiated out to space. And the volume of water inside the tank is the amount of heat in the atmosphere.

What might we do to increase the water level in the tank?

We might increase the speed of the pump that is adding water to the tank. That would raise the water level. But if the pump is already running at nearly its top speed, I can't add water any faster. That would fit the 'It's Saturated' claim: the pump can't run much faster just as the atmosphere can't absorb the Sun's heat any faster

But what if we restricted the outlet, so that it was harder for water to get out of the tank? The same amount of water is flowing in but less is flowing out. So the water level in the tank will rise. We can change the water level in our tank without changing how much water is flowing in, by changing how much water is flowing out.

water tank

Similarly we can change how much heat there is in the atmosphere by restricting how much heat leaves the atmosphere rather than by increasing how much is being absorbed by the atmosphere.

This is how the Greenhouse Effect works. The Greenhouse gases such as carbon dioxide and water vapour absorb most of the heat radiation leaving the Earth's surface. Then their concentration determines how much heat escapes from the top of the atmosphere to space. It is the change in what happens at the top of the atmosphere that matters, not what happens down here near the surface.

So how does changing the concentration of a Greenhouse gas change how much heat escapes from the upper atmosphere? As we climb higher in the atmosphere the air gets thinner. There is less of all gases, including the greenhouse gases. Eventually the air becomes thin enough that any heat radiated by the air can escape all the way to Space. How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.

atmosphere
(OK, I'm Australian so this image appeals to me)

So if we add more greenhouse gases the air needs to be thinner before heat radiation is able to escape to space. So this can only happen higher in the atmosphere. Where it is colder. So the amount of heat escaping is reduced.

By adding greenhouse gases, we force the radiation to space to come from higher, colder air, reducing the flow of radiation to space. And there is still a lot of scope for more greenhouse gases to push 'the action' higher and higher, into colder and colder air, restricting the rate of radiation to space even further.

The Greenhouse Effect isn't even remotely Saturated. Myth Busted!

Basic rebuttal written by dana1981


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

 

Last updated on 7 July 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Related Arguments

Further reading

V. Ramanthan has written a comprehensive article Trace-Gas Greenhouse Effect and Global Warming.

Comments

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Comments 551 to 586 out of 586:

  1. Well if you want to push the sleeping bag analogy, increasing the insulation strength will always increase the temperature (Fourier Law). However, you cannot push the analogy too far. The key to understanding the saturation argument is undertstanding the importance of the temperature profile to absorption. The Modtran outputs you posted looked fine so I only assume you are not understanding how they work. Try this discussion.

    Ultimately though, it is great to try and understand the impact of the equations, but it is unreasonable to deny the lab and field tested solutions. When you can directly measure the increase in radiation from added CO2, then obviously the effect is not saturated.

  2. Pringlesx:

    You raise an interesting question.  Fortunately, the answer can be easily calculated.

    According to this web site, insulation r values add.  I am a cheap SOB so I buy cheap R=1 m2 T/W sleeping bags (metric units).  Since I have 99 cheap sleeping bags the total R value is 99 mT/W.

    To calculate the internal temperature we use the equation:

    Watts = m2 x deltaT devided by R

    My sleeping bags are 2 meters long and 2 meters around so they have a surface area of 4 meters square.  A human body generates about 100 watts of energy while sleeping.

     

    Plugging the data into the equation I find the temperature difference after you stay in the bags to equilibrium is 100W x 99R devided by 4 = about 2475 degrees C.  If it is -50C outside than the center of the bag is 2425C.  That is hot enough to melt steel!!  If you add a cotton layer it would have little effect on the temperature (R<<1), but you would be dead after a night in your 100 sleeping bags.  If I buy better quality R=2 sleeping bags it will be 5,000C at equilibrium.

    We will all be dead if we follow your advice to do nothing about Global Warming.

  3. GwsB,

    At 547 you said:

    "It is based on the idea that photons don't just disappear. They may be absorbed, but are emitted again within a fraction of a second. So I have problems with the first paragraph of post 546 by Michael Sweet which seem to suggest that there is no conservation of photons." my emphasis

    This is incorrect.  The CO2 molecule has many collisions (millions or higher) with other molecules before it can emit a new photon.  The collisions convert the photon's energy into heat in the surrounding molecules. 

    As soon as a photon is absorbed by a CO2 molecule, the energy of the photon is converted into vibrational energy in the molecule and the photon no longer exists.  The collision rate is many orders of magnitude faster than the emission rate so the energy is distributed by collisions to other molecules in the air.  Other CO2 molecules, that are boosted into the excited state by molecular collisions, emit photons that effectively replace the original photon.

    This is the primary mode of heat transfer in the atmosphere so it cannot be considered negligible.

    It is my understanding that little heat is "reflected" back.  Energy is absorbed by a layer of the atmosphere.  Then new photons are emitted, both up and down, according to the temperature of the layer as described by the Boltzmann equation.  

    It seems to me that you are trying to model a system you do not understand well.  I recommend you read what specialists in the field say to learn faster how the greenhouse effect works.

    The emission altitude (about 10,000 meters) is the key point for the greenhouse effect.  Here the atmospheric pressure is only about 25 kPa, 1/4 sea level pressure, and the temperature is -50C.  The cold freezes out water (vapor pressure of .0039 kPa versus 1.2 kPa at 10C) and the effective CO2 concentration is 1/4 sea level concentration.  Saturation is not an issue at 10,000 meters, nor is overlap of water bands.  Discussing saturation at the Earth's surface is incorrect.

  4. GwbS@542:

    Please do not make strawman arguments. I explicitly said that the diagram in comment 529 applies to the absorption ONLY of radiation, and that I have not considered emission. In comment 534 I give a list of other factors that must be considered. #3 is the mission of radiation. You do yourself no favours by arguing against a position that I have explicitly addressed as incomplete. When ONLY considering absorption, the decay is indeed exponential, and when considering the probabilty of a surface-emitted photon reaching space in one step, absorption is the only relevant factor. Photons emitted in the atmopshere above the surface are - by definition - not emitted from the surface..

       You also refer to "reflected" IR radiation. IR radiation is not reflected. Reflection results in photons travelling in a different direction, but remaining at the same wavelength/frequency as they were before reflection. IR radiation is first absorbed, then re-emitted. The emission, as others have stated, is not dependent on the wavelength of the radiation that was absorbed - it depends on the temperature and characteristics  of the molecule that is doing the emitting.This may be another CO2 molecule, but it may also be another greenhouse gas. It almost certainly won't be the exact same molecule that did the absorbing. This distinction between "reflection" and "absorption/re-emission" is critical in understanding atmospheric radiation transfer, and you do yourself no favours by conflating the two.

    In 547, you state "They may be absorbed, but are emitted again within a fraction of a second". This is basically true, but the amount of time it takes a CO2 molecule to lose the energy by collision is a lot shorter than a "fraction of a second". Eli Rabett has done the math for us:

    http://rabett.blogspot.com/2013/04/this-is-where-eli-came-in.html

    The time estimate between collisions is 10 us. A CO2 molecule that absorbs IR radiation almost always loses it to other molecules via collision. CO2 molecules that emit IR radiation are almost alwys getting that energy from other collisions.

    You also state "the fraction exiting at the top is inversely proportional to the length of the column (or the density)." Physical measurements in units of distance are irrelevant. What matters is the number of particles/molecules/etc. along a path. This varies with altitude depending on the local absolute concentration (not ppm, but molecules/unit volume).

    Proper radiation calculations take this into effect.

    I repeat what I said in post 534: "The only "saturation" that occurs is for useless and innacurate descriptions of the process." That specific wavelengths show zero direct tranmission of radiation from the surface to space is not an argument against the effects of increasing atmospheric CO2.

  5. PringlesX @ 548:

    You say you "found a [sic] interesting site from chicago university that simulates the band saturation."???

    How did you find it? That is the exact link I gave you in comment #540. You are reading the comments people make in response to your posts, aren't you?

    Now, given that you have provided a series of graphs from that model "that simulates the band saturation", can you please provide us with an explanation of:

    1. exactly what in those diagrams "shows" what you claim is "saturation"? and
    2. exactly what the significance of that "saturation" is, with respect to CO2 and the greenhouse effect?

    Right now, it looks like you are just throwing stuff at the wall hoping something sticks.

  6. The hole tread starts with an even simpler analogy of a water tank with pipes used to try to debunk the saturation effect. 

    With little googling, i found my analogy is used elsewhere, so it seems i wasnt that far out anyway.  (see links)

    So i am interested if its possible to debunk the saturation effect by setting up the scenario in the more correct way.



    https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/a-greenhouse-effect-analogy.html

    https://skepticalscience.com/SkS_Analogy_09_Greenhouse_effect_stack_of_blankets.html

  7. Bob,

    Your link to Eli Rabbit was very informative.  I had not previously seen data on how many collisions are needed to relax a CO2 molecule.  Previous discussions I have seen suggested 5-10 collisions.  Eli Rabbit provided data showing 105 collisions were needed!!  That meant that there are only about 100,000 relaxing collisions before the average time of emission and not many millions as I posted above.  The rate is a little lower at the escape altitude because it is colder and the concentration of molecules is lower.

    The point that most excited CO2 molecules relax and distribute their energy to nearby molecules and do not re-emit the photon still stands.

  8. It seems like i wasnt alone to make that analogy.
    If possible, please change the scenario in any way you like, that explains what you believe is happening during a CO2 increase.

    https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/a-greenhouse-effect-analogy.html

    https://skepticalscience.com/SkS_Analogy_09_Greenhouse_effect_stack_of_blankets.html

  9. Pringlesx,

    It seems to me that your analogy fails becasue you used way too many sleeping bags. (100 bags with doubling CO2 equal to the hundredth bag).

    A better analogy would be one sleeping bag with doubling CO2 equal to another bag. 

    You also use a base concentration of CO2 as 400 ppm.  The pre-industrial revolution concentration of CO2 was 270 ppm so it will be doubled at 540 ppm and not 800 ppm as you stated.

  10. Analogies are a tool for promoting understanding by transferring understanding from a known process into a new area where the elements of the analogy are applicable. They are especially useful for explaing things to people who lack the technical background to work through real process.

    What you cannot do is disapprove a theory by inappropriate use of an analogy.

    If you want to prove some theory is wrong, then you need to show that correct application of the theory results in predictions that are incompatible with observation. Radiative theory so far spectacularly matches observation. You need to focus on understanding rather than looking for some reason to dismiss science.

  11. What you cannot do is disapprove a theory by inappropriate use of an analogy.

    How do you feel about that the whole tread starts of with using an analogy of a water tank.

    "Lets think about a simple analogy: We have a water tank."

  12. Pringlesx,
    It seems to me that your analogy fails becasue you used way too many sleeping bags. (100 bags with doubling CO2 equal to the hundredth bag).
    A better analogy would be one sleeping bag with doubling CO2 equal to another bag.

    It has been demonstrated that the difference is happening in the TOA. The transmission layer. And the CO2 is saturated in its absorption band. And the athmosphere is not only CO2, GHE is mostly due to water vapour.
    So go from one sleeping bag into two sleeping bags is very off.

  13. Scaddenp:
    Analogies are a tool for promoting understanding by transferring understanding from a known process into a new area where the elements of the analogy are applicable.

    They are especially useful for explaing things to people who lack the technical background to work through real process.

    I agree 100%. So is it possible in this case?  If you were to have a lecture for a room of people with different backgrounds. What would you say is happening going from 285ppm to 400ppm to 500ppm?

    Thanks in advance.

  14. PringlesX @563,

    The usual 'adding layers of insulation' analogy only works so far. It is the reduced temperature at the altitude where the IR emits into space that sits at the heart of the AGW mechanism. This is thus not akin to an extra insulating layer which maintains the outside layer temperature and boosts the inner layer temperature with more layers. Your idea of leaky outer insulation @549, or perhaps a space blanked backed by insulation layers, may be a way to a better physical representation in the analogy, but I'm not entirely sure it would greatly assist understanding.

    Concerning a 'lecture', it depends if you are just describing the actual GHG mechanism (which would on its own take about 3 minutes to fully explain) or an actual 'lecture' which can be usefully stretched to include background stuff like the S-B relationship, Planck spectrum, depth of the atmosphere, IR path-lengths, outward radiation at the TOA, why GHGs are GHGs, why they operate at particular wavelengths, etc; stuff you are probably already familiar with.

  15. PringlesX - CO2 is not saturated where it matters, at the TOA where emission to space occurs. And we have direct evidence of that, for example Harries et al 2001, which demonstrates that there is decreasing energy leaving the TOA at greenhouse gas absorption frequencies between 1970-1997, creating an energy imbalance between incoming and outgoing radiation that can only result in the entire atmosphere warming.

    As to analogies - you can draw parallels between aspects of known and unknown systems with an analogy for instructive purposes, but the analogy isn't the real thing. You cannot disprove with analogies, only with the real science and system in question. In logic this is referred to as the False Analogy fallacy - easy to fall into, but best avoided.

  16. "How do you feel about that the whole tread starts of with using an analogy of a water tank."

    There are three level of explanation on this topic. Basic, Intermediate, Advanced. The Basic version starts with an analogy because it is trying to help someone new to the topic, without technical background, understand the issue.

    You appear to be trying to disprove established science. Nothing wrong with that - science makes progress that way - but you cannot do that through pushing an analogy. Most break down at some point. You need to start with the Advanced and then move to a textbook on radiative physics if you have a  strong reason to believe CO2 is saturated, but I dont think you have grasped the importance of the temperature profile.

    Just remember, observations win in science. What we observe matches the theory.

  17. Thr insulation argument is nonsence!

  18. qball17, science has always been political: thats exactly how your mates got rich and powerful in the first place and why you are defending their right to remain so....

  19. " What would you say is happening going from 285ppm to 400ppm to 500ppm?"

    Well simply that theory predicts that globally averaged irradiation of the surface will increase by 3.7W/m2 for every doubling of CO2; and that measurements OLR and DLR confirm these calculations.

  20. The model in 542 is wrong I have to admit. It is wrong for two reasons:

    1) My impression was that vibrational energy and the kinetic energy mv2/2 were systems with little interaction. That is not the case. Michael Sweet in post 553 and Bob Loblaw in post 554 correct me here. Here is another reference (which gives a proportion of 10**9 instead of 10**5)
    https://sealevel.info/Happer_UNC_2014-09-08/Another_question.html

    So in the new model the photon at a wavelength of 15 μm travels an average of 25 m before being absorbed by a CO2 molecule which goes into a vibrational state, and which then collides (whatever that means (distance between the centers of the molecules less than the minimum of the two radii?)) with a Nitrogen or Oxygen molecule and falls back into the zero vibrational state (why?) and transfers the vibrational energy into kinetic energy over the two molecules. So CO2 transforms the energy of photons of certain wavelengths into kinetic energy of the atmosphere close (around 25 m) to the position where the photon was emitted.

    2) According to Fig 1 in Zhong & Haigh (2013) of the 239 W/m2 outgoing longwave radiation only 22 W/m2 comes directly from the earth. This is from Trenberth & Fasullo (2012). In Tremberth, Fasullo & Kiehl (2009) it is still 40 W/m2.

    Looking down from outer space for each photon leaving the earth system at TOA (which is 100 km above the surface according to Google. Is that correct?) one should be able to specify its wavelength and the level above the earth surface where it originated. Around 9% originate at the surface. It would seem that 90% originates close to the surface, say less than 1 or 2 km, except for the wavelengths around 15 mm, which originate at 10 km. (In figure 4 in Zhong and Haigh (2013) the red line follows the Boltzmann-curve for 290K rather than 260K, see figure 3, the temperature at 5 km).

    The saturation of CO2 for certain wavelengths shown in the black blue and green graphs in Figure 6(c) in Zhong & Haigh (2013) suggest a transmission which decreases like the inverse of the concentration of CO2 as it approaches the limit value. That agrees with the model in post 542 but I do not see how the new model will give this result.

    I think concentration (ppm) is the variable of interest, not density (parts per m3). The twenty layers of my original model each contain the same amount of matter. Their height may vary. The effective CO2 concentration at 10 or 20 km is the same as at sea level. See for instance Aoki et al. (2003) Carbon dioxide variations in the stratosphere over Japan, Scandinavia and Antarctica. Tellus (2003) 55B, 178--186. CO2 is 50% heavier than oxygen or nitrogen, so one would expect it to settle down at the bottom. If it did it would form a layer of pure CO2 more than three meters high. A hundred years ago that was only a bit more than two meters!

  21. You are progressing a little.

    Concentration is measured as Molarity which is moles per liter.  Ppm is a fraction of particles of dry air and is not concentration . For gases, molarity is directly proportional to pressure.  This varies with height.  Sometime pressure is used for concentration.

    It is a waste of time to attempt to model systems you do not understand.  The system is not saturated.

  22. What michael sweet said...

    Also, pressure is simply the weight of all overlying gases. If air density were constant, air pressure would drop linearly with height. Air density isn't constant, because pressure drops with height. In the end, air pressure basically decreases logarithmically with height (to a first approximation).

    https://en.wikipedia.org/wiki/Atmospheric_pressure

    In atmospheric models, they often use pressure as the vertical coordinate. Layers spaced equally in pressure would be roughly equally-spaced on a log(height) scale, or logarithmcially-spaced on a linear height scale.

  23. Three weeks ago there was a congress in Amsterdam of Flat Earthers. I don’t believe the earth is flat. Neither do you. But what do you reply if your child asks “Why isn’t the earth flat?” Do you say “99.9% of the scientists say that the earth is a ball floating in space.” What if your daughter persists, and asks “But why is the earth a ball floating in space?”

    I think I can give a sensible answer to that question. If I am asked whether reducing CO2 will have an influence on the climate I am not able to give convincing arguments why a reduction at the present level makes sense.

    The Zhong&Haigh (2012) article is well written and convincing, but if one reads it a second and a third time one realizes that the paper contains no arguments. Figure 2 is on a scale which makes it impossible to see the effect of the shoulders and wings of the absorption around 665/cm. The vertical scale covers 12 orders of magnitude. There is no indication of the calculations performed to yield the plots in Figure 6.

    Figure 3 suggests that between 750 and 1000/cm the IR radiative flux emitted at TOA follows the Stefan-Boltzmann curve for 280K and between 600 and 750/cm the S-B curve for 220K. This is a model-generated curve but quite close to the observed curve IRIS spectrum dd May 5 1970 over the Sahara at 12.00, see
    https://disc.gsfc.nasa.gov/datasets/IRISN4RAD_001/summary
    This observation was made almost fifty years ago. Where can one find more recent plots? A clear difference between 1970 and 2019 would be evidence that there is as yet no saturation.

    There is a nice explanation of molecular radiation and collisional lifetime (which distinguishes elastic and non-elastic collisions) at https://noconsensus.wordpress.com/2010/08/17/molecular-radiation-and-collisional-lifetime/

    DJ Wilson and J Gea-Banacloche (2012) Simple model to estimate the contribution of atmospheric CO2 to the Earth's greenhouse effect (Am. J. Phys. 80, pp 306-315) presents good quantitative arguments for the greenhouse effect of CO2. Does anyone know of more recent literature, in particular on the topic of saturation?
    If so that might help me convince my daughter that reduction of CO2 emission makes sense.

  24. Hello,

    Most denier arguments i receive i can answer & understand thanks to studies in mechanical engineering and having a decent grasp on the science behind what im reading. But this one has me stumped as its not an area im well versed in, and im wondering if anyone can afford the time to help me understand if what he is saying is correct/incorrect, and why:

    ___________________

    You are linking to Skeptical Science which is under the control of cartoonist John Cook and his friends. This website has been repeatedly known to provide false information and is deceitful. But I will address the issues raised here in the claim that the effect is not saturated.

    There is a limited amount of IR emitted from the Earth at each frequency.

    At the center of the 15 micron band ALL of the IR is captured by CO2. There can be no more captured. This is not up for debate in any way shape or form.

    The method by which IR is captured by CO2 depends upon the ability of the CO2 molecule to match the IR being emitted in both frequency and in orientation of the charge formed by the atoms. The frequency of IR has to match the frequency of the CO2 molecules. It also has to match the orientation in space of the charge of the molecule.

    The CO2 molecule vibrates at a certain frequency determined by the atomic weights and charges of the Oxygen and Carbon Atoms. This frequency has a minor variation from the center frequency as one travels outward from the center of the 15 micron band.

    SO as more CO2 molecules are added to the atmosphere we see absorption increase at the center of the 15 micron band so that total absorption of all the IR is accomplished closer to the ground. No additional IR becomes absorbed. The Center becomes saturated with respect to its ability to absorb IR. No more IR is absorbed in the center.

    Will some CO2 molecules added capture a few additional IR photons further from the center. Yes, But the numbers will be constantly declining in a logarithmic fashion because the CO2 is not vibrating at the correct frequency. This declining logarithmic function is well known because the frequency distribution of the CO2 molecule causes it to not absorb IR at the edges of the 15 micron band. This gives rise to the requirement of a doubling of CO2 per unit increase of temperature. So if for example there is a 1 degree increase for a doubling of CO2 then for the next degree of increase you need 4 times as much CO2 added.

    The function of the ability of CO2 to absorb IR follows a bell as it drops off. Only at the Center of the 15 micron band can any absorption of note take place.

    The analogy of restricted flow given in the website is totally wrong. You are not adding water which is restricted by the diameter of an outflow pipe. You are adding heat to the atmosphere which has several methods for releasing it from the Earth, As CO2 populations are added there are more molecules in the stratosphere and above to release the energy to space. CO2 does not just stratify near the ground. Further CO2 does not act as a reservoir for IR energy. The energy is spread over all the atmospheric particles s kinetic energy. Oxygen, Nitrogen, H2O are all absorbing the kinetic energy and being transported vertically and toward the poles throughout the atmosphere.

    CO2 molecules become re-excited at every level of the atmosphere via collision. 1.4 % in the 15 micron band frequencies. Throughout the atmosphere below the Stratosphere, The re-excitation of these molecules is a net reduction in atmospheric temperature. Eventually there are feedbacks that serve to increase emission to space such as convection, transfer via circulation of Hadley Cells to the poles and the fact that at the poles emission to space takes place at a lower height. If these feedback mechanisms were not present the Earth would have burned to a cinder long ago. But in the lower atmosphere the excited molecules are quenched again and again by collision they cannot add to the temperature because they subtracted from it to become excited once more.

    So why is there this idea that CO2 can absorb outside its natural frequency range floating about on Skeptical Science? Because there are experiments performed with CO2 laser systems where the populations within the laser are manipulated artificially and you CAN cause an expansion of the absorption range by applying charges. It does not occur naturally. But you are considered a know nothing by SS and they have no objection to misleading you. within the laser. this does not occur in the natural world.

    The explanation of IR escaping from higher colder regions therefore less IR can escape because it is not energetic enough? Well Electromagnetic radiation energy levels are not determined by temperature. They are determined by frequency. Every electronic technician will tell you that a received signal strength depends on frequency. For example to transmit a VHF TV signal requires substantially less current draw than to transmit a UHF TV signal. That is why Channel 6 in Philadelphia refuses to switch to a UHF channel. The range of the signal is lower but it costs OH so much less. If a 15 micron band photon escapes then a 15 micron band photon escapes and the energy levels are the same.

    The idea of IR re-radiation is a false one. Because the collisions in the lower atmosphere constantly are quenching an excited CO2 molecule before it can re-emit. The timing constants are on the order of a billion collisions to one re-emission governed by the Einstein A co-efficient. Only in the upper atmosphere where the molecules are far enough apart to allow for there to be no quenching by collision is there any significant re-emission. This is how the Earth loses energy.

    The AERI instruments at the Great Plains and North Slope of Alaska detect IR directly. They are designed to detect a range of frequencies and CO2 is one of them.They are unable to detect incoming CO2 IR without manipulating the received signal against a model frequency. The signal is so small that it can be dismissed as an artifact of generating the simulated signal.

    The concept of IR scattering is a false one. The photon either passes through the atmosphere or it is absorbed. At the edges of the absorption curve some IR photons radiate directly to space at 186000 miles per second and some is absorbed and converted directly to heat. It depends on whether or not the CO2 molecule is resonant with the photon frequency.

    ___________________

    any assistance is greatly appreciated, just looking to further understand the issues and evidence/counterevidence i may come across

  25. Sgt_Wookie , your friend's comments are an interesting mixture of truths, half-truths, and plain falsehoods.

    Somehow, for whatever reason [probably Motivated Reasoning] he has gotten himself into a tangled jungle of confusion.  Perhaps he is arguing in bad faith (and is trying to mislead himself and/or his readers) ~ or perhaps it's worse than that, for in places he is bordering on a "word salad" of scientific terms.

    He needs to go back to the basic textbooks, and start from scratch.  Though I suspect he has too much hubris to accept that the expert scientists have knowledge that he himself lacks.  If he were more reasonable, he could start by reading the OP of this thread, and the 500-ish comments thereafter (which also contain some pearls of explanation).   But he has closed his mind to the mainstream science (science, easily found via SkS).

    Best if you find some indirect way of exposing him.  You would waste too much time in correcting him point by point, for he seems the tiresome argumentative sort of fellow who would spend hours in a rearguard battle as he retreats.

    (BTW, I love his comment:  "[SkS] has been repeatedly known to provide false information and is deceitful."   What a laugh!   And another strong sign of the Dunning-Kruger Syndrome.)

  26. Sgt_Wookie92 @574,

    You present a 1,000-word denialist essay on why an increase in atmospheric CO2 will not reduce IR out into space. It is an interesting polemic as it does quite a good job of addressing to some extent all the various descriptions of the GHG mechanisms, descriptions both actual and through analogy. It is however, as described by Eclectic @575, a pack of nonsense.

    I could go through paragraph by paragraph if you wish. A blow-by-blow account would be required as the central misconception the denialist employs isn't presented entirely within any single paragraph. Perhaps it would be easier to describe the GHG mechanism and allow to pick out the crazy talk for yourself.

    ....

    The planet surface emits IR in the waveband roughly 5μ to 50μ with the peak at 15μ. The profile is dependent on temperature. If there were no GHGs, all that IR would shoot off into space. But the GHGs actually capture pretty-much all of this surface-emitted IR, the energy converted into waggles in GHGs and almost all of those waggles, through collisions, are converted into thermal energy.

    But GHGs also go waggly because of those numerous collisions and that ensures the GHGs will effectively emit just as much IR as it is receives. CO2 absorbs/emits at 2.9μ, 4.3μ and 15μ but only the 15μ operates as the atmosphere/planet is too cold for the shorter wavebands.

    And at 15μ, CO2 is the only GHG operating so all the IR at 15μ that reaches space will all be emitted by CO2. The amount of 15μ IR is now depentent on the temperature of the CO2 emitting it out into space. For that the CO2 needs a clear shot at space, high enough so the CO2 above it is no longer a complete blanket. Presently that altitude-with-a-clear-shot-to-space is up in the cold upper troposphere. The graphic below shows that CO2 temperature is far lower than the surface temperature. (The black trace is measured, the red is modelled by MODTRAN, an on-line model from UoC.)

    IR emissions

    If more CO2 is added to the atmosphere, that altitude-with-a-clear-shot-to-space will get higher (CO2 is well-mixed up to 50km, well up into the stratosphere) and, while that altitude remains below the tropopause, the clear-shot temperature will get colder so less IR will be emitted into space. (The very central part of the 15μ waveband does have a higher clear-shot altitude above the tropopause and is seen in the graphic as a little spike. That spike will grow with additional CO2 while the size of the surrounding dip(s) will continue to increase. See Zhong & Haig 2013).

    ....

    Most of the nonsense set out within the denialist polemic should be understandable given this description (although I'd happily expand on individual points, perhaps some brickbats to lob back at the denialist). I'd just add here that some may not be acquainted with Feldman et al (2015) which is the paper that measured CO2's IR on the "Great Plains and North Slope of Alaska."

  27. Thank you very much for your responses, 575 Eclectic & 576 MA Rodger.

     

    1. this is exactly what I was worried about, incorrect information with enough truth to make it seem legitimate - I fear presenting it won't do much for the comments author who seems wholey subscribed to his reality, but has given me a better understanding to answer any similar points made in the future, and some new papers to read. Thanks again.
  28. Sgt_Wookie , I take my hat off to MA Rodger for his short description of the physics.  Not a full exposition, but nicely succinct.  And for myself, I have taken a copy of his graph of infrared energy leaving the planet ~ it's a fine demonstration of the Atmospheric IR windows and the absorption effect of water, carbon dioxide, ozone, and methane.

    Your denialist friend is probably so heavily invested in his Motivated Reasoning that he's not persuadable to change his mind (or his attitude), so there's little point in trying to educate him.   Though I'm not knowing the circumstances of your "interaction" with him, nevertheless it's the case that most online interactions have a number of silent observers ~ and they benefit when denialist nonsense gets contradicted.   But I am sure you're already aware of that . . . and aware of the old saying regarding:  ".... when good men do nothing."

  29. IMO the explanation is much too complex. 

    In the lower atmosphere, absorption is saturated, that's true.

    But in the highest layer it is not, because the molecule density is too low. So there is ample room to increase absorbtion there by increasing CO2 density. The highest layer is the pane of the proverbial greenhouse. 

    Old Arrhenius used in his paper 1896 the concept of the "radiating layer", which is of course the top layer.

  30. dien:

    Please explain exactly what you mean when you say "In the lower atmosphere, absorption is saturated". I have yet to hear a decent definition of "saturated" where this is true.

  31. dien @579,

    I will be more wide-ranging with my questioning of you than Bob Loblaw @580 although I perhaps understand what you are trying to say.

    Can you tell us which "explanation" you are describing as being "much too complex"?

    When you use the term "molecule density", to which molecules are you referring, all air molecules or just CO2?

    Are you referring to Arrhenius (1896) 'On the influence of carbonic acid in the air upon the temperature of the ground'? and if so, where doe he use the term "radiating layer"? Arrhenius talks of an "emitting layer" but this is not the CO2 emitting layer and thus not what you term "the top layer."

    You will note that I don't ask about your meaning of "saturated" although this does not directly apply to CO2's GHG effect being saturated. I feel your overly awkward explanation is essentially correct. That is, if by 'saturation' you meaning that all radiation emitted by CO2 is absorbed and fails to escape to space, this is mainly true in the lower atmosphere. From there, an increase in CO2 (which is well mixed within the atmosphere to a height of perhaps 50km) will increase emission/absorption in the lower atmosphere as well as the upper. (So it is not just "in the highest layer" where there is "ample room to increase absorbtion there by increasing CO2 density.") In so doing, the altitude where all CO2 radiation is absorbed (thus in your words "saturated") does have "ample room to increase" in altitude and, if that increase is still within the troposphere, it will thus to decrease in temperature. It is this decreasing temperature (or to be more exact, decreasing net temperature) which determines whether the GHG effect from increasing CO2 is saturated or not.

  32. @ 580 and 581.

    First thx for investing thought about it, which may make things clearer.

    I would like to refer to the reference to Angströms experiment in the first part of the "advanced debunking". Not all outgoing IR is absorbed, there is this absorption window (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174548/) . But a certain IR band is absorbed by CO2, and for this band, the absorption lenght is in the order of magnitude of some meters at sea level. This is what I meant with "saturated". 

    BTW, this is the first point of the myth, which is actually not true, as stated above, because only the IR outside the transmission window will be absorbed.

    So the heat energy has to propagate via multiple absorptions to the top layer. You are right, insofar having more CO2 molecules will already hamper this propagation process. My image for this is a stack of frosted glass, each representing one absorption length. The IR will be absorbed and re-emitted in all directions by each pane. To add CO2 means then to add a lot more of those panes. And those will increase the ratio between input and output power. 

    I have my difficulties with the statement, that the increase of the CO2 concentration pushes the emission layer up, where it is colder, where therefore less heat will be emitted. For me it's the other way around: because more "frosted glass panes" alias absorption lengths are stacked within the atmosphere, we have less power arriving at the top and therefore its temperature will be lower.

    This - the lower top atmosphere temperature - is only the case as long as the earth is still warming up. In a new equilibrium, a couple of years after we hopefully managed to keep the CO2-level steady, the top atmosphere will be as warm as before, because it will emit exactly all incoming power. Only of course the surface temperature will be much higher than before. 

    With the word "complex", I tried to express a certain diffuse discontent with the explanation above. It has actually not explained, how in earth the heat, having been absorbed in the first meter or so, manages to reach the top layer in 50 km or so height nonetheless. Only if we give this explanation, we can make the effect of the additional absorption plausible. 

    The water metaphor is not bad, but it is a boundary - and conservation-of-energy argument. To use the actual propagation mechanism between the boundaries  would imho more enlightening.

  33. Dlen @582 , I am puzzled by what you say in your fourth-to-last paragraph.

    Surely, regardless of the number of "frosted glass panes", the power arriving (upwards) at the top must always be the same*  and equal to the solar heat entering the system (the system being the sub-TOA system i.e. the planet minus the stratosphere).

    Of course, the same*  will be very slightly more - or less - according to whether the planet is cooling or warming in transition to a new equilibrium surface temperature.

  34. dlen @582,

    The difficulty I have with this discussion is that it is attempting to provide an analogy for the GHG mechanism, something which can never be exact because if it were, it would be too complex when its puropse is to be simple to understand.

    You say "So the heat energy has to propagate via multiple absorptions to the top layer" with CO2 acting to "hamper this propagation process."
    This is not the best of wording. It is true that the planet sheds energy solely by radiation, something like 240Wm^-2 to be in equilibrium. Yet within the planet's energy flows, very little of this outward energy is 'propagated' from the net radiative energy flux from the surface. The surface is only radiating a net 60Wm^-2, of which 40Wm^-2 is the radiation passing through the "the transmission window" (so plays no part in the GHG mechanism) leaving just 20Wm^-2 which "has to propagate via multiple absorptions to the top layer."  Joining this surface radiative energy flux as it 'propagates' upward is 100Wm^-2 of convective and insensible heat transport from the surface as well as 80Wm^-2 from direct solar heating of the atmosphere to yield the full 200Wm^-2 being radiated from the atmosphere out into space. And in being able to radiate at atmospheric temperatures, CO2 does not "hamper" the process but instead assists it.

    Your fouth-last paragraph is entirely wrong. It is not the CO2 which warms the atmosphere (ie the troposphere) and determines its temperature profile. The temperature profile (lapse rate) is well balanced so as to hold convection back from running amok. (We would live in an interesting surface environment without this balance!!) The temperature profile (as opposed to the temperature) is certainly not determined by radiation.

    The planet surface and atmosphere does of course have to warm because an increase in CO2 results in it emitting into space from higher cooler parts of the atmosphere. While CO2 is well mixed up to perhaps 50km, the effective emission altitude for CO2 is nothing like that high - more like 10km. And while the whole climate system (up to the tropopause) will warm as a result of increased CO2 to allow the radiative balance to be restored, the flux within the CO2 waveband will still remain smaller than previously, while the flux elsewhere (where the effective emission altitude remains unaffected) will be greater.

  35. @ ma rodger, #584: Thx for the lengthy answer and the little lecture about heat pathways. I got the impression, before developing ad hoc heat propagation models, I should have done some reading about convective-radiative heat transfer in the atmosphere. 

    So, if I interprete your post correctly, the main transport mechanism to the effective emission height is convection, with radiation from the soil being nearly insignificant. This should be named as such in the explanation. It is not very complicated, not hard to understand.  

    The effective emission height is rising. This is sufficiently well explained in the text. What is not explained is, why it is colder in higher levels of the atmosphere. I see two aspects here: 

    1. adiabatic expansion of rising air packets. This is a general explanation for the lapse rate. The rising air packet uses up internal energy for expansion work.

    2. After the earth has been warmed sufficiently, the now higher effective emission layer will not be colder anymore. The rising air packets will start with a higher temperature = internal energy and so will be warmer even after having risen to a higher effective emission layer. 

  36. Dien @585 ,

    heat rises through the atmosphere by radiation, convection, and latent heat changes (water phase-change).  Consult the famous "Trenberth cartoon" to see the proportions of these.

    The lapse rate can be viewed in the simplest term, as like the multiple layers of clothing you wear on a cold day ~ the thermodynamic heat flow across the temperature gradient, from warm innermost layer to coolest outermost layer.  You can look at the complexities of each mechanism: but the ultimate effect is a simple gradient, from planetary surface up to the effective radiation "escape" layer.

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