This is awesome, the wife is downstairs watching a movie, I’ve finished my work and have a little time for blogging. Not a lot, but some…
There are too many pressures in my head. Today a commenter, who is anonymous to me, left a slayer-style comment which has none of the Doug Cotton inflections about it. (new guy!) I am truly curious about the understanding of this group because I have worked hard at it and they represent something which doesn’t make any sense to me. We know slayers see global warming as a complete farce rather than the pseudo-science based money printing machine it has become. I have different replies from each individual from this group and hope to gain some understanding of where they separate from basic science.
It is an interesting challenge which I think careful second-law readers here will find ironic. — So how does one find the bulk opinion of a group of moderately independent variables? 😀
nope one more thermo-smiley
Two beers in and I’m already having fun.
Anyway, this is the comment left on the last (very old) thread:
If you believe that planetary surface temperatures are all to do with radiative forcing rather than non-radiative heat transfers, then you are implicitly agreeing with IPCC authors (and Dr Roy Spencer) that a column of air in the troposphere would have been isothermal but for the assumed greenhouse effect. You are believing this because you are believing the 19th century simplification of the Second Law of Thermodynamics which said heat only transfers from hot to cold – a “law” which is indeed true for all radiation, but only strictly true in a horizontal plane for non-radiative heat transfer by conduction.
The Second Law of Thermodynamics in its modern form explains a process in which thermodynamic equilibrium “spontaneously evolves” and that thermodynamic equilibrium will be the state of greatest accessible entropy.
Now, thermodynamic equilibrium is not just about temperature, which is determined by the mean kinetic energy of molecules, and nothing else. Pressure, for example, does not control temperature. Thermodynamic equilibrium is a state in which total accessible energy (including potential energy) is homogeneous, because if it were not homogeneous, then work could be done and so entropy could still increase.
When such a state of thermodynamic equilibrium evolves in a vertical plane in any solid, liquid or gas, molecules at the top of a column will have more gravitational potential energy (PE), and so they must have less kinetic energy (KE), and so a lower temperature, than molecules at the bottom of the column. This state evolves spontaneously as molecules interchange PE and KE in free flight between collisions, and then share the adjusted KE during the next collision.
This postulate was put forward by the brilliant physicist Loschmidt in the 19th century, but has been swept under the carpet by those advocating that radiative forcing is necessary to explain the observed surface temperatures. Radiative forcing could never explain the mean temperature of the Venus surface, or that at the base of the troposphere of Uranus – or that at the surface of Earth.
The gravitationally induced temperature gradient in every planetary troposphere is fully sufficient to explain all planetary surface temperatures. All the weak attempts to disprove it, such as a thought experiment with a wire outside a cylinder of gas, are flawed, simply because they neglect the temperature gradient in the wire itself, or other similar oversights.
The gravity effect is a reality and the dispute is not an acceptable disagreement.
The issue is easy to resolve with a straight forward, correct understanding of the implications of the spontaneous process described in statements of the Second Law of Thermodynamics.
Hence radiative forcing is not what causes the warming, and so carbon dioxide has nothing to do with what is just natural climate change.
Carrick had a very useful comment on a Lucia thread a week ago on the matter of lapse rates.
As Nick says, the g/cp = 9.86/1.006 = 9.6°C/km lapse rate is a correct theoretical result only for dry air (note the lapse rate is defined as the negative of the change in temperature with elevation, hence Nick has an extraneous minus sign). This result is satisfying in that it can be derived exactly but it really is the “spherical chicken” approximation of climate. When you include moisture, the maximum sustainable lapse rate is reduced from ~ 10 to around 6.5 °C/km. This is referred to as the “environmental lapse rate”, and can be predicted from theory fairly accurately in the troposphere using the known vertical wind-speed profile and a prescribed vertical humidity gradient.
Manabe and Strickland 1964 is the classic reference for from-first-principles calculation. It is written in a very comprehendible way for people with a physics/engineering background.
What you see from this is that the radiative lapse rate is even larger than the dry-air lapse rate, and hence is never physically realized in the troposphere.
I don’t think Nick is right that radiative transfer is an “underrated factor”, unless he means in the semi-lay blogosphere. I think it’s role has been well understood since Manabe’s days.
Basically radiative transfer acts to keep the tropospheric lapse rate to be maintained near the maximum stable value (the radiative equivalent of keeping tension on a string). So it plays a critical role in atmospheric dynamics and converts a dynamic calculation into basically a static one (read simpler problem), but doesn’t play a direct major role in the vertical transfer of heat energy (see below for numbers).
If convection were impossible, the temperature at the top of the atmosphere would be the same, but the surface temperature would be about 35°C warmer than it is now (using Fig 4 of Manabe). Note that a dry atmosphere it would be about 10°C warmer.
What Fig 4 is basically saying is that a radiation-only atmosphere has a much larger greenhouse gas effect than a convective dry atmosphere, and an atmosphere with moisture acts to further reduce the greenhouse gas effect from what it would be in the radiative only model. I think these are as, now well, agreed to results.
There’s a bit additional non-controverial results, which are summarized in Ramanathan 1981.
Note that about 3/4s of the net feedback effect from GHGs is due to convective heat energy transfer in this model.
I should mention there is an important controversy relate to the tropical lapse rate & the “missing hot spot”. Probably its resolution is the violation of the assumption you can treat the atmosphere as a vertical stack of air.
I think all of this is appropriately “off topic” for a thread on “DC”. Note that in online gaming, DC also mean “Dis-Connected” which also seems like an appropriate alternative moniker for the individual in question.
There is a pile of information there so nobody – except a couple of us – would literally check all of the links but the discussion doesn’t need to get this deep with those who don’t believe CO2 warming is a real effect. In order to understand this phenomenon, what we need to do is find out where the standard physics and those who don’t agree with it, part ways.
So this was my reply to the individual, whom the readers here are far more likely to know the identity of than myself.
Work, heat, entropy are all bulk concepts. The second law is a law only in the bulk context. It is a law in that after twenty trillion rolls, the probability is toward the heavy side of the die.
Backradiation is a sub-process which in no way “violates” the second law. This is a common misunderstanding from those who didn’t grok the meaning of their basic physics rules. Saying it can or can’t be explained by either theory is rather amusing to me because mathematically – en bulk – they are equivalent. Where slayers here have faltered is that they don’t give a coherent message and too many members are scientifically weak.
I would be very happy to debate this issue. We have to start with fundamentals though and work our way up from there. This is necessary because I have been taught classical physics and we need to determine where our understanding bifurcates.
Why make this post?
Tis’ a good question. Recently there was a minor kerfuffle between the slayers and Roy Spencer. Some gauntlets were thrown challenging mathematical proofs with models. I really failed to understand the point of the “modeling” — mostly because of the discontinuity of the slayer argument but there was another reason. My interpretation of the discrepency is that both standard theory and PSI theory are mathematically equivalent WRT bulk properties, yet fail on other levels. Still, not a single PSI member has succintly explained to me the difference between standard physics and their version. Tellingly, nobody from the group has demonstrated a basic working understanding of the main-stream principles of the second law of thermodynamics such that they could address and refute the discrepancies. The problem is apparent enough to shut the group out entirely and ignore them but I would rather understand the discontinuity.
The other reason for this post is that when you consider the second law, the sum of the rate of energy transfer is delta temperature only. Therefore, from my known slayer energy transfer explanations the energy transfer is the same no matter which religion you subscribe to. They have said, electromagnetic energy stops going backward when other greater energy is coming forward, thus E = E1 – E2. Standard physics also says E = E1-E2 . The real challenge for slayers should be to mathematically show any difference at all for physics rather than show how one is better. Instead we have a lot of PSI “papers”, chock full of unsupported conclusion.
I am frustrated with the whole thing.
While writing this post, the discussion continued on the previous thread. This has to be kept short because we are here to understand not nitpick. My very simple challenge to the slayers therefore is as follows, each of the 3 points with 300 words or less and no links:
1 Define and describe the probability characteristics of Second Law of Thermodynamics as interpreted in classical physics using your own words. Demonstrable understanding of the standard version of the second law is important so that we have common ground.
2 Describe standard physics interpretation of radiation absorption from a cold to hot body.
3 Describe the PSI interpretation of the Second law highlighting differences in energy transfer from the standard interpretations.
4 Describe the PSI interpretation of what happens to radiation from a cold to hot body, with focus on temperatures.
The discussion below will be open to all. 300 words, no links will be strictly enforced.