I was honoured to be invited to the annual regional conference for Norwegian journalists, taking place annually in a small town called ‘Hell’ (Try Earth Google ‘Hell, Norway’). During this conference, I was asked to participate in a panel debate about the theme: ‘Climate – how should we [the media] deal with world’s most pressing issue?’ (my translation from Norwegian; by the way ‘Gods expedition’ means ‘Cargo shipment’ in ‘old’ Norwegian dialect).
This is the first time that I have been invited to such a gathering, and probably the first time that a Norwegian journalists’ conference invited a group of people to discuss the climate issue. My impression was that the journalists more or less now were convinced by the message of the IPCC assessment reports. This can also be seen in daily press news reports where contrarians figure less now than ~5 years ago. But the public seemed to think that the scientists cannot agree on the reality or cause of climate change.
I find that the revelation of a perception of the climate problem within the climate research community that doesn’t match that of the general public problematic. What I learned is that this also seems to be true for the journalists: it was stated that their perception of climate change and its causes were different to the general public too.
The panel in which I participated consisted of a social/political scientist who had investigated how media deals with the issue of climate change and the public perception thereof, a science journalist, an AGW-skeptic, and myself. Despite the name of the place, the debate was fairly civil and well-behaved (although the AGW-skeptic compared climate scientists to mosquitoes, and brought up some ad hominem attacks on Dr. Pachauri).
The science journalist in the panel advocated the practice of reporting on issues that are based on publications from peer reviewed scientific literature. I whole-heartedly concur. I would also advice journalists to do some extensive search on the publication record of the individuals, and consider their affiliations – are they from a reputable place? Also, it’s recommended that they consider which journal in which the article is published – an article on climate published in the Journal of American Physicians and Surgeons is less likely to receive a review of competent experts (peers) than if it were published in a mainstream geophysics journal. Finally, my advice is to try to trace the argument back to its source – does it come from some of those think tanks? But I didn’t get the chance to say this, as the debate was conducted by a moderator whose agenda was more focused on other questions.
Short of telling the journalists to start to read physics in order to understand the issues at hand, I recommended the reading of Spencer Weart’s ‘The Discovery of Global Warming’. The book is an easy read and gives a good background about the climate sciences. It also reveals that a number of arguments still forwarded by AGW-skeptics are quite old and have been answered over time. The book gives the impression of a déjà vu regarding the counter arguments, the worries, politics, and the perceived urgency of the problem. I would also strongly recommend the book for the AGW-skeptics.
One reservation I had regarding the discussion is being cut off when I get into the science and the details. I had the feeling of taking part in a football match where the referee and all the spectators were blind and then tried to convince them that I scored a goal. The problem is that people without scientific training often find it hard to judge who’s right and who’s wrong. It seems that communication skills are more important for convincing the general public that scientific skills. Scientists are usually not renowned for their ability to explain complicated and technical matters, but rather tend to shy off.
I’d suggest that journalists should try to attend the annual conferences such as the European (EMS) and American (AMS) meteorological societies. For learning what’s happening within the research, mingling with scientists/meteorologists, and because these conferences have lot to offer media (e.g. media sessions). Just as journalists go to the Olympics, would it not be natural for journalists to attend these conferences? – but I missed the opportunity to make this suggestion.
Hell seems to be fairly dead on a Sunday afternoon. I almost caught a cold from the freezing wait for the train – although the temperature was barely -3C. This January ranked as the third warmest in Oslo, and I have started to acclimatise myself to all these mild winters (the mountain regions, however, have received an unusually large amount of snow). Our minister of finance was due to attend the meeting to talk about getting grief, but she didn’t make it to Hell due to a snow storm and chaos at the air port (heavy amount of wet snow due to mild winter conditions).
Jim Cripwell asks in 300 : “Please show me where I used the word “impossible” in this exchange. I cannot find it.”
Certainly, here you go, verbatim :
Post 281: “Ref 280. No. My position has always been that the physics of CO2 absorption is such that AGW is impossible.
Comment by Jim Cripwell”
Jim Cripwell wrote: “Please show me where I used the word ‘impossible’ in this exchange. I cannot find it.”
In the comment currently numbered 281, posted 24 February 2008 at 1:07 PM, you wrote:
You’ve been repeatedly asked to provide the “hard measured independently replicated experimental data” that you claim supports your “position” that “the physics of CO2 absorption is such that AGW is impossible”. You not only fail to offer any such “data”, but you respond by “forgetting” that you made the claim to begin with.
You continue to demonstrate that there is no reason to take you seriously.
Re Jim Bullis @ 301: “The reason for my question is that the presentation at Wikipedia seems to show that in the spectral band where co2 acts as a filter, it is already 100% blocking the upgoing thermal radiation.”
First, don’t forget, some of the IR energy that is absorbed is released through collision, warming other gas molecules, the rest is subsequently emitted as new IR photons, and a portion of that emitted IR proceeds upward to be absorbed again, and so on, and so on until it escapes to space. In that sense, absorption can never be 100 percent. Second, pressure broadens the spectral absorption band, so increasing CO2 concentration does increase the amount of IR absorption in the wings.
Re #301 Jim Bullis: play with the model at
http://geosci.uchicago.edu/~archer/cgimodels/radiation.html
It shows you the outgoing radiation, both as a spectrum and as a sum total (That’s not quite the same as the forcing though). Try doubling and re-doubling CO2, how much it changes outgoing radiation; then try to compensate (get back to the original, non-doubling, output) by specifying a ground temperature offset (Hold water vapour at “Rel. Hum.”). Note that there isn’t any “saturation”: every subsequent re-doubling adds roughly the same amount.
It’s only a model, but in this matter it behaves realistically. Jim Eager explained the why.
Jim Cripwell writes:
[[The only data I am aware of, are the various data sets of temperature versus time.]]
Well, that’s part of your problem right there. There’s a lot more data than that available.
Besides, you said you had hard, experimental data that showed that AGW was impossible. Have you forgotten saying that?
[[I conclude that such data shows the world temperature has passed through a shallow maximum in recent years, and temperatures are now on the decline. ]]
Wrong again:
http://members.aol.com/bpl1960/Ball.html
[[As to any other data, there is not one scintilla, not one single solitary jot of experimental data that shows a connection between the recent rise in CO2 concentrations, and the recent rise in world temperatures. By “recent” I mean post 1960.]]
Well, the AFGL tape is from the ’60s, and the most recent version of HITRAN is from 2003, I believe.
What kind of experimental data do you want? Please be specific.
Jim Bullis posts:
[[The reason for my question is that the presentation at Wikipedia seems to show that in the spectral band where co2 acts as a filter, it is already 100% blocking the upgoing thermal radiation. ]]
That’s almost true. Very little radiation from the ground gets into space, and nearly all such radiation in CO2’s main absorption bands is absorbed fairly low down (1-8 km).
That doesn’t diminish CO2’s potency as a greenhouse gas or mean that adding CO2 won’t mean more warming. If you want a detailed explanation as to why, let me know and I’ll email you an article I wrote on the subject. You can just email me at bpl1960@aol.com if you don’t want to reveal your email address in this blog.
Barton Paul Levenson wrote to Jim Cripwell: “What kind of experimental data do you want? Please be specific.”
It has become apparent that Mr. Cripwell wants experimental data on how much time he can get people to waste on responding to his comments.
One of my problems with AGW, as an EE, is imagining the IR photon headed from the Earth’s surface back into space having much interaction with any (highly rarified) CO2 molecule. 380 PPM. Put simply, that’s lots of IR photons and few CO2 molecules. And the CO2 molecule a photon does encounter? It’s virginal, i.e. unaffected by prior photons? If it’s not virginal, the new interaction adds to or cancels the previous interaction? Once a CO2 molecule is bent, or twisted, or vibrating, being struck by a new photon causes it to bend more, twist more or vibrate more without bound? I don’t doubt the temperature change, but I think its tiny and insignificant compared to other mechanisms.
I think the idea that CO2 “forces” and water vapor “feeds back” is great marketing but bad science.
I understand it makes little difference what I think, but I have partially explained why you do not have my vote or my financial contribution.
[Response: Since we are gainfully employed scientists, we ask for neither. However, I would direct your attention to a spectra at the top of the atmosphere which shows, very clearly, the absorption of photons by CO2 (and water vapour and ozone…etc.). What you can imagine is usually trumped by what you can measure. – gavin]
Re #309:
Hmmm, don’t look at CO2 molecules in isolation. A CO2 molecule that has an elevated energy level (e.g. having absorbed a photon), will radiate this energy out again (in any direction) very quickly. Also molecules exchange energy by collisions, the time between which is also very short, at least in the lower atmosphere. There is local thermodynamic equilibrium between all the molecular species in the air (i.e., it’s not just the CO2 that’s heating up). All the molecules contain all the time heat energy (so no, they are rarely if ever virginal = in the ground state?) and (at least the greenhouse ones) may emit some of it as photons even without receiving a photon first. It’s a statistical process.
Just the other way around… it’s scientifically spot-on (and known since Arrhenius). And you not being aware of this suggests that this understanding could do with some better marketing ;-)
By the logic of #309, I refuse to believe that 1200 ppm of carbon monoxide is Immediately Dangerous to Life or Health, as NIOSH claims. What significant effect can this tiny amount have in the presence of roughly 210,000 ppm of oxygen?
Yes, great, I understand the spectra of absorption. But, a photon has to encounter a CO2 molecule to affect it. If there are lots of CO2 molecules, then encounters will be common. If there are a small number of CO2 molecules, then the molecules are spread far apart and encounters are rare. Plus, anytime I know that something is nearly two orders of magnitude more common, then I expect interaction to be much more prevalent. It is significant that there is nearly 100X water vapor in the atmosphere compared to CO2. It is also significant that the water vapor absorption spectra is more comprehensive.
I can understand small things controlling big things, but the mechanism should be evident. The argument that CO2 causes a lot of warming and that warming increases water vapor significantly seems circular and nonscientific to me.
[Response: The mechanism is evident! Just look at the spectra. That shows that however unlikely you might think it is that photons interact with CO2, they do it anyway. How can you insist on the converse? – gavin]
Re Ken Coffman @ 309: “And the CO2 molecule a photon does encounter? It’s virginal, i.e. unaffected by prior photons? If it’s not virginal, the new interaction adds to or cancels the previous interaction? Once a CO2 molecule is bent, or twisted, or vibrating, being struck by a new photon causes it to bend more, twist more or vibrate more without bound?”
Ken, you have overlooked the rather simple answer to this question: it does not matter, energy that is absorbed does not stay absorbed, it is subsequently released. Any CO2 (or H2O or CH4 or O3 or CFC) molecule that absorbs an IR photon and gains energy later gives up that energy, either by collision with another gas molecule, or by spontaneously emitting a new IR photon. It is then again “virginal,” as you put it, and free to absorb another IR photon. It’s the gift that keeps on giving, at least for as long as that molecule remains in the atmosphere.
The answer to this and other questions abut the basic mechanisms of how greenhouse gases work can be found in Spencer Weart’s The Discovery of Global Warming, which is available free on-line at http://www.aip.org/history/climate/index.html
It’s also the first link under “Science Links ” in the right hand column on the RealClimate home page.
You may want to avail yourself of this resource, because what you think does matter, but it is incumbent upon you to inform your thoughts with the facts.
Regarding the spectra, Gavin, that is trapped by the atmosphere, you make a good point and I will ponder it.
Thanks.
Ken, ask yourself how much less (~10 ppm) of ozone can make surface and shallow water macroscopic life possibe, by sufficiently absorbing incoming UV.
If I understand Ken Coffman’s version of atmospheric physics, an infrared CO2 analyzer seemingly could not work. Yet, they are used routinely for analysis and monitoring of CO2 in industry, science, medicine, etc (a Google search using key words “infrared CO2 analyzer” yields 57,700 hits,e.g., http://www.qubitsystems.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=QS&Product_Code=S151).
Martin (293) says, “#287: Rod, loudly repeating something doesn’t make it true.” You mean like Consensus! Consensus! Consensus! ? [;-}
Ray (297), I’m just picking and choosing here — I know not proper, but I’ve been gone and can’t hardly catch up. Besides I’ve almost beat my assertions to death. None-the-less you say, “…warming on other bodies in the solar system might have something to do with that on Earth. This cannot be a matter of opinion. It is simply false. The energetics of Earth and of bodies in the outer solar system are completely different.” Aren’t you overstating the case considerably? Or are you really asserting that Mars operates under different laws of physics than Earth does??
Rod, you’re entitled to your own personal definitions.
You’re not entitled to say someone else “really asserting” something based on using your personal definition of a word. Of course not.
Start with the definitions others use.
Energetics, for example. You can look this up. It means how energy behaves in a particular environment, that needs to be defined.
http://scholar.google.com/scholar?q=energetics
Barton Paul Levenson (306) — Your link leads to a “Sorry, we can’t find that page” message.
Ken Coffman, I appears that much of your confusion could be resolved by simply “doing the math”. Atmospheric pressure is 760 mm Hg. A 15 micron photon can interact with any molecule within a wavelength of it–let’s say any molecule within 10 microns to make the math simple. That means the column of air that can interact with a 15 micron photon weighs about 3.25 mg. To find out how much CO2 is in that column, we need to convert from ppmv to ppmm by multiplying by ~44/28–which gives ~2 micrograms of CO2, or about 2.7E16 CO2 molecules with which the photon might interact. Now, true, there are more H2O molecules, but the photon with this wavelength is much more likely to interact with a CO2 molecule. What is more, H2O peters out at cloudtop level, while CO2 remains well mixed into the stratosphere.
Don’t just assume you understand the physics. Learn the physics.
Rod, The physics is the same–but the source of the energy is very different. On Mars, it all depends on how much light is blocked by dust storms. On Jupiter and it’s inner moons it all depends on gravitational or tidal forces (the sun is very feeble out there). On Saturn, even more so. Sunlight is mostly an afterthought in the outer solar system.
Hank, huh? I’m missing your point in #319 entirely…..
Ken Coffman, of course, has been my opponent for several very long, perhaps exponential at least in feeling, months. This is the concept I simply could not convey. He denies the chemical properties of CO2! His tactics with me elsewhere on the net resemble a Hamilton/Burr type showdown. Of course, I play Burr, my family’s former houseguest, with accurately placed bullets. Facts are stubborn things!” John Adams.
Nice work guys!
>319
Rod, ‘energetics’ doesn’t mean what you think. Ray had it right.
http://www.google.com/search?q=energetics+planetary+atmospheres
Ken Coffman wrote: “But, a photon has to encounter a CO2 molecule to affect it. If there are lots of CO2 molecules, then encounters will be common. If there are a small number of CO2 molecules, then the molecules are spread far apart and encounters are rare.”
Writing as a humble non-scientist, Ken Coffman’s assertion makes no sense to me even at the level of basic logic.
Here’s a thought experiment: imagine a bucket with a screen on the bottom. The bucket is filled with marbles of various colors, all thoroughly and randomly mixed. Among them are a very small number of black marbles, scattered throughout the bucket. Now we direct a large water hose into the bucket, so that a stream of water continually flows through the entire bucket full of marbles. Ken Coffman is arguing that since the black marbles are “small in number” and are “spread far apart” that they won’t get wet.
“Encounters” between photons and CO2 molecules may be more “rare” than “encounters” between photons and other, more common molecules, but so what? That doesn’t mean anything. The photons pervade the atmosphere, and CO2 molecules are still “encountering” photons all the time.
Lorne Gunter, a well known conservative journalist in Canada, published this anti-global warming article in the National Post.
http://www.nationalpost.com/story.html?id=332289
I sent him an email stating the following:
“What always amazes me about the global-warming-isn’t-happening camp is their complete lack of interest in researching the issue or reading any of the actual studies and making reasoned responses to the research. They, like you, seem desperate to grasp the slightest straw and hold it up as absolute evidence that it isn’t happening and that humans have no influence on it. Your article is a great example of this.
Typical arguments are:
“it was really cold yesterday (or last week, or this winter) in Podunk, Alaska thus all the research is hogwash”. This kind of argument hardly represents an intelligent or convincing rebuttal to the millions of man-hours of collected data indicating otherwise.
Someone with no qualifications or expertise is quoted as saying its hogwash thus it is. A good example is your use of Dr. Oleg Sorokhtin’s article in the Russian News and Information Agency (known to be a bastion of impartiality and a source for hard scientific research). Google comes up with 6309 hits on him. Every one of the hits refer to this same article and none to anything else he has every said, written, or published anywhere. Obviously he must be pretty renowned in his field. It only takes a cursory review of the scientific literature to discover that his theories of the degree of influence that solar expansion and contraction have of terrestrial temperature isn’t worth the paper it’s written on. (see the IPPC Fourth Assessment Report Chapter 2).
Second, the misuse of an actual scientist name or research without having read or understood the research. You state, wrongly, in your article that somehow the research of Robert Toggweiler and Joellen Russell support the it isn’t happening camp when nothing could be further from the truth. All you have to do is read their research. They agree that global warming is a fact and their research concerns the mechanisms by which global warming affects the oceans, polar caps and associated winds.
Is it just that it is easier to not look at facts or try to rebut the facts in a scientific manner? Is it laziness? Does global warming violate some religious beliefs? Why can’t the anti global warming camp pick up a piece of sound research and say that Dr. so and so when he collected such and such data failed to incorporate factor x,y, z and thus the correlation results were off by a factor of a? Or would that require too much thought?”
His response to me:
“What I find amazing about the global-warming-IS-happening camp is that they think they are the only people who do any research and everyone else is just making stuff up.
–Lorne G”
Gunter did not do research, he was making stuff up.
http://scienceblogs.com/deltoid/2008/02/dont_trust_anything_you_read_i_1.php
“What I find amazing about the global-warming-IS-happening camp is that they think they are the only people who do any research and everyone else is just making stuff up.”
–Lorne G
That could be because so many of those who assert that global warming is not happening, or that something other than increasing greenhouse gasses are causing the warming DO make things up, time and time again.
Someone should advise Mr. Gunter that good scientific research does not consist of queries to Google. Neither does good scientific journalism. But then, what do you expect from the National Post?
Luis Watts,
“Never try to teach a pig to sing. It wastes time and annoys the pig.”–Mark Twain
Thank you Ray, I will think about what you’ve said very carefully. I appreciate your calm and patient tone. Regarding the black marbles, I don’t think that’s a helpful analogy. I agree that a black marble will get wet. I understand and believe that CO2 analyzers work. I know CO in low concentrations is harmful.
I can imagine making an array of 2500 marbles. Then I will add a tube with an opening the same size as one marble to the array. I will drain away all the water that interacts with that tube to the outside. Then I will imagine the significance of the water collected by the tube to the water that passes by and does not interact with the tube. And I will be unimpressed that the tube has much hydrodynamic affect. For fun, we can ponder stacking additional arrays on top of each other and jetting some of the water collected by the tubes into random directions. Are there other enhancements I should make to my experiment to make it more useful for modelling atmospheric dynamics?
He still thinks it’s the water. At this point one can only assume learning is not wanted.
Ken, Well, the problem is that you aren’t working with “marbles,” but rather harmonic oscillators–and the frequency they resonate at corresponds to light with 15 micron wavelength. It does not matter that you may have other oscillators around that respond to different frequencies–they are transparent to 15 micron IR. However, what chance do you think the light has of tiptoing past ~1E16 oscillators without interacting? Moreover, each oscillator can also emit light that can in turn interact with the oscillators above it, and so on. Once you ponder this, you’ll probably come back with the argument that the effect is saturated. We’ll deal with that once it happens.
Ken, do you know the term “mean free path” and how to look it up? That’s the average distance something (an infrared photon, in this case) travels freely in some environment before interacting with something else.
Ken, you really cannot formulate an analog model of a system unless you first understand the physics of the system you are modeling. That lack is why you keep confusing the behavior of your visualized mechanical analog with the actual behavior of radiation exchange in gases.
Ray, I’m trying to understand the basic (1st level) math of CO2 absorbing photons. I didn’t understand the statement in #321, “…15 micron photon can interact with any molecule within a wavelength of it–let’s say any molecule within 10 microns….” At any rate I calculated the surface IR radiation between 13 and 17microns wavelength is about 83watts/meter2. At a 15u energy level I then calculate roughly 6×1021 photons/m2/second. It is hard to see (though I don’t know) how 2.7×1016 CO2 molecules in the air column can turn the absorbed photons over (transferring their absorbed energy by collision) and keep up with the stream. It implies each and every molecule has to absorb a photon and transfer its energy about 200,000 times each second, to get them all. Can/does it? Or am I misreading the number of molecules you calculate in #321?
Re Ken @ 331: “I can imagine making an array of 2500 marbles. Then I will add a tube with an opening the same size as one marble to the array. I will drain away all the water that interacts with that tube to the outside.”
Ken, I don’t know who got you started on water and marbles (oh, I see it was SecularAnimist), but it is a very poor analogy because the water only flows one way. In the atmosphere each time an excited greenhouse gas molecule relaxes by spontaneously emitting an IR photon it can go in any direction, up, down or sideways. Since the density of gas molecules is higher below the point of emission, the mean free path is shorter in that direction, thus insuring it does not get far before being absorbed. Meanwhile, the mean free path is longer in the upward direction, allowing the photon to travel further before absorption. Thus a net upward flow is favoured, but adding more greenhouse gas raises density further, keeping more energy in play for longer, thus warming the atmosphere until the amount of energy ultimately making it to space once again equals the amount of solar energy reaching the surface.
Another point, don’t forget that CO2 is not the only greenhouse gas that has increased in the atmosphere, so have methane and nitrous oxides, and CFCs did not even exist before we created them. While far fewer in absolute numbers of molecules, they are far more potent IR absorbers, plus they absorb different wavelength bands then CO2 or water vapour.
Rod, well, your first problem is that the column of air I am talking about is a circle 10 microns in radius (the distance inside which we can expect an interaction an IR photon and a CO2 molecule)–so the 2.7E16 CO2 molecules increases to 8.6E25. What I was trying to estimate was the number of CO2 molecules an IR photon would encounter on a straight-line path out to space. Avogodro’s number is indeed a wondrous thing.
As I recall there are several energy levels available in a CO2 molecule (that’s from the homebuilt CO2 laser website); that’s why those have helium added to the nitrogen/CO2 gas mix. That’s because the CO2 molecules at intermediate energies can lose it by emitting lower-energy infrared photons, or lose energy by bumping into nitrogen molecules. Those pages say the added helium carries off remaining energy from the CO2 molecules that are at an intermediate energy level, dropping them quickly to their lowest energy level so the electric current can boost them to the high-energy level again. Get enough at the high energy level all at the same time in the tube and lasing happens. Anyone with the slightest actual physics can correct me, but I won’t understand the math anyhow. Point being it’s more complicated than we who deal only in words can describe.
Ray, thanks. This makes more sense, at least intuitively. It says in a column one meter square (or its rough steradian equivalent) there are (ballpark) 10,000 CO2 molecules to catch each photon/second in a wavelength band from 13 to 17 microns. It also says that the column has ~100 moles of CO2. Without thinking about it I would have guessed much more. Shows the benefit of thinking of stuff first, I suppose!
Hank,
The subject is as complicated as you want to make it. However, the basics are pretty simple. In equilibrium, you have a certain amoung of energy in the IR, and a certain amount in kinetic energy, vibrational energy, etc. In the case of the atmosphere, though, you don’t have equilibrium, since you have IR radiation from down below where it is much warmer rising into the cool regions above. That means you have proportionally more energy in the IR. By equipartition, that energy will have to find a way to flow into the other degrees of freedom–first via exciting the vibrational modes of CO2, then via collisional relaxation into the kinetic energy of the all gasses in the neighborhood. Deep Throat told Woodward and Bernstein to follow the money. In physics, you just follow the energy.
David B. Benson,
When I type
http://members.aol.com/bpl1960/Ball.html
into the address window in Internet Explorer, and hit [Enter], it takes me to the page. I’m not sure what went wrong above.
Rod writes:
[[At a 15u energy level I then calculate roughly 6×1021 photons/m2/second. It is hard to see (though I don’t know) how 2.7×1016 CO2 molecules in the air column can turn the absorbed photons over (transferring their absorbed energy by collision) and keep up with the stream. It implies each and every molecule has to absorb a photon and transfer its energy about 200,000 times each second, to get them all. Can/does it? Or am I misreading the number of molecules you calculate in #321?]]
I imagine it does. How long does it take light to travel about 1 kilometer?
Rod B #340:
Yep — that’s 4400 g = 4.4 kg, as CO2’s molecular mass is 44. Corresponds to a layer of 4.4 mm thick at the density of water (a good way of visualization). The full atmosphere is equivalent to 10 m of water, of which this is some 440 ppm by mass (the ppm by volume is smaller, 29/44 times or 290 ppmv, usually quoted).
The human-added part of this is smaller still, a bit over 1 mm water equivalent.
“As I recall there are several energy levels available in a CO2 molecule (that’s from the homebuilt CO2 laser website); that’s why those have helium added to the nitrogen/CO2 gas mix. That’s because the CO2 molecules at intermediate energies can lose it by emitting lower-energy infrared photons, or lose energy by bumping into nitrogen molecules. Those pages say the added helium carries off remaining energy from the CO2 molecules that are at an intermediate energy level, dropping them quickly to their lowest energy level so the electric current can boost them to the high-energy level again. Get enough at the high energy level all at the same time in the tube and lasing happens. Anyone with the slightest actual physics can correct me, but I won’t understand the math anyhow. Point being it’s more complicated than we who deal only in words can describe.”
To get a laser to work you need an inversion, that is the upper energy level must be more populated than the lower one (the opposite of normal). In the CO2 laser this is done by collisionally activating the upper level with excited N2 and at the same time collisionally deactivating the lower one with He.
“At a 15u energy level I then calculate roughly 6×1021 photons/m2/second. It is hard to see (though I don’t know) how 2.7×1016 CO2 molecules in the air column can turn the absorbed photons over (transferring their absorbed energy by collision) and keep up with the stream. It implies each and every molecule has to absorb a photon and transfer its energy about 200,000 times each second, to get them all. Can/does it? Or am I misreading the number of molecules you calculate in #321”
CO2 certainly can, at atmospheric pressure there are about 5 collisions/nanosecond, average collisional deactivation time ~microsec as I recall.
Barton Paul Levenson — Your link in comment #342 works with Firefox 1.5. Thanks.
And how ‘long’ is a nanosecond at lightspeed?
http://www.jamesshuggins.com/h/tek1/grace_hopper_grace4.htm
Chips magazine (April 1992) remembering Rear Admiral Grace Hopper — Shows RADM Hopper displaying 12 inches of copper wire. This is the distance an electron moves in one nanosecond.
Don’t fail to page down to the bottom of his main page to see this: http://www.jamesshuggins.com/h/tek1/first_computer_bug.htm
Jim Eager wrote: “Ken, I don’t know who got you started on water and marbles (oh, I see it was SecularAnimist), but it is a very poor analogy because the water only flows one way.”
I didn’t intend the “marbles and water” to be an analogy for the physics of the interaction of CO2 molecules with photons. My point was that if the atmosphere is continually bathed in photons, if the photons are pervasive, then the relatively small numbers of CO2 molecules doesn’t logically imply that encounters between CO2 molecules and photons will be “rare” as Ken was saying.
CO2 lasers will lase without Helium, just not so well. The electric discharge pumps vibrational levels of nitrogen which cannot radiate, but efficiently transfer energy to CO2 vibrational levels (the asymmetric stretch). This places a population inversion into the asymmetric stretch vibrational levels, since the bending and symmetric stretch modes are non-resonant with N2 vibrations. The lase occurs between the asymmetric stretch levels and the lower symmetric stretch/bending levels. You can find an energy level picture here
Helium depopulates the lower levels by collision (esp the symmetric stretch level which cannot radiate.
I agree the array of 2501 marbles is not a very good analogy if we assume they’re placed close together. The analogy would be better if there was a certain amount of empty space between them. Our atmosphere is not very dense from a photon’s perspective.
So, Eli, my wishful thought is that there’s some tool
http://www.haarp.alaska.edu/haarp/ion4.html
that could pump energy into CFC or CO2 molecules at the top of the atmosphere — in a wavelength tuned to raise those at intermediate or low levels up to the highest level, from which they might kick out a high energy infrared photon — which would have good odds of leaving the planet.
Heat pump, so to speak. Lots of bicycles or windmills or solar panels to drive the transmitters, of course.
Tell me I’m nuts, so I can quit daydreaming?