This thread debates the Miskolczi semi-transparent atmosphere model.
The link with the easiest introduction to the subject is http://hps.elte.hu/zagoni/Proofs_of_the_Miskolczi_theory.htm
This thread debates the Miskolczi semi-transparent atmosphere model.
The link with the easiest introduction to the subject is http://hps.elte.hu/zagoni/Proofs_of_the_Miskolczi_theory.htm
Neal,
– You now seem to be saying that it’s the radiative equilibrium assumption that is at fault. However, you haven’t provided any reasons for rejecting it; you’re just asserting that it’s false.
– In the following: “But it seems to be key to M’s derivation that the Earth’s atmosphere take the fastest one he has in mind, even though doing so involves some kind of alteration of the water-vapor concentration or cloud cover of the atmosphere – elements that heretofore have not entered the discussion.” I’m not sure where you’re coming from or where you’re going for a few reasons:
i) Miskolczi doesn’t talk about “fastness” anywhere in the paper. My feeling is that you’re just changing his words to set up a bit of straw man here. The word he uses is “efficient,” which, if nothing else, sounds less ridiculous than “fast.” If I hold up a pen (=increase this pen’s potential energy) and then let I let it go, gravity will see to it that the potential energy is disposed as efficiently as possible. Is there a problem with this statement? Or I could say, “the pen will move as fast as possible towards the ground.” Alright, same meaning, but it sounds a little ridiculous. The wording suggests intentionality within the pen, rather than the deterministic workings of the laws of physics. So… are you just playing with words here?
ii) Do you agree or do you disagree that the earth-atmosphere system takes H2O from the oceans in the process of cloud formation?
– Mars, as stated, it would be more interesting to wait for Dr. Miskolczi’s response to your detailed questions.
– Ken Gregory’s response, perhaps if he’s still out there he might respond himself to this one.
I’ve been thinking about this some more. This quibbling about “fastness” & Miskolczi’s usage of “efficient” is a red herring & a distraction. “The principle of minimum energy requires the most efficient disposal of the thermal energy of the atmosphere.” There is nothing at all odd about this statement of the law. It’s the second law of thermodynamics & I find no substantive difference between this statement and the one at Wikipedia. I feel a decided sense of déjà vu after arguing for 30+ pages at the CA BB about his equally reasonable statement of Kirchhoff’s law.
The argument is much simpler:
A. “long-term radiative equilibrium between the solar and terrestrial radiation…” MM2004, p. 210.
B. second law of thermodynamics
C. therefore, “the internal energy will decrease and approach a minimum value at equilibrium,” Wikipedia’s statement.
It seems your only objection is with point A so you should probably focus on the evidence against this.
Alex Harvey:
– “Radiative equilibrium at fault”: No, I’m just pointing out that it’s not correct for you to state that the Earth’s atmosphere is in equilibrium. Steady-state is not the same as thermal equilibrium.
– “Efficient vs fast”: You’re picking on words. The point is that the fact that the final state for a system (or more accurately, subsystem) in thermal equilibrium has the minimum energy does not dictate any specific path towards getting there: most efficient, least efficient, fastest, slowest, greenest, cutest – there’s no implication. Miskolczi attempts to draw one, hence he maximizes the radiative transport rate to get his tau = 1.87 result. I don’t see any reason to follow him there.
The most popular minimal principle associated with dropping a pen is the principle of least action, where the action is the integral of (KE – PE) over time. There is no reason to consider that particularly “efficient” however.
– “H2O taken up from the ocean in the process of cloud formation”: Yes, so? The point is that M is looking for a mechanism that will make his tau = 1.87 true. So he’s picking on cloud formation at altitude 2 km (p.35) or look at other possibilities at the bottom of p.23. From my point of view, there is just no reason that the atmosphere should be obligated to accommodate him. Actually, it’s very similar to the game several people have already mentioned about his use of the virial theorem: Even if the VT applies (and I’ve argued that it doesn’t give what he wants), there seems to be no sensible way to turn a relationship concerning bulk energies into a relationship on fluxes (rates of energy transfer). Analogously, here he is trying to turn a principle regarding the existence of a minimum-energy configuration into a condition on rate of energy loss. In my view, that dog won’t hunt.
– I have dropped Miskolczi a line reminding him that I am still interested in clarification of my questions: According to what he said earlier, he should be back in town by now. Until I hear from him, I will frankly not be too interested in trying to salvage sections of the argument: It is the author’s responsibility to make sure a paper hangs together, not the reader’s responsibility to find parts that work. I am willing to be convinced that it makes sense; but only if I get answers that make sense to me.
Alex Harvey:
I thought of another argument explaining my doubt of the derivation. A Gedanken-experiment, as it were:
– M claims, on the basis of all these principles (conservation of energy, minimum energy, etc.), that the optical depth of the Earth will always be 1.87. So if we dump a lot of CO2 into the atmosphere, the magic number will be achieved by cloud formation at 2 km.
– So now we construct a new Earth, exactly the same as the first – but then we remove all the water.
a) Do all the principles that applied to the old Earth still apply? If not, which ones fail?
b) If we now dump that extra CO2 into the new atmosphere, what will happen to keep the optical depth at 1.87? There is no water available to make clouds.
Neal,
– fast / efficient:
fast: as mentioned above, this concept does not appear in the paper at all.
efficient: although the word appears in the text, the assumption that the critical optical depth will be found at the maxima for B0 does not derive from any actual assumption of “efficiency.” The word you’re making so much about is just a word in the text. Delete the word and we can still follow the paper. Perhaps it is awkward? Who cares?
– In the following link: http://asd-www.larc.nasa.gov/~yhu/paper/thesisall/node54.html it appears to my layperson’s eyes that a similar procedure is being applied. By the looks of these are Miskolczi’s colleagues at Langley, no less.
– radiative equilibrium / thermal equilibrium / steady-state: is that a yes, no, or a maybe? Miskolczi’s assumption is not steady-state, and it’s not thermal equilibrium. The assumption again is radiative equilibrium — “long-term radiative equilibrium between the solar and terrestrial radiation…” MM2004, p. 210. It is this assumption and this assumption only we are talking about. It appears that you reject the assumption. If so, why? What are your reasons / evidence for rejecting the radiative equilibrium assumption?
– If I drop my pen, do the laws of physics specify a particular path by which the pen will come to rest or not? I think they do.
– Your thought experiment: crucial in Miskolczi’s model is the existence of a near-infinite supply of H2O on the earth in the oceans. I fail to see where you’re going with this.
From the link above above:
We will prove that the equilibrium state is the state with the maximum entropy if we consider the Earth, the Sun and the surrounding vacuum as the system.
Is this not the same as assuming, A. radiative equilibrium; B. 2nd law of thermodynamics; therefore, C. entropy is maximised / energy is minimised?
Here’s a detailed explanation of why Miskolczi’s paper is wrong:
Miskolczi’s errors
George Tobin writes:
The predicted warming has occurred, the troposphere is warming, and absolute humidity is rising (relative humidity, of course, is not). You’re wrong on all three points. For humidity, here’s an empirical study:
Brown, S., S. Desai, S. Keihm, and C. Ruf (2007), Ocean water vapor and cloud burden trends derived from the topex microwave radiometer. Geoscience and Remote Sensing Symposium 2007, Barcelona, Spain, IGARSS 2007, IEEE International, 886-889.
As I said, precitable water vapor has been going up at about 0.9 mm/decade, consistent with Clausius-Clapeyron.
kim writes:
Wrong on both counts. For water vapor, see:
Brown, S., S. Desai, S. Keihm, and C. Ruf (2007), Ocean water vapor and cloud burden trends derived from the topex microwave radiometer. Geoscience and Remote Sensing Symposium 2007, Barcelona, Spain, IGARSS 2007, IEEE International, 886-889.
For temperature:
Tim Ball’s errors
Tilo Reber’s errors
BPL:
1. “According to the Kirchhoff law, two systems in thermal equilibrium exchange energy by absorption and emission in equal amounts…” [Miskolczi 2007]. In fact, Kirchhoff’s Law states that for a body in local thermodynamic equilibrium (LTE), emissivity and absorptivity must be equal at a given wavelength. Miskolczi confuses emission with emissivity. This can lead to large numerical errors, since emissivity is of course constrained to the range 0 – 1 by definition, but emission can have any nonnegative value, and is typically in the hundreds of watts per square meter for low levels of atmosphere.”
We’ve all heard this objection before, but it is shown above that a standard textbook on atmospheric radiation also uses Kirchhoff’s laws to equate absorption & emission. Therefore, it might be more interesting to begin by acknowledging this fact.
BPL: Another question: your website previously stated that you were writing up your objections to Miskolczi’s theory as a journal article that would be submitted to peer review. If accepted, you would provide a link to your published article. There is no mention of this any longer, and a revised version of your original page seems to have reappeared. Since a lot has been made of the fact that Miskolczi’s paper was rejected by the peer reviewers from some major journals, it seems only fair to ask what happened during the peer review of your own paper?
Alex Harvey (05:04:31) :
– “Eliminate the word ‘efficient'”: I believe you’re missing the thrust of M’s argument:
a) He claims there is a minimum-energy state.
b) He claims that the atmosphere will achieve this state as efficiently as possible.
c) “The most efficient cooling of the clear atmosphere requires a total optical depth that maximizes B_o.”
If you eliminate the word “efficient” or replacement words, you have no reason to require that B_o should be maximized, and you have no basis for (B9), B(10) and ultimately “tau = 1.87”. You’ve taken the engine out of M’s argument.
– I looked at your link to Hu’s pages. Since you follow this up with a later query, I will deal with it a bit later. I’m trying to figure out exactly what it is that Hu is trying to show. I’m a bit hampered by the fact that I think his equation (6.5) is wrong: it lacks any dependence on the radius of the Sun, which is important if you’re trying to convert a flux at the Sun to a flux on the Earth. I also think he’s confusing entropy flux (as in (6.4) with entropy change (6.6). But this will take more study.
– “Radiative equilibrium / thermal equilibrium / steady-state”: My point is that these are all somewhat different concepts. A thermal equilibrium is a steady state, but not all steady states are in thermal equilibrium. Radiative equilibrium would be a requirement for a steady state, but not necessarily the other way around (although in most cases it would be true).
– If you drop your pen, the path it follows is dictated by Newton’s laws, NOT by the mere existence of a lowest-energy state. For instance, that lowest-energy state will be the same whether or not the pen is dropped in a vacuum or in a very thick atmosphere; but the path in space-time of the pen will be modified by the absence/presence of air.
– If the existence of a near-infinite supply of water is essential to the equations, please indicate where the chain of equations he has drawn up fails in the absence of water. When you think about that carefully, I think you have to conclude that the argument is no more cogent in the presence of water. Because I think the crux of his argument is: “This cooling process would happen fastest when tau = 1.87. Therefore, the Earth’s atmosphere has to find some way to achieve tau = 1.87.” My answer: “No, it doesn’t.”
statePoet writes:
No one is saying there’s going to be a “runaway greenhouse effect.” On the present Earth you can’t have one. What climatologists are saying is that the greenhouse effect is being enhanced by human production of greenhouse gases, and that the effects on our agriculture and economy will be severe.
It is finely balanced, but it has gotten out of balance many times, e.g. during the “snowball Earth” episodes 2.3 billion, 800 million and 600 million years ago. What keeps it approximately balanced are feedback mechanisms such as the carbonate-silicate cycle. But we are pouring carbon dioxide and other greenhouse gases into the air much faster than natural cycles can easily handle.
Bruce Cobb writes:
Well, you know, science doesn’t deal in “proof.” That’s for mathematics or formal logic. Science deals in evidence.
The evidence for AGW is that:
1. Carbon dioxide is a greenhouse gas (Tyndal 1859).
2. Carbon dioxide is rising (Keeling et al. 1958 and many others since then).
3. The major source of the new carbon dioxide is human technology (Suess 1955 and many others since then).
4. The temperature trend of the last 150 years is up (Mann et al. 1998, 1999, and many others since then).
5. Other sources for the warming are not plausible.
Peter writes:
I didn’t say the runaway greenhouse effect couldn’t happen. It can’t happen on present-day Earth, but it certainly did happen on Venus. I think you mistook me critiquing Miskolczi for what I believed. If Miskolczi’s theory is correct, Venus shouldn’t be anywhere near as hot as it it.
Alex Harvey writes:
As it happens, Alex, I have my copy of Goody and Yung 1989 to hand. The passage you quote on page 3 runs “Since clouds, ground and atmosphere do not differ greatly in temperature, it follows from Kirchhoff’s laws that emission and absorption are approximately equal.”
You are mistaking a special case for a general law. Yes, if two bodies are at about the same temperature and have the same composition, emission and absorption will be about the same. But this is NOT Kirchhoff’s Law, which states that at a given wavelength or frequency, emissivity and absorptivity are equal for an object in local thermodynamic equilibrium. In fact, if you look on page 39, you find this spelled out in greater detail: “In a constant-temperature enclosure, Iν = Bν, by definition, and, from (2.61) and (2.75),
Bν = Jν = Iν, (2.76)
regardless of the collisions. This is Kirchhoff’s second law, showing that our treatment is appropriately consistent with classical thermodynamics.”
The fact is, Goody and Yung doesn’t deal much with atmosphere modeling, and therefore Kirchhoff’s Law is mentioned only a few times and in an off-hand fashion. For clearer statements about it, try these:
“…there is a very simple relation between emissivity (ελ) and absorptance (αλ)
ελ = αλ [2.5]
This is known as Kirchhoff’s Law and indicates that at the same wavelength, good emitters are equally good absorbers.”
–Henderson-Sellers, A. and Robinson, P.J. 1986. Contemporary Climatology. NY: Wiley. p. 35.
“…the relationship between absorptivity a and emissivity ε is embodied succinctly in Kirchhoff’s Law, which states that:
ελ(θ,φ) = aλ(θ,φ). (6.12)
Note that this equivalence is strictly valid only for monochromatic radiation at a given wavelength λ and when the viewing directions θ and φ are specified…”
-Petty, G.W. 2006. A First Course in Atmospheric Radiation (2nd Ed.). Madison, WI: Sundog Publishing. p. 126.
“A little learning is a dangerous thing/Drink deep, or do not drink, of the Pierian spring.”
-Alexander Pope
Alex Harvey writes:
Surely. I submitted it to JGR, but they told me that since Miskolczi’s article hadn’t appeared there, I couldn’t reply to it there. So I decided to just put the article up on my web site.
Alex Harvey (05:23:08) : “We will prove that the equilibrium state is the state with the maximum entropy if we consider the Earth, the Sun and the surrounding vacuum as the system.”
More confusion I have about what Hu is doing:
– It’s essentially the foundation of thermodynamics that the equilibrium state is achieved when the entropy is maximized. So I don’t quite see what it is that Hu is actually trying to show.
– When I look at the end of Hu’s page, I get the impression that he’s aiming at (6.9), relating the Earth’s temperature to the Sun’s temperature at the point when the rate of entropy production is minimized. But actually, (6.9) is dimensionally impossible; however, it’s clear that Hu means:
T_earth = T_sun * sqrt(r_earth/(4L)).
– In (6.5) and (6.6), Hu writes a factor of pi*(r_earth)^2 when he really should have 4*pi*(r_sun)^2. When this is corrected, (6.9) becomes
T_earth = T_sun * sqrt(r_sun/(2L)). This answer is inherently more reasonable than Hu’s (6.9), that would suggest that a planet’s steady-state temperature depends strongly on its radius. That would mean that a planet could have an arbitrarily small temperature, even if it’s near to the Sun, provided that you make the planet small enough. That seems pretty unlikely to me!
– The part of Hu’s derivation that you are relying upon, between (6.7) and (6.8) , is the least clear.: “The rate of entropy production is always positive, but there is a T_earth which it is minimized.” First, this is an explicit call for a entropy-production rate-minimization principle (not the same thing as a minimum-energy principle), which might relate to some theorem in non-equilibrium thermodynamics, but doesn’t seem to have much justification here. Secondly, I notice further that (6.8) looks as though it should be the result of differentiating (6.7) – but it’s not! In fact, Hu says “The minimum value of delta_S_dot is achieved (very close to but greater than 0) when the incoming solar radiation is balanced by the outgoing terrestrial energy.” But this point you would get that by using the straight-forward “what would you get for Earth’s temperature if there were no greenhouse effect?” equation. (Except that, as noted before, he gets (6.8) wrong so he gets (6.9) wrong.)
Sorry, Alex, this paper is a real loser:
– 4 out of the 9 equations are flat-out wrong.
– The motivation for minimizing a rate is an explicit call for minimization of a rate, not a call for the existence of a minimum state.
– The final result is in actual contradiction to the cited rationale. Steady-state radiation balance implies my result, not his:
T_earth = T_sun * sqrt(r_sun/(2L))
Alex, this took a lot of time to read, understand, and ultimately de-bug. In the end, this turned out to be a poorly written, poorly thought-out article, and mostly irrelevant to the point. If you cite another article that seems to have those characteristics, I will not give it this level of attention again.
BPL:
Thanks for your learned response.
I am mistaking a special case for a general law am I. That’s funny, though. Since the specific bodies in this “special case” appear to be those “layers of the atmosphere” we care about. The text continues, “Terrestrial radiation is therefore passed from layer to layer in the atmosphere … The situation differs in the upper atmosphere because Kirchhoff’s laws are not obeyed if the pressure is very low.”
But then you continue, this is NOT “Kirchhoff’s Law.” Followed by lots of lovely examples of statements of Kirchhoff’s Law in italic font that aren’t relevant to Miskolczi’s paper.
So who really cares whether it’s Kirchhoff’s Law or a special case of Kirchhoff’s Law or a consequence of Kirchhoff’s laws plural?
Where is the contradiction here? Perhaps what you really want to say is that the textbook is wrong? If so, say it. Also, can you explain to me how a textbook called “Atmospheric Radiation” can not be relevant to atmospheric modeling?
Apologies, Neal. I foolishly supposed that since I got the paper from the NASA/Langley website it would be correct. I certainly didn’t mean for you to analyse the conclusions of the paper in detail. It’s looking a bit like the quality of the science at NASA is falling somewhat.
Alex Harvey:
I guess it just shows you can find junk on the internet anywhere.
But this document may not be that recent: It is dated 21 December 1996.
It might be an early draft of something that never got very far. If anyone reviewed it and didn’t catch problems…
BPL writes:
The other problem (further to my post above) is that several physicists (apparently including Neal J. King above) have assured me that eq (2.76) is an equation relating fluxes.
Therefore, would it be possible for you to explain a little more clearly how an equation relating absorption & emission that is denoted “Kirchoff’s second law” can possibly be adduced in support of your assertion that
when to a layperson such as myself (who perhaps hasn’t drunk deeply from the rivers of knowledge) it appears to stand in outright contradiction. Thanks.
Actually, I shouldn’t say “contradiction.” Clearly, a law known commonly just as “Kirchhoff’s Law” is used to equate absorptivity & emissivity in LTE as you say. Perhaps this is the one familiar to climatologists? I note that your quotes all came from climatology textbooks rather than physics textbooks. At any rate, equally clearly, Kirchhoff’s laws are also used to equate absorption & emission. Try this: go to Google and type in “kirchhoff’s law absorption emission.” You’ll see there are 73,800 pages returned. Then, if you type in “kirchhoff’s law absorptivity emissivity” you’ll only get 26,500 pages. Now repeat this at Google Scholar and you’ll get a ratio of around 4,000 to 1,000 in favour of matches against ‘absorption’ & ’emission’. Now I realise that this doesn’t prove anything in itself, but as I start reading the abstracts I find over & over again that “Kirchhoff’s laws are used to relate absorption & emission.”
And 59,200 for “kirchhoff’s law -absorptivity -emissivity absorption emission” (i.e. with pages containing both words ‘absorption’ & ‘absorptivity’ / ’emission’ & ’emissivity’ deleted).
Alex Harvey writes:
The textbook is not wrong. You didn’t understand it.
Because it’s a book about radiation theory, not about how to write atmosphere models. The former long predates the latter. There is some discussion of atmosphere modeling in Goody and Yung, but that’s not the primary focus of the book.