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Comments 101 to 125 out of 201:

101. KR at 01:14 AM on 23 February, 2011
     RW1 - To use a database like HITRAN, you set up your parameters (in whatever spectral software you are using, such as JavaHAWKS) for two different conditions, run it twice, and look at the differences between the outputs. The output of interest is the summed energy radiated from the atmosphere given a particular surface temperature and atmospheric mix. The difference between them (~3.6 W/m^2 for doubling CO2 with HITRAN data, 3.7 for more up to date models) is the difference in total radiated energy - outgoing energy. Not isotropic radiation from a particular level of the atmosphere, but the difference in total emissions. Changes in atmosphere modify the emissivity of the Earth, as per the Stefan–Boltzmann law; the amount of thermal radiation emitted at any particular temperature. And that leads to imbalances with incoming sunlight that result in climate changes as energy accumulates or leaves. It's as simple as that - what is the sum difference between radiated powers after an atmospheric change. That 3.6/3.7 Watts is the integrated difference in total radiation going out to space at a particular temperature - which is the very definition of "radiative imbalance".
102. scaddenp at 12:15 PM on 23 February, 2011
     RW1 - you are asking for documentation of what is implicit in the equations. Lets see if I can attempt it. At heart of equations, you consider a small slice of atmosphere. It has radiation from in from below, (from surface and lower layers) and from above (from upper layers in atmosphere). The equations capture absorption, transmission, emission (in ALL directions - which of course is the inputs to layers above and below) for a given gas composition, P,T. The integral of all the layers is what then allows you to calculate what comes out of the top. All the interaction is captured. You know it correct because the model results agree with empirical measurement. Science of doom explains the textbook.
103. RW1 at 11:49 AM on 24 February, 2011
     scaddenp, I'm not finding the information and/or documentation I'm looking for to verify the claims made by you and KR. You are saying the 3.7 W/m^2 increase is not the reduction in the atmospheric window?
104. scaddenp at 13:57 PM on 24 February, 2011
     Sigh. The Science of Doom takes you through text book. Is that documentation enough? The problem seems to be that you are looking for a statement that doesnt exist because it would make no sense. The way real physics is done is bears little relationship to way you are trying to approach it. We are trying desperately to show why that is. As far as I can see you either: a/ study the physics b/ see that since model matches measurement so model must be right. I am guess that are ignoring the textbook, SoD, papers, because they dont relate to George White's "logic" and you search in vain for an analogous treatment. However, this is the right way to do it. I'm beyond my power to help you further.
105. RW1 at 14:06 PM on 24 February, 2011
     My goodness, the answer is yes or no. You are claiming the 3.7 W/m^2 does NOT represent the reduction in the atmospheric window, right? (This is what I'm assuming you're saying). I do not find this information in the stuff you've referenced, and I've continued to search online to no avail. What we are talking about here represents a fairly simple thing. I sent an email to one of the links from the source you referenced to inquire: SpectralCalc.com Hopefully they will respond.
106. muoncounter at 14:25 PM on 24 February, 2011
     Rahmstorf 2008, linked in the Advanced version of this post, gives 3.7 W/m^2 as an undisputed figure for CO2 forcing. Without any feedbacks, a doubling of CO2 (which amounts to a forcing of 3.7 W/m2) would result in 1°C global warming, which is easy to calculate and is undisputed. ... consensus holds that a doubling of CO2 causes a radiative forcing of 3.7 W/m2, which in equilibrium would cause 3°C±1.5°C of global warming.
107. scaddenp at 15:09 PM on 24 February, 2011
     muon - the issue is does "reduction in the atmospheric window" mean the same thing to RW1 as I think it means. You can say yes, but I suspect that RW1 then has corollary from that shows a very different understanding.
108. muoncounter at 16:07 PM on 24 February, 2011
     scaddenp - Yeah, I thought that was a peculiar phrase, which seems to add an unnecessary layer of complication. All I did was point to the link, as it seemed (in #105) that he couldn't find it. How he chooses to interpret this particular 3.7 W/m^2 is up to him, although both KR and you have made it very clear.
109. KR at 01:16 AM on 25 February, 2011
     I believe the "atmospheric window" issue is tied (again) to George White - he believes the window of IR going straight to space is >90 W/m^2, whereas Trenberth estimates 40 W/m^2, and asserts that all greenhouse gas effects operate by narrowing that window. He seems to neglect lapse rate and GHG concentration effects raising the altitude (and dropping the temperature) of emission, and in addition argues that the 90 W/m^2 represents a limiting band on GHG effects. RW1 - The models operate by calculating upwards and downwards emissions from all levels of the atmosphere, and the 3.7 W/m^2 represents all the effects: band broadening due to higher GHG concentrations, band deepening due to higher effective altitudes of emission to space, higher reemission to the ground, etc. So the answer to your question is partially, although not readily picked out of the other effects.
110. scaddenp at 08:23 AM on 25 February, 2011
     The problem of getting your "physics" from George White instead of from a textbook. Is George untroubled by lack of match with empirical data?
111. RW1 at 09:54 AM on 25 February, 2011
     KR, My question isn't related to what the number for the window is. scaddenp, No, the problem is no one is answering my question.
112. RickG at 10:03 AM on 25 February, 2011
     @ #111 "No, the problem is no one is answering my question. Or perhaps its just not the answer you want to hear.
113. scaddenp at 10:39 AM on 25 February, 2011
     RW1 - "You are saying the 3.7 W/m^2 increase is not the reduction in the atmospheric window? " Hmm, but we have this rather odd expression about "reduction in the atmosphere window". What does this mean? KR identifies it with a GW idea. Can you phrase the question in a way that we can understand, and preferably makes physical sense?
114. RW1 at 11:17 AM on 25 February, 2011
     scaddenp, I'll break it down into a series of separate small questions: 1. Do you agree that some of the emitted surface infrared power passes through the atmosphere unabsorbed by GHGs or clouds? 2. Do agree that the remainder is absorbed by the atmosphere? 3. Does the 3.7 W/m^2 of 'radiative forcing' represent a reduction in the atmospheric window of 3.7 W/m^2? 4. Does the 3.7 W/m^2 of 'radiative forcing' represent an increase of 3.7 W/m^2 in the amount of infrared absorbed by the atmosphere. My understanding is your answer to 1 & 2 is YES and your answer to 3 & 4 is NO. Is this correct?
115. KR at 11:53 AM on 25 February, 2011
     RW1 - The answers to your four questions are "Yes, ~40 W/m^2", "Yes, although a fair amount of energy also goes into the atmosphere via convection and latent heat (~20%)", "Only partially", and "Almost, it's the amount prevented from leaving via various effects - more absorption and higher/colder emissions". Sorry, but these are obviously important questions for you, and I would be doing a disservice by giving un-nuanced answers.
116. RW1 at 12:23 PM on 25 February, 2011
     KR, The actual number for the atmospheric window is irrelevant to the particular question at hand here. Whether it's 40 W/m^2 or 90 W/m^2 - it doesn't matter, nor do I care. The estimated 3.7 W/m^2 from 2xCO2 either represents a reduction in the atmospheric window or not. The fact you seem to be side stepping this fundamental question is quite revealing. It's a ridiculously simple and straightforward question with a simple yes or no answer. I can see no one here is interested in getting to bottom of this, so it appears like I'll have to do some more searching around and figure out for myself.
117. KR at 12:31 PM on 25 February, 2011
     RW1 - "The estimated 3.7 W/m^2 from 2xCO2 either represents a reduction in the atmospheric window or not." Wrong. It's partially a reduction in the "window", and partially a reduction, a drop in the intensity, in the GHG bands - the ones already inhibited by the presence of greenhouse gases. Not yes or now, but "in part". As GHG concentration rises, the effective emission altitude goes higher and higher in the troposphere, and hence (due to the lapse rate) comes out of colder and colder GHG's. They emit less than warmer lower GHG's - the additional altitude means that the repeated reduction in IR transmission as part gets emitted up (to higher levels) and parts down attenuate the IR levels. That and widening bands, the reduction of the window, combine to provide the 3.7 W/m^2 effect from doubling CO2. That is why I gave a nuanced answer, one that actually answered your question without conveying incorrect information. It's not A or B - it's both.
118. RW1 at 12:52 PM on 25 February, 2011
     KR, Let's take this one question at a time. What does the atmospheric window represent? Please define it for me.
119. RW1 at 13:05 PM on 25 February, 2011
     KR (RE: 117), Then the answer is no. What's so hard to understand here? I'm trying to find specifically where the disagreement lies. This is pretty basic stuff.
120. scaddenp at 13:51 PM on 25 February, 2011
     RW1 - actually that's what I dont understand. What do you mean by "atmosphere window"? A clearer understanding of that might illuminate this.
121. RW1 at 13:52 PM on 25 February, 2011
     By 'atmospheric window', I'm referring to the amount of the emitted surface power that passes through the atmosphere completely unabsorbed by GHGs or clouds.
122. KR at 14:53 PM on 25 February, 2011
     RW1 - The answer is not "no", it is "in part". I've (repeatedly) clearly answered your question - narrowing of the atmospheric window is part of the 3.7 W/m^2, and deepening of the intercepted bands due to higher effective emission altitude is also part of the 3.7 W/m^2. It's not an either/or question!
123. RickG at 23:01 PM on 25 February, 2011
     RW1: By 'atmospheric window', I'm referring to the amount of the emitted surface power that passes through the atmosphere completely unabsorbed by GHGs or clouds. How do you distinguish what is surface emitted from other emitted sources. And why do you use the word "power"? What is power?
124. Tom Curtis at 23:48 PM on 25 February, 2011
     RW1: 1) When physicists refer to "the atmospheric window" they refer to a portion of the spectrum in which radiation is not absorbed, so radiation can pass through that "window" without appreciable loss or distortion. The atmosphere has several windows - one at the frequencies of visible light, another in the IR spectrum, and still others in the radio spectrum. 2) One of the atmospheric windows in the IR spectrum is in that range of frequencies where the majority of the surfaces IR radiation is emited. As a result, about 40 w/m^2 of IR radiation escapes to space without being absorbed by any atmospheric components (except clouds, if present). 3) Increasing CO2, O3 or H2O content into the atmosphere, or introducing novel GHG can narrow this window slightly, but the effect is very small. 4) Outside of the atmospheric window, IR radiation from the Earth's surface is entirely absorbed by GHGs; but 5) Those GHGs then emit radiation at the same frequency at an intensity that depends on their temperature. The IR radiation emitted towards space by GHGs is then absorbed by higher GHGs, which in turn emit radiation at an intensity depending on their temperature, which is in turn absorbed and so on until the atmosphere is thin enough for the upward emitted radiation to escape to space. 6) Because the radiation outside the atmospheric window that escapes to space is emitted high in the atmosphere, it is emitted by gases that are much cooler than the surface. Therefore, that radiation has a much lower intensity, ie, transmits much less energy than the radiation emitted from the surface at the same frequency. The difference between the energy that is radiated to space outside of the atmospheric window and the energy originally radiated from the surface at those same frequencies is the fundamental basis of the green house effect. 7) If you increase the concentration of a GHG, then the altitude at which radiation from that GHG will effectively escape to space will increase. Because the altitude has increased, the temperature of the radiating gas is lower, so the total energy radiated is also lower. 8) If you double the CO2 concentration, the atmospheric window will narrow slightly as the absorption band of CO2 widens. This does not mean no IR radiation will escape in the frequencies where the absorption band widens - it just means that the IR radiation in those frequencies will come from a higher, ergo cooler, ergo less energetic altitude, reducing the total IR energy escaping in that frequency band by about a third. 9) At the same time, IR in the frequencies of the previously existing absorption band will come from slightly higher in the atmosphere, and therefore carry less energy (because the emitting CO2 is colder). 10) The combination of these two effects will reduce the total energy leaving the atmosphere by 3.7 w/m^2 That is the full and complete answer to your questions (given space limits). It has been given to you ad nauseum above but you refuse to hear the answer because it is not framed according to the frankly fallacious model of the Green House effect used by George White. However, we cannot ignore the physics and give you answers that only make sense if framed in terms of George White's fallacious physics. If you try frame your question in terms of the actual physics, however, you will find you have already been answered repeatedly.
125. scaddenp at 06:27 AM on 26 February, 2011
     " And why do you use the word "power"? What is power?". It's the surest sign that you are dealing with someone who has got their education from George White. This incorrect usage has been pointed out to RW1 before.

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