I have been away a while, so this might seem to be a bit old-hat for the more regular readers, but I felt I needed to get it off my chest, so to speak (though, having read some of our more regulars, it might be pertinent): there seems to be some misunderstanding about my understanding of CO2 and its role in the atmosphere; some have called me misguided, not in full possession of all the facts, and not a scientist; the last of those is correct, the second has a high probability of being correct, and the first point might also be correct. Others have just dismissed me as a fool; another point that might be correct, but does that justify dismissal and/or vilification? Part of this misunderstanding could be because I have tried to communicate my point in few words, to reduce the chances of boring you with my missives; please humour me, and allow me to clarify my understanding in a more verbose manner, and I would welcome correction on any points where you consider me wrong. Just telling me that I am wrong, without explanation, will be of no help whatsoever to anyone, least of all myself, and I feel justified in recommending that anyone who attempts that be ignored, else there could be some risk of derailing the discussion. Please bear in mind that I might feel obliged to partake of rather pedantic definitions, knowing that there are some who might be reading who will take great delight in unpicking every slight nuance, while ignoring the general thrust of the discussion.

The fact that CO2 can act as a “greenhouse gas” – i.e. absorbs energy from radiation (in this case, in the infra-red end of the spectrum) – is not disputed. It has been witnessed in laboratory experiments, where the contents of a closed container enriched with CO2 rises in temperature faster than a control closed container of ordinary air when both have been subjected to infra-red radiation (similar experiments have also shown this to fail, but let us ignore those, for now). However, that this phenomenon has such an effect that CO2 becomes the key driver of atmospheric temperature has to be doubted.

Reasons for this doubt:
(1) CO2 exists as a minute proportion of the atmosphere; thus, for it to imbue a noticeable increase of heat energy into the atmosphere, each molecule would have to absorb a remarkable amount of radiative energy. This absorption could be enhanced if CO2 was an attractor for the outgoing radiation – an IR magnet, so to speak – but that is an absurd idea. This absorbed energy would then need to be distributed to the surrounding air molecules via conduction and convection, as well as re-radiating part of it, less than half of which would be downwards. At present concentrations, each CO2 molecule would have to share this energy with an average of at least 2,500 other air molecules. This suggests that an awful lot of energy is required for it to have a noticeable effect over such dispersal.

(2) There are other “greenhouse gasses” extant within the atmosphere, many of which having been shown to be more effective than CO2 (with some considerably so) at absorbing radiative energy, and at least one of these existing in far greater concentrations than CO2; why are none of these considered to have an impact as significant as that claimed for CO2?

(3) Bearing in mind the “environmental sensitivity” being xK per doubling of CO2, what would be the calculated temperature if Earth’s atmosphere was 99% CO2? This is a little more than an 11-fold doubling (11.27) of present levels (rounded to 0.04%), thus giving us a theoretical temperature rise of about 11xK; thus, if x = 1, global temperatures would rise at least 11K.
(3a) What was the average global temperature when CO2 concentrations were about 4,000ppm, ten times present concentrations, or somewhat under 7 doublings (i.e. 6.65)? Is there evidence that it was more than 6xK the present average? Why were the Minoan, Roman and Mediaeval Warming Periods as warm as or warmer than today, when CO2 levels are generally agreed to have been lower? If x is a real number, then logic dictates that they should have been cooler than the present.
(3b) Venus has an atmosphere that is about 96.5% CO2 (11.24 doublings). At an altitude where the atmospheric pressure on Venus is the same as Earth’s (1,000mb), the average temperature is about 66°C, which, it has been calculated, is what the Earth’s atmosphere would be, were its orbit the same distance from the Sun as Venus’s. Why is the Venusian atmosphere at this altitude at this temperature, and not ~77°C (or (66+11x)°C)?
All this suggests that either the “environmental sensitivity” is considerably lower than continues to be thought (not less than 1K, but perhaps as high as 4.5K, though these figures continue to trend downwards), or that the “greenhouse effect” theory is wrong. Occam’s Razor, whereby the simplest explanation is the most likely to be the correct explanation, suggests to me that it is the latter of these.
And, finally:

(4) CO2 concentrations in the atmosphere continue to rise, while temperatures do not.

Possible explanations for a warm atmosphere? My guess (ref: Richard Feynman) is that it is a combination of many things, such as, but not limited to: the application of the gas laws; conduction of surface heat to the air in contact with it; and convection of said heat – which vultures and other gliders take great advantage of, which does indicate that there is some serious energy involved. With convection, there is movement; with movement there is friction; with friction, there is heat – this will be minimal, and may not actually be measurable, which, I would moot, puts it in the same category as the “greenhouse gas” effect – perhaps there, possibly influential, but not measurable. That said, I would also guess that radiated heat is more likely to be intercepted by particles, solid and/or liquid, in the atmosphere, as they are far larger than molecules, thus presenting a far greater surface area to intercept the radiated energy, they probably exist in far greater quantities than most of the supposed greenhouse gasses, and absorb a broader spectrum. However, the greatest absorption of the heat is from the top down, with the atmosphere directly absorbing the energy of the Sun. The reason the sky is blue has been shown to be because of particles in the air absorbing some of the visible solar radiation (a.k.a. light); that it is blue does suggest that it is the red end of the spectrum that is being absorbed. The red end of the spectrum is where the heat is (hence the use of infra-red lights in the experiments mentioned in the second paragraph); this red light has been absorbed – where has its heat gone? Teleported, perhaps, into the deep, deep oceans? If so, why has it waited until recently to turn that mechanism on?

Another good example that supports this guess is a clear, cloudless night, especially if there is no air movement. While the quantities of greenhouse gasses remains more-or-less constant (less so with water vapour, admittedly), the temperature plummets. If there are particles in the atmosphere, such as dust, mist, fog (i.e. denser mist) or clouds, then the temperature fall is considerably less. Anecdotal support: I have slipped on ice formed from a trail of water from a leaking tap; it was early in the morning after a very clear, cloudless night in the Persian Gulf. While the air temperature was observed to be in double figures (and the man with me expressed no cold discomfort, dressed in shorts and short-sleeved shirt), the surface, evidently, was not.

This supports yet another guess – the vast majority of the atmosphere comprises of nitrogen and oxygen; both of these are acknowledged as being very poor absorbers of radiative energy. My understanding is that if something is a poor absorber of radiation, it is also a poor emitter of that radiation, thus both gasses are good retainers of heat when the principal heat source is removed (i.e. it is night-time); cooling of the air occurs when the turbulence of air movement causes loss of heat through conduction with cool surfaces. In the anecdote given above, the air had been remarkably still, so ensuring that there was little, if any, turbulence for the air not in contact or close to contact with the ground to be able to lose its heat through conduction; hence the air temperature at human-height seemed warm, yet the surface temperature was not, the surface having radiated its energy virtually unimpeded through the clear air during the night.

Without wishing to bore you yet further, I suppose I had better leave it, there.

Thank you, BoFA (such an apt name). One of the problems that I have encountered is trying to get as much meaning into as few words as possible; it doesn’t always work. The downside to a full explanation is that it can look scaringly long. Aware of that, I have tried write it to be easier to read than many of the papers often cited; whether I have succeeded or not is only for others to judge.

Thank you, Martin A. So, the theory is that increasing CO2 effectively increases the opacity of the atmosphere, leading to greater heat retention. An analogy could be the heat within a room being retained by the glass of a window; CO2 is a fly-speck on that glass, and so increasing its effectiveness in retention. Quite why this fly-speck could have the dramatic effect that is claimed is what grates with me. My own inclinations are to agree with you – the “missing heat” is not there.

Hold on! Haven’t you gone a bit off-topic, here? How does the formula for diodes equate to CO2, the evil greenhouse gas? As analogies go, it is a rather desperate ploy (somehow, my fly-speck seems so much more appropriate)!

Are there any estimates (proxy readings) for temperatures when CO2 concentrations were more than 6 doublings of present levels? I would moot that, if there are, and they are NOT 6xK higher, then the idea that CO2 is the dominant factor in atmospheric temperatures is dead in the water, and the very principle of “greenhouse gas” is holed below the water-line.

Okay. Good points. You just moved into an area of electronics, which I consider to be more magic than science, and I am just a muggle.

Ssat: I have no trouble with the “greenhouse effect”, as it seems logical that the atmosphere will retard the radiation of energy to space. That a “greenhouse gas” is required for this is where I balk; I find it difficult to accept that a gas that exists in very small quantities could have such an impact. What happens in the Persian Gulf in summer time is, with the inter-tropical convergence zone (ITCZ) moving over the region, it gets covered by a thermal inversion – where the temperature stops cooling with height – and the heat gets trapped, leading to what can be quite dangerous air temperatures (sea-level temps of 40+°C are common; 50+°C can occur) coupled with high humidity; a good analogy would be to liken it to the lid on a pressure cooker. In the anecdote I gave (occurring in the winter), all that was lacking in the atmosphere was particles (liquid or solid), and exceptionally still air. To replicate the anecdote, all that would be required would be to surround an area of desert (preferably of dark colour) with a high wall, to minimise air movement over the ground, cover the ground with a thin layer of water and then sit back and wait for a clear, cloudless night. Curiously, when I was at school, this is what I was told was a common way of getting ice in Arabia.

I conclusion, I do agree with you: climate science is fooling itself – which would be no great shakes in a real world, but we no longer live in a real world; we live in the world of Mann, Dibble, Yeo and other assorted troughers, which is even more ludicrous than any that Lewis Carroll or others could possibly envisage, and climate “science” is fooling everybody.