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.
Robany says:
January 20, 2012 at 9:20 am
Robany, you are right about the real atmosphere. We are talking about the atmosphere in Stygia, the planet described in Hans Jelbring’s thought experiment. Our real atmosphere is not at equilibrium so (as you note) it has a temperature gradient. Take away all external sources of energy, as in Jelbring’s thought experiment, and at equilibrium it will be isothermal.
w.
Willis says at 1/20 2:19pm:
“I say the column will be isothermal, meaning all at the same temperature top to bottom.”
This violates the 2nd law, KE + PE = constant at each h in the presence of an inexplicable gravity field in the gaseous cv of interest, namely an adiabatic (no gain or loss of heat from CV) GHG-free air column.
Willis’ statement, I believe, derives from the top post which says in part:
“On average, just as many molecules move up, with exactly the same velocity/kinetic energy profile, as move down…”
This too is a violation of 2nd law conservation of energy PE + KE = constant since in my view: each molecule moving up in the presence of an inexplicable gravity field cannot have exactly the same velocity/kinetic energy as those moving down in presence of gravity field PE (= ngh) since KE changes with h for energy constant to stay the same, therefore KE must change. Only outlaws need run from this sheriff.
The kinetic energy will vary with h thus P*V will vary and since V is constant in the cv, P must vary. Thus ideal gas thru PV=nRT must vary the temperature so the cv of interest is a non-isothermal air column. No work can come out of it b/c air column’s one macro object is in equilibrium given all 3 laws so we do not have free energy forever (Willis says at 1/20 3:18pm).
Bart says:
January 19, 2012 at 11:28 pm
Unfortunately, I find that my argument regarding non-constancy of the solution is lacking. The modified and adjusted zeroth order Bessel function of the second kind is an eigenfunction, but so is the modified and adjusted zeroth order Bessel function of the first kind, and these can be independently weighted with a time dependent amplitude function. I believe, offhand, that these may be added in such a way as to produce a constant. Therefore, a result which thus converges to a constant is possible. I think it is not physically realizable, but I haven’t <i<proven it yet.
So, I must come up with another argument justifying the approach to 0K at infinity. When I resolve this, one way or the other, you all will be the first to know.
It seems self-evident, though. Using the Earth as an example, with the standard greenhouse hypothesis, it otherwise never would get warm enough to produce water vapor to initiate the greenhouse warming. This is an unstable situation, because the Earth always has the capability to nosedive back to -18C, and become a bleak and barren ice planet. In Nature, whatever can eventually does. That which is not forbidden is compulsory.
Anyway, it’s back to the books for proof. Will keep you all posted.
Willis Eschenbach says:
January 19, 2012 at 11:48 pm
<So in the Jelbring thought experiment you are saying the atmosphere never, ever achieves thermal equilibrium? If not … why can’t we pull work out of it with a thermocouple?"
You can. Remember, there is an outside energy source which is constantly adding energy to the system. Is the Earth at equilibrium? How do windmills work?
Joe Born says:
January 20, 2012 at 5:30 am
“An atmosphere of the type you describe would acquire energy from its source only when its temperature is less than the surface’s.”
This is not a constraint. The surface can get hotter at the same time. Stefan-Boltzmann does not limit it as A) the system is not in steady state and B) even in steady state, SB only puts an upper bound on outgoing radiative energy, but not an upper bound on temperature.
Besides, constant flux from the external heating radiator is more like current than voltage. See section 2.3 here.
DeWitt Payne says:
January 20, 2012 at 12:38 pm
“You can also assert all you want about the SB equation not applying, but you have given no evidence or citation that it doesn’t.”
But, you have no evidence or citation that it does. SB is always couched in terms of steady state, or at least a quasi-steady state.
SB radiation is an outlet for energy flow, so that incoming and outflowing are equal in the steady state. When you have energy conducting outward in large volume, then the individual particles of the surface do not have to be radiating to maintain balance.
“Even if the emissivity does vary with wavelength and angle, one can still integrate the Planck equation, B(λ,T) and get the total emission.”
The Planck distribution describes the energy distribution of particles making up the surface when in thermodynamic equilibrium and unable to transition to a lower energy state through any means other than radiation.
“A molecule that was actually in orbit would indeed have very high kinetic energy relative to the molecules around it.”
We don’t consider that in calculating temperature, though. As I pointed out, satellites moving in LEO at 7500 meters per second do not radiate as though they were at 30,000K. A full treatment would need to be couched in terms of relativistic four-momentum, which is always conserved, and for which the time-like element is the energy. I don’t think we really want to get into that, here.
DeWitt Payne says:
January 20, 2012 at 9:39 am
“As pointed out above, your first crack at the capacitor example was correct.”
As I pointed out in the reply to Joe, no it isn’t.
“Even a constant current source reverts to a constant voltage source at some voltage.”
Not an ideal current source. This is like the assumption of an ideal non-radiating atmosphere. In fact, at some point, every real current source breaks down, and every real atmosphere radiates.
“Bart,Your argument begs the question.”
You are right. It does. See the top response to myself in this post. I did not recognize it because I had dismissed the other eigenfunction and thought no more of it.
Phil. says:
January 20, 2012 at 1:02 pm
“What it should say is that ‘the heat accumulates in the atmosphere until the layer of gas nearest the surface reaches the surface temperature at which point heat transfer ceases due to ΔT=0.”
The surface temperature is increasing, too. There is no limit on the temperature of the surface, only on radiated energy. If you are not at equlibirum, then you are not generally radiating at the SB limit. That which is not forbidden is compulsory.
I am still puzzling over the idea that a column of air will reach an isothermal state or not. I took Dr. Brown’s explanation as a starting point and made changes to it that reflect my view. I hope he doesn’t mind. Who would think that such a simple thought experiment would be so complex.
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 but the upper layer has a higher potential energy. 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.
In equilibrium, the density of the upper and lower layers, while not equal, cannot vary. 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. However, the molecules moving downward are accelerating, therefore increasing in kinetic energy while the ones moving upward are losing kinetic energy for potential energy. The molecules below had a higher temperature, and 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 and cooling, sure) and carry energy from the lower slice to the upper. The upper slice (lower temperature) has fewer molecules moving faster —However, at the interface, the MB distribution is equal owing to the average energy of the upward and downward flows being equal There are therefore equal molecules that move the other way at the same speeds that the molecules from the lower slice deliver (allowing for gravity). Thus, average kinetic energy is unchanged in both layers. 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 upper slice is cooler than the lower, due to the conversion of potential energy to kinetic energy as they fall. Therefore, a vertical column of air at equilibrium will be cooler at the top than the bottom.
Willis said, “I’ve not usually seen that assumption made. In general, conduction of both sensible and latent heat is not “assumed negligible” unless it is in fact negligible for the particular phenomenon under study.”
Convection and Latent are considered. I have not see conduction properly considered. CO2 impacts the conductivity of mixed gases as well as the radiant impact. That impact is considered negligible when it appears not to be. Trenberth’s latest cartoon reduced the conductive impact, (thermnals he uses for combined conductive/convective) even while increasing the surface temperature. If you have a link that addresses conductive change, I would like to see it.
“IF GRAVITY ACTUALLY SEPARATES TEMPERATURE, WE HAVE FREE ENERGY FOREVER!”
This assumes a heat engine can transfer energy from its source as efficiently as transfer of energy into its source. I do not believe this assumption has been justified where conditions at the source are not the same as conditions at the sink. .
An ideal sink assumes the same temperature as its surroundings because there is perfect heat transfer from the sink. Same for an ideal source. If the source is not ideal, the “effective” source temperature will be at lower temperature compared to its surroundings. Vice versa for a heat sink.
Consider the effect of gravity on the density of gases and the impact this can have on the ability to conduct thermal energy by conduction.
Until it is demonstrated that the physical conditions for transfer of thermal energy around the source and sink are favourable (i.e. the do not fully negate the temperature difference we are trying to exploit), the arguments in this post cannot be supported using notional heat engines.
Willis,
You said
” I offered up a proof that no possible mechanism involving a transparent, GHG-free atmosphere could raise the temperature of a planet above its theoretical Stefan-Boltzmann temperature.”
Sounded like a refutation to me, since there is nothing in the theory that requires greenhouse gases.
And you said:
“if you can’t explain it in an elevator speech, it [sic] you don’t understand it”
which sounds like an assertion that no one understands it, or did someone win the prize for a coherent elevator speech demonstrating clear understanding? If so I missed it. But in any case understanding a hypothesis that is wrong seems almost a contradiction in terms.
I have here some background on the journal in which the Jelbring paper appears. It provides some insight into the way in which peer reviewed journals validate or fail to validate what they publish.
“This assumes a heat engine can transfer energy from its source as efficiently as transfer of energy into its source”
Oops – “transfer into its sink”
PeterGeorge said, “7. Willis is right. Gravity won’t produce any temperature gradient. It does, of course, produce gradients in pressure and total energy content (as a function of temperature), but not temperature.”
Completely isolated as in your reply, true. Gravity appears to impose a low limit on the atmospheric sink temperature to the energy required for obtaining escape velocity. Gravity interactions with the moon and sun do add some tidal energy to the system. I think the escape velocity limit is what is causing the confusion. I haven’t seen it explained very well anywhere. There are a number of things about the tropopause I have not seen explained very well.
Willis wrote;
“If you are fighting basic ignorance of science, you will be deluged with ignorant people. Not much I can do but just keep putting the facts out there.”
With all due respect, I am most certainly NOT ignorant of science. With multiple Master’s Degrees in Optics and Electronics and three decades of reconciling computer predictions with actual observations I am quite familiar with all of the relevant disciplines necessary to understand the “Greenhouse Effect”.
Ironically enough, the FLAW in the GHE HYPOTHESIS is actually more of an accounting error than a science error. When the energy returns to the surface from the “GHG” you cannot ADD it to the energy arriving from the Sun to produce an alleged “energy budget”. The energy returning from the “GHG” has already travelled once through the system leaving cooling (at the previous location it departed from) in its wake. So we have sequential warming/cooling/warming/cooling…. events occurring from ONE bundle of energy that came from the Sun. So one bundle of energy from the Sun simply warms the surface multiple sequential times, since these warming events are followed by equivalent cooling events and are separated by finite time delays YOU CANNOT ADD THEM TOGETHER and get a correct result. Doing so is the equivalent of creating energy, which you must admit violates the First Law.
One of the clues to this accounting error is the use of the terms; “Net Energy Gain” and “Extra Energy” as used in the climate science community.
In the engineering community we use the existence of “extra energy” as a RED FLAG to tell us our analysis is wrong.
Engineers that routinely calculate “Net Energy Gains” either get fired or promoted into management.
Regarding why the Earth is at the average temperature it is, I have yet to hear any one explanation that makes common sense. But knowledge always expands and we will likely know why sometime. Although from a practical sense it seems to make very little difference.
But it most definitely is not the result of the GHE.
The GHE appears to cause some energy to travel through the system (bouncing as it where) between the gases and the surface all the while dissipating energy to Space via radiation. The end result is a slight delay to the energy as it travels from the Sun to the Earth through the Atmosphere to the Universe.
The “missing heat” is currently travelling as a spherical IR wavefront that is “X+d” light years away from the surface. In this equation X represents the elapsed time since the sunlight arrived (i.e. 100 years for sunlight from 1912) and d represents the slight delay from the GHE and is likely about 5 milliseconds. “d” is actually a statistical distribution which will of course have a different specific value for each photon travelling through the system. Some will bounce many times and take longer to exit, while others may not bounce at all and exit directly to space.
Just because people disagree with you does not necessarily mean they are ignorant of science, another possibility is that you are mistaken in some way. I know the GHE theory has been written down in papers and textbooks, but so was the theory that stress and spicy food
caused stomach ulcers.
Cheers, Kevin.
I cross posted this at an aerospace blog I frequent:
There are two ways of looking at the problem:
1) You can claim that the atmosphere will continually conduct heat away only until everything is at equilibrium, so that the surface is at the temperature set by the Stefan Boltzmann formula such that incoming and outgoing radiation balance. At this point, the atmosphere is at constant temperature throughout, so there are no more heat flows to disrupt the radiative equilibrium.
The problem with this point of view is that it is a circular argument. It iassumes a priori that equilibrium will be established, therefore the Stefan Boltzmann relationship will hold.
2) Another, equally plausible, scenario is that the system is unstable, such that equilibrium is never attained, even asymptotically. Then, the Stefan Boltzmann relationship does not hold, and there is no limit to surface temperature.
The temperature profile of the atmosphere due to the surface/atmosphere conductance has to satisfy the heat equation. Solutions of the heat equation exist for both of these alternatives, as I have had to acknowledge in my lastest posting here. But, the runaway scenario #2 is more satisfying from a stability viewpoint. If scenario #1 is the case then, since water freezes at the non-atmospheric equilibirum temperature of the Earth, a question arises as to how the effect ever got started, and there remains a possibility of slipping back to that lower energy equilibrium state.
And, if you want to know the perils of dismissing the possibility of transition to a lower energy state from a quasi-stable higher energy state… Well, the denizens of this site know where to look.
I am sifting through the problem to try to find some requirement which will decide the question one way or the other. When I find it, I will let you know. Other inputs which would contribute to that search are welcome, but baseless assertions, based on the standard way most people think things should be, are not. As of right now, mostly what I have gotten are baseless assertions that SB must hold regardless of anything else going on, and that argument has no foundation.
“If W=FD and F = mg then W can be done by heated air rising IF volume changes. ”
Agreed. There is no denying that hot air heated by blackbody radiation near the earth’s surface gains energy, the gas expands as it heats up and rises. As it rises it cools loses energy and the molecules have higher potential energy because they are higher up the gravity field. In essence, work done by the Sun (radiative energy) has heated the Earth and in turn heated the air. The Work is added by the SUN not gravity. Another transformation happens when the Suns radiative energy causes warmth and water to evaporate however this energy gets stored in another form of potential energy or properly described as “latent heat” – later on when water condenses this latent heat is released.
The point is that it is not “gravity” which is actually doing any of the Work or creating any energy or any heat. It is just a passive bystander. For sure as molecules move up and down in a gravitational field they gain and lose kinetic energy in exchange for potential energy but there is no Work or net energy being added by gravity itself to the system as a whole. Gravity plays a strong influencing role on atmospheric properties and how the atmosphere behaves but it does not create or add net heat to the system. External sources of Heat and Energy come from things like meteor impacts, cosmic rays, solar wind, radioactive decay, the Sun and chemical reactions.
When you drive your car or turn up the heat in your home or have a meal or pretty much anything (like breathing) then you are using up stored energy from our Sun. The Sun’s energy has been stored by plants and the main storage mechanism is to create Carbon from CO2 (that is how plants grow – by stealing Carbon from the air). Animals consume Carbon by oxidizing it with Oxygen and releasing CO2. When you burn fossil fuels then you are burning carbon energy that was stored by plants using energy from the Sun. When you use electricity then it comes from the Sun also. Even Wind Power and Hydro is all from the Sun while tidal power would be mostly Moon and Sun. Hydro power simply comes from the Sun’s energy heating water that rises and then eventually cools and condenses and precipitates at altitude on some mountain. Even in the case of Hydro power it is not gravity that provides the source of energy.
When Sisyphus pushes his boulder up the hill it would be the energy from the lunch he ate that creates the potential energy of the boulder that is released when it falls back down – gravity has not done anything.
For most of us the Sun is the source for everything including the heat engine that drives our atmosphere. There are some life forms that seem to work from heat of radioactive decay or heat left over from when the Earth formed (Sulphur based?) but the majority of life forms seem to be Carbon based.
Downdraft says:
January 20, 2012 at 3:37 pm
“I am still puzzling over the idea that a column of air will reach an isothermal state or not.”
It will, but if and only if equilibrium is established. So, it becomes a circular argument.
Phil;
That is a totally unrealistic surface temperature as it assumes the dark-side of the planet is at absolute zero, which is a totally unrealistic case and far from what is observed, it isn’t even realistic for the moon which has a 14-day ‘night’ and no atmosphere!>>>
EXACTLY!
The question then becomes:
WHY?
We cannot answer “why?” unless we know what the theoretical starting point is. Beginning with a theoretical starting point of 253K which can only be achieved by a uniform insolation is wrong, wrong, wrong.
How is it that everyone wants to use SB Law to calculate a theoretical equilibrium surface temperature, and when I show that the theoretical surface temperature calculated by averaging P produces a false number, everyone jumps up and says:
“well your theoretical number cannot be correct because when we look at practicaly measured instances like the moon, we don’t get anything like your theoretical number”.
AND THAT IS THE POINT!!!
The moon doesn’t reach that theoretical number because even though it doesn’t have an atmosphere, it still has:
a) heat capacity
b) conduction
so those factors tend to make the temperature more uniform even given a 14 day night. It is the exact same discussion as before. What are the factors that redistribute energy on the moon, and by how much for each, and how does that affect the measured “average” temperature across the entire surface versus the theoretical average arrived at by black body provided that conduction is zero and heat capacity is zero?
The point I’m trying to get at here is that the moon does not in fact meet the theoretical effective black body temperature profile, and hence, we can assume that the difference between the observed temperature distribution and the theoretical distribution is due to factors such as heat capacity and conduction.
The same is true of the earth except that with earth we have to throw in all the atmospheric and oceanic processes that move energy around on top of heat capacity and conduction.
The value of 255K is meaningless as a theoretical value, it applies in no way shape or form to the actual earth. We cannot possibly sort out how much of the observed temperature profile is due to heat capacity, conductance, atmospheric and oceanic processes if we start with a mythical number in the first place. If we’re going to start out with the “theoretical” black body temperature of the earth and then subtract that from the observed temperature of the earth to figure out how much of the difference is due to GHE and other factors, of what value is doing the theoretical math against a theoretical black body temperature that is wrong in the first place? Of what value is pointing out that the moon doesn’t adhere to the theoretical black body temperature in the first place when what we’re trying to measure is WHY it doesn’t match, not if it matches. Unless conduction and heat capacity on the moon are zero, why would anyone possibly expect the measured temperature profile to match the theoretical profile which is calculated in the absence of those factors?
DeWitt Payne said @ur momisugly January 20, 2012 at 1:53 pm
“Understand: To comprehend; to apprehend the meaning or import of; to grasp the idea of.” [from the OED]
Oddly enough, my understanding of QM came from Feynman’s lectures. Are you saying that he didn’t know what he was talking about? Or are you really Gavin Schmidt putting a different meaning on “understand”?
Willis Eschenbach
For some reason the idea that the atmospheric pressure of a planet plays a dominant role in the temperature make sense to me, after all, the second law of thermodynamics is expressed in terms of entropy, pressure, volume, energy and temperature. While I have only a BSME, I thought I would look at this from an engineering standpoint. In M.E. heat transfer is by conduction, convection or radiation. My text on the subject does have some combined conduction-convection problems but radiation problems are generally restricted to heat transfer between bodies in a vacuum, except for some inside a furnace problems.
So I will looks at this as a free convection problem and while this could be solved directly from the differential equations for, momentum, continuum and, energy or the corresponding integral equation for free convection, we engineers generally use working correlations derived from experimental investigations carried out for a vast number of situations. These investigations resulted in a number of dimensionless properties derived from ratios of state properties. The ones I will use here are:
Re = Reynolds Number = U*l/v
Gr = Grashof Number = (g*l(^3)*beta*Delta-T)/v(^2)
Pr = Prandlt Number = (mu* C(sub p))/ k
Nu = Nusselt Number = (h*l)/k
Statement of the problem: What is the effect of atmospheric pressure on the free convection from a surface? I will calculate the energy needed to be input into a plate 1m X 1m so as to maintain its upper surface (lower surface insulated) temperature of 40C. I will calculate it for the plate being in 0C air at 1 Atm and 25 Atm. We need to gather some data:
L = characteristic length = Area/Perimeter = (1m X 1m)/4m = 0.25m.
v = kinematic viscosity
k = thermal conductivity
beta = coefficient of thermal expansion
Pr = coef. of dynamic viscosity * specific heat / density
From Wolfram Alpha at average air temp of 20C:
For Air at 1 Atm:
v= 15.09 X 10(^-6) m(^2)/s
k= 2.56 X 10(^-2) w/m-C
beta = 3.41 X 10(^-3)/C
Pr = 0.713
For Air at 25m:
V=6.24 X 10(^-7), k=2.68 X 10(^-2), beta=3.41 X 10(^-3) and Pr =0.726
h(what we are looking for) = heat transfer coef = Nu*k/L
Nu = 0.54*Ra(^0.25) for 2.6 X 10(^4) < Ra < 10(^7)
Nu = 0.15*Ra(^.33) for 10(^7)< Ra < 3 X 10(^10)
So at 1 Atm:
Gr = ( 0.25(^3)*9.8*3.4 X10(^-3)*40)/(15.09 X 10(^-6))(^2) = 91.724 X 10(^6)
Ra = Gr*Pr = 65.399 X 10(6)
Nu = 0.54*(65.399 X 10(6))(^2) = 48.56
h = 48.56*2.56 X 10(^-2)/0.25 = 4.98 w/m(^2)-C
Similarly for 25 Atm
h = 54.5 w/m(^2)-C
One would need to input over ten times more heat to maintain the surface temperature at 25 Atm than at 1 Atm. This says to me that I would expect to see a significant difference in the atmospheric temperature profile (with height) for identical planets except atmospheric pressure.
KevinK,
Thankyou for that lucid and well presented argument which I endorse right down to the fate of engineers that get it wrong!
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.”
Thank you very much for telling me that there exist data. I don´t know if you ever heard about the Wangara and Koorin expedition i Australia. All types of mesurements were made every 3 hours for 30 days including solar irradiation and IR radiation. “The Koorin expedition, Atmospheric boundary layer data over tropical savannah land. Measurments were taken from 0 to 3000 m.
There were never any IR backradidiation or forward radiation to earth exdceeding 100 W/m^2 during this period. The book is 360 pages mostly containing data. this was during a time before “back radiation was invented”.
If back radiation existed i would be able to go out in the middle of the night and let the radiation hit my face and I would get a nice brown tan in the middle part of winter in northern Sweden when the sun is not shining at all. Even high school kid can figure out that it is impossible. Prefessor Gerlisch has written about this fraud in the G&T falsification of the Greenhouse Effect.
You might know that you quickly get a sun tan in a snowy area since the solar irradiation is coming both directly and is reflected from the snow. Photons works directly from the point they are emitted. If the infamous 390 W/m^2 plus the 330 W/m^2 “downwelling” was real we would get an equivalent to sunshine everwhere regardless if is dark or sunshine. The whole thing is just Alice in the Wonderland Fairtale.
DR wrote;
“There is something wrong with the GHE hypothesis as it has been promoted lo these many years.. I’m not qualified to enunciate what it is in technical jargon, but I don’t need to be an atmospheric scientist or physicist to know something is wrong. Does anyone else feel like they’ve been sold a lemon? Even here on WUWT, with the arguing going back and forth, the “theory” is no better explained or proven than it was 25 years ago.”
I initially started from a position of disbelieving the stated accuracy of the computer models. We use computer models in engineering all the time and have a saying; “If your hardware does not perform as predicted by your model you need to improve your model”. The level of hubris required to predict the Earth’s temperature in 100 years is STAGGERING.
After looking into the GHE hypothesis a little bit, I am now convinced it is fatally flawed. See my previous post (assuming it went through) for details.
So I guess I didn’t actually BUY the lemon, but I did pick it up, squeeze it, look it over and then I took a pass.
Nice YouTube, I actually went to school when we still used chalkboards, is there a chalkboard museum around someplace to preserve them ?
Cheers, Kevin.
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.
The final sentence is incorrect.
What is being described is Perpetual Motion of the Second Kind, in which energy is precisely conserved.
Willis wrote:
a) show that there is no problem with a sealed system performing continuous work with no energy inputs or exchange with the outside world, (my bold)
You stipulate conservation of energy, and then suggest that energy is not being conserved. All that is being done is internal rearrangement of the sealed system.
As for your challenge, it will be done, in an unmistakeable manner.
For now, I offer a single word:
Rain.
In the calculations above I typed Ra(Raleigh Number) for Re by mistake..
Trick,
That doesn’t look like the Second Law to me. Where’s the entropy term?
Adiabatic expansion ignores conduction, which is a reasonable thing to do in a normal atmosphere. But the atmosphere of a spherical planet with an isothermal surface isn’t normal. There would be no circulation once an adiabatic lapse rate was achieved. At that point, conduction dominates even if it isn’t fast. Conduction is proportional to the temperature gradient. Movement of energy from hot to cold raises the temperature of the cold and decreases the temperature gradient. Eventually, Bart notwithstanding, the temperature gradient approaches zero and the atmosphere becomes effectively isothermal. The entropy of an isothermal atmosphere is higher than for an atmosphere with an adiabatic lapse rate. So the Second Law requires that when work isn’t being done on the atmosphere by circulation between areas on the surface at different temperature (ruled out by the definition of the problem), it becomes isothermal.
Bryan says:
January 20, 2012 at 10:24 am
Willis says
” To believe that gravity can affect temperature, you have to have a weak grasp of physics, an unshakable belief in your correctness, and a willingness to ignore a bunch of folks who actually understand physics. That’s a bad combo.”
“Yet only last week Willis believed in an adiabatic distribution for a thermally isolated column of gas in a gravitational field.
This week he has ‘seen the light’.
Don’t be so hard on yourself Willis.”
I would for sure want him to get as much insults from the audience here that he has provided to me during this last week and certainly I don´t pitty this clown that tries to be scientific. He can tell where I am wrong in my paper which is common rutin in science or skip the thing. The article is peer reviewed and it stands as it is. And the clown wants an “elevator speach” from me since he “does not understand” what I have written. What comedy.
Willis says:
“IF GRAVITY ACTUALLY SEPARATES TEMPERATURE, WE HAVE FREE ENERGY FOREVER!
If sealed thermally isolated containers of air were to gravitationally separate, with warm air at the bottom and cool air at the top, then we could build tall insulated cylinders and pull power out of them forever.”
Why would the inside of this thermally insulated column of air find a different equilibrium from the equilibrium that existed before you built the containers? Which changes its equilibrium? The air inside the containers or the air outside the containers and why.
Bart says:
January 20, 2012 at 3:35 pm
Bart says:
January 19, 2012 at 11:28 pm
Phil. says:
January 20, 2012 at 1:02 pm
“What it should say is that ‘the heat accumulates in the atmosphere until the layer of gas nearest the surface reaches the surface temperature at which point heat transfer ceases due to ΔT=0.”
The surface temperature is increasing, too. There is no limit on the temperature of the surface, only on radiated energy. If you are not at equlibirum, then you are not generally radiating at the SB limit. That which is not forbidden is compulsory.
You’re dreaming, kindly explain how the temperature of the surface is increasing?
The original post referred to a uniformly heated planet with a transparent atmosphere, the only way that conduction can reduce the radiation loss from the surface is by cooling the surface. If the surface is heating up and still continually losing heat by conduction that’s some bizarre physics you’re proposing!