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Post by steve on Nov 22, 2010 10:57:44 GMT
But Steve; You cant discuss only absorbing or emitting since colliding CO2 molecules either cool or heat surrounding molecules. Free photons are emitted by CO2 molecules due to collisions with other molecules. If free photons are able to be absorbed by CO2 molecules will also free photons be released from them. Otherwise would it not be photons available in this wavelength. The line broadening due to partial pressure will be for both absorbing and emitting molecules. The net effect of this is the stunner. Yes. The main part of my post was to note that most collisional excitation (and deexcitation) of a CO2 molecule is vastly more likely than excitation due to absorption of a photon or deexcitation due to emission. The broadening is indeed for both emission and absorption.
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Post by af4ex on Nov 22, 2010 11:39:51 GMT
northsphinx> The net effect of this is the _stunner_. Guess I missed something. What is the stunner? Also I think you should all review your thermodynamics laws: en.wikipedia.org/wiki/Laws_of_thermodynamicsThe internal energy of a system must be conserved (1st law), meaning that it won't change unless energy is imported or exported, e.g. absorbing or emitting a photon, which enters or leaves the system. The internal energy is not changed by elastic collisions of molecules, it's just diffused until equilibrium is reached (0th law). When IR photons arrive from the Sun and are absorbed by CO2 molecules, they get "hotter" (move faster) because of the added energy. But then that energy is diffused again (heat transfer, 0th law) such that the entire system warms up a bit, to a new, higher temperature but always lower than the temperature of the hot CO2 molecules (2nd law). Thus, on Earth, where O2/N2 molecules don't absorb directly from the Sun, this "GH warmth" is drained off by these leech-like O2/N2 molecules. Yes, all these collisions seem to generate some thermal 'noise', maybe Doppler effects, which broaden some of the spectral lines. But this isn't evidence for a "heat amplifier", which you imply happens on Earth to make the GH effect stronger. That would require a mixed CO2/O2/NO2 system perturbed by an IR event to settle down to a higher temperature than a pure CO2 system, violating the 2nd law. The apparent "heat amplification" observed on Earth (i.e. the 33K comfort blanket) is mostly due to the effects of water vapor, clouds and the oceanic control knob. Yes, even Arrhenius recognized the tremendous heat absorbing properties of CO2. You can easily see the CO2 absorbing bands in the atmosphere (Arrhenius could see them), but I see CO2 having little or no effect on Earth's climate system because of the miniscule quantities in our atmosphere. Why is this? Because we can clearly see that CO2 has little or no warming effect on Mars, where it is an order of magnitude more abundant. So you can see I'm not making this up. My conclusions are solidly based on observation and application of classical laws of physics.
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Post by steve on Nov 22, 2010 12:59:44 GMT
Traditionally, the "greenhouse effect" is described thus:
The Sun emits mostly in the visible region. Most of its energy reaches the earth's surface without interacting with greenhouse gases.
The suns energy heats the earth's surface which emits in the infrared region (because it is cooler than the sun). The infrared radiation *does* interact with the greenhouse gases (H2O, CO2, CH4 etc.), and so warms the atmosphere.
The amount that the earth's infrared warms the atmosphere will depend on the amount of the energy absorbed by the atmosphere. This is why the width of the spectral lines is relevant.
An individual molecule does not have a temperature - it has a velocity and quantum energy state. When a CO2 molecule absorbs a photon it is the quantum energy state that is changed. When it collides with another molecule this additional quantum energy could be converted into a higher velocity of one or both of the molecules - ie. heating. ie from left to right in this reversible interaction:
CO2(energised) + O2 --> faster CO2(not energised) + faster O2
The second law is a statistical law, so at a molecular level the process can happen in either direction, it is just that the probability of the process will conform to the second law. While you are warming the gas by irradiating it with infrared, the process happens from left to right more than from right to left as you are enhancing the proportion of CO2(energised).
When the gas reaches equilibrium, the equation is in balance.
If you switch of the radiation, the process happens more often from right to left (as some of the energised CO2 molecules emit photons to space) and the gas cools.
Probably an appreciation of the statistical behaviour of gases would help your understanding.
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Post by af4ex on Nov 22, 2010 13:24:00 GMT
> Probably an appreciation of the statistical behaviour > of gases would help your understanding.
Perhaps my insistence on talking about single molecules led you to that conclusion. I did that because it is important to understand that the laws of energy and momentum conservation must hold, even for individual molecules.
And a "temperature" for single molecule could be established by merely computing the average kinetic energy etc as the actual value.
But I agree that would be misleading and largely meaningless. So we can fix that misleading perception by merely looking at all of the CO2 molecules heated by IR absorption (from the Sun or whatever). The heated CO2 molecules diffuse with the colder O2/N2 molecules and the collective temperature of the CO2 drops. Conclusion: the GH effect on Earth, due to CO2 alone, is even less than on Mars because of this cooling effect of O2/N2.
The entire system temperature rises, but not as much as would happen if the whole atmosphere were composed of CO2.
Show me some specific experimental results which prove that your "CO2 line-broadening heat amplifier" actually exists. You can't just wave your hand and say "spectral lines are broadened, Earth is warmer, so it must be the broadening".
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Post by steve on Nov 22, 2010 15:06:01 GMT
If you put a fixed volume of Mars atmosphere and a fixed volume of earth atmosphere in two different large insulated vessels, and irradiate each one with the same amount of energy then the former will warm more than the latter.
But they are on a planet, not in an insulated vessel. Here the Mars atmosphere will also *cool* more rapidly than the earth atmosphere, because CO2 is both a good absorber and a good emitter (Kirchoff's law of thermal radiation)
To put it in the terms you are using, take a large black body fixed at 300 Kelvin. Cover it with an N2/O2 atmosphere with 390ppm of CO2 all at 250 Kelvin. Initially, the CO2 will absorb the radiation from the black body, but more often than not the CO2 will transfer its energy to an O2 or N2 molecule. This will happen until the atmosphere is in equilibrium with the black body.
If you repeat the exercise with a Martian atmosphere, equilibrium will be reached more quickly, but the temperature of the two atmospheres will depend on the temperature of the black body. You would not expect the O2/N2 atmosphere to be colder simply because the energy absorbed by the CO2 has "diffused" with the colder O2/N2 molecules.
The estimation of the greenhouse effect is based on an assumption of equilibrium having been reached - where the rate of warming *balances* the rate of cooling.
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Post by af4ex on Nov 22, 2010 15:43:58 GMT
steve> You would not expect the O2/N2 atmosphere to be colder > simply because the energy absorbed by the CO2 has > "diffused" with the colder O2/N2 molecules. No, in fact I said: > The entire system temperature rises, but not as much as > would happen if the whole atmosphere were composed of CO2. Rewind back to the original discussion. I pointed out that the GH effect of CO2 is demonstrably weak on Mars. You (and Andy Lacis) implied the GH effect on Earth wouldn't have this weakness because of "line broadening". Never mind the effect of water vapor, clouds, oceans, ice etc. Let's see your proof that "line broadening" makes the GH effect of CO2 "less weak".
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Post by steve on Nov 22, 2010 17:09:41 GMT
af4ex I am responding to what seem to me to be misconceptions. The paragraph I posted on in my previous post was followed by this: There is no obvious reason why a CO2/O2/N2 system would settle to a different temperature from a CO2 only system. If O2/N2 were added to the Mars atmosphere, but not sufficient to change the amount of pressure broadening by much, then the theoretical equilibrium temperature would be much the same as it is now. If you accept for a moment that line broadening is a real effect, then you simply have to look at the Modtran output: geoflop.uchicago.edu/forecast/docs/Projects/modtran.orig.htmlSet everything to zero except CO2. The amount of radiation intercepted by the CO2 is reflected by the area of the CO2 line under the ideal curve. This amount of radiation heats the atmosphere. If the CO2 line were narrower (ie. if the pressure were lower), then less of the radiation would be absorbed by the CO2 and so the atmosphere would not get so warm. The area under the ideal curve cannot get larger by the line getting deeper as it gets narrower, as the bottom of the absorption line is due to emission from the coldest part of the atmosphere.
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Post by af4ex on Nov 22, 2010 17:40:12 GMT
steve> I am responding to what seem to me to be misconceptions ... ... and to avoid answering the "line broadening" question? I'm starting to think you're a troll. :-| > There is no obvious reason why a CO2/O2/N2 system > would settle to a different temperature from a CO2 only system. Uh, the entire premise of the Greenhouse Warming Effect is that certain gases, e.g. CO2, absorb IR heat, in contrast to non-GHG's, which allow IR to 'escape'. So a system containing GHG's will retain more of the heat input (and thus destroy civilization as we know it). In other words, the presence of CO2 increases the amount heat retained by the system, thus raising the internal energy (and equivalently the temperature). The non-GHG's only diffuse this heat and do no direct absorption of IR, so act as a 'coolant'. So the more of these little heat-absorbers you have, the more heat is retained, according to your own AGW theory, not mine. It's a logarithmic relationship, of course, due to saturation. But you alarmists have all along maintained that unbounded increases in CO2 spells doom for the planet. Has that changed? Are you suggesting that there is no "Greenhouse Effect" at all? Then how will you scare nations of people into redistributing their wealth? OK, time-out has ended. Please answer the 'line broadening' question! And (to save time) don't bother to suggest that line broadening moves the CO2 lines "out in the open" from behind obscuring water absorption lines. If you will glance at the absorption chart back a few pages, you'll see that the main band (15 micron) is situated half-way up the slope of a steadily increasing water band. So, half the lines have moved out "into the open" (hurray!), the other half have moved into even more obscuration (boo!), by the same amount. Net result: no change.
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Post by northsphinx on Nov 22, 2010 18:21:41 GMT
But steve use real world numbers. You write "The amount of radiation intercepted by the CO2 is reflected by the area of the CO2 line under the ideal curve. This amount of radiation heats the atmosphere. "
You forget the important issue here. There must be a temperature difference between surface and absorbing layer to enable heat transfer. Without a difference in temperature is there no heating. Basic. So what average real world temperature difference is it between heat radiated from the surface and absorbed by AVERAGE CO2 molecule. Remember 70% of earth is water. Average temperature difference? Let see here, what can the distance be with a normal lapse rate, at surface pressure, and average humidity. Yes a few meter at earth surface. With a lapse rate of 6 K/1000 m.
Hmmmm not much of a heating available by radiation. And on top of that a negative feedback since if the atmosphere is heated the temperature difference decrease.
When the CO2 thins out in high altitude, low pressure, do the average distance increases and You have a increased heat transfer by radiation in CO2 band.
Which average CO2 temperature do we see from space? Let me remind You; 220 K. Located where? Troposphere? No. Tropopause or lower stratosphere. Add more Co2 and You increase radiation leaving system Earth in CO2 spectra. A cooling stratosphere. But not a warmer surface since the atmosphere is not heated by radiation. That is because the average temperature difference between surface and atmosphere is to low to enable net heat transfer by radiation.
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Post by steve on Nov 22, 2010 18:22:52 GMT
Don't be silly. I've tried to answer as best I can with references I can find. You won't read the reference or do your research and simply insist that because I am not expert enough to give you a noddy guide that the effect can be ignored.
I believed in pressure broadening long before I heard of global warming because I trusted my lecturers and tutors. I don't need to prove it to myself, but I've found enough information to know that I didn't remember my lectures wrongly.
If I told you that the theory predicts a warming of the atmosphere and a cooling of the stratosphere, you should start to realise that some of your thoughts are not quite on track.
Due to the increase in the amount of sarcasm, I'll make this my last reply.
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Post by af4ex on Nov 22, 2010 18:40:42 GMT
steve> Don't be silly.... I think my suspicion has been confirmed.
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Post by steve on Nov 23, 2010 10:29:52 GMT
steve> I am responding to what seem to me to be misconceptions ... ... and to avoid answering the "line broadening" question? I'm starting to think you're a troll. :-| Takes one to know one
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Post by af4ex on Nov 23, 2010 15:17:10 GMT
> Takes one to know one
Stop. You're digging yourself in deeper. I suspected your intent very early because of your ambivalence and your tendency to shift the topic and dodge questions.
No problem, you haven't broken any laws and you're anonymous so your personal cred is safe. And we needed someone to play the part of the AGW foil and you did that OK. Hopefully you did not withhold any real arguments that could disprove my hypotheses. (Unlike some other groups, I never believe the science is settled and am not upset when I'm proven wrong. I learn from it).
I don't know how many other AGW-ers there are on this site, but it's possible some of them don't really believe the CAGW theory anymore, but still pretend to defend it for other reasons (like being funded to believe).
It sort of reminds me of the Flat Earth Society. They have a few genuine crackpots who believe the Earth is flat. The rest are trolls who enjoy tweaking our noses.
The CAGW community is fast becoming a similar society of deniers. All they've got left are a few shrinking glaciers and some doctored temperature records. The rest of their arguments are being voided on a daily basis (check out WUWT).
The evidence for CAGW was really never there. If human CO2 flatulence can be detected, so what? The Mars Greenhouse clearly shows that small amounts of CO2 have virtually no GH effect. Water, not CO2, appears to be the main control knob of our climate.
I'm not interested in discussing these main AGW issues. You've got other forums for that.
This forum was established solely for investigating the 'classic' CO2 GH warming effect (sans H2O) and its impact on Mars and Earth.
Live well, Steve. and be true to yourself.
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Post by steve on Nov 23, 2010 15:43:35 GMT
I was concerned that your original posts indicated that you had read widely on sceptic physics, but you seemed open to alternative points of view and I know I've ditched many wrong ideas gaining my still limited understanding of the subject.
I am obviously not able to make myself clear to you which is either my lack of communication skills or your lack of comprehension skills, or likely a combination of both.
But I test my understanding against my own physics experience and knowledge as well as against the experience and knowledge of a wide range of people. As an example, I started out this discussion with a vaguely remembered understanding that the breadth of spectral lines was a function of pressure. You challenged this and I validated *my* view by finding a number of physics (not climate science) sources. Thank you for that challenge.
I also discovered a source that descibed the strength of the back radiation on Mars (a measly 12W/m^2) that aligned with my own very rough calculations done with Modtran (an equally measly 18W/m^2) - again your challenge helped me learn something new for myself.
On the other hand you haven't yet given any indication that you've attempted to research the topic yourself or follow up and challenge my sources, but got sarcastic when we started to miscommunicate.
No you are not a troll, but you are deeply impatient with those with whom you differ. I enjoyed it while your patience lasted.
The problem with your position is that even sceptic physicists agree that the greenhouse effect is a valid concept - go argue with "Flat Earth Society" members Richard Lindzen, Roy Spencer, John Christy and Pat Michaels.
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Post by af4ex on Nov 23, 2010 16:22:54 GMT
> On the other hand you haven't yet given any indication > that you've attempted to research the topic yourself or > follow up and challenge my sources, but got sarcastic > when we started to miscommunicate. > > No you are not a troll, but you are deeply impatient > with those with whom you differ. Actually I did look at the references you gave me (the ones that weren't behind a pay wall). All I found were discussions related to rendering, resolving and the stability of laser beams. Didn't see any explanation of the CO2 warming issue and the heat amplification effect. I asked you for specifics. You gave me hand waving (at the references). I very patiently sketched out my side of the arguments, down to single, animated molecules. Perhaps you should have shown more patience and sketched your side out in similar detail. I did not grow impatient with your reference materials, but with you, simply trying to get you to answer a single, pointed question: How does "line broadening" amplify the CO2 GH warming effect?" You may know more about this subject, overall, than I do. But, yes, you don't communicate it very effectively. [edit: ... even though you did manage to suck up a lot of the oxygen and bandwidth on this thread: solarcycle24com.proboards.com/index.cgi?action=viewthreadposts&board=globalwarming&thread=1443] > ... even sceptic physicists agree that the greenhouse effect is a valid concept Oh, I believe the CO2 GH effect is real, but only that its effect is very small in trace amounts. That's why none of those gentlemen you cited are CAGW advocates.
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