Guest Post by Willis Eschenbach
Since at least the days of Da Vinci, people have been fascinated by perpetual motion machines. One such “perpetuum mobile” designed around the time of the civil war is shown below. It wasn’t until the development of the science of thermodynamics that it could be proven that all such mechanisms are impossible. For such machines to work, they’d have to create energy, and energy cannot be either created or destroyed, only transformed.
I bring this up for a curious reason. I was reading the Jelbring hypothesis this afternoon, which claims that greenhouse gases (GHGs) are not the cause of the warming of the earth above the theoretical temperature it would have without an atmosphere. Jelbring’s hypothesis is one of several “gravito-thermal” theories which say the heating of the planet comes from gravity rather than (or in some theories in addition to) the greenhouse effect. His thought experiment is a planet with an atmosphere. The planet is isolated from the universe by an impervious thermally insulating shell that completely surrounds it, and which prevents any energy exchange with the universe outside. Inside the shell, Jelbring says that gravity makes the upper atmosphere colder and the lower atmosphere warmer. Back around 2004, I had a long discussion on the “climateskeptics” mailing list with Hans Jelbring. I said then that his theory was nothing but a perpetual motion machine, but at the time I didn’t understand why his theory was wrong. Now I do.
Dr. Robert Brown has an fascinating post on WUWT called “Earth’s baseline black-body model – a damn hard problem“. On that thread, I had said that I thought that if there was air in a tall container in a gravity field, the temperature of the air would be highest at the bottom, and lowest at the top. I said that I thought it would follow the “dry adiabatic lapse rate”, the rate at which the temperature of dry air drops with altitude in the earth’s atmosphere.
Dr. Brown said no. He said that at equilibrium, a tall container of air in a gravity field would be the same temperature everywhere—in other words, isothermal.
I couldn’t understand why. I asked Dr. Brown the following question:
Thanks, Robert, With great trepidation, I must disagree with you.
Consider a gas in a kilometre-tall sealed container. You say it will have no lapse rate, so suppose (per your assumption) that it starts out at an even temperature top to bottom.
Now, consider a collision between two of the gas molecules that knocks one molecule straight upwards, and the other straight downwards. The molecule going downwards will accelerate due to gravity, while the one going upwards will slow due to gravity. So the upper one will have less kinetic energy, and the lower one will have more kinetic energy.
After a million such collisions, are you really claiming that the average kinetic energy of the molecules at the top and the bottom of the tall container are going to be the same?
I say no. I say after a million collisions the molecules will sort themselves so that the TOTAL energy at the top and bottom of the container will be the same. In other words, it is the action of gravity on the molecules themselves that creates the lapse rate.
Dr. Brown gave an answer that I couldn’t wrap my head around, and he recommended that I study the excellent paper of Caballero for further insight. Caballero discusses the question in Section 2.17. Thanks to Dr. Browns answer plus Caballero, I finally got the answer to my question. I wrote to Dr. Brown on his thread as follows:
Dr. Brown, thank you so much. After following your suggestion and after much beating of my head against Caballero, I finally got it.
At equilibrium, as you stated, the temperature is indeed uniform. I was totally wrong to state it followed the dry adiabatic lapse rate.
I had asked the following question:
Now, consider a collision between two of the gas molecules that knocks one molecule straight upwards, and the other straight downwards. The molecule going downwards will accelerate due to gravity, while the one going upwards will slow due to gravity. So the upper one will have less kinetic energy, and the lower one will have more kinetic energy.
After a million such collisions, are you really claiming that the average kinetic energy of the molecules at the top and the bottom of the tall container are going to be the same?
What I failed to consider is that there are fewer molecules at altitude because the pressure is lower. When the temperature is uniform from top to bottom, the individual molecules at the top have more total energy (KE + PE) than those at the bottom. I said that led to an uneven distribution in the total energy.
But by exactly the same measure, there are fewer molecules at the top than at the bottom. As a result, the isothermal situation does in fact have the energy evenly distributed. More total energy per molecules times fewer molecules at the top exactly equals less energy per molecule times more molecules at the bottom. Very neat.
Finally, before I posted my reply, Dr. Brown had answered a second time and I hadn’t seen it. His answer follows a very different (and interesting) logical argument to arrive at the same answer. He said in part:
Imagine a plane surface in the gas. In a thin slice of the gas right above the surface, the molecules have some temperature. Right below it, they have some other temperature. Let’s imagine the gas to be monoatomic (no loss of generality) and ideal (ditto). In each layer, the gravitational potential energy is constant. Bear in mind that only changes in potential energy are associated with changes in kinetic energy (work energy theorem), and that temperature only describes the average internal kinetic energy in the gas.
Here’s the tricky part. In equilibrium, the density of the upper and lower layers, while not equal, cannot vary. Right? Which means that however many molecules move from the lower slice to the upper slice, exactly the same number of molecules must move from the upper slice to the lower slice. They have to have exactly the same velocity distribution moving in either direction. If the molecules below had a higher temperature, they’d have a different MB [Maxwell-Boltzmann] distribution, with more molecules moving faster. Some of those faster moving molecules would have the right trajectory to rise to the interface (slowing, sure) and carry energy from the lower slice to the upper. The upper slice (lower temperature) has fewer molecules moving faster — the entire MB distribution is shifted to the left a bit. There are therefore fewer molecules that move the other way at the speeds that the molecules from the lower slice deliver (allowing for gravity). This increases the number of fast moving molecules in the upper slice and decreases it in the lower slice until the MB distributions are the same in the two slices and one accomplishes detailed balance across the interface. On average, just as many molecules move up, with exactly the same velocity/kinetic energy profile, as move down, with zero energy transport, zero mass transport, and zero alteration of the MB profiles above and below, only when the two slices have the same temperature. Otherwise heat will flow from the hotter (right-shifted MB distribution) to the colder (left-shifted MB distribution) slice until the temperatures are equal.
It’s an interesting argument. Here’s my elevator speech version.
• Suppose we have an isolated container of air which is warmer at the bottom and cooler at the top. Any random movement of air from above to below a horizontal slice through the container must be matched by an equal amount going the other way.
• On average, that exchange equalizes temperature, moving slightly warmer air up and slightly cooler air down.
• Eventually this gradual exchange must lead to an isothermal condition.
I encourage people to read the rest of his comment.
Now, I see where I went wrong. Following the logic of my question to Dr. Brown, I incorrectly thought the final equilibrium arrangement would be where the average energy per molecule was evenly spread out from top to bottom, with the molecules having the same average total energy everywhere. This leads to warmer temperature at the bottom and colder temperature at elevation. Instead, at thermal equilibrium, the average energy per volume is the same from top to bottom, with every cubic metre having the same total energy. To do that, the gas needs to be isothermal, with the same temperature in every part.
Yesterday, I read the Jelbring hypothesis again. As I was reading it, I wondered by what logic Jelbring had come to the conclusion that the atmosphere would not be isothermal. I noticed the following sentence in Section 2.2 C (emphasis mine):
The energy content in the model atmosphere is fixed and constant since no energy can enter or leave the closed space. Nature will redistribute the contained atmospheric energy (using both convective and radiative processes) until each molecule, in an average sense, will have the same total energy. In this situation the atmosphere has reached energetic equilibrium.
He goes on to describe the atmosphere in that situation as taking up the dry adiabatic lapse rate temperature profile, warm on the bottom, cold on top. I had to laugh. Jelbring made the exact same dang mistake I made. He thinks total energy evenly distributed per molecule is the final state of energetic equilibrium, whereas the equilibrium state is when the energy is evenly distributed per volume and not per molecule. This is the isothermal state. In Jelbrings thought experiment, contrary to what he claims, the entire atmosphere of the planet would end up at the same temperature.
In any case, there’s another way to show that the Jelbring hypothesis violates conservation of energy. Again it is a proof by contradiction, and it is the same argument that I presented to Jelbring years ago. At that time, I couldn’t say why his “gravito-thermal” hypothesis didn’t work … but I knew that it couldn’t work. Now, I can see why, for the reasons adduced above. In addition, in his thread Dr. Brown independently used the same argument in his discussion of the Jelbring hypothesis. The proof by contradiction goes like this:
Suppose Jelbring is right, and the temperature in the atmosphere inside the shell is warmer at the bottom and cooler at the top. Then the people living in the stygian darkness inside that impervious shell could use that temperature difference to drive a heat engine. Power from the heat engine could light up the dark, and provide electricity for cities and farms. The good news for perpetual motion fans is that as fast as the operation of the heat engine would warm the upper atmosphere and cool the lower atmosphere, gravity would re-arrange the molecules once again so the prior temperature profile would be restored, warm on the bottom and cold on the top, and the machine would produce light for the good citizens of Stygia … forever.
As this is a clear violation of conservation of energy, the proof by contradiction that the Jelbring hypothesis violates the conservation of energy is complete.
Let me close by giving my elevator speech about the Jelbring hypothesis. Hans vigorously argues that no such speech is possible, saying
There certainly are no “Elevator version” of my paper which is based on first principal physics. It means that what I have written is either true or false. There is nothing inbetween.
Another “gravito-thermal” theorist, Ned Nikolov, says the same thing:
About the ‘elevator speech’ – that was given in our first paper! However, you apparently did not get it. So, it will take far more explanation to convey the basic idea, which we will try to do in Part 2 of our reply.
I don’t have an elevator speech for the Nikolov & Zeller theory (here, rebuttal here) yet, because I can’t understand it. My elevator speech for the Jelbring hypothesis, however, goes like this:
• If left undisturbed in a gravity field, a tall container of air will stratify vertically, with the coolest air at the top and the warmest air at the bottom.
• This also is happening with the Earth’s atmosphere.
• Since the top of the atmosphere cannot be below a certain temperature, and the lower atmosphere must be a certain amount warmer than the upper, this warms the lower atmosphere and thus the planetary surface to a much higher temperature than it would be in the absence of the atmosphere.
• This is the cause of what we erroneously refer to as the “greenhouse effect”
Now, was that so hard? It may not be the best, I’m happy to have someone improve on it, but it covers all the main points. The claim that “gravito-thermal” theories are too complex for a simple “elevator speech” explanation doesn’t hold water.
But you can see why such an elevator speech is like garlic to a vampire, it is anathema to the “gravito-thermal” theorists—it makes spotting their mistakes far too easy.
w.
Joe Born says:
January 20, 2012 at 12:35 pm
Joe, all considerations about the mechanism go nowhere. Consider the outcome. If it’s true that gravity can separate molecules by temperature, then we can pull energy out of tall insulated cylinders of air, Jelbring is right and we never have to worry about energy again.
Do you believe that we can do that? Really?
w.
Bart says:
January 20, 2012 at 3:35 pm
Thanks, Bart. You seem to have momentarily forgotten that in the Jelbring thought experiment, the planet and atmosphere are surrounded by an impermeable perfectly insulating sphere which doesn’t allow any energy in or out. It is a sealed-off portion of the universe, with a planet and an atmosphere.
It is in that world, which I have nicknamed “Stygia” for the stygian blackness inside the shell, than Hans says the atmosphere will be thermally stratified by gravity.
Since (as you say above) the inhabitants of Stygia could pull work out of such a temperature difference, then they could use it to light up their eternal darkness.
As you know, that would be a perpetual motion machine, so Jelbring’s hypothesis is falsified.
w.
Please can anyone point out any logical flaws in the following reasoning:
Consider two systems, one gravitating and one not. Each is surrounded by a perfectly insulating, perfectly reflective shell and contains a spherical, homogeneous, black-body planet with a homogeneous, transparent atmosphere.
In both cases the surface of the planet radiates energy which is reflected completely back onto the planet’s surface by the shell, yielding no net radiative transfer from the planet. There exists a boundary condition at the surface of the planet such that the planet’s temperature and the atmospheric temperature are the same.
In the non-gravitating case, any temperature differences in the atmosphere will be eliminated by conduction. Thus the atmosphere is a uniform temperature that matches the surface temperature of the planet and has uniform pressure and density at all altitudes.
Now add gravity to this system. By doing so we have added a considerable amount of total energy to the system in the form of gravitational potential energy. The mass distribution of the atmosphere changes to ensure that at each altitude the pressure is equal to the pressure exerted by the atmosphere above it. The compression of the atmosphere at lower altitudes causes it to heat up, as per the ideal gas law. We now have pressure, density and temperature gradients decreasing with altitude as we are all familiar with from Earth.
Now we must return to our boundary condition: the planet’s surface must be the same temperature as the atmospheric temperature at the boundary. The temperature of the atmosphere at the surface has risen as it was heated by compression. There is now a temperature difference between the planet’s surface and the surface layer of the atmosphere. Thus energy will flow from the hotter body to the cooler, from the atmosphere to the planet until our boundary condition is restored.
The gravitating planet’s surface is now hotter than the non-gravitating planet. The GPE released by redistributing the mass of the atmosphere was converted to thermal energy. Now we turn to our other boundary condition: the insulating, reflecting shell that makes this a closed system. No energy can leave the system and a gravitating system has greater total energy than a non-gravitating one. Since the atmosphere is transparent the increased radiation of the hotter black-body planet is perfectly reflected back by the shell to the planet. The gravitating system has higher total energy and higher planet temperature. The increase in total energy is proportional to the GPE of the atmosphere which is proportional the the mass of the atmosphere. More massive atmosphere yields higher temperatures.
A non-gravitating system is isothermal, a gravitating one is not.
So, unless someone wants to point out the flaw in the logic, we now have a stable system containing a temperature gradient that should persist indefinitely.
Now let’s turn to the perpetual motion issue with the heat engine. I think we all agree that the heat engine will operate (do work) as there is a temperature gradient. However in doing work to produce light, the heat engine must reduce the temperature gradient that makes it operate since this is a closed system. If thermal energy is converted to light, there’s less thermal energy to go round. Stygia is now lit but colder. The surface temperature boundary condition ensures that the planet cools.
Let’s suppose that the heat engine is a real one and not 100% efficient, it gives off heat. This will heat the atmosphere locally and the atmosphere will radiate the heat. Since the atmosphere is transparent and the reflective shell is perfect, the only place for this radiated heat to be absorbed is by the planet (which is now cooler thanks to the heat engine).
Stygia is lit but colder. With the perfectly reflecting shell the light will bounce around the system indefinitely until it is absorbed. The only absorber is the planet. As the planet absorbs the light, the light’s energy is converted back to heat and the planet warms. As the planet warms, so does the surface layer of the atmosphere and the thermal gradient in the atmosphere is increased once more.
We’ve ended up with a system where energy is converted by the heat engine to light and local heating of the atmosphere depleting the temperature gradient available to the heat engine. The heat engine would theoretically convert all energy in the system to light making the system uniformly cold and the heat engine stop working. However the local heating of the atmosphere and the energy in the light is reabsorbed by the planet as there is nowhere else in the closed system for it to go. This heats the planet and restores the temperature gradient which means the heat engine keeps running.
The entropy in the system can only increase OR STAY THE SAME. The theoretically perfect, lossless system described can operate because the specification of perfect losslessness means the entropy change for all the steps is zero. Thermodynamic laws are NOT violated.
I think where the column of air arguments are failing is that they do not account for the redistribution of energy in a perfect, closed system. Taking energy from the column of air must either deplete the energy in the air column or it must be replenished by taking energy from the rest of the system. Taking the energy from the rest of the system depletes the thermal gradient that is being used to generate the energy thus energy generation will eventually stop. Still no free, limitless energy for everyone.
Downdraft says:
January 20, 2012 at 3:37 pm
Forget about the mechanism, Downdraft, and start with what makes sense.
Suppose Jelbring were right and that a tall insulated cylinder of air would thermally stratify by gravity, with warm air at the bottom and cold air at the top. If so, we could use that temperature difference to do work.
Of course, the operation of our heat engine would cool the warm bottom air inside the tall insulated cylinder, and warm the cool air at the top. That’s what heat engines do. But Jelbring says no worries, gravity will separate the warm air and cold air again so the heat engine can continue running indefinitely.
Now Downdraft, be honest with me here … do you really think we can pull work forever out of a tall, perfectly insulated cylinder of air?
I didn’t think so. Which means that the air in the cylinder must be isothermal, and that Jelbring’s hypothesis cannot be right.
If you start thinking about mechanisms from there, from what you know to make sense, you’ll have more chance of sussing it out.
All the best.
w.
I don’t think Dr Brown appreciates the tiny, but significant, exchanges of kinetic for gravitational potential energy between his layers. Additionally, he treats these layers as being much more dense than they are. Even at the surface, 99.9% of a volume of air is vacuum. A conduction model doesn’t work well here, I think.
Let’s assume the atmosphere is made from mostly empty layers (it is mostly vacuum, afterall) that are 10^-5cm think. This is about the average distance a molecule in air travels before colliding with another molecule. Also assume a molecule traveling about 500 m/s. This is also the mean speed of an air molecule at the surface.
It has kinetic energy (ignoring rotational energy) of an N2 molecule then is
1/2 * 28 * 1.66 x 10^-27 kg * (500 m/s)^2 == 5.81×10^-21 J.
A molecule passing through the mostly empty space from the bottom of a layer to the top of the layer has kinetic energy converted to gravitational potential energy so that
28 * 1.66 x 10^-27 kg * (9.8 m/(s^2)) * 10^-5 cm = 4.56×10^-32 J of kinetic energy is lost (or gained if moving down from a higher layer).
This seems small but it is significant.
Imagine one molecule at the bottom of the atmosphere made energetic by contact with the surface of the Earth hitting another molecule 10^-5cm above it and so on through the layers as the atmosphere tries to reach equilibrium. Each time a lower molecule loses some kinetic energy to gravitational potential energy as it travels across the current layer before it strikes a molecule in the next layer above it. At 10km, 4.56×10^-21 J has been converted to gravitational potential energy — a significant amount when compared with the 5.81×10^-21 J at the start. The reverse is true, too. Molecules propelled upward are matched by molecules falling downward and each downward falling molecule gains 4.56×10^-32 J of kinetic energy as it falls through a 10^-5cm layer.
These differences in kinetic energy in each layer must translate into different temperatures in each layer.
Of course linear kinetic energy in the direction normal the surface of the Earth isn’t the only energy in a N2 molecule. There is kinetic energy parallel to the surface. There is also rotational energy, too. A thermometer will integrate all these to determine a temperature. This is one reason why the temperature of the atmosphere at 10km is higher than what is predicted. Still, much energy is in the form of vertical kinetic energy and this is converted from kinetic to gravitational as molecules move upwardly. The absence of this kinetic energy must be reflected in a lower measured temperature.
Looks like the very basics of “science” are still not settled 😉
Lets forget the gravity for a moment. Claim of many of us is, that the bulk atmosphere itself (N2+O2) is from a considerable, if not full part, responsible for warmer average than Moon (and much less diurnal variations, which is at least so important).
Earth day is much cooler than on the Moon. We have clouds, water surface evaporation, cloud/snow albedo and air thermals cooling our day. Without bulk atmosphere, none of it should work. The main “greenhouse gas” – water vapor – in its various forms causes net daytime cooling.
Earth night is much warmer than on the Moon, on average by tremendous 240° C. Temperature in 2m altitude, measured by thermometer, is equal to number of molecular collisions per given area per given time unit, and their speed of movement. Without bulk atmosphere, there are no molecular collisions to be measured. Mere presence of “greenhouse gases” is not sufficient. Mars black body temperature and actual temperature is the same – 310K – even there is 6,000 ppm of CO2 in its atmosphere. However, this is already 95% of the whole atmosphere, it means it is very thin. There is nothing, which should hold the warmth from the surface, heated by sunlight (or long-wave IR coming from that CO2, if we believe so). How thick would be the back radiation arrow in Kiehl-Trenberth diagram for Mars? How many Watts would be assigned to it? Net result is still ZERO. Still 310K.
The ultimate point of all that is to say, that the claim “greenhouse gases raise surface temperature by 33K” is totally wrong; 33K is wrong and the whole attribution to “GHG” only is wrong as well.
Jordan says:
January 20, 2012 at 3:48 pm
Thanks, Jordan. You and several others have said that practical problems in utilizing the heat to do work invalidate the proof. They do not. The existence of the temperature difference means we can extract work, whether or not we’ve invented a way to do so yet.
In fact, there is a lovely plan upthread to use two columns of different gases. As they have a different specific heat Cp, at every level but one they will be at different temperatures. This gets past the question of the distance between the ends of the thermocouples.
Also, your “rate of transfer” argument above doesn’t work. All I have to do is turn off the heat engine for a little while. Then gravity (says Jelbring) would re-sort the molecules by temperature. Tomorrow, I turn on my heat engine again. Perpetual motion.
w.
KevinK says:
January 20, 2012 at 4:04 pm
Dang, bro’, with all due respect, I didn’t say you were.
w.
Bart says:
January 20, 2012 at 4:23 pm
I don’t understand. Are you claiming that the temperature in a tall insulated cylinder of air will never reach equilibrium?
w.
Willis Eschenbach says:
January 20, 2012 at 11:48 pm
Are you certain? Suppose the engine were a Stirling engine. A Stirling engine could do no work as the gas inside the engine would stratify just as the gas in the insulated cylinder.
Having read Willis’ comments, and Jellbring’s comments about Willis’ comments, I am quite surprised. How on earth is it possible that Jellbring has such a weak grasp of physics? Yes, his paper was peer-reviewed, which is what is just so very surprising! And as Willis points out, this is not an ad hominem attack, I have read his comments and come to the conclusion he has some very basic concepts wrong. He says:
I have already pointed out that a “perpetuum mobile” is possible to construct in our real atmosphere since the cold air at the top of Mount Everest for sure is colder than air at the surface.
Yet he does not understand what is obviously wrong with that statement. That’s not a perpetual motion machine, that’s just another energy source like any other that we have today. The energy is derived from outside sources (the sun), which in turn causes the temperature gradient, which in turn allows you to extract work.
Willis is correct, if gravity were to provide a temperature gradient, then you could create a perpetual motion machine, you could do work from that gradient, which in theory would reduce the temperature gradient, but of course the theory states that gravity would restore the gradient once more (that’s the Jellbring theory!), thus enabling the perpetual extraction of work! This is energy creation from nothing other than a force (gravity), hence impossible.
And of course we have other commenters like fred berple pointing out that temperature gradients exist in the real world. How utterly irrelevant.
Meanwhile, tallbloke keeps making comments that exhibit a very weak understanding of basic physics, not even using the terminology correctly for basic concepts such as energy, work, and temperature.
I just don’t understand how people who clearly have a weak grasp of physics to be so utterly and totally oblivious to the fact that they have a weak grasp of physics.
Dewitt Payne: “The entropy of an isothermal atmosphere is higher than for an atmosphere with an adiabatic lapse rate.”
You believe that. Willis believes that. Robert Brown believes that. I believe that. But our believing it doesn’t make it true. Nor does Willis’s heat-engine “proof,” because it begs the question. I.e., by assuming that the heat engine will work, he’s assuming that the adiabatic-lapse-rate atmosphere’s entropy is lower than an isothermal one, which, ultimately, is what he set out to prove.
The only proof would be to show that the number of states that fall within the “isothermal” definition vastly exceeds the number that fall within the adiabatic-lapse-rate definition. And, of course, your response would be that you have indeed seen such proofs.
But have you really? Here I’ll help you The Coombes and Laue paper discussed at Tallbloke’s Talkshop’ Loshmidt thread, http://tallbloke.wordpress.com/2012/01/04/the-loschmidt-gravito-thermal-effect-old-controversy-new-relevance/ , does indeed purport to provide a proof that the maximum-entropy state is isothermal even in the presence of gravity.
However, the Velasco et al. paper also discussed at that site demonstrates that Coombes & Laue’s conclusion is only an approximation asymptotically approached as the number of molecules gets large; for any finite number of molecules, the maximum-entropy state has a non-zero lapse rate given implicitly (for a monatomic ideal gas) by the (altitude-dependent) expression I set forth above.
Does the mean that Helbring is right? No. The lapse rate at which Velasco et al. arrive is much less than the adiabatic lapse rate. Indeed, by most people’s standards, it is negligible for any number of molecules of which we’d take notice.
But what it does mean is that neither Willis’s nor Robert Brown’s nor your “proof” is valid; none of them does anything more than state a conclusion. (The same is true of that Science of Doom discussion the summer before last.) And, technically, that conclusion is wrong.
Or, at least it’s wrong if Velasco et al. are right. Now, I’m no physicist, and I found Velasco et al. (and the Román et al. paper on which it depends) tough sledding. But the relationship they derive, namely (3E/(5N-2))(1-mgz/E) for the mean single-molecule kinetic energy, where N is the number of molecules, E is total system energy, m is molecular mass, g is the acceleration of gravity, and z is altitude, is clearly correct for N = 1, unlike the isothermal conclusion everyone thinks he remembers.
Willis, you said:
“It is in that world, which I have nicknamed “Stygia” for the stygian blackness inside the shell, than Hans says the atmosphere will be thermally stratified by gravity.”
This is correct.
“Since (as you say above) the inhabitants of Stygia could pull work out of such a temperature difference, then they could use it to light up their eternal darkness.”
Briefly. Extracting heat energy from the atmosphere would result in net cooling.
>As you know, that would be a perpetual motion machine, so Jelbring’s hypothesis is falsified.
Incorrect. It is falsified but not for the reason you state (that it will not re-stratify). If Jelbring says that the atmosphere will re-sort the temperature into a stratified one, he is correct. If he does not mention that the system will have cooled (net) he is missing something. If he thinks gravity will add heat to the atmosphere he is incorrect. The moment he says that, he has created a perpetual motion machine.
Re-stratification does not mean ‘re-heating’. There is no energy input. The energy extraction from the heat engine will work. The atmosphere will indeed re-stratify. It is not re-heated while doing so; no net gain in energy from gravity, there being no mechanism for it. Ergo your clear statement that re-stratification = perpetual motion is incorrect.
Suppose you employed a 100% efficient heat engine in a stratified atmosphere. Wherever it was placed, it would cool the system. Overall, the system would cool and eventually have no heat left. The fact that a less efficient heat engine would take longer, and involve re-stratification, does not change the physics: work can be done using the temperature difference. The system will wind down. How is that a perpetual motion machine? It is the extraction of energy from a heat battery. Nothing more.
If Jelbring says it will continue to generate energy indefinitely, that is a contradiction of the Law of Conservation. If you say that the atmosphere will not re-stratify, that is a contradiction of the Universal Gas Law. You are correct to say his claim creates a perpetual motion machine IF he states that the upper gas will gain energy from gravity as it drops lower. It will warm, but not to the previous temperature.
A ‘gas packet’ will increase in temperature when it goes down, but temperature is not a measure of energy. Energy is thermal mass times temperature. If you cram more mass into a unit volume, the temperature rises because there is more mass in there not because each unit making up that mass, on its own, gained energy. “Temperature” is a measure of how many bangings there are into the thermocouple. You can’t measure energy with a thermocouple.
It is akin to heating a spring v.s. compressing a spring. Both are reservoirs of energy. You cannot tell how much energy is in the spring by measuring the temperature only. Stacking springs vertically in a gravitational field will compress the bottom one the most and it will have more energy that the top ones, even if they are all the same temperature. You can extract work by decompressing the bottom springs to the same length as the top ones, but it reduces the total stored energy. Imperfect analogy but the point needs to be made – extracting energy will wind down the system. Gravity will not make it up.
jae says:
January 20, 2012 at 6:53 pm
First, I fear that what happens on other planets is of little interest to me. The planets are so different from the Earth, and we understand our own climate so poorly even though we live in it, that what is happening on Jupiter or Venus can provide little insight, falsification, or support for theories about the Earth.
Second, I’m still not clear (other than planetoids) what evidence you say exists in the “papers”.
Third, I don’t know what “papers” other than Huffman you are discussing. There is no evidence in Jelbring’s paper that I know of.
Fourth, Joel pointed out above that the planetary “evidence” in N&Z is a fit of an equation with many free parameters, viz:
I am not impressed by a fit with four visible free parameters plus selection parameters. That has no evidentiary value at all.
As to whether I “ignore” the question of the planets, no, I don’t. I’m just not impressed by arguments about what’s happening on Venus. Down at the bottom of the Venusian atmosphere, CO2 is neither a gas nor a liquid, but a supercritical liquid. If you think that has some relevance to the Earth’s climate, I don’t see it.
Finally, you ask why I “do not confront it/explain your position. Is it confirmation bias? Old age? Ego? What, Willis?”
I am under no obligation to either confront something, or explain why I have not done so, merely because you think it is important. Look at this thread. How many people have posted how many different theories and claims and explanations and evidence and insights and all the rest?
Some of it I reply to. Some I don’t. Some I follow up on. Some I don’t. Time is short, the road is long.
A fit of an equation with 4 free parameters to a bunch of carefully selected planetary data is not something I follow up on.
And if I do or don’t follow up on it, I do not owe you an explanation. In this case I didn’t discuss it, because, frankly, it is meaningless.
I am not amused by your accusations of confirmation bias and the rest. I advise you to leave them off the next post. Bear in mind that it may not be answered, for the reasons listed above. I have answered you this time in part so you will know why I may not answer you in the future.
w.
I have finally found time to re-run my empirical experiment into the N&Z hypothesis. This time I followed “Joules Verne’s” suggestion and regulated the pressure in the test chambers. I used an air bladder (hot water bottle) and weights (bricks) to maintain constant pressure in the high pressure chamber.
Due to thunderstorms and rain I was unable to use sunlight as a long wave source and had to use a flood lamp (too much IR). However the results were just as before. The chamber with the higher pressure always rises to a higher temperature when illuminated. I should point out that illumination is only started when the chambers have been pressurised and allowed to equalise temperatures.
With just 6 house bricks on the air bladder, chamber temperature differentials of over 4 degrees were observable. Again I reiterate that low and high pressure chambers were allowed to equalise in temperature before illumination.
When the weather clears I will re run the tests with sunlight instead of a floodlamp. In the meantime I am confident in claiming that Nicolov and Zeller are correct and that Willis and Joel are entirely wrong. Again.
scf says:
January 21, 2012 at 1:37 am
How can you be certain work could be done from that gradient? Gravity may prevent that.
The working substance in a heat engine, after doing work, must move to the cold sink. The cold sink in this hypothetical perpetual motion machine is high above the heat source. Energy must be used to raise it. I suspect the energy required to do that is equal to the energy that appears can be extracted from the gradient.
jae says:
January 20, 2012 at 8:22 pm
It was a suggestion offered in friendship, in support of you getting some traction, jae. No reason to be upset.
w.
Willis Eschenbach: “If it’s true that gravity can separate molecules by temperature, then we can pull energy out of tall insulated cylinders of air.”
Without realizing it, you’ve begged the question. “We can pull energy out of tall insulated cylinders of air” in which a non-zero lapse rate prevails, but only if that air is not at maximum entropy–and you have not shown that maximum entropy necessarily requires a zero lapse rate.
You think you know it’s true. And, as I mentioned above to DeWitt Payne, people like Robert Brown think they’ve proved it. But the only real way to prove it is to show that the number of states that exhibit isothermality greatly exceeds the number thereof that exhibit a non-zero lapse rate. And, to this non-physicist at least, the Velasco et al. paper, together with the Román et al. paper on which it relies, shows that it does not.
Now, as I mentioned above to DeWitt Payne, that doesn’t mean that Jelbring is right; in fact, it shows he’s wrong. But it also shows you haven’t proved he’s wrong.
Willis Eschenbach says:
January 20, 2012 at 11:41 pm
DeWitt Payne says:
January 20, 2012 at 9:59 am
Hans Jellbring,
“Any surface radiation power exceeding 100 W/m^2 is bull regardless if it is from equatorial, midlatitude or polar regions during days or night. Just show how this fantasy power radiation changes between day and night in polar regions as an exsample.”
Here’s a plot of upwelling IR radiation measured over 24 hours at Desert Rock, NV by a SURFRAD station there. It looks to be more than 100W/m² to me. Note that the time axis is UTC. Desert Rock is -8 hours from UTC so local noon would be 2000 on the time axis.
There are seven SURFRAD stations in the US. You can access the data here.
People, please pay attention to this interchange. Hans Jelbring asserted categorically that “Any surface radiation power exceeding 100 W/m^2 is bull.”
In response, DeWitt posted up an actual measurement from a surfrad station. It shows a 24 hour plot. The MEASURED, OBSERVED surface radiation swings between 300 (night) and 400 (day) watts per square metre
———————-
Here are all the radiation flows (In and out) for Table Mountain Co. SURFRAD station for the 24 hour period of Nov, 29, 2009. (I did this more than a year ago so that is why the date) .
http://img140.imageshack.us/img140/4109/tablemountainall.png
http://img12.imageshack.us/img12/3225/tablemountainnets.png
How you can dismiss the atmospheres of the other planets I find incredible. They all obey the same laws of physics. It is just that you GHGers are wedded to the claims that somehow a trace gas drives temperature.
You also fail to accept that compressing a gas will increase its kinetic energy which results in a higher temperature. That is what adiabatic means.
How about this for an add on to the compression theory. Convecting gas in the atmosphere will cool as it rises at the Saturated Adiabatic Lapse Rate, around 5C/Km rise, and form clouds at height. This rising air causes air at height to descend but this air is dry, having formed clouds, and warms at the Dry adiabatic Lapse Rate, 9.8C/KM, so will arrive back at the surface warmer than when it convected. (Like a vertically looped Chinook Wind). This warms the surface above the theoretical BB temperature not the GHG theory that violates the laws of thermodynamics.
I wonder if you can be bothered to get down this far in the reply list?
Willis Eschenbach says:
January 21, 2012 at 12:33 am
“You seem to have momentarily forgotten that in the Jelbring thought experiment, the planet and atmosphere are surrounded by an impermeable perfectly insulating sphere which doesn’t allow any energy in or out.”
Well, you can’t forget what you never knew. To be truthful, I haven’t looked at the Jelbring hypothesis much – it sounded fishy to me from the get-go. The setup you describe, and which I have now looked at the paper to see for myself, is IMHO very contrived. If you take away the insulation, and there’s no influx, then the atmosphere will freeze and even the usual caveats about the ideal gas law go out the window.
I have been looking at the standard greenhouse theory and trying to find loopholes in its physical basis. What I have found is that it depends very much on an assertion that a derived formula (SB) intended for matter in thermodynamic equilibrium holds even in situations which are far from that condition. This is a loophole.
In researching the topic, I have found relatively narrow experimental results existing for non-equilibrium radiative behavior, and there is evidently quite a bit of current research going on into the very question of how it works. To borrow a phrase, the science is not settled. It appears plausible to me that rapid conductance of heat could significantly reduce thermal radiation, as the heat gets conducted away before the particles can radiate away their energy.
I have also found that the standard explanation that IR emitters heat the surface has a mirror image explanation with the same resulting steady state behavior, but with very different non-equilibrium dynamics. Looking at things from this perspective gives an actual reason for why an equilibrium condition in an emitting atmosphere is even approached, and solves a couple of other dilemmas which I have pointed out now:
1) How did the Earth ever heat up enough to unfreeze the water vapor that presumably contributes most of the “greenhouse” warming to heat the planet to its present state?
2) Why is there a gap in IR emitter bands at TOA when the IR radiation broadcasted back to the Earth should simply re-radiate back out?
To those, I will add a third I only just started thinking about. We all know by now that CO2 and CH4 levels increase after emergence from an ice age, and not before. Why? Well, if IR emitters actually make things colder, then recovery should proceed after enough of them have been sequestered by a change of state, and the warming which releases them again should set into motion a new decline. And, that is what we see.
Willis Eschenbach says:
January 21, 2012 at 1:21 am
“Are you claiming that the temperature in a tall insulated cylinder of air will never reach equilibrium?”
The SB loophole allows this to be a physically realizable possibility.
jae says: “you did not really read his stuff and pay attention to the DATA (aka, EMPIRICAL EVIDENCE!). Same with the other papers. It seems that the atmospheres of other planetoids that have atmospheres have temperatures that are not correlated in any way to the amounts or types of GHGs present in those atmospheres. ”
I don’t understand how this is supposed to be evidence. You have a small sample set. You have a million other variables with each of those planets, You might as well be claiming that the colours of those planets are the cause of the unknown temperature differentials, rather than the size.
And, in another forehead slapping moment, I suddenly realized I do not even have to argue that SB violation is possible. That argument is tailored for a fictitious planet with a non-radiating atmosphere, which can never actually exist. All that is needed is to establish that there is a tendency for heat to accumulate in an atmosphere (which there trivially is).
As the heat rises, the emitters in the atmosphere will draw more and more of it off, increasing the allowable temperature rise of the surface to remain in radiative equilibrium according to SB. The rising temperature stops when the emitters have taken enough out such that the surface temperature induced radiation balances with the incoming flux from the Sun and the backradiation from the emitters.
Under this dynamic if, for example, you had no IR emitters, but emitters only say in the visible part of the spectrum, the temperature would climb until those emitters can establish an equilibrium. The total emissions still balance on the way up because the energy radiated by those emitters is orders of magnitude more energetic than IR emitters.
So, in this way, a planet’s equilibrium temperature is set by the minimum threshold at which available emitters can balance all the fluxes.
And, adding more IR emitters to the Earth’s atmosphere will tend to cool, rather than heat, it.
So, your temperature rises to the SB limit. The tails of the first major emitter back-radiate, which allows your temperature to rise more within the SB limit. So, you get more back-radiation, and your allowable temperature rises some more. And, so on, until you have reached the point where your surface is radiating significantly into the main lobe of the emitter, and you reach an equilibrium.
That’s it!
Thanks for pointing out my errors A Physicist.