Guest Post by Willis Eschenbach
I’ve been reflecting over the last few days about how the climate system of the earth functions as a giant natural heat engine. A “heat engine”, whether natural or man-made, is a mechanism that converts heat into mechanical energy of some kind. In the case of the climate system, the heat of the sun is converted into the mechanical energy of the ocean and the atmosphere. The seawater and atmosphere are what are called the “working fluids” of the heat engine. The movement of the air and the seawater transports an almost unimaginably large amount of heat from the tropics to the poles. Now, none of the above are new ideas, or are original with me. I simply got to wondering about what the CERES data could show regarding the poleward transport of that energy by the climate heat engine. Figure 1 gives that result:
Figure 1. Exports of energy from the tropics, in W/m2, averaged over the exporting area. The figures show the net of the energy entering and leaving the TOA above each 1°x1° gridcell. It is calculated from the CERES data as solar minus upwelling radiation (longwave + shortwave). Of course, if more energy is constantly entering a TOA gridcell than is leaving it, that energy must be being exported horizontally. The average amount exported from between the two light blue bands is 44 W/m2 (amount exported / exporting area).
We can see some interesting aspects of the climate heat engine in this graph.
First, like all heat engines, the climate heat engine doesn’t work off of a temperature. It works off of a temperature difference. A heat engine needs both a hot end and a cold end. After the working fluid is heated at the hot end, and the engine has extracted work from incoming energy, the remaining heat must be rejected from the working fluid. To do this, the working fluid must be moved to some location where the temperature is lower than at the hot end of the engine.
As a result, there is a constant flow of energy across the blue line. In part this is because at the poles, so little energy is coming from the sun. Over Antarctica and the Arctic ocean, the sun is only providing about a quarter of the radiated longwave energy, only about 40 W/m2, with the remainder being energy exported from the tropics. The energy is transported by the two working fluids, seawater and air. In total, the CERES data shows that there is a constant energy flux across those blue lines of about six petawatts (6e+15 watts) flowing northwards, and six petawatts flowing southwards for a total of twelve petawatts. And how much energy is twelve petawatts when it’s at home?
Well … at present all of humanity consumes about fifteen terawatts (15e+12) on a global average basis. This means that the amount of energy constantly flowing from the equator to the poles is about eight-hundred times the total energy utilized by humans … as I said, it’s an almost unimaginable amount of energy. Not only that, but that 12 petawatts is only 10% of the 120 petawatts of solar energy that is constantly being absorbed by the climate system.
Next, over the land, the area which is importing energy is much closer to the equator than over the sea. I assume this is because of the huge heat capacity of the ocean, and its consequent ability to transport the heat further polewards.
Next, overall the ocean is receiving more energy than it radiates, so it is exporting energy … and the land is radiating more than it receives, so it is getting energy from the ocean. In part, this is because of the difference in solar heating. Figure 2, which looks much like Figure 1, shows the net amount of solar radiation absorbed by the climate system. I do love investigating this stuff, there’s so much to learn. For example, I was unaware that the land, on average, receives about 40 W/m2 less energy from the sun than does the ocean, as is shown in Figure 2.
(Daedalus, of course, would not let this opportunity pass without pointing out that this means we could easily control the planet’s temperature by the simple expedient of increasing the amount of land. For each square metre of land added, we get 40 W/m2 less absorbed energy over that square metre, which is about ten doublings of CO2. And the amount would be perhaps double that in tropical waters. So Daedalus calculates that if we make land by filling in shallow tropical oceans equal to say a mere 5% of the planet, it would avoid an amount of downwelling radiation equal to a doubling of CO2. The best part of Daedalus’s plan is his slogan, “We have to pave the planet to save the planet” … but I digress).
Figure 2. Net solar energy entering the climate system, in watts per square metre (W/m2). Annual averages.
You can see the wide range in the amount of sunlight hitting the earth, from a low of 48 W/m2 at the poles to a high of 365 W/m2 in parts of the tropics.
Now, I bring up these two Figures to highlight the concept of the climate system as a huge natural heat engine. As with all heat engines, energy enters at the hot end, in this case the tropics. It is converted into mechanical motion of seawater and air, which transports the excess heat to the poles where it is radiated to space.
Now, the way that we control the output of a heat engine is by using something called a “throttle”. A throttle controls the amount of energy entering a heat engine. A throttle is what is controlled by the gas pedal in a car. As the name suggests, a throttle restricts the energy entering the system. As a result, the throttle controls the operating parameters (temperature, work produced, etc.) of the heat engine.
So the question naturally arises … in the climate heat engine, what functions as the throttle? The answer, of course, is the clouds. They restrict the amount of energy entering the system. And where is the most advantageous place to throttle the heat engine shown in Figure 2? Well, you have to do it at the hot end where the energy enters the system. And you’d want to do it near the equator, where you can choke off the most energy.
In practice, a large amount of this throttling occurs at the Inter-Tropical Convergence Zone (ITCZ). As the name suggests, this is where the two separately circulating hemispheric air masses interact. On average this is north of the equator in the Pacific and Atlantic, and south of the equator in the Indian Ocean. The ITCZ is revealed most clearly by Figure 3, which shows how much sunlight the planet is reflecting.
Figure 3. Total reflected solar radiation. Areas of low reflection are shown in red, because the low reflection leads to increased solar heating. The average ITCZ can be seen as the yellow/green areas just above the Equator in the Atlantic and Pacific, and just below the Equator in the Indian Ocean.
In Figure 3, we can see how the ITCZ clouds are throttling the incoming solar energy. Were it not for the clouds, the tropical oceans in that area would reflect less than 80 W/m2 (as we see in the red areas outlined above and below the ITCZ) and the oceans would be much warmer. By throttling the incoming sunshine, areas near the Equator end up much cooler than they would be otherwise.
Now … all of the above has been done with averages. But the clouds don’t form based on average conditions. They form based only and solely on current conditions. And the nature of the tropical clouds is that generally, the clouds don’t form in the mornings, when the sea surface is cool from its nocturnal overturning.
Instead, the clouds form after the ocean has warmed up to some critical temperature. Once it passes that point, and generally over a period of less than an hour, a fully-developed cumulus cloud layer emerges. The emergence is threshold based. The important thing to note about this process is that the critical threshold at which the clouds form is based on temperature and the physics of air, wind and water. The threshold is not based on CO2. It is not a function of instantaneous forcing. The threshold is based on temperature and pressure and the physics of the immediate situation.
This means that the tropical clouds emerge earlier when the morning is warmer than usual. And when the morning is cooler, the cumulus emerge later or not at all. So if on average there is a bit more forcing, from solar cycles or changes in CO2 or excess water vapor in the air, the clouds form earlier, and the excess forcing is neatly counteracted.
Now, if my hypothesis is correct, then we should be able to find evidence for this dependence of the tropical clouds on the temperature. If the situation is in fact as I’ve stated above, where the tropical clouds act as a throttle because they increase when the temperatures go up, then evidence would be found in the correlation of surface temperature with albedo. Figure 4 shows that relationship.
Figure 4. Correlation of surface temperature and albedo, calculated on a 1°x1° gridcell basis. Blue and green areas are where albedo and temperature are negatively correlated. Red and orange show positive correlation, where increasing albedo is associated with increasing temperature.
Over the extratropical land, because of the association of ice and snow (high albedo) and low temperatures, the correlation between temperature and albedo is negative. However, remember that little of the suns energy is going there.
In the tropics where the majority of energy enters the system, on the other hand, warmer surface temperatures lead to more clouds, so the correlation is positive, and strongly positive in some areas.
Now, consider what happens when increasing clouds cause a reduction in temperature, and increasing temperatures cause an increase in clouds. At some point, the two lines will cross, and the temperature will oscillate around that set point. When the surface is cooler than that temperature, clouds will form later, and there will be less clouds, sun will pour in uninterrupted, and the surface will warm up.
And when the surface is warmer than that temperature, clouds will form earlier, there will be more clouds, and higher albedo, and more reflection, and the surface will cool down.
Net result? A very effective thermostat. This thermostat works in conjunction with other longer-term thermostatic phenomena to maintain the amazing thermal stability of the planet. People agonize about a change of six-tenths of a degree last century … but consider the following:
• The climate system is only running at about 70% throttle.
• The average temperature of the system is ~ 286K.
• The throttle of the climate system is controlled by nothing more solid than clouds, which are changing constantly.
• The global average surface temperature is maintained at a level significantly warmer than what would be predicted for a planet without an atmosphere containing water vapor, CO2, and other greenhouse gases.
Despite all of that, over the previous century the total variation in temperature was ≈ ± 0.3K. This is a variation of less than a tenth of one percent.
For a system as large, complex, ephemeral, and possibly unstable as the climate, I see this as clear evidence for the existence of a thermostatic system of some sort controlling the temperature. Perhaps the system doesn’t work as I have posited above … but it is clear to me that there must be some kind of system keeping the temperature variations within a tenth of a percent over a century.
Regards to all,
w.
PS—The instability of a modeled climate system without some thermostatic mechanism is well illustrated by the thousands of runs of the ClimatePredictionNet climate model:
Note how many of the runs end up in unrealistically high or low temperatures, due to the lack of any thermostatic control mechanisms.
– Larry Ledwick says:
December 24, 2013 at 1:17 pm
@Stephen Fisher Wilde
The cooling with height involves no loss of energy. Instead it involves an exchange of kinetic energy for gravitational potential energy.
That gives cooling with height for a radiatively inert atmosphere and no need for radiation to space from the top of the atmospheric column.
Yes you are correct that decompressional cooling due to the increase in altitude trades temperature/pressure for gravitational potential energy. Thus the rising parcel of air will cool as it rises, but its total energy will remain constant!.-
Ok. Next:
–It will continue to rise only as long as the air parcel is less dense that other parcels at that altitude. This is the basis for the initiation of vertical convection. However if you cap off that rising column of air so that it cannot continue to rise (thermopause) and it also cannot radiate away excess energy, you create the same thing as an inversion, where vertical convection ceases and the entire layer below that cap begins to stabilize at a near uniform temperature and the driving force for the convection disappears. ….–
Don’t get what mean by “(thermopause)”. Tropopause would make more sense to me.
I would say one “caps off” and are “capping off” convection at tropopause.
But seems one could also say where the tropopause is located depending amount energy of the atmosphere [in troposhere] in a particular region [I suppose also, if want to talk about it globally].
But anyhow, the term thermopause refers to a zone which is much higher up, then I would associate with convection: “The thermopause is the atmospheric boundary of Earth’s energy system, located at the top of the thermosphere.”
And assume you using this term with different meaning.
http://en.wikipedia.org/wiki/Thermopause
And so see what you wrote next as definitional of tropopause:
-The lower parcels of air are at essentially the same temperature but higher pressure (more dense) than the parcels above them they are no longer buoyant and simply hang there only mixing and moving due to random turbulence and any other forced disturbance. Take away a momentary disturbance and they return to their original altitude because that is where they are neutrally buoyant.-
And in terms the following. An important element water and it’s changing phase of gas to liquid
which an element not emphasized:
-I agree with you regarding the trade of gravitational potential energy for thermal and pressure energy that is required by conservation of energy laws. You cannot get work (raising the altitude of a parcel) without inputting some energy to drive that motion. The only way to get that heat flow to maintain persistent convection like you have in a long lived thunderstorm, is to have both a constant source of heat at the bottom of the convection column and a constant loss of “heat energy” (note I did not say temperature!) at the top. This creates a heat engine which converts heat energy to kinetic energy of convection.-
–At the top of the convection column where buoyancy no longer drives vertical motion the kinetic energy of motion is converted back to heat increasing the total thermal, pressure and gravitational potential energy of the parcel. If it cannot cool it will never fall down to lower altitudes because it will always be warmer than the below it. It is briefly pushed up above its equilibrium altitude by inertia but then falls back to its neutral buoyancy altitude. (over shooting top on a thunder storm) Only when it cools through radiant heat loss to space will it get dense enough to fall back down to lower altitudes. Without radiant heat loss to space that rising air would turn into the stopper in a bottle and block all vertical convection below.-
I will mention that droplets of water unlike a gas [even if gas is H20] is quite good at radiating heat into space. Or humans don’t make such “nano droplet radiators”- or they are “better” and larger radiators than we normally construct.
Though we do things spray water or use wet material to cool air- which is somewhat related- though kind of the opposite. Both are cooling, human use evaporation, atmosphere uses condensation which then radiate heat into space.
Kristian says:
December 24, 2013 at 5:55 pm
Kristian, I fear that makes absolutely no sense to me. What does that have to do with pressure and a planet with no GHGs in the atmosphere that I’m discussing?
Sorry, but I can’t find your meaning in there.
w.
I would say that the essential characteristic of a gas molecule rather than a molecule of a surface solid is that it has sufficient radiative absorption capability to lift it off the solid surface when radiation is absorbed.
Zero radiative absorption means no lift off, no gas and no atmosphere.
That definition then includes Argon despite its near zero radiative absorption capability.
Once lift off occurs then the absorption capabilities of mass via conduction take over and from that point render radiative absorption capabilities irrelevant because the amount of energy absorbed by mass via conduction is many magnitudes greater than the energy absorbed radiatively.
On that basis the fact that Argon’s radiative capability is near zero doesn’t matter in practice and Willis’s assumption that its near zero radiative capability can be ignored is wrong.
A slight change to my terminology is needed.
It is radiative emission capability that enables a gas molecule to lift off from a solid surface rather than the radiative absorption capability because it is that emission that enables the molecules to move further apart than would otherwise be permitted by the intermolecular attractive forces.
As we can see from the Argon example any emission capability greater than zero can be enough and all mass has an emission capability greater than zero hence the ability of all solids to vaporise at high enough temperatures.
— Kristian says:
December 24, 2013 at 6:30 pm
gbaikie says, December 24, 2013 at 5:34 pm:
“Second you never actually ever lose energy. It’s always transfer into different forms of energy.
So if “cools because it loses energy”, the question where and how do you “lose energy”- where does the energy go?
And I think Larry Ledwick explains well.”
Did you even read what I wrote? —
Yes.
You quoted what Larry Ledwick wrote.
Followed by a sentence of “No.”
And went on explain what you considered a more correct way to explain it.
In my reply I said “No”.
Because In my opinion Larry was not corrected by your explanation.
So I saw nothing particularly wrong in quoted statement of Larry Ledwick.
— Did you even read what I wrote?
The energy disappears from the expanding air parcel. It goes to the air masses surrounding it. It doesn’t disappear from the atmosphere as a whole. Until it’s radiated away to space. —
Which is fine I suppose but I think:
Larry Ledwick says, December 24, 2013 at 1:17 pm:
“Yes you are correct that decompressional cooling due to the increase in altitude trades temperature/pressure for gravitational potential energy. Thus the rising parcel of air will cool as it rises, but its total energy will remain constant!”
Is a better explanation.
If one were to follow the air parcel as it rises with a thermometer, it would read a lowering of temperature. But the energy remains, it does not lessen.
If “*something/somehow* stopped it” from decompressional cooling, the temperature remains constant. Or it would not cool. And it’s correct to say it’s trading “temperature/pressure for gravitational potential energy”
[Though it should be mentioned that when one talks of “parcel of air” one does not necessarily mean the same molecules at lower level are traveling upwards. But rather they could possibly be, as with wind/updraft, but, it’s the energy of the kinetic energy of gases which move upwards. Or if cooler parcel of air, it falls. And of course with air parcel compressing and heating- or “trades temperature/pressure for gravitational potential energy”]
–
joeldshore writes ” I agree that higher pressure will tend to be associated with more radiation absorbed, i.e., a larger greenhouse effect both because, higher pressure means more greenhouse gases if some fraction of the atmosphere is greenhouse gases AND higher pressure also means more pressure-broadening of the absorption lines of the greenhouse gases in the atmosphere.”
I was beginning to worry that I was finding myself agreeing with what joeldshore was writing. But then he wrote this 🙂
Higher pressure does indeed mean more radiation absorbed but not because there must be more GHGs (your assumption). Higher pressure doesn’t mean a broadening of the absorption lines except where you have more GHGs (your assumption again) Absorption is what it is. The so called “broadening” is simply due to increasing probability it will be absorbed as it passes through the atmosphere where there are more GHGs in the way.
After all absorption is pretty much complete within 10’s of meters in the earth’s atmosphere. Adding a couple of hundred ppm CO2 for example, doesn’t appreciably change that.
No, the atmosphere will be warmer because emission reduces. Instead of having time to radiate, the GHGs pass off more energy towards the atmosphere (when it is thicker) through collision. The ERL depends not only on the amount of GHG above but also on the rate of emission and that increases with decreasing collision rates (ie thinner atmosphere)
Stephen 12:43am – “Once lift off occurs then the absorption capabilities of mass via conduction take over and from that point render radiative absorption capabilities irrelevant..”
Again, Lord Kelvin 1862 paper points out atm. convective energy transfer takes over, is dominate. His work is still good today. I observe some Stephen thinking progress on the magnificent climate heat engine in this thread though.
So Stephen et. al. imagines an Ar atm. beginnings. Think about the feeble Ar DWIR, esp. at night. The UWIR, feeble emission to space from stratosphere. Think about the feeble solar absorption by the Ar atm. Consider the differences from today’s baseline radiative, convective, conductive energy transfer theory affects on near surface equilibrium Tmean, troposphere Tmean and stratosphere Tmean.
Now consider (in Stephen’s case imagine) exchanging from Ar considerable O2, N2, CO2, CH4 and their IR active bands in the mix on all the control volume Tmeans. Especially consider (imagine) what happens to earth’s BB curve scenes looking down as observed by the earth Argonite’s satellite instrumentation as their climate changes due O2,N2,CO2 et. al. accumulation. Consider how the temporal and spatial averages change, how the theoretical effective emission level changes, how atm. layer opacity changes.
Happy holiday thinking cap for y’all.
***
lsvalgaard says:
December 23, 2013 at 5:10 pm
If you have a completely transparent atmosphere that doesn’t absorb anything, you might as well not have any atmosphere at all. I was under the false assumption that we were somehow talking about real planets with H2O, CO2, CH4, NH3, O3, etc…
***
I’d agree — every atmosphere in our solar system has at least traces of CO2, H2O, methane, etc, including the gas giants. Doubt if “pure” non-GHG atmospheres can exist, given that the GHG gases are so ubiquitous, at least in trace amounts.
TB says:
December 24, 2013 at 1:35 pm
“Weather is highly chaotic and therefore unpredictable (beyond around 7 days at best).”
———–
Believe it or not, …. but one can predict a “change” in the current weather pattern, and be right more often than not, …. if one predicts that the current “hot spell” or “cold spell” will persist until the Full Moon comes in. (or the New Moon, I forget which)
Stephen Wilde says:
December 25, 2013 at 1:15 am
I challenge you to find one single authority who claims that a gas must emit and absorb infrared in order to be gaseous. You’re just making things up at this point to try to salvage your claim. In fact, because it is monatomic, argon is almost a perfect non-emitter and non-absorber of infrared, and despite that it liquifies at -309°F, and boils at -302°F.
In other words, you’re not only grasping at straws, you are manufacturing straws to grasp at.
w.
“I challenge you to find one single authority who claims that a gas must emit and absorb infrared in order to be gaseous. ”
Can you say what makes it gaseous then?
If energy is transferred only by conduction then it remains a solid.
On the face of it some sort of energy transfer other than conduction must be needed to overcome the intermolecular attractive force to make it gaseous and then keep it as gaseous.
I’m not grasping at or making straws, I am looking for answers.
The radiative capability of all matter, however small that radiative capability might be, seems to be the only option available.
Since all matter has some radiative capability there is always a temperature at which any solid will vaporise.
TimTheToolMan says:
December 25, 2013 at 1:29 am
Thanks, Tim. People have this mistaken idea that IR is like light, and that once it is absorbed the game is over. They say things like “It’s like piling sand on a flashlight. Once the light is covered, more sand does nothing at all.” And you are correct that after some tens of metres, almost all absorption is complete.
But since the IR is usually absorbed and re-radiated more than once as it makes its way out of the atmosphere, adding more CO2 definitely changes the picture. This is because increasing the CO2 concentration increases the average number of times that the IR will be absorbed on its path through the atmosphere, which increases the poorly named “greenhouse effect”.
In other words, the idea that once the radiation is absorbed the game is over is only true for visible light. For IR, it’s not true in the slightest.
w.
Stephen Wilde says:
December 25, 2013 at 9:18 am
Thanks, Steven. I’ll take that to mean that you don’t have any authorities to back up your claim.
What makes things gaseous is that their temperature is increased (in whatever manner) until the thermal energy is enough to shake the atoms loose from the forces that bind them into either a liquid or a solid. The amount of energy required differs depending on the binding forces. Since argon is an inert monatomic gas, the forces binding it as a liquid are quite weak, and so it doesn’t take much energy to convert it from a liquid to a gas. As a result, it gasifies at a very low temperature, -302F.
Turning from a liquid to a gas has absolutely nothing to do, however, with IR radiation.
All the best,
w.
beng says:
December 25, 2013 at 6:23 am
Thanks, beng. I presented it as a “thought experiment”, not as an analogue of a real world. I want to make it clear why, if the atmosphere is transparent to IR (e.g. argon, which neither emits nor absorbs thermal IR), the pressure of the atmosphere alone cannot warm the planet. See my post called “A Matter of Some Gravity“.
w.
Samuel C Cogar says:
December 25, 2013 at 8:21 am
Sorry … I don’t believe that about the weather changing at some point in the lunar cycle. It’s not true, as far as I know, in anything but the most general sense, that of “persistence”.
The “general sense” is that in the absence of any knowledge to help guide us, our best bet for the future is usually the past (persistence). That is to say, if you guess that tomorrow’s weather will be like today’s weather, over a year you’ll be right more than wrong. (Known as a “high lag-1 autocorrelation” for the math inclined).
But bringing in the moon into the persistence forecast? Doubtful. The moon does have an effect on the weather, in particular through the existence of lunar tides in the atmosphere. It also affects the weather through ground-level “tidal winds”. Think about an area like Alaska, where the tide might swing 20′ (6 metres). All that air has to go somewhere, so you get tidal winds. They blow like the earth itself inhaling and exhaling, a long, slow, even breath, and they blow upriver on incoming tides, carrying the smell (and the temperature) of the ocean far inland.
And I’ve sailed on the “moon wind”, the wind that blows across the moon’s “terminator line”. The lunar terminator line is the line between the area of the earth lit by moonlight, and the dark area of the earth where the moon is not above the horizon. The sun also has a terminator line, which we call either “sunrise” or “sunset” depending on which way we’re crossing that one line.
And because the moonlight warms the earth, even though ever so slightly, there is a generally undetectable wind that blows across the lunar terminator line. You need very calm conditions, no wind and no waves at sea, or no wind and open land ashore, to be able to detect it. I’ve only ever seen the moon wind at moonrise, and never at moonset although it must blow then as well. I think the onset is stronger (warming from the light) at moonrise than is the cutoff (cooling from no light) when the moon is sinking, so I’d expect the moon wind to be stronger at moonrise.
It occurs mostly in the week or so after full moon, and is easier to detect at sea. On a dead calm night at sea, after the night goes from pitch black to the increasing glow as the moon nears the underside of the horizon, the moon wind kicks up just before the upper edge of the moon first becomes visible. It lasts ten minutes or so, and then dies off again.
Now, like most all winds, a “terminator wind” blows from the cold to the hot. So it always blows toward either the moon or the sun. In regards to the sun, these are called “dawn wind” and “dusk wind”. Dawn wind always blows toward the east, of course, and dusk wind towards the west. Naturally, the solar terminator winds blowing towards the sun are much, much stronger than the lunar terminator wind blowing towards the sun. I’ve only experienced the moon wind a few times in my life.
So yes, predicting yesterday will be like today will win the bet more than half the time. And the moon affects the weather. But the weather doesn’t ‘turn’, whatever we might define that to mean, at a certain instant in the lunar cycle. Sadly, the world is not that simple.
I would not be surprised, having said that, if different atmospheric conditions generally prevailed during times of high versus low atmospheric tides. I remember there was some work done on that a while back, but I haven’t heard much about it lately. Another victim of the CO2 craze … I’ll have to put that on my long, long list of things to investigate someday …
Best regards,
w.
Trick says, December 24, 2013 at 6:57 pm:
““Whenever conduction/convection/evaporation enter the stage, their results are no longer valid. Because the situation is no longer a BB in a vacuum situation.”
A vacuum situation is not an assumption in the Planck or S-B derivation, only that the system be in thermal equilibrium, convex which is the usual reasonable assumption for sun, earth, atm. system over eons.
This BB necess. emitting to vacuum seems to be a popular misconception, the source of which I have not been able to track down. Neither of your links notes a vacuum requirement or any link I can find and it is not mentioned as a requirement in Planck 1914, Brehm 1989 or Bohren 2006.”
OK, I’ll explain a bit closer.
No, there is no necessity of a vacuum. But if you read what I wrote in full I said it requires EITHER a vacuum (no temperature at all) OR surroundings that are much, much colder than the object in question.
Then read the hyperphysics pages I linked to. They’re very interesting and revealing. Why do they keep talking about hot objects and not just objects? Because in a real situation, like on Earth, the object needs to be hot to be a pure radiatior. In space it is surrounded by a vacuum (which practically does not have a temperature), so there the object does not need to be hot in order to be a pure radiator. Earth as a planet in space would be a good example.
Now, compare the actual Stefan-Boltzmann equation: P/A = s T^4 (P/A = e s T^4 for gray bodies) with the radiative heat transfer equation: P/A = e s (T_1^4 – T_2^4).
The former describes a BB or a GB in a vacuum or in surroundings that are much, much colder than the object in question. This way (and ONLY in these ideal situations) the radiation being emitted from the object can be deduced directly from its temperature (and emissivity).
The latter, however, is different. There we can no longer assume that the radiation being emitted from the warm object can be directly derived from its own temperature alone. Here the temperature of the surroundings (or nearby objects) comes into play in addition. Because this temperature is close enough to the object’s temperature to make a difference. The warm object is no longer a pure radiator.
In the Stefan-Boltzmann equation, the temperature gradient away from the object can be considered infinitely steep. In the heat transfer equation it is less so. Hence, the emitted radiative flux from the warm object (P/A) will be less than ideal, less than the maximum potential. It is no longer what the Stefan-Boltzmann equation says it CAN be.
P/A is the radiation going from the warm object to its cooler surroundings. P/A is the radiative flux that we actually physically detect. Remember, this is what the definition of HEAT is, simply the energy transferred from hot to cold. That is the radiative flux. P/A. Power over area. W/m^2. J/s/m^2.
T^4 is NOT a radiative flux, neither in the S-B nor in the heat transfer equation. That is just the temperature of the object raised to the fourth power. It doesn’t mean or signify anything physical on its own. It’s an abstract expression utilised only to obtain the actual radiative flux, P/A.
For the surface of the Earth, then, if it holds a temperature of 288K, then we can’t just say that it emits a radiative flux of 390 W/m^2. Because it doesn’t. We can’t use the Stefan-Boltzmann equation in this case. Because the Earth’s surface is NOT a black or a gray body in a vacuum, neither is it a surface much, much hotter than its nearest surroundings. The temperature gradient away from the surface is far from infinitely steep. The surroundings have a temperature that matters.
Accordingly, we have to apply the equation for radiative heat transfer instead. Doing so, we find that the REAL radiative flux from the global surface of the Earth is somewhere between 50 and 60 W/m^2, where only about 30 go to the atmosphere.
So, the 50-60 W/m^2 of radiative flux from the surface doesn’t mean its temperature is a mere 175-180 Kelvin. It means the temperature gradient away from it is such that it doesn’t allow more to be emitted.
As you can hopefully see, as you move from the ideal-situation Stefan-Boltzmann equation to the more real-world radiative heat transfer equation, then we also move from direct (to the fourth) dependency on the emitting object’s temperature to direct (to the fourth) dependency on the temperature difference between the emitting object and its surroundings. That is a very different proposition.
And this is where the misconception lies. The Earth’s surface doesn’t emit 390 W/m^2 by necessity, receiving back 330-340 W/m^2 from the atmosphere. That’s not how it works. That’s simply based on a misinterpretation of the heat transfer equation, where one mistakes the T^4 elements as real fluxes that flow in the opposite direction from one another (as IF the surface and the atmosphere were separately radiating as in the S-B equation into a 0 K vacuum – they’re NOT).
There is nothing in that equation that says anything about two opposite fluxes. It only describes ONE flow of energy, the P/A. And this always and exclusively goes from hot to cold. The HEAT.
Willis,
I see that we were at cross purposes in that I was considering he entire radiative spectrum whereas you referred to the IR bands.
Nonetheless my point remains that once a gas molecule lifts off the surface then the conductive energy transfers involving the entire mass of those molecules are magnitudes greater than the radiative transfers, even for GHGs, so the radiative considerations fade into insignificance.
It is the conductive exchange which keeps the surface warmer than S-B with S-B only needing to be satisfied at some point above the surface.
Kristian said:
“As you can hopefully see, as you move from the ideal-situation Stefan-Boltzmann equation to the more real-world radiative heat transfer equation, then we also move from direct (to the fourth) dependency on the emitting object’s temperature to direct (to the fourth) dependency on the temperature difference between the emitting object and its surroundings. That is a very different proposition.”
I like the sound of that.
A planet with an atmosphere does not and cannot have the same surface temperature as a planet without an atmosphere and the conductive / convective process does interfere with the S-B equation which applies only to a planet without an atmosphere.
The effect of conductive / convective activity resulting far more from mass than radiative capability is to shift surface thermal behaviour away from the S-B narrative.
In the process the location that S-B must be applied is raised off the solid surface to some point within the atmosphere.
Stephen Wilde says:
December 25, 2013 at 4:38 pm (Edit)
Thanks, Steven. First, argon neither absorbs nor emits thermal IR. So in my planet with an argon atmosphere, the only thing radiating the heat back to space is the surface.
And this means that the surface cannot be “warmer than S-B”, because if it were warmer, it would EMIT MORE RADIATION THAN IT IS RECEIVING on a constant basis … and that is simply not possible in a universe burdened by the hugely unfair Second Law of Thermodynamics … me, I think we should hold a Constitutional Convention to repeal the Second Law, it never did us any good anyhow …
w.
Willis Eschenbach says:
December 24, 2013 at 2:08 pm
———————————————-
Willis,
Thank you for your response to my question.
It was not intended as a trick question, and you are correct that water vapour would of course be dominant in the process both in driving buoyant uplift and later allowing radiative energy/buoyancy loss and subsidence of air masses. CO2 and other non condensing radiative gases play a minor role in radiative cooling, most notable in the descending limbs of tropospheric circulation cells.
So for the question –
“Without radiative gases, would strong vertical tropospheric convective circulation cease with the bulk of the resultant stagnant atmosphere trending isothermal through gas conduction?”
So far my results are –
Dr. Roy Spencer (sceptic) “Yes”
Willis Eschenbach (sceptic) “Yes”
Konrad (sceptic) “Yes”
Nick Stokes (AGW believer) “No”
Tim Folkerts (AGW believer) “No”
Joel Shore (AGW believer) “No”
“Trick” (AGW believer) “No”
Doug Cotton (Slayer) “No”
Davidmhoffer (lukewarmer) “No”
“TB” (AGW believer) “No”
Stephen Wilde (Sceptic) “No”
The next question of course would be what would this mean for a non-radiative atmosphere above a desert planet. And for this the following statement is relevant –
“For a gas column in a gravity field, the relative height of energy entry and exit from the column is critical to determining the average temperature of the gas column.” – K.
(note – it has taken “Trick” over a year to concede that the above statement was true, which should give some indication of it’s importance.)
My closure on this thread: I consider Piers Corbyn to be a pioneering experimentalist, trying to apply science in every sense, good bad and ugly. I looked over his older forecasts from previous years, and I’m aware of his making adjustments in his forecasts in response to criticisms. I see the successes in the spite of the forecast mistakes and misstatements. If you were in his shoes trying to get a new way of doing forecasting off the ground, you may be prone to some of the same issues. Many things in his forecasts are a matter of interpretation, and some plain wrong at times.
In the last 24 hours or so I’ve seen a lot of people claim someone else here misinterpreted or mischaracterized their points in this particular blog. I’ve seen emotional reactions with a lot of bluster to these perceived slights and so on from more than person here. I think some of you aren’t being fair to each other or Piers. That’s the way it is. Never-ending personality conflicts.
Piers is not an object of hero-worship for me or other customers. We respect his efforts in breaking new ground. Like it or not, we here are all on the same team, aren’t we? Then’s it time to pull together, leave animus behind, and rally behind what we know is true: IT’s THE SUN, not CO2 that drives the weather and climate.
This past three months especially have been very interesting weather-wise, and in a desire to understand the solar-earth connections better myself, and to get a handle on the success of his methods, I have been documenting spaceweather and earth weather for that period, and I’m evaluating those forecasts with all the data I can muster together in a video style format, to be completed and released on my new YT channel hopefully first week in January. Time is short for us politically, and want to get my thoughts out to this free-thinking free-wheeling blog to get your thoughts, which have I valued for over six years, in the hope of making a difference just like all of you.
I am an electrical engineer. I troubleshoot lots of things, including weather-climate issues. Looking back over the solar wind history and extreme weather event history has been very revealing. So many good examples of outside forcing of weather to talk about, I can’t wait to get it all out ASAP.
This effort I am making is specifically about MY ideas regarding the weather and climate, and they are not dependent on Piers’ successes or failures. Trying to smear him to smear me is narcissistic behaviour. That’s what warmists do. DON’T BEHAVE LIKE THEM! Until or unless some one provides me with a name of someone who is objectively better, Piers is it.
Stephen Wilde says:
December 25, 2013 at 4:46 pm
1. Yes, a superconducting planet (or one heated by a thousand evenly spaced suns) with an argon atmosphere will have the same surface temperature as if it had no atmosphere at all. This is because the atmosphere plays no part in the heat loss, which is only from the surface, and because the atmosphere and surface don’t exchange any energy.
2. Where on earth did you get the idea that the S-B equation is only valid in a vacuum? As far as I can find, that’s not true in the slightest. A citation to your source would be useful
w.
PS—You are correct that for example, if we added an argon atmosphere to the moon, it would end up warmer than it is now.
This is for a curious reason. Adding an argon atmosphere to the moon won’t change its radiation properties, or push it above the S-B calcs. But the atmosphere will circulate, driven by the pressure differential that creates terminator winds.
This circulating argon atmosphere will transfer energy by conduction/convection from the equator to the poles, cooling the equator and warming the poles by the same amount of energy.
Here’s the curious part. During the day, the moon’s surface gets up to about 90°C, and at night it goes down to -180°C. So we’d say that the temperature average is about -45°C, dang cold.
But the moon gets the same solar radiation as the earth, about 340 W/m2, with an equivalent blackbody temperature of about 5°C. So why isn’t the moon at 5°C? It’s because the radiation varies as the temperature to the fourth power. Because of that, any variation in the surface temperature will lead to a lower overall average temperature.
Now, 90°C ( ≈ 360K) gives a blackbody radiation of about a thousand watts per square meter (W/m2) … and -180°C ( ≈ 90K) gives off a whopping 4 W/m2. Since the temperatures vary by a factor of 4 (90K to 360K), the radiation varies by a factor of 16.
And as a result of that, anything that reduces either the day/night or the equator/poles temperature difference will raise the average temperature. In particular, if we transfer a packet of energy X from the equator to the poles, despite the fact that the total energy content of the system is totally unchanged, it will increase the average temperature …
What a planet.
Willis;
90^4 = 65,610,000 and 360^4 = 16,796,160,000. 1679616/6561 = 256, not 16. Or 4^4 = 256.
Willis writes “Yes, a superconducting planet (or one heated by a thousand evenly spaced suns) with an argon atmosphere will have the same surface temperature as if it had no atmosphere at all.”
And just above Steven wrote “It is the conductive exchange which keeps the surface warmer than S-B with S-B only needing to be satisfied at some point above the surface.”
Its pretty clear the Argon will warm via conduction and although it will play no part in radiative effects, when the sun is on the other side of the planet, the warmer Argon atmosphere will be conducting its energy back to the planet which Willis has said is [thermally] superconducting and so that will indeed contribute to the surface temperature on the other side.
If you’re going to put forward a thought experiment, you may as well explore it fully 😉
I think it is interesting discussing atm. science in context of the atm. magnificent heat engine based on the text books and published papers. Here’s what caught my interest since last post. I like to give a clip of a post not the whole text b/c the whole text is right there to ref. in the thread.
Kristian 3:45pm: “But if you read what I wrote in full…”
I did. I commented on an interesting part of it. There is no requirement in derivation and application of Planck’s law or S-B for either a vacuum or surroundings much, much colder than the object in question that I can find in the text books I mentioned. So your long post fails to agree with even Planck himself in his own writings. It is too long to parse.
Specifically Planck, Brehm, Bohren formulas all calculate the avg. global surface of the earth at Tmean around 288K emits around 396 W/m^2 give or take not 50-60 W/m^2 so I don’t buy your arguments.
Earth surface instrumentation looking down measures every day in the range of 396 UWIR nowhere near constantly 50-60. So ~396 comes from theory and experiment & adds up across many authors & experimentalists in the field where 50-60 does not.
******
Willis 5:41pm: “..despite the fact that the total energy content of the system is totally unchanged, it will increase the average temperature …”
This obviously fails 1st law. Are you just creating energy from nothing to raise the Tmean or what in the world do you really mean?
“But the moon gets the same solar radiation as the earth, about 340 W/m2 with an equivalent blackbody temperature of about 5°C. So why isn’t the moon at 5°C?”
The moon BB temperature is –2.45C (270.7K) based on the bond albedo of 11 and the 340 W/m^2. Believe they ~confirm this from Diviner mission measuring soil surface and in situ a few cm down in the soil where the surface T swings are largely eliminated.
http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
Willis 5:02pm: “First, argon neither absorbs nor emits thermal IR.”
All matter .GT. 0K emits and absorbs IR. Argon is matter. In natural systems .GT. 0K, argon absorbs and emits IR but rather feebly.
This is why they can’t get to 0K experimentally; pumping down to only a few nanoKs above 0K is currently possible.
“…me, I think we should hold a Constitutional Convention to repeal the Second Law, it never did us any good anyhow …”
The 1st law is ok with with unforced macro energy flow cold to hot as long as energy is conserved. The 2nd law is needed to stop that nonsense. 2nd law can’t be repealed for that reason.
If you read the history of the 2nd law, Sadie Carnot almost had it developing his cycles, all he needed to do was write it down. Then all the post-Carnot thermo. theorists in 1800s became more and more concerned the 1st law was ok with macro cold to hot and invented the 2nd law to eliminate their concern. Clausius wrote it down as you know.
“Entropy is a virus that has escaped from the laboratory and infected many people who are not scientists, especially people with a literary bent.” – Bohren 1998 p. 135. I recommend reading the whole passage.
“…students rarely find energy so formidable as entropy.” No kidding. However entropy is a very elegant concept in science, not so much in literary applications.
******
Stephen 4:46pm: “…the S-B equation which applies only to a planet without an atmosphere.”
You are backsliding on me. There is no such constraint found in modern text books. Or even ancient ones after invention of S-B.
Stephen 9:18am: “..I am looking for answers.”
Please Stephen, do as I have long recommended, conquer the pre-req.s, read the basic atm. thermo. and atm. radiation modern text books and find your answers. Take a few long winters nights. It just can’t hurt a dang thing to do so. Get them for free from the library. I continue to be astonished that you don’t.
Actually I’m going to reverse my previous decision on this and suggest that Willis is correct.
In my clarifying thought experiment I simply got rid of the suns. They were distracting. And instead I considered an internally powered thermally superconducting planet whose non-changing power output was such that the plant attained a temperature of say 300K.
Then add the cool argon atmosphere and the surface temperature will drop until conduction has warmed the atmosphere to also be 300K and thereafter conduction down will equal conduction up with no resulting change in overall temperature.
It doesn’t matter how thick the atmosphere is, once both atmosphere and planet reach the same temperature, net conduction is zero and can have no impact on the planet’s overall temperature.