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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 51 to 100 out of 123:

  1. #45 VeryTallGuy at 19:42 PM on 20 December, 2010 "what's the difference in heat capacity for an atmosphere with 560 vs 280 ppm CO2?" Almost no difference The difference is the height of the tropopause It results in the following outline of the greenhouse effect in 5 points: 1. The atmosphere is divided into two parts, in essence, bottom the troposphere with a lot of convection, where the weather is and where we live, and top the stratosphere without convection, with a possible move the border between the two spheres. 2. The temperature gradient in the troposphere is (almost) constant - even when changing the thickness of the troposphere. This consistency is result of convection. 3. The almost constant optical thickness of a changing stratosphere. This constancy is due to radiation and is due to the scaling (scaling) of the radiation transport equation for change in optical thickness with change in concentration of CO2. 4. If the temperature gradient exceeds a certain threshold, the air can not stay calm and stratification becomes unstable - and the convection is the characteristics of the troposphere 5. In the steady state (ie, even though time passes, the state no changes) does mean the heat of the earth just as great as the heat absorption - would otherwise be the temperatures change constantly. But this would contradict the stationarity. These 5 points provide a basic sensitivity of the average surface temperature as a result of changes in concentrations of CO2. Addition: The thicker troposphere has a greater temperature difference between top and bottom, and this greater temperature difference is so distributed to warming bottom and cooling top, that the total radiation of the Earth is equal to the total absorption.
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  2. @RSVP #40 Again, what makes you think that B relates to A, being: A = "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." B = "How does a packet of energy that raises the troposphere's temperature, also raise the temperature of the Earth's surface or ocean waters? Afterall, hasnt it been said that all this extra energy is accumulating in the oceans and raising water temperature? If that little bit more of IR gets absorbed at a lower altitude due to the extra CO2, this should raise its kinetic energy or that of the gases around it,... in which case the work is done and accounted for... end of story. How can it then do "double-time", going off and warming other things? " [SIC] You took a simple dynamic process (A) yet one you don't understand and cast it into The Brothers Menaechmus (B). Basically you are saying "something I have no clue violates the law of conservation of energy! What about that!?!?". I was tempted to answer that and explain it to you, as many patiently do here daily. But I think that you, as any learner, must do your effort, and as I am sure you are not here because of control issues or 'being a playa, yo' or 'I'm making them mad with my observations because they have no clue' or 'There's no AGW because I have no clue but still I get them in a swamp trying to explain it to me' or anything like that, God forbid, I suggest you to start by explaining what "unexcited" means in A.
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  3. Ebel I don't think so. Indeed, ozone is one of the main factor affecting our troposphere/stratosphere structure. As far as I know, we'd not have a temperature inversion in the stratosphere without ozone; this has been recognized around the 1930s of last century and never changed. But sure I won't fall into the mistake of thinking that only one factor matters.
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  4. Without ozone heating would be no inversion - but the temperature gradient would still fall to nearly 0. The ozone mass is very little (lower 5 mbar). Stratosphere lower 200 mbar. See http://www.skepticalscience.com/news.php?p=5&t=245&&n=468 #234
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  5. A few questions about the different vibration states (3 IR ones) and the frequency of the IR packet? What I understand that CO2 will not (~90%) transition between the different oscillations so is the energy frequency absorbed and re-emitted the same (as in the same band) or is it on one of the other two bands? If this is so would it not change the shape of the spectrum (frequency absorbed and re-emitted) with altitude? I understand band winging etc. But I have heard both answers (Same and not the same frequency) from people in the field. I know it is more of a quantum mechanics but I have not been able to get an answer or a better undemanding of the changing frequency in the oscillations states. I know what the answer would be if it was the electron changing states but not with vibration states. If you have a reference would be nice. My last quantum mechanics class was late 70s so sorry for a basic question. Thanks
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  6. danielbacon - That depends a bit on altitude and pressure. At surface pressures a CO2 molecule will collide with ~1000 other molecules before it has time to transition down and emit a photon. This means that an individual absorption is unlikely to directly result in an emission, but rather emission is driven by the air mass average temperature of thermally (re)excited CO2. The energy state of the CO2 molecule will be changing continuously due to collisional interactions, not just absorption events, and the emission spectra will reflect that. At stratospheric pressures/temperatures, of course, collision frequency will drop, but there should be >>1 collisions before emission down to roughly single Torr pressures.
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  7. #56 KR at 02:59 AM on 21 December, 2010 "The energy state of the CO2 molecule will be changing continuously due to collisional interactions," The energy state of the CO2 molecule will be changing not continuously, but in quantum. See also Milne, Edward Arthur: The effect of collisions on monochromatic radiative equilibrium ( http://adsabs.harvard.edu/abs/1928MNRAS..88..493M ) Atoms in Milne = molecules in the atmosphere
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  8. Ebel - Sorry if I was unclear. The energy of the CO2 molecule will vary greatly over time, including both quantum effects (electron orbital states), vibrational energy, and the more continuously variable rotational values. By continuous I meant over time, not total energy. Due to the frequent collisions and energy exchanges emission energies of any particular CO2 molecule will have at most a very weak correlation with previous absorption energies.
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  9. @RSVP: "Let's see. If an IR "photon", energy packet, (however you want to call it) is emitted from a roof's slate shingle, and is captured by a CO2 molecule two feet away, has not the roof lost the energy, and the air gained the energy? And in losing this energy, has not the roof effectively "cooled"?" Indeed. However, without the GHG molecule, the IR photon would be more likely to escape into space, while here it is being captured by a CO2 molecule and re-radiated, possibly back to that rock, re-warming it. Eventually the Earth will reach temperature equilibrium, but all this extra time the IR photons spend in the atmosphere and back to the ground means higher temperatures overall. You know this already. Please stop wasting everyone's time.
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  10. danielbacon to elaborate a little bit on what KR said, once excited, the molecule have two possible paths to jump back to the fundametal state, emit the excess energy at the same frequency or give it away as kinetic energy to other molecules by collision. The first proces is radiative, the second is not because the vast majority of mouecules in the atmosphere is IR inactive. In principle, higher order processes may occur, but they can be safely neglected. Having said this, I think the best way to understand it is look at an emission spectrum.
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  11. I am the one unclear here sorry. With Kirchhoff’s law and no molecule collision the frequency absorbed and re-emitted are the same correct (or am I making a mistake here). Now as we move up now adding collision you are saying that the emitting of IR is more due to molecules collision creating one of three vibration states then emitting, is more dominate then ad-reemit? As the collision drop off absorbed and re-emitted would be stronger. Now are both collision and the major absorbed are both dominate on one particular vibration state and if so which a-sync or one of the two bending states.
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  12. danielbacon - Collisions will dominate energy transfer down to <1 Torr, or about 1 millibar (0.75 Torr/millibar). That means any part of the atmosphere below about 48km, the top of the stratosphere: As the current topic is discussing tropospheric and stratospheric radiative states, not mesospheric or thermospheric, we can consider collisional effects dominant. As to which particular energy states, I can't speak to the statistical distribution between various vibrational/electron states. - perhaps someone else can. Is it relevant?
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  13. Good article. Very educational. Shame RSVP has scrawled graffiti all over the comments section by denying the very principle that we all know from merely getting under a duvet when we go to bed. Or perhaps I'm still dreaming...
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  14. Xplain: "Shame RSVP has scrawled graffiti all over the comments..." Indeed.
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  15. RSVP: "As the context is electromagnetic radiation, and the exchange of heat from solids on the ground to CO2 molecules that make up the atmosphere, it is hard to understand where the obscurity lies." You assume that everyone knows what level of understanding you have. I generally assume denialists have a poor understanding of science. Hence coming from such a person, a packet can mean anything. You clearly do not explain yourself clearly in order to disrupt and play games. That isn't clever and is considered to be morally corrupt by some.
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  16. danielbacon at 04:45 AM on 21 December, 2010 says Its more a question of opacity, a molecule will emit proportional to its T^4, so at higher altitudes, CO2 is still emitting at 15 micron, but much less intensely than at the surface(and also, just because something can absorb a wavelength, dosnt mean it emits it, if its T is not sufficient, take O3, absorbs UV, emits 9-10 micron , Kirchhoff's law is really just saying you cant heat something above the T o the source radiation.) The reason being, that at just above the surface, the atmosphere is extremely opaque to 15 micron, so even though it is emitting much more intensely than at the tropopause, what is emitted is absorbed within 3m. So it doesn't loose energy through radiation in this wavelength at these path lengths. Where as when you rise through the atmosphere, and it becomes more rarefied, the amount of energy moved through radiation increases, just because the probability of what it emits being reabsorbed in close proximity to it decreases. The path length shortens. So the vast majority of the energy emitted from just below the tropopause in 15micron escapes directly to space, some is absorbed in transit, and re emitted, and this emission can be seen as a spike in the center of the 15micron band looking down from space. Because its more intense than what is emitted from the tropopause(around 220K). I think Ebel and Tom Curtis both posted graphs of this in the other thread. Truth is, the net flow of energy is from the stratosphere to the troposphere, and this is a result of the transparency to LW in the stratosphere, but opacity to UV, so it emits more to the troposphere than it absorbs coming up from the troposphere. Good paper on stratospheric tropospheric radiative interaction that im going to post yet again, because it does give some great insights. Quantum mechanics is not my thing however, but emission is T dependent.
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  17. #61 danielbacon at 04:45 AM on 21 December, 2010 "With Kirchhoff’s law and no molecule collision the frequency absorbed and re-emitted ..." There is no re-emission, but only an emission according to the temperature. Absorption and convective heat transfer only replace the emitted energy, so that the gas temperature remains approximately constant.
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  18. #4 Alec Cowan "then it becomes "less rarified" by a factor of about 1.0009" Thanks for that but it didn't quite answer my question. I have no problem with the size of the increase. Bob seems to describe the KE method as revolving around the increase in collisons of molecules associated with this increase. Your answer would suggest this process is insignificant as well. I'm really interested why molecules are more likely to collide while IR and molecules aren't more likely to collide when CO2 is increased in the stratosphere?
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  19. #68 HumanityRules at 17:00 PM on 21 December, 2010 "I'm really interested why molecules are more likely to collide while IR and molecules aren't more likely to collide when CO2 is increased in the stratosphere?" The collisions with CO2 molecules are a tiny minority of all collisions - but still makes sure that the ratio is of excited CO2 molecules to CO2 molecules in the ground state is the Maxwell-distribution corresponding to the gas temperature equals [exp (-hv/kT)]. If the radiation intensity corresponding to the local gas temperature, it would be Maxwell-distribution accurat. If the radiation intensity is lower, exist less excited states, at a higher radiation intensity exist a little more excited states.
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  20. archiesteel #59 "Indeed. However, without the GHG molecule, the IR photon would be more likely to escape into space, while here it is being captured by a CO2 molecule and re-radiated, possibly back to that rock, re-warming it." ...at which point, the CO2 molecule cools. If I move a dollar from one pocket to another all day as I go window shopping, my buying power hasnt changed. archiesteel #59 continues... "...but all this extra time the IR photons spend in the atmosphere and back to the ground means higher temperatures overall." Furthermore, last time I checked, my pocket yields an interest rate of exactly 0.00000%
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  21. The Ville #65 "That isn't clever and is considered to be morally corrupt by some. " I think Socrates had to down hemlock for this same accusation. So I take this as a compliment which I really do not deserve.
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  22. Alec Cowen #52 "I suggest you to start by explaining what "unexcited" means in A. " Sorry, this was a quote from the featured article.
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  23. RSVP: "If I move a dollar from one pocket to another all day as I go window shopping, my buying power hasnt changed." The US government isn't printing trillions and trillions (etc) of dollars per second all day. The Sun however... Your discussion is centred around a fixed energy scenario where there is no further input of energy. Even in the scenario you suggest no energy is lost, which is the point. The only way for the energy can escape is to be radiated to space eventually. To be honest your silly game is juvenile.
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  24. @RSVP #72 I knew, as I called that paragraph A. Again, I insist you to start by explaining what UNEXCITED means in A. When you get it you'll comprehend the error in your initial thoughts ... if you're looking for knowledge. I want you to know that your comments are extremely valuable to me for educational purposes. I'm making a collection of your comments for some of my students to work on them during 2011.
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  25. RSVP - Please, you've been on this website for quite a while, and know better than to treat this as a zero-sum fixed quantity issue. Energy comes in continuously from the sun, greenhouse gases slow the exit of that energy to space at any particular temperature (higher emission altitude, lapse rate from there to the ground, or just by looking at effective TOA emissivity), temperatures increase, and outgoing energy increases as well as the Earth system tries to balance in/out energy. Please stop with the inappropriate analogies, such as fixed amounts of change in your pocket (unworkable analogy, it doesn't reflect any aspect of the climate system). We've had that discussion before, on the "Waste Heat" thread, regarding the Bad Analogy logical error.
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  26. @RSVP: "I think Socrates had to down hemlock for this same accusation." Socrates used logic, and pursued a quest for truth, while you appear to engage in scientific sophistry designed to stall the debate on AGW. There really is no comparison possible. "So I take this as a compliment which I really do not deserve." It isn't a compliment, and you do deserve it.
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  27. @RSVP: "...at which point, the CO2 molecule cools." A more accurate description would be that it returns to its previous temperature. The extra amount of IR radiation is still in the system, therefore raising the temperature of the system until a new equilibrium is reached. Quod erat demonstrandum. "Furthermore, last time I checked, my pocket yields an interest rate of exactly 0.00000%" I am not interested in your incorrect analogies. Try logic instead.
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  28. @HR: "I'm really interested why molecules are more likely to collide while IR and molecules aren't more likely to collide when CO2 is increased in the stratosphere?" I'd like to answer this question, but it's so badly written I can't figure out what it means. Contrarians, please try to eschew obfuscation in your arguments. Thanks.
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  29. @HR: "I'm really interested why molecules are more likely to collide while IR and molecules aren't more likely to collide when CO2 is increased in the stratosphere?" They will collide whatever their state... but if they have less energy than what they collide with, they will absorb energy from the more excited molecule(excitation is normally referring to increased T/energetic excitation, kinetic motion of a molecule) And if they have more, the exchange is reversed. So if CO2 is radiating away more energy than its receiving via absorption, it will remove energy from the surrounding molecules... simple, the net flow of heat is from hotter to colder.
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  30. re the main post - I think it's more straightforward to note that the CO2 molecules tend towards the same temperature as the rest of the air in a given volume, because of the frequent molecular collisions (reality diverges from this above some level where the air is too rarefied, but this is above the stratosphere), which means some fraction of them will be in various states. At a given wavelength, they can emit as well as they can absorb, in that a given path will absorb the same fraction of incident radiation as the fraction of blackbody radiation it emits, the later being a function of temperature; this fraction approaches 100 % with increasing path length and increasing CO2 concentration for a given path length (specifically it 'decays' from 0 to 100 % exponentially) - except that if the temperature varies, the emission from a path is a weighted averaged of the blackbody value over the path; greater opacity concentrates that weighting closer to the near end of a path, so the emitted radiation would become more similar to the blackbody radiation for the temperature near the end of that path. This weighting is the same distribution of absorption for radiation coming from the opposite direction; it corresponds to what you can see coming from that direction. When more CO2 is added to the atmosphere the outgoing radiant flux is reduced because the weighting is concentrated into the higher, generally colder levels of the atmosphere, and less is at the generally warmer surface, etc. Water vapor feedback does the same thing, at different wavelengths. Warming must occur in order to bring the flux back into equilibrium with solar heating - because the CO2 (and positive greenhouse feedback) reduce the net upward flux at the tropopause level, some warming must occur beneath, and given the convective coupling of the surface and troposphere, the surface and levels of the troposphere tend to warm together. Because the atmosphere is more transparent at some wavelenghs, and at least for the effect of CO2, it's transparency has not been decreased at all wavelengths, the warming that is necessary to bring the outgoing flux back to what it was before will increase the outgoing flux beyond what it was before at some wavelengths, which means it will still be less than what it was before at other wavelengths, which means that the highest portion of the atmosphere, from which the strongest parts of the CO2 band emit to space, will be colder than what it was before. (The H2O feedback could be more complicated). (PS I learned this from a discussion at RealClimate). There is some additional stratospheric cooling that is transient - the stratosphere is initially cooled by the addition of CO2 by a larger amount than the final equilibrium, because some (small) fraction of the increase in radiation from the troposphere+surface upon warming will be absorbed in the stratosphere and cause warming there - this is after the decrease in radiation from below (from increased CO2) that, along with increased downward radiation from the stratopshere (from increased CO2), minus the reduction in downward radiation from the stratosphere (from stratospheric cooling), forces the warming. Also, the solar heating of the ozone layer, making the upper stratosphere warmer than otherwise, increases the stratospheric cooling caused by addition of CO2 (in the highest part of the atmosphere that can emit signficantly, as the concentration of a greenhouse gas is increased relative to the concentration of a gas that absorbs solar radiation, the temperature will generally tend to fall).
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  31. #80 Patrick 027 at 16:47 PM on 22 December, 2010 True, where much is absorbed, there is also emitted much - but the importance of adaibatischen moist circulation for the temperature characteristic is forgotten, as well as changing the height of the tropopause.
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  32. KR #75 "Please stop with the inappropriate analogies" I will grant it is possible to draw poor analogies, yet all cognition ultimately depends on simple mental models. If what I posted is oversimplified or can be shown to be inappropriate, feel free to explain why. Alec Cowan #74... instead of clarifying your position, you attempt here to place the burden of explaining what you think on me. As above, why not simply say it as it is? archiesteel #76 You write that I am wasting everyones time, stalling the "debate" on AGW (herein admitting there is something to debate).... The idea being that you can debate it as long as you agree with it!
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  33. RSVP - In short, your analogies are all fixed-sum in basis. The change in your pocket, single packets of energy changing positions, etc. The reality (the complex system your analogies refer to) is one of continuous energy flow. Solar energy comes in, IR goes out to space at a rate dependent on temperature and the emissive properties of the Earth. Greenhouse gases change those emissive properties (framed here as changing the altitude distribution of IR emission), causing an energy imbalance, and changing the temperature. There are no fixed sums of energy packets, photons, or pocket change - what comes in goes out again, with the environment determining the rate/temperature relationship. However, every post I've seen from you on this topic includes fixed amounts as part of the framing. Bad analogies lead to incorrect conclusions if you try to reason from them.
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  34. @RSVP: "You write that I am wasting everyones time" Indeed you are. "stalling the "debate" on AGW (herein admitting there is something to debate)" Yes, there is, i.e. what to do about it (not whether it's true or not). "The idea being that you can debate it as long as you agree with it!" No, the idea being that bringing up the same debunked myths and refusing (or being unable to) respond to counter-arguments isn't debate, it's propaganda. It is obvious to *anyone* here that you're not interested in debating the issues, but rather you seek to push the same old talking points and stalling the debate on a point that is already settled, i.e. AGW is real, and happening now. As far as incorrect analogies go, they are tools of sophistry, not intelligent debate. Please stop using them. Thanks.
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  35. KR #83 Consider a cylindrical thermos container with a double plated glass on one end, filled in two cases with two distinct mixtures of a hot gas at the same temperature. In the first case, the mixture is N2, and in the second, it is CO2. I assume you would agreee that in pointing an IR detector at the glass (from outside the cylinder), the detector would register higher for the CO2 than for the N2, since the CO2 is able to emit more energy per unit time. In the same way, the more CO2 there is in the atmosphere, the more capacity for emanation, or at worst, any downward emanation should be compensated for this reason. This line of reasoning looking at the problem from a macro level just happens to coincide with the simple photon accounting explanation, and seems to agree with Figure 3 above. For all practical purposes, the two curves are sitting one on another, making more of a case against AGW than for it. I am not saying more CO2 is a good thing, and who knows, maybe it is causing warming in some way, but as the story is being told so far, these explanations seem incomplete, and fairly susceptible to critique (or at least debate archiesteel). Or if the bad CO2 really does slow down cooling, does that mean instead of the temperatures dropping to ten below by midnight, it happens five minutes later? (in which case, is this really a problem?)... or what relation does half of airports shutting down in Northern Europe last week due to bad weather have to do with any of this? Etc.
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  36. RSVP - Another fixed sum experiment/analogy? With pre-heated bottles? A more realistic rate experiment consists of two containers (CO2 and N2 filled), each with a piece of dark paper (or perhaps some dirt) in the bottom. Add energy with a visible light lamp, measure the temperatures. The CO2 filled container will rise to a higher temperature because the CO2 inhibits the thermal radiation from the paper, the visible light absorber. Visible light comes in, warms the surface, IR is emitted, and the CO2 slows it's exit rate by re-radiating part of it back to the surface. Rates, RSVP, not fixed sums.
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  37. @RSVP #82 As I told you, you had from the very beginning a problem understanding what "unexcited" means. You must solve that in order to make the simplest step further. You also made a mistake judging what's going on: Almost anybody here is in need of "clarifying [their] positions" because you and another guy simply don't understand the underlying physics. Get it crystal clear: I don't see here any fellow adopting positions and debating them with you. We are just trying to make you to understand physics by building bridges. You may cross that bridges or ignore them or spit on them or even burn them, but still there's no "positions" in this level. That's the marvel of physics: the universe is not build from opinions. Just in case this is not clear, this post, as many of them in this site, is built with bricks got from experimental science. Your comments are answered "get the fact and logic straight" what is a previous condition to design any experiment. I suspect that find some pleasure from debating matters beyond your actual education and at some point beyond your potential abilities. Your verbal and social abilities -your ability to understand the social effect of a debate- is a thousand times stronger than your ability to pile up simple units of physical laws and principia and make sound inferences from that. And it's this wolverine-like attitude and militant skepticism of yours (the buzz-word skepticism I mean) what I find most interesting and valuable in you. Imagine your comments and the answers we give you analyzed in School -that's what I did, do and intend to do- not within a frame of boring physics but within a multidisciplinary frame including social sciences and studying how common people is manipulated. All the students became suddenly interested and they even learn the scientific method and some physics! That's the opportunity that comes from the pseudo-debate implying the reality of climate change. You shouldn't mix up social debate which includes some shreds of tottery physics, what you appear to have embraced, with a debate about physics: you voluntarily have put yourself out of that sphere. Just keep your comments coming, no matter they take a sentence here, shake it a bit and convert it in another thing. But you may also return to what unexcited is and your 'two-timing' packets and fix your initial mistake.
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  38. KR #86 If the mixture in the chamber is observed to get warmer for containing a GHG, temperature of the back plane surface upon which the light is shining can only be taking that much longer to rise. A fair experiment would include monitoring both temperatures over time and plot comparative profiles, with and without "GHGs". In these plots, what you should find the plate surface taking that much longer to rise, owing to the GHG picking up this same "fixed sum" energy. The warmed gas should then act as a vehicle for heat transport, not unlike occurs for the convective cooling of a fluid on a solid. The cylinder's construction (or configuration) will then determine to what extent this heated gas can help cool the back plate and the gas just above it. Unless the experiment is set up with provision to replicate the equivalence of an open sky with pressure dropping as you go upward, etc., its value may be limited in "proving" anything. At least as a thought experiment it may provide some food for thought, however given what has already been said, this too is doubtful.
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  39. RSVP - I have to disagree with your post completely; the chamber containing GHG's in my example will show the plate and chamber temps rising faster than in the non-GHG case. Note: in the following example the actual numbers are whole cloth - but they illustrate the point, and the directions of change observed Take two insulated chambers (as before) with black plates at the back, no GHG's in the air, and a 100W bulb (visible light) shining in. At dynamic equilibrium the plates (at some temperature) will radiate 100W of thermal energy back out. Add GHG's to one chamber, keeping the pressure the same (to avoid any other effects). The plate receives 100W, radiates 100W, but now (let's say) 10W of IR get absorbed by the GHG's. They then warm and radiate 10W IR in all directions (atmospheric equilibrium). The box now receives 100W, but only emits 95W (imbalance). The plate receives 100W of visible light, plus 5W of IR backradiation. Not surprisingly, the plate warms up. The plate in the non-GHG box does not change temperature. At dynamic equilibrium the (warmer) plate will receive ~105W of radiation, lose the same 105W (mostly radiation), the atmosphere will radiate something like 10W (all directions), and the box will once again emit 100W of IR. With the plate and air in the box warmer than the non-GHG box.
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  40. KR #89 For purposes of the discussion, I think you would allow the heat source to be substituted with a heating filament. One that is embedded in the backplane. This is not necessary as the lamp will do, however, it might be helpful for illustrating what follows. I would agree that that backplane would heat faster as you say if it were covered with an ideal layer of insulation. However, it is my understanding that this GHG only insulates partially, and as the featured article explains, passes energy off to surrounding molecules in the gas mixture. This being the case, and these in turn having their own thermal interia, will in fact require an instantaneous portion of the energy coming from the source, such that the temperature of the backplane will take longer to reach its maximum, as opposed to heating faster as you say above. So it is not clear to me which of these two factors wins out. Furthermore, it would seem that the larger the cylinder (and greater its volume regardless of GHG concentration), the more it would tend to do what I say, vs what you say. The backradiation should never be greater than the GHG upward radiation, since I assume the top is temperature controlled and much cooler than backplate in order to approximate something like an open sky, a factor independent of the fact the area of heat emission is now greater than the that of the plate on its own due to radiative contributions from the "GHGs".
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  41. RSVP - I posted my "box example" to illustrate greenhouse gas warming: the GHG box plate warms at some rate, while the non-GHG box plate (and gas) do not warm at all. I'll note that "I assume the top is temperature controlled and much cooler than backplate in order to approximate something like an open sky" is something I did not say - please do not introduce strawmen. In a single-plane GHG example (which the box example is, as there isn't enough room for convective lapse rates) the IR leaving the GHG layer will equal that going back to the surface. In the actual™ climate, however, by the time the greenhouse gases thin enough to emit to space, the lapse rate means that those layers are very cold, and hence emit much less than surface level GHG's. Hence there is a big difference between IR traded around at ground level and that emitted to space. Which is a big part of the Stratospheric Cooling and Tropospheric Warming discussed on this topic.
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  42. KR #89 "The box now receives 100W, but only emits 95W " KR #90 "please do not introduce strawmen." Unless there is some place for the energy to go, it is not clear how the box can emit anything. I have no intention (or need) to introduce strawmen, as in fact the discussion started with the following.... An earlier post of mine #85 "Consider a cylindrical thermos container with a double plated glass on one end...I assume you would agree that in pointing an IR detector at the glass (from outside the cylinder), " All this goes back to the "double duty" comments on this thread. The idea that it normally takes energy to raise something's temperature, coupled with the idea that you cant normally create energy, and that when you consider a surface plus a gas, you are talking about more things, not less things. So any IR energy from the surface responsible for heating a GHG, is lost from the surface. Whether an IR energy packet gets picked up by a GHG or reaches outer space is indifferent to the surface. It looses this energy the same. And in taking a step backwards and considering the entire "system" that includes both fluids and solids, the same energy from the Sun is now simply more dispersed if more of it is retained in the fluid part. Overall, it would appear there is more ways for the energy to escape, not less. However, if this represents slightly higher transient atmospheric temperatures during the day, it also represents slightly lower surface temperatures in kind... and I will grant that the surface cooling is also tempered by the backradiation you are talking about, which will normally be much much less than what is emited by the surface.
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  43. RSVP - "it is not clear how the box can emit anything" Through the same clear window through which the 100W bulb light comes in. Energy (visible light) continuously comes in, warms the black plate, continuously radiates out (Stephen-Boltzmann equation) as IR - an ongoing flow. GHG's make the flow out less efficient, energy builds up, the plate temperature rises, until outgoing equals incoming again. Again, rates, not fixed amounts! Honestly, RSVP, if you cannot understand these very basic characteristics of the greenhouse effect, and of the analogy, after so many cycles of explaining it to you, there's really nothing more I can say - you either won't or can't listen.
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  44. RSVP - I will have to qualify my last post; this particular example hasn't been discussed much, and there may be some points I wasn't clear on. However: The greenhouse effect is all about rates, not fixed amounts, and your "double duty" fixed amount postings are a complete strawman - an incorrect distortion of the system under discussion. It's a deeply invalid analogy, and arguing from it is a logical fallacy.
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  45. @RSVP: "Whether an IR energy packet gets picked up by a GHG or reaches outer space is indifferent to the surface. It looses this energy the same." Sure, the surface does lose the energy, but the capture IR packet is eventually released, and may go back to the surface, warming it again (and thus making the system retain more energy than if it escaped into space). Stop running in circles, and try learning some actual science.
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  46. Both of you guys can do yourselves a favor by going to this website (there are many others)... http://www.engineeringtoolbox.com/radiation-heat-transfer-d_431.html q = ε σ (Th4 - Tc4) Ac ...and note that radiation loss depends on two distinct temperatures. That of the emiter AND the receiver. That is your last heads up from me. See ya.
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  47. @RSVP #96 Thank you, thank you, thank you! " ... AND the receiver!" This will be commented for ages.
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  48. few questions (apologies if they've been answered already) "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." Has any additional radiation out of the stratosphere been measured? What else could cause stratospheric cooling other than the enhanced greenhouse effect? Also, can you point me to an image showing what the actual temperature change profile looks like? TIA
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  49. Mango @98, I'm not sure where you are going with your questions. What is your end game or goal with this line of questioning? Thanks.
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  50. @99 People tell me i am wrong and point to SkS, so i thought i would ask here
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