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Climate Hustle

Stratospheric Cooling and Tropospheric Warming - Revised

Posted on 18 December 2010 by Bob Guercio

This is a revised version of Stratospheric Cooling and Tropospheric Warming posted on December 1, 2010.

Increased levels of carbon dioxide (CO2) in the atmosphere have resulted in the warming of the troposphere and cooling of the stratosphere which is caused by two mechanisms. One mechanism involves the conversion of translational energy of motion or translational kinetic energy (KE) into Infrared radiation (IR) and the other method involves the absorption of IR energy by CO2 in the troposphere such that it is no longer available to the stratosphere. The former dominates and will be discussed first. For simplicity, both methods will be explained by considering a model of a fictitious planet with an atmosphere consisting of CO2 and an inert gas such as nitrogen (N2) at pressures equivalent to those on earth. This atmosphere will have a troposphere and a stratosphere with the tropopause at 10 km. The initial concentration of CO2 will be 100 parts per million (ppm) and will be increased to 1000 ppm. These parameters were chosen in order to generate graphs which enable the reader to easily understand the mechanisms discussed herein. Furthermore, in keeping with the concept of simplicity, the heating of the earth and atmosphere due to solar insolation will not be discussed. A short digression into the nature of radiation and its interaction with CO2 in the gaseous state follows.

Temperature is a measure of the energy content of matter and is indicated by the translational KE of the particles. A gas of fast particles is at a higher temperature than one of slow particles. Energy also causes CO2 molecules to vibrate but although this vibration is related to the energy content of CO2, it is not related to the temperature of the gaseous mixture. Molecules undergoing this vibration are in an excited state.

IR radiation contains energy and in the absence of matter, this radiation will continue to travel indefinitely. In this situation, there is no temperature because there is no matter.

The energy content of IR radiation can be indicated by its IR spectrum which is a graph of power density as a function of frequency. Climatologists use wavenumbers instead of frequencies for convenience and a wavenumber is defined as the number of cycles per centimeter. Figure 1 is such a graph where the x axis indicates the wavenumber and the y axis indicates the power per square meter per wavenumber. The area under the curve represents the total power per square meter in the radiation.

Figure 1

Figure 1. IR Spectrum - No Atmosphere

The interaction of IR radiation with CO2 is a two way street in that IR radiation can interact with unexcited CO2 molecules and cause them to vibrate and become excited and excited CO2 molecules can become unexcited by releasing IR radiation.

Consider now the atmosphere of our fictitious model. As depicted in Step 1 of Figure 2, N2 and CO2 molecules are in motion and the average speed of these molecules is related to the temperature of the stratosphere. Now imagine that CO2 molecules are injected into the atmosphere causing the concentration of CO2 to increase. These molecules will then collide with other molecules of either N2 or CO2 (Step 2) and some of the KE of these particles will be transferred to the CO2 resulting in excited CO2 molecules (Step 3) and a lowered stratospheric temperature. All entities, including atoms and molecules, prefer the unexcited state to the excited state. Therefore, these excited CO2 molecules will deexcite and emit IR radiation (Step 4) which, in the rarefied stratosphere, will simply be radiated out of the stratosphere. The net result is a lower stratospheric temperature. This does not happen in the troposphere because, due to higher pressures and shorter distances between particles, any emitted radiation gets absorbed by another nearby CO2 molecule.

Molecules

Figure 2. Kinetic To IR Energy Transfer

In order to discuss the second and less dominant mechanism, consider Figure 1 which shows the IR spectrum from a planet with no atmosphere and Figures 3 which shows the IR spectrums from the same planet with CO2 levels of 100 ppm and 1000 ppm respectively. These graphs were generated from a model simulator at the website of Dr. David Archer, a professor in the Department of the Geophysical Sciences at the University of Chicago and edited to contain only the curves of interest to this discussion. As previously stated, these parameters were chosen in order to generate graphs which enable the reader to easily understand the mechanism discussed herein.

The curves of Figures 3 approximately follow the intensity curve of Figure 1 except for the missing band of energy centered at 667 cm-1. This band is called the absorption band and is so named because it represents the IR energy that is absorbed by CO2. IR radiation of all other wavenumbers do not react with CO2 and thus the IR intensity at these wavenumbers is the same as that of Figure 1. These wavenumbers represent the atmospheric window which is so named because the IR energy radiates through the atmosphere unaffected by the CO2.

Figure 2

Figure 3. CO2 IR Spectrum - 100/1000 ppm

A comparison of the curves in Figure 3 shows that the absorption band at 1000 ppm is wider than that at 100 ppm because more energy has been absorbed from the IR radiation by the troposphere at a CO2 concentration of 1000 ppm than at a concentration of 100 ppm. The energy that remains in the absorption band after the IR radiation has traveled through the troposphere is the only energy that is available to interact with the CO2 of the stratosphere. At a CO2 level of 100 ppm there is more energy available for this than at a level of 1000 ppm. Therefore, the stratosphere is cooler because of the higher level of CO2 in the troposphere. Additionally, the troposphere has warmed because it has absorbed the energy that is no longer available to the stratosphere.

In concluding, this paper has explained the mechanisms which cause the troposphere to warm and the stratosphere to cool when the atmospheric level of CO2 increases. The dominant mechanism involves the conversion of the energy of motion of the particles in the atmosphere to IR radiation which escapes to space and the second method involves the absorption of IR energy by CO2 in the troposphere such that it is no longer available to the stratosphere. Both methods act to reduce the temperature of the stratosphere.

*It is recognized that a fictitious planet as described herein is a physical impossibility. The simplicity of this model serves to explain a concept that would otherwise be more difficult using a more complex and realistic model.

Robert J. Guercio - December 18, 2010

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Comments 101 to 123 out of 123:

  1. Hi Mango @99,

    OK. What are they claiming that you are wrong about?
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  2. MangoChutney:

    "Has any additional radiation out of the stratosphere been measured?"

    It's a bit difficult to attribute any part of IR radiation to a particular altitude. However, the stratospheric temperature (as measured with the various satellite instruments) indicates a notable cooling trend in the stratosphere:


    [Source]

    "What else could cause stratospheric cooling other than the enhanced greenhouse effect?"

    One additional cause is human-emitted CFC gases. The stratosphere is warmed in part by UV absorption from the sun, and decreases in ozone due to CFC's have reduced this absorption. Given the bans on CFC's (~1987), this influence should be declining, decreasing this particular cooling effect. However, the mesosphere is also affected by greenhouse gases, is not warmed by ozone/UV absorption, and has cooled 5-10°C as well (Beig 2006) - reinforcing the part played by GHG's in the stratosphere. I believe Beig 2006 has at least mesopheric and thermospheric temperature profiles.

    ---

    So: Yes, there are other influences pushing towards stratospheric cooling (ozone depletion), but GHG's are part of the picture, and the influence of GHG entrapment of IR can be seen more separably in the mesosphere and thermosphere. Surface and tropospheric warming caused by (for example) increases in solar energy, would on the other hand warm the entire atmosphere, hence the stratospheric trends contradict an insolation change as the forcing behind global warming.

    Overall, the measured temperature changes match what is predicted by the radiative physics.
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  3. KR @102,

    Our current understanding of stratospheric temperature changes is nicely summarized in a recent paper by Seidel et al. (2011):

    "The temporal and vertical structure of these [stratospheric temperature] variations are reasonably well explained by models that include changes in greenhouse gases, ozone, volcanic aerosols, and solar output, although there are significant uncertainties in the temperature observations and regarding the nature and influence of past changes in stratospheric water vapor."

    And

    "For example, the increased attention over time to radiosonde and satellite data quality has contributed to better characterization of uncertainty in observed trends both in the troposphere and in the lower stratosphere, and has highlighted the relative deficiency of attention to observations in the middle and upper stratosphere. In contrast to the relatively unchanging expectations of surface and tropospheric warming primarily induced by greenhouse gas increases, stratospheric temperature change expectations have arisen from experiments with a wider variety of model types, showing more complex trend patterns associated with a greater diversity of forcing agents."

    The stratosphere is very deep so when talking about temperatures there one has to be careful about which portion one is referring to, as different drivers (e.g., Ozone) are more or less important in different layers.
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  4. @KR & Albatross

    Thanks. I know and accept the stratosphere has cooled, but it's nice to see a good graphic to illustrate.

    Ozone cools the upper stratosphere and warms the lower stratosphere (Clough and Iacono, JGR, 1995), do we know the pattern of cooling over the satellite period? Is it the whole stratosphere or just the upper stratosphere?

    Bob Guercio tells us "Therefore, these excited CO2 molecules will deexcite and emit IR radiation (Step 4) which, in the rarefied stratosphere, will simply be radiated out of the stratosphere. The net result is a lower stratospheric temperature.", so this is presumable measurable. Do you guys know if the rise in outgoing radiation has been measured?

    Sorry for all the questions, really am trying to understand
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  5. Mango,

    We would be better able to help you if you answered my question @101. Specifically, what statements have you made that "they" have told you were wrong. I am not trying to be difficult, I am trying to focus the discussion. Thanks.
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  6. 104, MangoChutney,
    Do you guys know if the rise in outgoing radiation has been measured?
    Refer to KR's response in 102, and realize that your statement is slightly mis-phrased.

    We know that overall outbound radiation should be less, not more, as the planet has an energy imbalance and is warming. This state should continue until the planet reaches a new equilibrium temperature, at which point out must roughly equal in, on average.

    Part of the greenhouse effect is the fact that the earth should radiate energy from higher altitudes. The earth will radiate energy from higher in the troposphere and less overall from the cooling stratosphere, but when the system is in or near equilibrium, total energy out will equal total energy in (i.e. not radiate less, but simply sourcing that radiation from different altitudes).

    As KR said, determining the altitude at which this energy is emitted is problematic.

    Anyone else, please step in and correct me if I'm wrong or mis-stating any aspect of this.
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  7. MangoChutney - "Do you guys know if the rise in outgoing radiation has been measured?"

    Outgoing radiation changes, primarily changes in the spectral distribution of energy (challenging to get an absolute number, given multiple satellites over a short time period, but relative numbers at different frequencies, spectra are very accurate) show greenhouse gas changes.

    Given global warming the total energy radiated to space is decreased (it's accumulating rather than radiating), and the relative spectra clearly show reduced thermal emission to space at GHG frequencies. IR from the stratosphere (only a part of the emission to space) is lowered due to the lower temperatures there, due in turn to the energy not coming out of the troposphere as effectively because of higher GHG concentrations (radiative insulation).

    Specifically attributing a particular IR photon to an altitude is quite difficult, an underdetermined problem - but the physics of radiative absorption and emission are quite well known, and can be modeled. Temperature measurements (satellite microwave measures, radiosondes) make it possible with some degree of accuracy to determine temperatures of various levels of the atmosphere (the thermosphere temperature is hard to measure, although estimates can be made), and those temperatures match/validate the radiative models.

    And as Albatross pointed out, there's ongoing work in reducing the uncertainties in ozone, GHG, aerosol, and other drivers.
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  8. Interestingly, one of the thermosphere temperature estimates referred to in Beig 2006 above is from looking at satellite decay rates.

    Near Earth satellites decay due to friction with the atmosphere - the cooling thermosphere (~17C cooler over the last 30-40 years?) has shrunken, reducing air friction and producing measurable slowing of NE satellite orbit decay rates.

    So, in fact, the sky is falling...
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  9. @Albatross

    Does it really matter why I'm here? As long as I am prepared to be convinced (and I am prepared), isn't that enough?

    @All

    We seem to agree that there could be 2 reasons for the cooling stratosphere, CO2 and / or ozone depletion. The answer seems to be where in the stratosphere the cooling is happening, so do we have the records to show if the cooling affects the whole of the stratosphere or just the upper stratosphere?

    -----

    The AGW hypothesis suggests outgoing longwave radiation should decrease.

    I've read the post: http://www.skepticalscience.com/American-Thinker-claims-to-have-disproven-global-warming.html

    which, as the author of the AT article confirms in the comments, shows that OLR has remained constant over the period to 2006 "We have increased the CO2 in the atmosphere about 17% from 1970 to 2006 (328ppm vs. 383ppm) and the OLR appears to have remained constant when you look at the raw data from these three papers".

    Essentially we have over 30 years of satellite data which seems to show no overall decrease in OLR and possible an overall increase (didn't read all the comments)

    My understanding is OLR has increased over the full satellite period, but I could be wrong, so:

    Has OLR slightly decreased, slightly increased, decreased significantly, increased significantly or stayed the same over the satellite period?

    If OLR has increased to any extent, what are the possible causes?

    If OLR has increased to any extent does this invalidate the enhanced green house effect hypothesis?

    TIA
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  10. Mango, consider Trenberth's energy flow diagram;



    From this we can see that:
    341 W/m^2 incoming solar radiation - 102 W/M^2 reflected solar radiation = 239 W/m^2 OLR

    Thus, we can also use this diagram to identify some things which could change the amount of OLR. For instance, an increase in OLR could be due to increased incoming solar radiation (which goes through a semi-regular cycle of about 11 years), increased surface reflection of solar radiation (e.g. due to higher snow coverage than usual), or increased cloud cover causing more atmospheric reflection of solar radiation.

    Thus, if you are angling for 'any increase in OLR for any duration disproves AGW' then you are incorrect... many things can and do cause short duration increases in OLR.

    Indeed, over the long term greenhouse gases have no impact on OLR. Energy out MUST equal energy in - though not immediately. An increase in greenhouse gases can cause an energy imbalance (note that Trenberth's diagram only depicts balanced flows) by temporarily decreasing the OLR rate until temperature rises enough that OLR becomes balanced again.
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  11. Actually, now that I look at the UNrounded values, it seems that Trenberth IS showing the radiative imbalance;

    341.3 incoming - 101.9 reflected = 238.5 OLR + 0.9 imbalance

    The imbalance is labelled 'Net absorbed' at the bottom middle of the diagram.
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  12. Mango, short answer...

    You are wrong in thinking that OLR has increased. There is a net 0.9±0.5 W/m2 imbalance... less, not more.

    The proper value is, I think, hard to detect reliably considering all of the noise inherent in the system and without better satellite measurements and longer time periods with which to accumulate averages (although Trenberth appears to have done so, and I'd have to look at his paper again to see how)... and sadly satellites keep failing to reach orbit and funding for them is rather dry with the Republican Party in power in the U.S. House.

    At the same time, however, KR's link to Is the CO2 Effect Saturated as well as this link to Have American Thinker disproven global warming? together show that while the total imbalance is difficult to detect, the expected changes in specific frequencies of OLR -- fingerprints not of any imbalance and warming, but of the effects of CO2 in particular -- are detectable and present.

    Your argument/question is not invalid. We simply don't have the resources to observationally support or refute the question of which substance, ozone or CO2, is more responsible for the cooling of the stratosphere.

    But we do have other observations that more than suffice to make us believe that answering that particular question is not all that important. No one really thinks for a minute, nor should they based on the wealth of other evidence, that CO2 is somehow not responsible for both warming the planet and cooling the stratosphere, exactly matching what is predicted by our firm understanding of the physics, but instead that ozone is cooling the stratosphere and some other mysterious, unnamed, unknown force is warming the globe, while CO2 is somehow surprisingly not behaving as all physics expects.

    So, you see, the proposition that ozone is responsible for cooling the stratosphere requires four huge assumptions:

    • Ozone is responsible for the cooling of the stratosphere.
    • Something else (as yet unknown) is responsible for global warming.
    • In spite of our good understanding of the physics and all other observations that support this, CO2 is somehow not warming the globe.
    • In spire of our good understanding of the physics and all other observations that support this, CO2 is somehow not cooling the stratosphere.
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  13. Mango,

    You see this is exactly why I asked my questions @10. I do not recall questioning why you are here. I am glad to here that you are willing to listen to the evidence, but we shall see.

    Now in order to help you and to focus the discussion I repeat, specifically, what statements have you made that "they" have told you were wrong. You made reference to that in your post @100 when you said:

    "People tell me i am wrong and point to SkS, so i thought i would ask here"

    Someone in the interim has replied to one of your other questions that asked after reading a post, but I am more interested in what you have been saying that people claim is wrong, the alleged real reason for you being here. Can we please help you address that?
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  14. Mango @109,

    "AGW hypothesis"

    Actually, it is the theory of AGW. There is a significant/important difference between a "hypothesis" and a "theory".
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  15. I'll read through the comments and get back to you, (-snip-)

    OK, albatross, you read the comments, seemingly everywhere! Posters at the BBC blog are always telling me I'm wrong about everything and they tell me all the answers lie at SkS. I do read the links, even though I suspect the posters at the BBV never read the links from the opposing camp

    And that's why I'm here - to engage in conversation. I'm not saying you will convince me, I really think the AGW "theory" is flawed, but I'm open to being convinced and I have, on several occasions at the BBC and WUWT, stated that we shouldn't read too much into papers that, for example, show lower climate sensitivity than the IPCC would have us believe, because the papers are still based on models not on empirical data

    (-snip-)
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    Response:

    [DB] Welcome to Skeptical Science.  Here we focus on the science, not on rhetoric or ideology; that focus immediately separates SkS from the other sites you reference. Please familiarize yourself with the Comments Policy of this site.  Note that a continued focus on "camps" or "tribes" detracts from one's credibility here.

    Inflammatory snipped.

  16. Hi Mango @115,

    "appears to be really worried about why I am here"

    "or do you not want to engage in civilised conversation"

    Now you are arguing strawmen, and are also being paranoid. You still have not specified exactly which statements you have made that people are alleging are wrong. instead you now say Posters at the BBC blog are always telling me I'm wrong about everything".

    Regardless, I and others here, are happy to engage in a cvil scientific discussion with you. What are say your three primary issues/positions that you have, that you have been told are wrong, and which you believe refute or call into question the theory of AGW? We can then address them on the relevant thread.

    I was under the impression, going by your very first comments on another thread, that they had something to do with temperature trends in the stratosphere no? Specifically, you seem to think that because the stratosphere has not cooled recently that this is a significant flaw in the theory (no quotation remarks required) of AGW.

    Let us look at the big picture shall we, instead of cherry picked short-term trends that have no statistical significance and which, as such, cannot be used to accept or reject the null hypothesis.



    [Source]
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  17. MangoChutney - "I'm not saying you will convince me, I really think the AGW "theory" is flawed..."

    With that as an opening statement, I would suggest reading through Newcomers, Start Here and The Big Picture pages, as well as looking at the excellent historical overview contained in The Discovery of Global Warming.

    As opposed to (for example) selecting one piece of information, arguing that it's problematic or unknowable, and from that claiming the entire theory of AGW, supported by multiple lines of evidence and the physics of the last 150 years, is flawed. There are uncertainties, there are multiple influences (in this case ozone, CO2, water vapor levels, etc.), and it's always important not to oversimplify or overgeneralize from your data...
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  18. Mango "... to engage in conversation. I'm not saying you will convince me, I really think the AGW "theory" is flawed, but I'm open to being convinced..."

    One thing that slipped by me the first time I saw your post. "AGW theory" - no-one yet has asked so I will.

    Do you realise that there is no AGW theory? What we have is climate science - AGW is merely a predictable sub-set of the general science. The core contributors to the discipline are physics, geology, astronomy, meteorology, chemistry, biology, oceanography, glaciology and other cryology, and a good couple of dozen others.

    Given what we know from physics of the radiative properties of CO2 and other long-lived gh gases, and the geology of many regions tells us more, we know what to expect when the atmosphere has an increased concentration of ghgs.

    And the measurements are telling us the physics, geology, chemistry et al are taking us pretty well where we'd expect to end up. How far and how fast we push ourselves along that path is a problem of interpreting and analysing those measurements.

    But it really is pretty straightforward. (From the comfortable perspective of someone who's never gone to work on a glacier or done super dangerous things in stormy seas or remote jungles just to collect the data we use.)
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  19. Hi guys,

    I presented the well-known fact of stratospheric cooling as evidence of AGW at ResearchGate, and one commenter posted the answer below. I gave Jones 2003 (from the Guide to Skepticism) as a reference.

    My knowledge does not allow to follow it. Is anyone here able to understand and put it into context?

    I'm sorry, but the assertion combined stratospheric cooling and tropospheric is consistent only with enhanced GHG's is simply incorrect. Even reference (6) by Alexandre states something quite different when you read the relevant sections of the paper.

    Quote:

    "For the stratosphere SO is by far the most dominant, cooling by 1.20 ± 0.11°C. As S has no influence on the stratosphere the stratospheric ozone component of SO causes this temperature change. [Tett et al., 2002]. The other forcings have much smaller contributions in comparison (The warming from G in the stratosphere is due predominantly to a warming region in the model over the North polar region [Tett et al., 2002])."

    SO here refers to the "combined response to changes in sulphate aerosol and tropospheric and stratospheric ozone". G refers to responses to changes in well-mixed greenhouse gases. S refers to responses to changes in solar irradiation.

    The effect of increased well-mixed GHG's on stratospheric temperatures is much smaller in amplitude and not distinguishable (yet) in the stratospheric temperature record.

    This is well established in scientific literature, see for example recent work by Polvani and Solomon [2012, submitted]:

    quote:

    "The eff ect of ozone depletion on temperature trends in the tropical lower stratosphere is explored with an atmospheric general circulation model, and directly contrasted to the e ffect of increased greenhouse gases and warmer sea surface temperatures. Confi rming and extending earlier studies we find that, over the second half of the 20th Century, the model's lower-stratospheric cooling caused by ozone depletion is several times larger than that induced by increasing greenhouse gases."

    http://www.columbia.edu/~lmp/paps/polvani+solomon-JGR-2012-revised.pdf

    But it is not well known outside of scientific literature.
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  20. Alexandre @119, your respondent was quite correct, there are several other potential causes of a cooling stratosphere and a warming troposphere. The include:

    1) A declining reflective particulate (Sulphate) layer in the upper troposphere/lower stratosphere;

    2) Declining ozone (O3) layer in the stratosphere; and

    3) Increased methane (CH4) and the chemical decay product of methane, water (H2O) in the stratosphere.

    We can ignore (3) because the known quantities of methane and water in the stratosphere are too small to cause the observed cooling (see the figure below). Further, methane is itself an anthropogenic greenhouse gas, so its implications are much the same as that from increased CO2. (Note that there has been an increase in water vapour in the stratosphere only because of the increase in methane.)

    Both (1) and (2) are known causes of a similar effect to CO2, and are known to have occurred recently. There are, however, important differences in their effects. Specifically, a declining ozone concentration will cool the upper stratosphere and warm the lower stratosphere. That is because reduced ozone means less UV radiation is absorbed in the upper stratosphere, and so is absorbed in the lower stratosphere or troposphere instead.

    (Source)

    In fact, what has been observed is very strong cooling in the upper stratosphere, and weak cooling in the lower stratosphere where CO2 and O3 have opposed effects which indicates that both effects are occurring as predicted.


    (Source)

    More importantly, warming of the troposphere by both ozone and sulphates work by modulating solar radiation. Consequently they are strongest when the sun is strongest, and weakest when the sun is weakest. That means for both, we would predict greater warming in summer than in winter; greater warming in daytime than in night time; and greater warming in the tropics than in the arctic. Greenhouse warming makes exactly the reverse prediction, ie, greater warming in winter, at night, and in the arctic. In fact, what has been observed is greater warming in winter than in summer; greater warming at night than in day; and greater warming in the arctic than in the tropics:


    (Source; note that two coauthors of this paper are well known deniers. Further, this paper used data known to be strongly contaminated by stratospheric data, weakening the effect being observed. They do not note this, nor take it into account in their conclusions. Never-the-less, the data speaks for itself.)


    (Source)

    Unfortunately in science things are often complex. In this case a complexity arises because a primary feedback on rising temperatures, the water vapour feedback, has the same temperature signature as an increase in CO2 in the troposphere (although it does not cool the stratosphere). The water vapour feedback on a greenhouse warming will reinforce the expected pattern of temperature changes in the troposphere. In contrast, it will counter the expected effect from solar related forcings such as changes in ozone or sulphate levels. Never-the-less, if the feedback is very strong, the feedback pattern will dominate. Therefore the patterns seen above do not by themselves prove the source of warming to be an enhanced greenhouse effect due to increased CO2. What they do prove is that either it is an enhanced greenhouse effect; or that climate sensitivity is high. As the initial warming effect of increased CO2 is well established science, however, a strong feedback also shows that the enhanced greenhouse effect is a genuine danger.
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    Moderator Response: [DB] Fixed html.
  21. Thanks, Tom. I had been wondering about O3 as well, and I felt an edge of sketchiness claiming increased GHG = TLS cooling. What you say takes the edge off.
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  22. Thank you Tom, that certainly helps me understand the context. As I understood your post, you seem to say that the overall stratospheric temp behaviour is not caused solely by the CO2 GHE, but its fingerprint there is discernible nonetheless.

    The part that intrigued me most was the paragraph in the Jones 2003 paper that says (as I understood it) that the observed stratospheric temp decline so far is not yet attributable to the enhanced CO2 greenhouse warming - sulphate and ozone forcings being still the dominant factors.


    Is this correct? If not, did I or the respondent misjudge something?

    If correct, I'm even wondering if it would justify a correction in the Guide...
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  23. Ok, in that discussion I mentioned on my comment #119 I replaced this assertion:

    "Troposphere is warming while stratosphere is cooling. This too is consistent only with an enhanced greenhouse efect"

    by this:

    "The vertical profile of the atmospheric warming is consistent with the human-enhanced greenhouse effect."

    It seems to be more accurate in light of Tom's explanation. I still have the nagging feeling that that would deserve a correction in the Guide (maybe in a future updated version?). As one of the translators, I'm very proud of it and I'd like it to be spotless.
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  24. What is the tiny peak at about 1300 wave numbers in fig. 3? Although it is in the vicinity of methane, if you set the methane to zero in the David Archer program. Also in Fig. 1 above that peak shows up with no atmosphere. ?????
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  25. I meant to say, if you set the methane to zero in the David Archer program the little peak still shows up. Anyone know what this is?
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  26. curiousd @124, if you look at the following diagram, you will see that one NO2 absorption band at around 7.5 micrometers wavelength (1300 cm-1 wave number) is shared with one of the absorption bands for CH4. Removing CH4 from Archer's model greatly reduces the size of the absorption band at 1300 cm-1; but, presumably, the remainder is the absorption by NO2. I have checked and NO2 is accounted for in the model, but its concentration cannot be adjusted in Archer's version.



    Please note that the solar and OLR spectrums shown in the diagram above are for globally averaged values. The actual power received from the sun by a surface at right angles to the incident sunlight is about four times that shown; and the actual black body spectrum of the sun, prior to attenuation by distance is about 4 million times greater than that from OLR. Further, the OLR is for a very humid clear sky situation, and is not typical.
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  27. All, that would be N2O (nitrous oxide), not NO2 (nitrogen dioxide)
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  28. I'm not satisfied by this story. See also how it is debunked in the comments. Let me propose a new theory here and see how people here think it adds up. The theory is somewhat similar to the story here. Maybe I am just explaining the same, but differently. My Theory:

    1) About CO2:
    - When a molecule collides with any other molecule, it either keeps its kinetic energy (KE) or gets in excited state (E).
    - When in (E): When it collides, the excitement might get converted to KE. Or, after a while, it turns to normal state by radiating some IR.

    2) About the atmosphere, for simplicity there just are:
    - An upper part, Stratosphere (S), low pressure.
    - A lower part, Troposphere (T), high pressure.

    3) About what changes:
    - The concentration of CO2 increases in both layers of the atmosphere.
    - All IR still travels in all directions through both layers, but the chance of hitting CO2 is increased.

    4) The explanation why S cools down and T warms up:
    - In S the CO2 molecules have less frequent collisions than in T, just by the lower pressure.
    - We have chance A: The chance that an excited (E) CO2 molecule radiates IR (chance A).
    - We have chance B: The chance that an excited (E) CO2 molecule turns back to normal state by the next collision radiates IR (chance A).
    - In S chance A is much higher than B.
    - In T chance B is slightly higher than A.

    Reactions are appreciated.

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    Moderator Response:

    [DB] "See also how it is debunked in the comments"

    It is not debunked in the comments.

  29. Josbert, when you have model for how something works, then science works by making predictions from the model and comparing them to observations. Cooling of the stratosphere while warming of the troposphere falls straight out the radiative transfer equations (RTE). The RTE are widely used (think about why US Air Force are people that developed the MODTRAN codes) and their predictions about observed radiation whether observed from earth or satellite are matched in equisite detail. However, this is a "shut up and calculate" approach to science and doing an explanation without the math for non-specialists is challenging. I dont like them. However, I can assure you that you are in for an uphill battle convincing anyone that the RTEs are wrong without doing the math and showing that somehow your model produces even better match to observations.

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  30. Josbert Lonnee @128,

    You present a hypothesis that relies on how a low pressure GHG gas radiates energy rather than how an increase in the GHG concentration impacts the net radiation. Here I will restrict the comment to low pressure, rather than low pressure with increased GHG.

    Perhaps the hypothesis can be stood on its head and used to argue that the low pressure gas would be warmer and unable to radiate energy away as efficiently as a high pressure gas. Your argument rests on the idea that an excited CO2 molecule has more opportunity to radiate a photon as there is more time between the collisions that put it into that excited state. Conversely, once the wicked deed is done, the CO2 molecule is no longer in this excited state and thus unable to radiate a photon and that period of unexcited time is far longer at 10mbar than it is at 200mbar. Thus the frequency of (E), the A-or-B situation will be lower and the excited CO2 photons radiated by the gas would be less even if the probability A is relatively higher than B in a lower pressure gas.

    Or just perhaps, these two effects cancel each other out.

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  31. @MA Rodger at 21:01 PM on 2 November, 2018

    I really do not understand what you are trying to tell here, sorry. What is your point?

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  32. scaddenp @ 129

    Do you understand that I am not challenging the observations that the troposphere is warming and the stratosphere is cooling?

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  33. I do understand that, but I have massive mistrust of hand-wavy models compared to precisely stated mathematical models which reproduce multiple types of observations. It isnt clear to me whether you are challenging the RTEs or trying to do a plain English explanation of the net effect.

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  34. scaddenp @ 133

    Im am not doing any of both. Please, can you, based on the RTEs, tell me why my theory is wrong?

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  35. Josbert Lonnee @131,lecules

    Mu point is that you are wrong. Your stated hypothesis contains a number of fundamental flaws. I set out just one (and it only requires one).

    You say the probability of an excited molecule emitting a photon following a collision is increased by an increased average path-length between collisions (thus your A:B ratio increases). You suggest this increase would increase cooling in S relative to T but you ignore the lower number of collisions that the molecules endure in S relative to T, a consideration which will cancel out your A:B increase.

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  36. MA Rodger @ 135

    The number of collisions between molecules stays the same, independent of the concentration of CO2. Only the CO2 molecules are less likely to pass all kinetic energy from collision to collision. So, the mode CO2 is in S, the more energy is radiated away as photons.

    I still do not get this point. Do you have another? You suggest you have more points.

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  37. Josbert Lonnee @136,

    Another point? Let us stick with this one. It is surely the most straightforward.

    You say the number of collisions stays the same, this presumably collisions per molecule. Your thesis is that a lower pressure in the stratosphere (relative to the troposphere) provides a longer time between collisions, more time for a photon to be emitted and so there will be more photons emitted, the gas will cool more.

    But if a molecule takes more time between collisions, how can there be the same number of collisions? Simply, there cannot be!!

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  38. MA Rodger @ 137

    What if one would isolate a (huge) amount of air from S and make it the same temperature and put it under the same (low) pressure as there.

    The theory is not that the time between collisions is (initially) longer between all O2, N2 and CO2 molecules etc. The time is just longer in S than in T because of the lower pressure. Hereby the CO2 concentration is irrelevant.

    After a while, after the gas (like in S) cooled down (slightly), there will be (slightly) less molecule collisions. That makes a difference, but for this it needs to cool down first. The theory is just that the CO2 molecules took the kinetic / heat energy out by readiating it out of the isolation.

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  39. Josbert, the relaxation time for a gasseous CO2 molecule is about 10 microseconds.  But during that timespan, a CO2 molecule (even in the cold lower statosphere) has roughly 10,000 collisions with neighbouring N2 (or O2) molecules.

    If a CO2 molecule does "relax" to emit an IR photon, the photon can travel only a very short distance until it is absorbed by another CO2 molecule.  So it is highly likely that the second CO2 molecule will lose this added energy, by collision with a neighbouring N2 (i.e. by warming the nearby air molecules).  

    As air density decreases, a few IR photons will be able to "miss" CO2 molecules and escape to outer space — in other words, the CO2 in the stratosphere will cool the stratosphere (while the stratosphere is being warmed by the lower atmosphere, which is being warmed from the planet surface by radiation & convection & H2O condensation).

    I am unclear on how your ideas fit in with this picture.

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  40. Josbert Lonnee @138,

    I am unclear about your reason for presenting your "picture."

    There is no need to set up hypothetical situations. The temperature of the lower stratosphere is no different to the temperature of the top of troposphere. All that changes is the reduction of pressure with altitude.

    Temp & pressure with height

    And the CO2 levels don't vary to any significant degree through these altitudes, as these coloured traces of CO2 for altitudes 8km to 18km demonstrate.

    CO2 at altitude

    As for photons escaping to space, that occurs mainly in the upper troposphere where the IR warming runs along side (and thus is in balance with) warming from atmospheric circulations.

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  41. Eclectic @ 139

    Interesting!

    Do you also mean that the stratosphere intercepts most infrared (as intercepted by the CO2 in it) and the troposphere intercepts it all?

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  42. MA Rodger @ 140

    What you tell here is not new to me and the theory is based on assuming that what you say here is true.

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  43. MA Rodger @ 140

    The point of the theory is to eplain why T warms up while S cools down. So I do not understand why you come up with these facts.

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  44. Josbert Lonnee @142/143,

    Correct me if I am wrong. When you talk of "the theory" you are meaning that set out @128 where you describe "my theory." In it you describe a mechanism for a cooling stratosphere and a warming troposphere. You suggest this may be a re-statement of the situation described in the post at the top of this thread [although it is not]. You base your "theory" on the probability of a CO2 molecule emitting a photon following a molecular collision in which it is excited and thus able to emit a photon of IR, a probability which will be greater if this CO2 molecule has longer before it is in another collision. If more photons are emitted by a gas (per molecule), more cooling will occur.

    That is what you appear to be saying.

    Your suggestion is wrong in a number of ways. The most straightforward error is to consider a higher probability of a CO2 molecule emitting a photon after a collision without considering the lower probability of CO2 molecules being in an appropriate collision. Simplisitically, the two probabilities cancel out. So it is not the case that more photons are emitted from lower pressure air.

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  45. MA Rodger @ 144

    It was already clear to me that you understand me all wrong all the time. With "the theory" I of course mean my theory from @128.

    There is no need to repeat your point.

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  46. Josbert Lonnee @145,

    While you appear to be struggling with the English language, I feel we have reached the end of this interplay. After five attempts to communicate with you regarding a blindingly simple concept, you complain that I understand you "all wrong all the time." If that were true, it is up to you to explain yourself properly. However, I do not consider it true. Your 'theory' set out @128 is nonsense and if you cannot grasp the blindingly simple idea that if CO2 takes longer to travel between collisions then there must be less collisions; if you cannot grasp that obvious truth then there is no point in my responding to you. [Mind, I will likely respond to your comments but not to you.]

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  47. Josbert @145 ,

    in your [post #128] scenario, the essential point is that the rate of CO2 molecules emitting IR photons is extremely low in comparison to the rate of collisions, in both the Stratosphere and the Troposphere.   In other words, the chance of a photon-emitting relaxation is (very roughly) around 0.01% compared with the chance of an intervening collision (the collision being likely to de-energize the CO2 molecule from its newly-gained photonic packet of energy).

    If, owing to different temperatures and densities, that percentage should vary between (very roughly) 0.03% and 0.003% [one order of magnitude] in the two layers of atmosphere . . . then you see that the absolute difference from the [almost 100%] collision chance, remains approximately equal for "S" and "T".

    Thus your #128 proposal is barking up the wrong tree.  You should focus on the absolute distances ~ the mean travel distance from one "emitting-CO2" to the next "absorbing-CO2".   This distance is very short, and (greatly enhanced by the relaxation "delay" period) is the reason why the appropriate IR takes a long time to rise from planetary surface up to the top of the troposphere and eventually make its escape (upwards) from there [and a smaller mount will escape upwards from the stratosphere ~ which is why increased solar irradiation of the stratosphere has a stratosphere-warming effect compared with the stratosphere-cooling effect of increased CO2 concentration [regardless of whether it's a human-caused or natural-caused CO2 increase]).

    Josbert, stay on MA Rodger's good side, and he may well provide a much more rigorous explanation than I can !

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  48. Eclectic @ 147

    What you say is very clear and shows my theory is false.

    MA Rodger just kept mentioning the same point and that I do not understand that. My English was to blame.

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  49. Josbert, I am happy to be of help.  The so-called Greenhouse Effect is rather counter-intuitive for many people (including me), and I find a deficiency of sites where it is explained completely all in one chapter.  In particular, the stratospheric cooling effect is interesting, partly because it demonstrates the falsity of some of the claims of the climate science denialists [the faux-skeptics].

    As you are aware, the large majority of 15-micron IR is lost from Earth at the altitude of the upper troposphere, yet a tiny amount is lost from the stratosphere itself, too.

    My apologies for my typographical error ["typo"] in my third paragraph of #147, where I wrote "and a smaller mount will escape" ~ the correct word would be amount.  This sort of typo must be troublesome and annoying for a reader who is not 100% fluent in English. 

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  50. Eclectic @ 149

    Yes, there is a deficiency of good, neutral articles on the Greenhouse Effect. I am actually trying to write something like that in Dutch. It is here:

    https://josbertlonnee.wordpress.com/2018/11/20/het-broeikaseffect/

    The stratospheric cooling is not mentioned there (yet). To fascinate a bigger crowd, things shoult get kept simple, but with this kind of subjects that is really hard.

    I already started reading more about the IR-spectrum of the earth's atmosphere. I learned you never know enough w.r.t. climate. For instance, how exactly do molecules transfer energy from photons to kinetic energy?

    I completely overread your typo. I am quite used to English; not to speaking it. Is my English really that bad?

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