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From: Bill Ward on 9 Dec 2008 12:07 On Tue, 09 Dec 2008 06:26:15 +0000, Don Klipstein wrote: > In <pan.2008.12.01.17.08.14.877184(a)REMOVETHISix.netcom.com>, Bill Ward > wrote: >>On Mon, 01 Dec 2008 08:29:43 +0000, Don Klipstein wrote: >> >>> In article <pan.2008.11.27.18.38.37.222361(a)REMOVETHISix.netcom.com>, >>> Bill Ward wrote: >> >><big snip of old post> >> >>>> I think the troposphere is there >>>>because of convection lifting the surface energy up to the cloud tops, >>>>maintaining a near adiabatic lapse rate. Radiative transfer is blocked >>>>by GHG's, and plays little part below the tropopause. Radiation models >>>>are thus largely irrelevant. >>> >>> The lapse rate is well short of adiabatic in much of the world, >>> especially much of the time where surface albedo is prone to change >>> from temperature change. Those parts of the world have upward mobility >>> in surface temperature. >> >>Can you explain more clearly what you mean and the physical mechanisms >>involved? > > Much of the atmosphere has horizontal temperature gradient. That causes > a tendency for tropical air from generally roughly the 500-200 mb level or > so to push poleward and polar air generally below roughly the 500 mb or > 600 mb so level to push equatorward. That alone reduces the lapse rate in > much of the troposphere, especially in areas ahead of warm fronts. OK, thanks. I think I see the problem. First, any movement caused by density difference has to be gravitational in origin. Second, the applicable lapse rate is along the path of motion - what the air actually sees, not necessarily vertical. So the nearly horizontal motion is still convective, it's just that the effective lapse rate is due to latitude differences, not altitude differences. The cold air displaces the warm air upwards - that's still convection, even though the motion is largely horizontal. Note the warm wet air still ends up at a higher colder altitude, no matter how far north it has to go. The latent heat has been lifted by the cold air sliding underneath it. It may help to visualize putting large air dams around the Earth at the tropic boundaries, allowing the system to come to equilibrium temperatures, then removing them. The cold polar air would flow under the hot tropicel air. > Also, ice-covered areas and polar areas in winter tend to receive > little sunlight and radiate away heat advected in from elsewhere. The > surface will cool less than air higher up that is also receiving > advected heat. > >> It appears to me they would still cool faster from increased >>convection, > > Although if surface warming is the cause of the increased convection, > the increase in convection merely slows down the heating. There are > plenty of areas where the surface has to heat a lot before convection > results. It's the integral heat loss from all the places that cool that counts. Places that don't cool much don't count as much. >> unless you're talking about places that are already cold, and >>thus don't do much cooling. > > I was including those. They do cool the atmosphere, which receives > heat from air coming in from warmer areas. If GHGs are increased, > they will cool the atmosphere less and be warmer. If they lose ice > cover and/or gain water vapor overhead from warming, then there is > positive feedback for warming. The smaller area and low sun angle would seem to diminish that effect compared to the large area and overhead sun in the tropics. It's that integral thing again. >>> Should the arctic and antarctic warm, then global convection from >>> the >>> tropics to the arctic and antarctic will slow down until the tropics >>> warm - though I still expect the arctic and antarctic (especially the >>> arctic) to warm more than the tropics. >> >>Why would the polar regions warm, when they already don't receive enough >>heat from the sun to maintain their existing temperature? Again, your >>causality seems backward. > > They maintain temperature that sunlight is insufficient to maintain > because warmer air comes in from elsewhere. The polar regions cool the > atmosphere in the global convection scheme, and the tropics warm it. But in the IR radiation cooling scheme, the hot tropics cool far more than the already cold poles. > If the polar regions gain GHGs and/or lose ice cover (to increase > reception of sunlight), then they will be warmer than otherwise. > Decrease in horizontal temperature gradient will reduce the "global > convection from tropics to poles" (which is advection - heat transport > by largely horizontal movement of air or ocean). If that decreases, the > tropics will warm slightly and partially restore "global convection". > >>> I do expect much warming in the portions of the world where there is >>> usually convection or lapse rate just short of causing convection to >>> depend on global albedo change - which is actually occurring, and >>> expected to occur as global warming causes loss of snow and ice cover. I must admit, it's hard for me to get excited by the change in albedo from ice melting at the cold poles when I look at a satellite image of the worldwide cloud cover over the hot areas of the world. It doesn't look like it would take much increase in clouds to make up for ice melting. >>> Furthermore, much of the actual problems to result from global >>> warming >>> is from loss of snow and ice cover - and most of that is in parts of >>> the world where the lapse rate from surface to tropopause is mostly >>> far short of producing thunderstorms. And thus not all that important to the actual cooling processes. >>The polar regions must receive additional heat from low latitudes to >>keep from getting colder. Convective heat flow tends to equalize >>temperatures, unless weather is somehow immune to the second law. > > Polar regions do indeed receive heat from lower latitudes - from air > movement mostly within 1 degree of horizontal, with lapse rate mostly > short of causing vertical convection. > >>> Radiative transfer is actually significant within the troposphere. >>> Radiative transfer can easily involve repeated absorption and emission >>> of photons along the way, such as (for extreme example) within the >>> "radiative layer" of the Sun. That excluding the core is a layer over >>> 100,000 km thick, and most of the heat produced by the sun is produced >>> in the core and has to pass through the core-exluding portion of the >>> "radiation zone", there is no convection, and most radiation gets >>> absorbed before going mere micrometers. >> >>The Sun is operating at considerably higher pressures and temperatures >>than the Earth. Can't you find a more relevant and convincing >>explanation that includes convection? > > GHG presence in Earth's atmosphere is great enough for radiation from > the surface to often be absorbed and re-emitted a few times before > geting to outer space. At night, radiation is largely how the surface > cools. Increasing GHGs will increase the number of times radiation will > be absorbed and re-emitted before getting to space, with more chances > for the radiation to be re-radiated downward. Increase of GHGs will > impede radiational cooling of the surface, and make the surface get a > warmer head start for the next day. I think that is one of the major sources of confusion, and needs to be explained. Assume a layer of pure CO2 at some temperature, in a stable non-turbulent atmosphere. Illuminate it with in-band IR from the bottom and watch what happens. The lower layer will absorb the IR, and get warmer. The hot gas will convect up and share it's energy with other CO2 molecules. At equilibrium, the layer of CO2 will be warmer, and, as all warm CO2 will do, radiating IR from the top at the new temperature. What goes on radiatively (or convectively) inside the gas is immaterial. It's just hot gas. It doesn't know or care how it was heated. EM travels at c. It doesn't matter how many times it's "absorbed and re-radiated", it still just heats the gas. The only way energy can be "trapped" in the gas is to raise it's temperature. Now if I have any major misconceptions about IR and CO2, I'm sure you'll take this opportunity to straighten me out. >>> Likewise, the Earth's surface receives significant radiation from >>> clear air below the 500 millibar level. >> >>Not more than it radiates, unless the WV is warmer than the surface. The >>Second law won't allow it. (OK, very very rarely by quantum theory.) >> But no actual radiative heating unless the source is hotter than the >>target. Net heat flow is from the surface to space. > > Less than it radiates - but enough to slow surface cooling. Of course. Thats just another way of expressing the Stephan-Boltzmann equation. It's simpler for me to understand if I look at the net flux by considering the target temperature rather than assuming both are radiating to 0K, then subtracting. It's easier to avoid inadvertent 2nd law violations. >>Thanks for your comments, but they aren't really specific enough to >>explain the physics behind the mechanisms you infer. I try to >>understand things down to the basics, with assumptions clearly stated. I >>think you must be making some assumptions I don't know about. That was helpful, thanks.
From: John M. on 9 Dec 2008 12:07 On Dec 9, 3:58 pm, bill.slo...(a)ieee.org wrote: > On 9 dec, 01:55, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: > > > On Mon, 08 Dec 2008 07:15:34 -0800,bill.slomanwrote: > > > On 8 dec, 05:42, d...(a)manx.misty.com (Don Klipstein) wrote: > > >> In article <tqb3j4pmpsqj32hes94kb9pni1vaup6...(a)4ax.com>, Whata Fool > > >> wrote: > > >> >bill.slo...(a)ieee.org wrote: > > > >> >>On 28 nov, 21:43, Whata Fool <wh...(a)fool.ami> wrote: > > >> >>> bill.slo...(a)ieee.org wrote: > > >> >>> >On 27 nov, 23:02, Whata Fool <wh...(a)fool.ami> wrote: > > >> >>> >> bill.slo...(a)ieee.org wrote: > > >> >>> >> >On 27 nov, 02:59, Whata Fool <wh...(a)fool.ami> wrote: > > >> >>> >> >> "DeadFrog" <DeadF...(a)Virgin.net> wrote: > > <snip> > > > > > >> > The CO2 spectra is mostly narrow spikes, and supposedly > > >> >those spikes are pretty much fixed to a certain range of temperatures, > > >> >show any reference that suggests otherwise. > > > >> The 15 um band of CO2 looks fairly broad here, comparable to the 2 > > >> broader water vapor bands at 6 and 2.5 um: > > > >>http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif > > > > This spectrum covers a wide range of wavelengths, and doesn't ressolve the > > > rotational fine structure. > > > I've not had much luck finding spectra that do show the fine structure. > > > > The best I've been able to do is here > > > >http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/35_3_WASHINGT... > > > > and since the pdf was generated by scanning a printed document, the > > > figures at the end of the document are none too clear. > > > >> > Actually, water vapor is almost BB at certain temperatures, > > >> >that can't be said for CO2. > > > >> Water vapor has significant gaps. > > > >> Same source: > > >> http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif > > > >> >>as it gets colder the number of phtotons emitted at shorter wavelegths > > >> >>goes down faster than the number emitted at longer wavelengths, which > > >> >>implies something rather from your "the frequency is determined by > > >> >>temperature". > > > >> > Exactly, so the net energy transfer is a function of relative > > >> >temperature differences, say it anyway you want, but 388 parts per > > >> >million is a very small amount. > > > > But quite enough to repeatedly absorb and re-emit all the radiation at the > > > CO2 wavelengths as it goes through the atmosphere. > > > Now what happens to the IR when it's absorbed? > > In the first instance, it raises the vibrational mode of the absorbing > molecule to the next vibrational quantum level and - almost always - > changes the rotational excitation. The extra energy gets redistributed > between vibrational, rotational and translational degrees of freedom > as soon as the molecule hits another, which happens pretty soon > (though sooner in the higher pressures of the lower atmosphere than in > the lower pressures and densities of the higher atmosphere) > > > It goes to heat. Heat convects. That "re-radiation" bit is bogus. > > Wrong.Every CO2 molecule in a first excited vibrational state has a > chance to decay to the ground state by emitting a photon. For the > asymmetric stretch and the bending mode the chance is high enough to > be important at every level in the atmosphere. At any temperature > above absolute zero there are always some molecules in the first > excited vibrational states (though the numbers drop rapidly with > decreasing temperature). > > Convection depends on the difference in densty between the warm gas > and its cooler neighbours, and ceases to be a significant mode of heat > transfer when the Raleigh number is less than 60, which it won't be > near and above the tropopause, where radiative heat transfer at the > CO2 spectral lines begins to get interesting > > >The gas is the same as any > > other, just warmer, and maintaining radiative equilibrium. I'm surprised > > you fell for that pinball explanation of radiative transport. IR travels > > at c. When it's converted to heat, it warms the gas, and allows > > convection to take place as soon as the lapse rate allows. > > The fact that you have difficulties with the "pinball" explanation of > radiative heat transfer reveals that you are no better equipped than BW has been told all of this many times over by myself and others. You're wasting your time on this loser. Just laugh at him like the rest of us do. He's another Whata Fool - with a bit more jargon.
From: Bill Ward on 9 Dec 2008 12:20 On Tue, 09 Dec 2008 06:33:06 +0000, Don Klipstein wrote: > In <pan.2008.12.02.04.09.57.211078(a)REMOVETHISix.netcom.com>, Bill Ward > wrote: >>On Tue, 02 Dec 2008 00:14:02 +0000, Don Klipstein wrote: >> >>> In <pan.2008.11.23.15.47.04.647543(a)REMOVETHISix.netcom.com>, Bill Ward >>> wrote in part: >>>> >>>>Wrong fiasco. I meant this one: >>>> >>>>http://www.denisdutton.com/cooling_world.htm >>> <SNIP> >>>>Here's the original, with graphics: >>>> >>>>http://denisdutton.com/newsweek_coolingworld.pdf >>>> >>>>> but subsequent observations doesn't suggest that it is to slowing >>>>> down any more. >>>>> >>>>> Do try to get your facts right. >>>> >>>>Right about now, you should be feeling a bit foolish. >>> >>> Check out HadCRUT-3v - good enough for The Register! >>> >>> Graph: >>> >>> http://www.cru.uea.ac.uk/cru/climon/data/themi/g17.htm >>> >>> Data in text form: >>> >>> http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3vgl.txt >> >>It's all depends on how you pick your data: >> >>http://www.worldclimatereport.com/wp-images/loehle_fig2.JPG > > Eeyore likes to post that one as a binary attachment in this newsgroup > (though I'm not saying that's where he got it from). The paper it comes > from has a link to the data in text form for that one - ending with 1980. > > The paper that comes from also has a "corrected global temperature > reconstruction" ending much earlier - I forget for the moment whether 1920 > or 1930. Splice HadCRUT-3 global or HadCRUT-3v global (smoothed) onto > that at any year covered by both Loehle's "corrected global temperature > reconstruction" and HadCVRUT and it looks like we are now warmer than peak > of MWP. > >>http://www.climateaudit.org/?p=2400 > > Points to Loehle. > http://www.climateaudit.org/?p=4475 This is also kind of interesting. ClimateAudit seems a bit more credible to me than RealClimate for some reason.
From: Bill Ward on 9 Dec 2008 12:31 On Tue, 09 Dec 2008 07:02:51 +0000, Don Klipstein wrote: > In <pan.2008.12.04.06.47.13.380842(a)REMOVETHISix.netcom.com>, Bill Ward > wrote: >>On Thu, 04 Dec 2008 03:35:12 +0000, Don Klipstein wrote: >> >>> In article <pan.2008.11.28.15.55.03.836887(a)REMOVETHISix.netcom.com>, >>> Bill Ward wrote: >>>>On Fri, 28 Nov 2008 02:26:40 -0800, bill.sloman wrote: >>>> >>>>> On 27 nov, 23:02, Whata Fool <wh...(a)fool.ami> wrote: >>>>>> bill.slo...(a)ieee.org ÃÂ wrote: >>>>>><SNIP to edit for space> >>>>>> >You've misunderstood. The surface of the earth is ultimately cooled >>>>>> >by radiation to outer space, but the "surface" that is cooled >>>>>> >depends on the frequency that is being radiated. >>>>>> >>>>>> ÃÂ ÃÂ ÃÂ The frequency is determined by >>>>>> temperature, isn't it? >>>>> >>>>> A black-body radiator emits a wide range of frequencies. The centre >>>>> of the range does move to higher frequencies as the temperature of >>>>> the emitter gets higher, but it doesn't move all that fast. >>>>> >>>>>> ÃÂ ÃÂ ÃÂ If the surface is moist, it will likely >>>>>> be 20 degrees F cooler than a dry surface, >>>>> >>>>> If the local relative humidity is less than 100%. Since the >>>>> "surfaces" I was talking about are mathematical abstractions - >>>>> essentially spherical shells around the earth located at various >>>>> heights above the ground, this isn't a useful comment. >>>>> >>>>>> ÃÂ ÃÂ ÃÂ And that doesn't mean that particular >>>>>> surface is cooled less. >>>>> >>>>> It seems that I haven't dumbed down my arguments anything like far >>>>> enough, >>>>> >>>>>> ÃÂ ÃÂ ÃÂ Your generalized statements about the >>>>>> cooling of Earth seem to follow a pattern suggesting some form of >>>>>> brainwashing. >>>>> >>>>> It isn't usual to describe a tertiary education in science as >>>>> brainwashing, but it is clear that my thinking has been exposed to >>>>> influences that yours has not. >>>>>> >>>>>> >At frequencies where the >>>>>> >atmosphere is transparent, this can be the surface that you stand >>>>>> >on (when there aren't any clouds overhead). >>>>>> >>>>>> ÃÂ ÃÂ ÃÂ There is rarely frost on most natural >>>>>> surfaces except for thin leaves, blades of grass and dark surfaces >>>>>> with low coefficient of conductivity. >>>>> >>>>> Irrelevant. >>>>> >>>>>> >At frequencies that are absorbed (and re-radiated) by water vapour, >>>>>> >this "surface" is fairly high in the troposphere, and for >>>>>> >frequencies that are absorbed (and re-radiated) by carbon dioxide >>>>>> >this "surface" is a good deal higher - 25% of the mass of the >>>>>> >atmosphere (and 25% of the CO2) is up in the stratosphere. >>>>>> >>>>>> ÃÂ ÃÂ ÃÂ ÃÂ So there is confusion about where >>>>>> the "surface" [is], or what the "surface" [is], shades of Bill >>>>>> Clinton. >>>>> >>>>> You clearly aren't following the argument. Each "surface" in this >>>>> particular discussion is defined as the level at which a photon of a >>>>> particular wavelenght first had an better than even chance of making >>>>> it out into space without being absorbed and re-emitted or otherwise >>>>> scattered. In principle this "surface" can be at any height in the >>>>> atmosphere, depending on the particular wavelength being talked >>>>> about. >>>>> >>>>>> ÃÂ ÃÂ ÃÂ ÃÂ Does your last sentence mean that >>>>>> carbon dioxide "cools" the stratosphere? >>>>> >>>>> Quite the reverse. The carbon dioxide in the stratosphere absorbs >>>>> infra-red radiation from the warmer troposphere and re-emits it with >>>>> a spectrum that matches the roughly -55C temperature of the bulk of >>>>> the stratosphere. >>>> >>>>That needs a little explanation. CO2 gas is not a BB radiator. At the >>>>temperatures in question, the 15u band should be the only radiation it >>>>can absorb or emit. How do you come to the conclusion it emits in a >>>>-55C BB spectrum? Do you have a link supporting that? >>> >>> Peak wavelength of blackbody radiation at 218 K is a bit over 13 um >>> (for >>> power per unit area per unit wavelength bandwidth). >> >>Yes. >> >>> A 218 K blackbody has spectral power distribution, in terms of power >>> per >>> unit area per unit wavelength bandwidth, above half the peak from about >>> 8.1 nm to about 24.1 um. >> >>Yes. >> >>> Looks like a 218 K blackbody emits 15 um at about 96% of its peak. >> >>Yes, and that's my point. CO2 can't radiate a blackbody spectrum, >>because the bond energies don't match outside the 15u band. If they can't >>absorb, how can they radiate? It's not a BB spectrum because the upper >>and lower tails are missing. > > I was merely claiming that CO2 does significant radiating in that nice > wide 15um-peaking band. > >>> The blackbody radiation formula is widely available. It is available >>> in >>> the "CRC Handbook" which is in the reference section of many, probably >>> most libraries, most undergraduate college general physics texts, and >>> certainly in at least one appropriate Wikipedia article. Such as: >>> >>> http://en.wikipedia.org/wiki/Planck%27s_law >> >>I also like the hyperphysics summary: >> >>http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c2 >> >>http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html#c4 >> >>> CO2's IR absorption feature of 15 um is actualy fairly wide and is >>> strong at 13 um, and accounting for most atmospheric IR absorption >>> within a few um of 15 um. >> >>Water is also active in that band, but is scarce in the stratosphere. > > http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif > makes it look like CO2 is more active than water vapor, even at their > degrees of presence in Earth's atmosphere as a whole. > > GHGs play a significant role in the troposphere. But only radiatively. Water has latent heat. >>> http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif >>> http://www.iitap.iastate.edu/gccourse/forcing/spectrum.html >> >>Surely you're not supporting Sloman's claim that cold CO2 gas can radiate >>a blackbody spectrum, are you? > > I think that was merely a poor choice of words on his part rather than a > claim that CO2 has its radiation spectrum looking like that of a > blackbody. I would hope so, but he missed several opportunities to clarify his remarks.
From: Bill Ward on 9 Dec 2008 12:36
On Tue, 09 Dec 2008 07:09:08 +0000, Don Klipstein wrote: > In <pan.2008.12.04.08.02.57.92862(a)REMOVETHISix.netcom.com>, Bill Ward > wrote: >>On Thu, 04 Dec 2008 03:45:45 +0000, Don Klipstein wrote: >> >>> In article <pan.2008.11.30.21.41.11.102553(a)REMOVETHISix.netcom.com>, >>> Bill Ward wrote: >>>>On Sun, 30 Nov 2008 07:28:18 -0800, bill.sloman wrote: >>>> >>>>> On 29 nov, 21:38, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>>>>> On Sat, 29 Nov 2008 09:58:21 -0800, bill.sloman wrote: >>>>>> > On 28 nov, 16:55, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>> <SNIP deeper levels of quotation> >>>>>> >> That needs a little explanation. ÃÂ CO2 gas is not a BB >>>>>> >> radiator. ÃÂ At the temperatures in question, the 15u band >>>>>> >> should be the only radiation it can absorb or emit. ÃÂ How >>>>>> >> do you come to the conclusion it emits in a -55C BB spectrum? >>>>>> >> ÃÂ Do you have a link supporting that? >>>>>> >>>>>> > I didn't say that it emitted a black body spectrum. It emits the >>>>>> > same spectrum as any volume of carbon dioxide at 218K would, which >>>>>> > is different from the spectrum emitted by warmer carbon dioxide. >>>>> >>>>> What I should have said here is that the radiation it does emit has >>>>> the same intensity as a blackbody radiator would emit at that >>>>> temperature. >>>>> >>>>> This follows from the second law of thermodydnamics - if it wasn't so >>>>> a blob of CO2 surrounded by a blackbody would end up at a temperature >>>>> other than that of the blackbody. >>>>> >>>>>> You said, "a spectrum that matches the roughly -55C temperature of >>>>>> the bulk of the stratosphere", not a "218K CO2 spectrum". >>>>> >>>>> Same thing. >>>> >>>>Isn't the CO2 absorption/emission spectrum a band, not a BB >>>>distribution? In part of your previous post (which you snipped) you >>>>linked to this: >>>> >>>>http://www.wag.caltech.edu/home/jang/genchem/ir_img7.gif >>> >>> That appears to be a sampling of a layer of CO2 representing less CO2 >>> than one has to pass through from surface to outer space. >>> >>> Another version of CO2 IR spectrum is at: >>> >>> http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif >>> http://www.iitap.iastate.edu/gccourse/forcing/spectrum.html >>> >>>>It doesn't look like a BB to me. Are you having trouble keeping your >>>>stories straight again? >>> >>> But CO2 is close to blackbody within some range of wavelengths where >>> emission is close to peak of a 218 K blackbody. And the range does >>> widen somewhat when there is more CO2 in the atmosphere. >> >>Look at this graph: >> >>http://upload.wikimedia.org/wikipedia/commons/7/7c/Atmospheric_Transmission.png >> >>Now please tell me if you think the CO2 absorption spectrum (3rd graph) >>is similar to the 210K blackbody emission spectrum line in the top graph. > > I did not claim that - I merely claimed (using maybe better words now > than before) that CO2 in the atmosphere radiates close as well as a > blackbody does within the 15um-peaking band. > > The 210K spectrum does indeed have its peak close to CO2's 15 um band, > so CO2's 15 um band will absorb and radiate some very significant amount > at 210K. My guess from looking at the spectra would be less than half as much, assuming the area under the spectrum is proportional to power. And water shares the band. >>Assuming you agree they are different, please explain how CO2 bonds >>could emit in wavelengths they can't absorb. >> >>>>>> > This follows from the second law of thermodynamics. The fact that >>>>>> > the 218K spectrum is going to be different from the spectrum >>>>>> > emitted by a warmer lump of gas depends on the proposition that >>>>>> > the numbers of molecules occupying higher energy vibrational and >>>>>> > rotational quantum states changes with temperature, and it is >>>>>> > this distribution across the accessible quantised energy levels >>>>>> > that dictates the shape of the emission spectrum. >>>> >>>>The "lump" would need to absorb and emit just enough to stay in >>>>thermal equilibrium. Why would the general spectrum suddenly change? >>>>What you are saying doesn't make sense to me. Please explain. >>>> >>>>>> Outside the 15u band? ÃÂ How much difference is there between >>>>>> the energy in the spectra at the two temperatures? >>>>> >>>>> http://en.wikipedia.org/wiki/Black_body >>>>> >>>>> work it out for yourself. >>>> >>>>Let me rephrase: I don't think there's a significant difference. Show >>>>why you think there is. Start by showing why you think it's a BB >>>>distribution. >>> >>> CO2 acts fairly like a blackbody at wavelengths within the 15 um >>> band. >>> 15 um is a wavelength where a blackbody has spectral power >>> distribution about 96% of peak. >> >>It appears to me both tails of a 210K blackbody spectrum are missing >>(looks like about half the total area). Cold CO2 is not a black body - >>it's a narrowband source. > > I was merely saying that CO2 is a significant absorber and radiator at > 210 K. OK, that I will buy. |