Discussion > An experimental demo of GHE.
This has become an absolutely brilliant thread so thank you Rhoda :)
However brilliant it is, I think it has strayed a bit from the question posed by Rhoda, in addition it seems that we do not all agree on exactly what the theory of the GHE actually IS?
Can we agree on thet before going further?
A greenhouse gas seems to be defined as a gas which absorbs and reradiates IR emitted by the earth. This IR is at a different wavelength to the incoming IR radiation from the sun (which causes the IR radiation from the earth).
However CO2 molecules absorbing and reradiating IR radiation from the earth are not warmed by the process, so in what way does the GHE change the near earth temperature? Surely the whole GHE theory depends upon back radiation either or both warming the earth and or causing more IRR from the earth?
So I propposed the following experiment:
A chamber constructed with a soil floor, walls which are transparent to all wavelengths of IR, a ceiling that is transparent to all wavelengths of IR. In the ceiling a source of IR which should be as close to the suns IR wavelength as possible, adjacent to the IR source a sensor to detect IR from the floor of the chamber. The IR source should be thermally shielded so that none of its radiation can reach the sensor.
Air should be passed through the chamber at a known CO2 content, a known speed and a known and controlled initial temperature. The strength of the IR source should be constant. The system should run until a steady reading on the IR sensor occurs.
At this point the CO2 content should be increased but all other parameters should be held constant. Do we then observe any change in the sensor reading?
Dung
Big Yin says quite rightly that we can not reproduce the atmosphere in a lab but surely the GHE theory contains elements that can indeed be tested by experiment as above?
If as a group, Bishop Hill could agree on an experiment surely we could ask a university to run it?
I am aware of things that need to be added to my experiment but as a group surely we can fix them or propose a better experiment?
Dung
Dung, the problem with your 'mini atmosphere' experiment is that it can always be refuted as being too crude a model of the real atmosphere. If it confirms the GHE, then they will like it. If it finds no GHE, then they will say your experiment does not model the real atmophere well enough.
Some problems:
"walls/ceiling which are transparent to all wavelengths of IR" and what do you propose to make these magical walls out of? Also, how will you account for 'lost energy' out through these walls ?- re-emitted IR is omnidirectional.
Not sure what your sensor will be measuring - it will be a mixture of reflected and re-emitted IR from the soil presumably.. so we prove the soil re-emits IR... that is not the GHE. and is not disputed (unless you DO dispute that soil re-emits, which would explain a lot?)
You'd need to analyse the frequency spectrum of the radiation to work out what was reflected and what was re-emitted, so you'd need a spectrum analyser.
You don't seem to be measuring temperature here, only directional IR. If the GHE exists, some of the IR will have been converted to kinetic energy in the air, which is what GHE is meant to produce- increase in temps.
TheBigYinJames
Dung, I just noticed this little hum-dinger in your previous post:
However CO2 molecules absorbing and reradiating IR radiation from the earth are not warmed by the process, so in what way does the GHE change the near earth temperature?
CO2 molecules are DEFINITELY warmed by absorbing longwave photons, where ever did you get the idea they were not? A CO2 molecule tends not to hang onto the enrgy very long though - it loses it either through re-emission of the photon in a random direction, or though kinetic collision with another molecule (which is highly likely to be an N2 or O2 molecule) - thus heating the atmophere.
This is the GHE in a nutshell. Shortwave photons pass through the air to the ground mostly unimpeded. Some of the longwave photons re-emitted by the ground get back up through to space, but in reality are intercepted by 'greenhouse' gasses and re-emitted in random directions. A single photon might hit and be re-emitted by a billion molecules (both gas and earth) before it eventually gets out of the atmosphere.
It's this 'delay' in getting out that causes the earth to be warmer. At any time there is a 'surplus' of photons in the earth and atmosphere (an energy flux). We're hanging onto the outgoing radiation longer, and it warms us. The net flow in/out cancels exactly, but at any time we're hanging onto a flux of photons.
TheBigYinJames
Well, in my opinion what is in doubt is not reradiation of IR by GHE, per se. What I'd like to see demonstrated is that the change in the proportion of CO2 in the lab produces the change claimed. Then I'd like to see that dupicalted in the actual almosphere. Then I'd like to know what happens to that re-radiated energy. Does it merely go round the roundabout twice or three times before going out to space? Does it result, all things being equal, in a slight increase in the height of the temp curve measured at the surface as it approaches its cold asymptote some time in the early hours of each day? Or is it ket somewhere? Where? In fact I want to see the whole mechanism laid ot in steps with an experimental or empirical proof at each stage. What is so hard about that? If it is indeed too small to measure what with all that noise and convection and conduction and state change, then just what is the problem? I refuse to be scared by something that is too small to measure. Which brings me to the point. In my judgment this is a scare. A typical scare story designed to make us do something we would not be sensible to do in the absence of the scare. As such, it needs to be confronted as such. Don't grant them any givens. They have it to prove. We should refuse to accept that they can't, and they can't show best evidence, and they can't even propose a demonstration of their phenomenon happening by experiment or observation.
rhoda
You've kind of changed the goalposts a little there rhoda. Now you're not trying to prove the GHE, but trying to prove how sensitive it is to increasing quantities of GH gases, which is a different proposition. It suffers the same problems though, if you can't duplicate the GHE in the lab, you're never going to be able to measure changes in it.
Each of the steps has been proved in a lab.
1. That shortwave radiation below 4nm passes through a mixture of O2 and N2 and various other small quantities of other gases pretty much unimpeded. Proved in the lab.
2. That a solid surface at a specific temperature and emissivity, absorbing a known quantity of shortwave radiation, increases in termperature according to the Stefan Boltzman law. Proved in the lab.
3. That this solid surface re-emits photons of longer wavelength according to its temperature, which can be calculated by applying the same Stefan Boltman law. Proved in the lab.
4. That some molecular gases, such as H2O and CO2 absorb certain known percentages of longwave radiation in this band. H2O takes the lion's share, but CO2 has a sizable absorption in this range. Proved in the lab.
5. Any particle which absorbs photons of any wavelength only has a few options. (1) to vibrate more - or heat up in lay terms, and transfer that kinetic energy to other particles through collison (2) to re-emit a photon of the same energy (3) a mixture of the two - increased vibration and emitting a photon of lower energy. Proved in the lab.
6. Emitted photons are randomly directional, so approximately half of them will find their way back to the ground at any time - doesn't need to be lab proven, it's self evident that from the point of view of a photon 100 feet in the air that the earth covers half the sky.
7. Extra longwave photons hitting the earth via 6 will mean that the temperature of the earth is raised by the same absorption mechanism as 2 (the ground doesn't care if it's LW or SW when absorbing). Self evident from previous points. The new higher temperature of the earth means its re-emitted photons can be slightly shorter wavelength (have more energy).
8. Some of these higher energy photons eventually reach the top of the atmosphere and escape into space. Doesn't need to be lab proven, self evident from the geometry.
9. This mechanism continues to heat the earth until the energy leaving the top of the atmopshere through these higher energy photons cancels the energy coming in via shortwave insolation. The earth is now in thermal equlibrium with the universe. Not lab proven, but we ARE in thermal equilibrium, or we'd know about it.
10. The consequence of all of thes steps is that at any time the air and ground are absorbing and re-emitting photons, and some of that energy is 'lost' to kinetic vibration (entropy) which heats the earth and atmosphere to the point where the total energy of the longwave photons out (according the SB) is the same as the energy from SW photons in. Obviously SW photons are more energetic, so the number of LW photons will be more) At this point the temperature stabilises.
11. Increasing greenhouse gases increases the effects of 4. We can tell how much each gas is contributing by spectrum analysing absorption of longwave radiation. We know CO2 is absorbing around 8% of all outgoing longwave radiation. This is a measurement. SO we can estimate that roughly 4% of it comes back to the earth. From this we can work out how much warming (in degrees C) must take place via the current CO2 concentration (in combination with H2O obviously).
11. Doubling the concentration of CO2 almost certainly doesn't double this effect, since it's a logarithmic effect and relies on a specific depth of atmosphere to provide all those billions of collisions and re-emissions. It cannot be duplicated in a lab flask, where most IR photons would just shoot out without a single collision.
So the bit you want to test is the bit LEAST amenable to lab testing. Dung wants to test all the previous steps, even the ones that are already proven.
TheBigYinJames
rhoda, TheBigYin
I can see from your last comments that your view of how the GHE causes elevated temperature is a bit different from my explanation of what is happening (which I am currently struggling to write up so it is comprehensible).
Would you be willing to critique my attempts at writing up the simple greenhouse model? If so maybe you could send an email to snake [D0T] oil [ÄT] tinhack [D0T] com?
Martin A
I don't think I'm moving the goalposts, if I accept reradiation but don't quite accept GHE. But let's look at your steps.
1. Agree
2. Agree
3. Agree
4. Agree
5. Agree, but in what proportion?
6. Agree
7. Hmm. Maybe could be restated, to take convection etc into account
8. Agree
9. We never achieve equilibrium, and that matters in the real world if not the ideal.
10. Agree
11. This is a real measurement? Not derived from modtran, which is a model? Reference?
12. I don't see why this has not been measured. The 2 watts/sq m we are supposed to have had already is really quite a big number. It is like trying to detect a 60watt bulb in your living room. Not too difficult. And of course it is an average of an integrated number. In fact there are probably at least 8 watts/sq m to be seen at the equator during the equinox, at noon on a clear day. Did nobody ever look? Is there no paper? This would be best evidence of what is claimed to be happening. If it exists, it has not come to my notice. You'd think if it did exist the warmists might mention it rather more often than all the model results and hockey sticks.
rhoda
5. Agree, but in what proportion?
The proportions vary with temperature, density etc but they are known can can be calcuated.
7. Hmm. Maybe could be restated, to take convection etc into account
At some point near the TOA the hotter (convected) molecules have to emit a LW photon to leave through the vacuum of space so I can't see how it can affect E photons in = E photons out . If the air is hotter, the photon has shorter wavelength. To an outside observer in space, a LW photon which came from a rock on the ground, and one which came from an excited CO2 molecule high in the atmosphere are identical.
Saying that, convection might help reduce the GHE by moving hot air higher, it makes it more likely that more energetic photons escape to space by putting them nearer the TOA. But I don't see how this effect would help with increasing GHE from more CO2, unless you posit some increase of convection due to increased CO2.
9. We never achieve equilibrium, and that matters in the real world if not the ideal.
The earth as a system is at thermal equilibrium, if it wasn't at thermal equilibrium we'd be steadily getting hotter or colder. Obviously, if you break the earth down, the the individual components, e.g. dark side / light side of the earth are never at thermal equilibrium and are constantly moving towards equilibrium, either by heating or cooling. But the entire system IS at thermal equilibrium, no matter how many constituent parts are hotter or colder than they want to be. So I'm not sure where you're going with that.
11. This is a real measurement? Not derived from modtran, which is a model?
I know people are allergic to SoD, but they do have some good graphs:
A graph comparing the theoretical model of absorption by atmospheric gases to the one measuring the actual detected radiation from a clear sky: http://scienceofdoom.files.wordpress.com/2010/08/olr-toa-goody-1989.png
A graph showing the difference between what arrives at the TOA (black) and what we get at sea level.
http://scienceofdoom.files.wordpress.com/2009/11/solar-toa-and-earth-surface-taylor-2007.png
As a quick and dirty calc for yourself to get to the 8% for CO2, trace this onto graph paper, and work out the area of black (which is 'absorbed radiation') by counting squares. Then work out the area of the two black wells on the right attributed to the CO2 absorption. The second figure will be approx 8% of the first figure. You can sort of eyeball this.
A graph showing what happens when we point a spectrum analyser at a night sky - we can see which molecules are emitting by the wavelength of the photons http://scienceofdoom.files.wordpress.com/2010/07/dlr-spectrum-wisconsin-ellingson-1996.png
12. I don't see why this has not been measured.
Because the change is in the noise, and we've only been measuring clear sky downward longwave for a short time. Maybe in 100 years we could detect a change, as Dung would say.
TheBigYinJames
That first graph is from 1969. What does it look like now? (Not holding you responsible for an answer)
rhoda
Hang on, I'll get me coat and spectrograph....
I would imagine not a lot different - the absorption amount for CO2 would be a little more, I expect, since we have more of it now, but possibly in the noise.
TheBigYinJames
TBYJ:
You've kind of changed the goalposts a little there rhoda. Now you're not trying to prove the GHE, but trying to prove how sensitive it is to increasing quantities of GH gases, which is a different proposition.
Not just changed the goalposts a little I think. But fair enough, after all this time :)
Thanks to Martin in advance for having a go at an explanation of (his understanding of) the GHE. It's not impossible with something this subtle - or because it's a simplification of such complexity - that the effect is both real and there are perfectly good alternative ways of explaining it. There are also, clearly, really bad ones. I agree with TBYJ that experimental contributions have challenges, to put it mildly. Sometimes the best model of the universe is the universe and all that. But if the product of the challenge is better explanation, that has terrific value.
Richard Drake
My sympathies this afternoon — not for the first time — are with RKS who (perhaps somewhat more trenchantly than I would have done) challenged TBYJ on various aspects of Nikolov & Zeller.
I didn't see any ad homs in there BigYin, but what I did see is the reaction of a man whose patience is wearing a wee bit thin. As is mine.
If there is one thing that makes a group of contributors to this site stick their fingers in their areas and sing 'la-la' it's mention of the words 'Nikolov' and 'Zeller'.
I thought we were supposed to be open to alternative ideas seeing as how the one thing we accuse warmists of is having closed minds and saying the science is "settled".
So I'll repeat a question I asked before (to the sound of some of you running for the exit as fast as you could).
Have you read Nikolov & Zeller? If not then why not read it before disputing with people who have (like RKS). And if you have read it, then explain in simple language where it falls down. If you can. From my limited understanding of the physics it appears to hang together, certainly a lot better than pretending the earth is a black body and the atmosphere is a greenhouse.
Mike Jackson
1969, 322 ppmv CO2, 2012 393 ppmv. If I have the formula right, there should now be an extra 1 watt/sq m showing. Are you telling me you can't measure it? It is about the amount of light in a working office (my previous 60watt bulb was wrong because most of that wattage is heat). It should be like finding a 200watt bulb in a normal room by its light alone. Now, what is so hard about that? And even the 1 watt is an average, so while the effect is at its peak we are talking about quite a big number. Four 200watt bulbs in a room., say. Lost in the noise?
Suspicious old Rhoda, without any justification, is inclined to think people have tried to measure this and have not produced the right result and therefore not proceeded to publish it. But that's just me. But who would put up a 43-year-old graph to make a point if later comparitive data showed their point? That would be pretty good evidence.
I know I'm not being fair to write the above. It is not the kind of argument which seeks the truth. But it is a challenge, albeit a robust one, which is fair in the political/policy context.
rhoda
Mike Jackson:
I thought we were supposed to be open to alternative ideas seeing as how the one thing we accuse warmists of is having closed minds and saying the science is "settled".
There isn't "one thing we accuse warmists of". One thing it was valid to question, after Climategate, was the difference between climate scientists' public statements of apparent certainty or near-certainty and their private doubts, for instance:
How come you do not agree with a statement that says we are no where close to knowing where energy is going or whether clouds are changing to make the planet brighter. We are not close to balancing the energy budget. The fact that we can not account for what is happening in the climate system makes any consideration of geo-engineering quite hopeless as we will never be able to tell if it is successful or not! It is a travesty!
Most crucial of all, the picture these guys painted of the science did not imply we had reason to be alarmed, let alone embark on trillion-dollar meddling with the global economy.
What should this imply for our interest or otherwise in Nikolov & Zeller? Not a lot. We don't have to be interested in every alternative theory. It's a matter of judgment how much time one spends on each. In the words of Martin A's review of Slaying the Sky Dragon a year ago "You cannot debunk global warming pseudo-science with gobbledegook science". The good news is we do not need to.
I've learned from this particular discussion, however, as I just indicated. Thanks Rhoda, Martin, TBYJ and others.
Richard Drake
Mike, challenge accepted, I will try to read it, and not just other people's opinion of it. Unfortunately I don't think my maths will be up to it. (which doesn't mean it's right) RKS was being very hostile, as he has been in the past. Yes, I'm sure it's frustration, but I've been there done that with him - he won't be convinced with ANY data.
rhoda, remember that the actual flux measured in a single spot varies wildly depending on water vapour, winds, temperature etc, and the change is small compared with the reading plus all this noise. I'm not saying it's impossible to measure, but like the temperature trend, it would be a tiny signal against a very noisy data set. And nobody is collecting hundreds of flux readings as it would require..
The lack of someone doing it or someone being able to find an upward trend in the flux does not prove it's not there. I don't think anyone would use a rising flux trend to 'prove' agw, because an increase in DLR is not really the hotly disputed part of agw for serious scientific skeptics - it's all about feedbacks. Only skydragons and etc are still trying to disprove the GHE.
TheBigYinJames
TBYJ
Thanks.That's all I ask. If someone can explain just where Nikolov & Zeller have gone astray in the physics I'll be quite happy. That is one of three papers (there may be more) that are challenging the received wisdom that CO2 can be any sort of driver of climate change.
What seems to me to be a fairly basic argument that in earth's atmosphere there is a correlation between temperature and altitude (ie pressure) is easily demonstrable by climbing a mountain — no complicated figures needed. So given that as a starting point I am quite happy to see where the rest of their arguments lead me. Not being a scientist I ask someone with greater knowledge than me simply to point out where these arguments go astray. No handwaving, no calling their hypotheses gobbledegook, just "are they wrong? where are they wrong?"
(Incidentally, I'm not sure my maths is up to it either, but I'm struggling on!)
Richard Drake
I apologise. I really did think that somewhere along the line I had heard that the science was settled, that CO2 was the Big Bad Wolf and that we were all going to roast or drown or boil depending on which got us first. Evidently I misheard.
Since I do not and never have believed in CAGW the only thing that really interests me is the politics which is what this whole farce has been about from the beginning. But the politicians will be a lot easier to convince if they come to believe that the "pseudo-science" was indeed just that.
So for that reason I am prepared to listen to all sorts of scientists who undertake research which might shed new light on the workings of the climate or which might demonstrate that at least some of MydogDSpartAlec's arguments are correct.
After all we have already identified several instances where the warmists have (at best) been slightly careless with the facts. Who is to say that the rest if their pseudo-science isn't even more iffy?
Stop shutting doors before you see and understand what is behind them.
Mike Jackson
Mike: I'm not shutting doors but you were, in this part of your argument:
I thought we were supposed to be open to alternative ideas seeing as how the one thing we accuse warmists of is having closed minds and saying the science is "settled".
As I said right away there isn't one thing we accuse warmists of, not least because there isn't a single 'we'. Best not to shut the door on any of the myriad of critiques people have, from Roger Pielke Snr to Roger Pielke Jnr, from Donna Laframboise to Tomas Milanovic. And if one of these people shows not an ounce of interest in Nikolov & Zeller I'm not going to sit in judgment on him or her for that. Just because X is not true and Y does not equal X we cannot argue that Y is true, nor browbeat people for not giving Y as much time as we think they should. We don't know what's true about much of the climate system. What we do know is that the evidence for imminent calamity is incredibly weak.
TBYJ is interested in reading Nikolov & Zeller and all strength to his maths as he does so. I wouldn't shut that door even if TBYJames gave me that power (an unlikely scenario, I think we'd all agree). I'm asking for the same tolerance in reflecting the wide, wide world of climate dissentients.
Richard Drake
I'm only a page in and it has me worried, but not for the reasons RKS might think. I got the spherical integration section (which appears to me to make the case that GHE is much bigger than we thought, rather than the reverse!) . The convection page is beyond me - I lost the will. I really don't see how any non-specialist is meant to refute this - the fact that it hasn't been refuted so far may well be a function of its complexity, not its fallability.
I can't believe it because I can't follow the maths. This is a problem, because I'm fairy numerate. if they can't convince me then they have no chance. Do I have to admit that Tallbloke, RKS, Roger Longstaff have a better mathematical understanding than me? Can they explain it to me?
I'll wait a bit. I'm not dismissing it because I can't get a handle on it. If no SoD or other followable refutation comes along, then I'll give it a bit more credence.
TheBigYinJames
Richard
I fail totally, yet again, to understand what the hell you are talking about.
How you can possibly argue that asking people to look at Nikolov & Zeller with an open mind is closing doors beats me.
We don't know what's true about much of the climate system. What we do know is that the evidence for imminent calamity is incredibly weak.Oh, well done! I've been saying that for the last 15 years, in the face of a lot of people whose opinions I normally respect but who took the line that since I wasn't a scientist how the hell would I know. That was not an easy furrow to plough, believe me.
And now I have to put up with your pontificating and patronising comments?
I think not. I'm done.
Mike Jackson
If you don't understand, return to what you yourself said. There isn't 'one thing we accuse warmists of', an over-simplification typifying the intolerance of the slayers.
Others, including myself, have had grave doubts about IPPC-led science and policy for longer than fifteen years. Nowhere have I said, for twenty years, that I'm not open to a critique such as N&Z's finally knocking the ball out of the park - who wouldn't be - but I do object to so much weight having been put on false arguments against the GHE in the last few years, as happened with the Dragon Slayers, with RKS harping on about back radiation, including in the last week, and with mydog mouthing abstrusenesses that became far less insightful the more people looked. As Jonathan Jones said on 2nd November:
I don't consider BitBucket a troll. Sure he's annoying, but no more so than AlecM, and unlike AlecM he is sometimes right.
That wasn't after failing to look into mydog's incomprehensibilities, was it? Nine months ago. Masses of time wasted and now, as TBYJ has just said, if N&Z have done better, we'll soon get to hear about it and give it more attention. Meanwhile there are more solid reasons to oppose the climate policy nexus than any of this. I'm sure you join me in that and I trust you can get over the lack of other encouragement, given that so much valuable time has already been taken up with what Martin A two days ago called "gobbledegook to the power of tosh".
Richard Drake
So, I've lost track, do 'they' claim back-radiation or not? Or is it TOA balancing at a different height? I've seen both, and I wonder if they are in fact meant to explain a complex phenomenon to the simple and as such not entirely accurate. Having said that I have a distinct recollection of some warmist academic posting (or being quoted) right here who made some astonishing claims re back-radiation. I need to search it out.
Oh, here's a genuine (rather than disingenuous) question. What's the difference between reradiated IR due to GHG and radiation from the non-GH gases in the atmosphere having a temperature? In wavelength and in energy content.
rhoda
rhoda -
Isn't it true that if a thing can't absorb then it can't radiate?
Martin A
rhoda,
GHG can absorb and re-emit photons in the appropriate wavelengths (4nm +). This is an electromagnetic effect, the exchange of photons. GHG can also convert photon energy into kinetic energy (heat) or a combination of both. But it is restricted to the energy content (wavelengths) of the photons is can emit by the emission/absorption properties of the molecule. e.g. a CO2 molecule could never emit or absorb a photon of 1nm. When it can't emit, it heats instead.
Other gases, such as O2 and N2 cannot absorb or re-emit photons in that LW band, so LW has little efect on them. They heat by kinetic collision with GHG molecules which have been excited by LW photons. By the same token, they cannot emit photoins in the LW band, so an O2 molecule can never emit or absorb a photon of 5nm. When it can't emit, it heats instead.
The kinetic energy (heat) that non-GHGs have in our atmosphere is not enough at the temperatures we're talking about to enable them to emit photons in the wavelengths they can do it in. e.g. this graph
http://nature.berkeley.edu/~penggong/textbook/images/atmospheric%20window2.jpg
You can see that O2 can only absorb and emit at high energies (short wavelengths) and unless you heated O2 to extremely high temperatures it will not be able to emit any photons. This is why O2 and N2 take verylittle part in the photonic process, but they can and do store heat energy in the form of kinetic energy.
TheBigYinJames
I'm not saying climate science is cosmology or evolution, just that it suffers from similar problems with practicality that these sciences do. It sounds 'obvious' to the lay person that something so 'physical' such as atmopheric physics should be repeatable under lab conditions, but I don't think it is - some of these effects only manifest in the macro world, you need a whole atmosphere of gas, or a whole sun's worth of solar insolation to see it happening, you can't reduce it to a handy desktop experiment
On the other points about the special pleading of climate science with regards to taxation, I agree with you rhoda, but we should be careful not to overstate our objections to the science in terms of financial concerns, since this plays into their hands, and mixes scientiifc rationality with political policy. "They only deny because they don't want to pay"
If it was true, I'd be happy to pay, and so would you I expect. So lets concentrate on the truthfulness of it, and keep the money out of it.