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.
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Stephen Wilde says:
December 31, 2013 at 1:41 am
Stephen, my question involves a thought experiment. One reason for doing thought experiments is to clarify a complex situation by simplification.
So I have simplified the day/night, equator to poles temperature imbalances by positing a world warmed equally and everywhere by a million suns. This was specifically so we didn’t have to deal with complexities like energy being exchanged between surface and air.
Now, AS I SAID BEFORE, once such a world reaches equilibrium, there is NO CONDUCTIVE EXCHANGE BETWEEN SURFACE AND AIR, because there is no temperature fluctuation to drive such an exchange.
My question was, in such a world, can pressure alone increase the temperature? I hold the answer is no.
You, on the other hand, wish to confuse and complexify, not simplify. As a result, you keep insisting that there will be some mythical reason that atmosphere and surface will be swapping energy back and forth … and then you claim the real question is where the energy to power your imaginary energy swapping will come from.
I can’t answer your question, Stephen, because in a constant-temperature world, the air is always and ever at the same temperature as the surface, and there is no such energy transference as you claim.
w.
Trick says:
December 31, 2013 at 8:28 am
Mario, for that to happen, the energy of the photon has to be transformed into something else. The photon doesn’t just “vaporize” as you put it.
And to make that transformation into another kind of energy, the energy has to be able to “grab onto” something. It has to be able to vibrate some mechanical bonds between atoms, make the molecule shake and dance. The energy needs to be absorbed by the atom in some physical manner, stretching or whatever. But there’s nothing in an argon atom to grab on to, nothing to stretch or vibrate. As a result, for thermal IR arising from earthlike temperatures, the transmissivity of argon is 1.0. The argon atoms and the thermal IR have no physical way to interact, so they simply don’t.
Here’s a way that you might be able to see what I mean. It’s no different from parts of the spectrum for water vapor or CO2. I think that you would agree that there are frequencies where both water vapor and CO2 do not absorb any IR at all. None. Why? Because the IR is the wrong frequency to be able to shake or bend the water or CO2 molecule, so there’s no way for the two to interact. As a result, although GHGs absorb thermal IR at certain characteristic frequencies, at certain other frequencies the emissivity of either water or CO2 is zero. Here’s a look at some of the frequencies.
See all of those white areas? Those are frequencies at which the gases are physically unable to absorb thermal radiation. Ozone and oxygen, for example, only have a few narrow bands where they can absorb IR. At all frequencies other than those narrow bands their emissivity is zero. Not small. Zero. They are transparent to IR at those frequencies, because they are physically incapable of interacting with it in the slightest.
The same is true for argon … but instead of being true for most frequencies like with say ozone, argon is incapable of absorbing any frequencies of thermal IR, all the way up to visible light. Just as CO2 or H2O or ozone neither emit nor absorb thermal IR at certain frequencies, argon at all frequencies below visible light has an emittance of zero.
w.
@Stephen Fisher Wilde says:
December 31, 2013 at 4:12 am
Mario,
That is a helpful summary and serves to show how easily confusion can arise.
It may help if I summarise what I think happens in the real world:
++++++++++++++++++++++++++
[My comments in brackets]
i) As soon as an atmosphere starts to form its mass lifts off the surface taking conducted energy with it. Obviously, that conducted energy is initially derived from absorbed radiation at the surface.
[agreed –and the conducted energy mixes and convection spreads the heat around.]
ii) The surface temperature drops whilst the atmosphere is forming but, because incoming radiation stays the same, equilibrium is soon restored by virtue of the fact that, during the process of forming the atmosphere, energy out is less than energy in due to the (temporarily) lower surface temperature.
[Here’s where my understanding diverges from what you explain. I am not saying you’re wrong, but to me this is a crucial fork in the road for how I see the problem. We both agree that the surface temperature drops because it conducts heat to the Argon (as long as the Argon is colder than the surface). AND most the most important difference in my line of logic is that the Argon does not leave the planet. It’s still part of the planet, but in gaseous form so it’s energy balance, plus the energy balance of the solid surface remains unchanged.) The argon does not go into space with its energy, nor does it radiate. If the argon condenses, the energy will be return to the planet to warm and possibly radiate the energy]
iii) At that point we have the surface at the same temperature as before with overall radiative equilibrium but at the same time there is then an additional store of energy in the atmosphere.
[ I cannot get past this point. Until I find out if this line of thinking is correct or not. I think the Argon acts like a buffer. It takes some of the heat away from the surface through conduction until it delta T approaches zero, likewise, it will cool the surface until the surface warms (assuming diurnal changes. There will be lags and leads in the system. At night, or as sunlight wanes, while the surface cooling lags (because the argon is losing heat to warm the surface, then then the surface will be warmer for longer and be able to radiate more heat to space. Likewise if the surface warming lags, then surface will radiate less heat into space. I am not sure if there is hysteresis or if it’s symmetrical.]
iv) That energy in the atmosphere is then adiabatically recycled between the bottom and top of the atmosphere (mostly the troposphere for Earth) so as to provide the energy needed to maintain the height of the atmosphere.
[Agreed]
v) The net radiative effect of the adiabatic exchange is zero because all kinetic energy leaving the surface by conduction and convection via uplift is matched by kinetic energy returned to the surface by the subsequent descent.
[Agreed]
vi) However, at all times at the surface, that additional conducted energy is present in the temperature of the air just above the surface…
[Agreed]
…which has an insulating effect.that must raise the average surface temperature above S-B.
[This is where I do not follow. The energy in the atmosphere was removed from the surface, which lowered the surface temperature by some non-zero amount. I think I use buffer, where you use insulate. A buffer has heat capacity, and insulator does not, I think]
vii) The height at which S-B is satisfied must rise off the surface purely as a result of the conductive / convective process which is caused by mass held within a gravitational field and not by radiative capability.
One has to get the correct sequence of events and then it becomes clear to me but, apparently, not to others.
Radiative gases are not necessary for any part of that purely mechanical process.
Mario said:
“This is where I do not follow. The energy in the atmosphere was removed from the surface, which lowered the surface temperature by some non-zero amount”
You didn’t notice that the lower surface temperature was only temporary because, while the temperature was lower, radiative energy in exceeded radiative energy out until the surface was back to the original temperature.
Meanwhile that ‘extra’ stored energy is still in the atmosphere and being recycled up and down adiabatically.
So the surface is then receiving the full package of incoming radiation and has returned to the original equilibrium temperature.
BUT at the same time it is receiving energy from and passing energy to the atmosphere to support the continuing conductive exchange.
The surface temperature must become warmer than S-B to provide the energy to simultaneously support radiation out AND the conductive exchange.
Well Willis, if you want to ignore the simple fact that there is no such thing as even heating on any planet in the universe then I cannot help you.
Willis Eschenbach says:
December 31, 2013 at 10:15 am
Trick says:
December 31, 2013 at 8:28 am
Willis 10:56 pm: “This is because the GHGs can absorb some of the radiation. But in my thought experiment, with a transparent argon atmosphere … well, no, it can’t.”
An argon atmosphere isn’t transparent. Here’s why I can write that simply and no simpler:
Two argon atoms traveling in earth’s atm., one behind the other from POV of an incoming IR photon from sun. The photon slams into the nearest atom and suffers annihilation, the Ar atom still exists. The photon behind is in the “shade” of this process.
Mario, for that to happen, the energy of the photon has to be transformed into something else. The photon doesn’t just “vaporize” as you put it.
+++++++++++++
Hi Willis: It was late when you wrote the response, which I agree with completely due to your explanation. However, I believe you meant to respond to Trick, not me 🙂 Even if the Argon did evidently vaporize in the physical sense, there would be latent energy soaked into the “vaporized” state of the argon and the energy balance would be satisfied. Trick’s response is wrong on so many levels.
Stephen Wilde says:
December 31, 2013 at 10:41 am
Well Willis, if you want to ignore the simple fact that there is no such thing as even heating on any planet in the universe then I cannot help you.
++++++++
I think you’re not getting what Willis said by paraphrasing the way you did. I think Willis was helping you on the point he made. His point was straightforward. He was pointing to that nugget of truth that shows where the problem is.
Stephen Wilde says:
December 31, 2013 at 10:39 am
Mario said:
“This is where I do not follow. The energy in the atmosphere was removed from the surface, which lowered the surface temperature by some non-zero amount”
[My responses below in brackets]
You didn’t notice that the lower surface temperature was only temporary because, while the temperature was lower, radiative energy in exceeded radiative energy out until the surface was back to the original temperature.
[I get that during irradiation, the surface temperature is lower than it would be without an atmosphere because it conducts to the atmosphere until delta-t approach zero. The time is affected by conduction and convection which affect the rate of change of the process. But, still this does not change the amount of total energy.]
[However, that said, I see what you mean, I think. Are you saying that if the atmosphere is warming (that which I called an energy buffer) it would lower the net outgoing radiation because the Argon soaks up energy, but does not radiate energy? Said another way, with regard to radiation, the energy (conducted from the surface to the Argon) is essentially hiding in the Argon atmosphere.]
[This energy accumulation condition would, to me, occur only until the buffer fills. The buffer would no longer fill once it equals the surface temperature. Whereas incoming and outgoing radiation continue for essentially infinity. Using calculus to integrate that energy over time, the buffer energy approaches zero relative to the ongoing radiation source.]
Meanwhile that ‘extra’ stored energy is still in the atmosphere and being recycled up and down adiabatically.
So the surface is then receiving the full package of incoming radiation and has returned to the original equilibrium temperature.
[YES, original equilibrium temperature]
BUT at the same time it is receiving energy from and passing energy to the atmosphere to support the continuing conductive exchange.
[If it is at equilibrium, there us not transfer of energy. It’s limited to the heat capacity of the Argon.]
The surface temperature must become warmer than S-B to provide the energy to simultaneously support radiation out AND the conductive exchange.
Willis 9:41am: Pour yourself a Beer for NYE. I recommend one of the Lambert flavor.
“Mario (sic), for that to happen, the energy of the photon has to be transformed into something else. The photon doesn’t just “vaporize” as you put it.”
Willis – as you require for other posters, use my written words exactly. I didn’t put it “vaporize”. I wrote 8:28am “annihilated”. The IR photon that collides head on with the Ar atom is annihilated (same as extinction) transferring the photon’s momentum to the atom creating “shade” for the atom behind.
If they are off angle then read up on Ar atmosphere attenuation by scattering (Ar mass scattering coefficient).
Obviously you have not read the cite I gave. Please do so and then show me where the basic physics is wrong and the argon atmosphere is really transparent as you incorrectly write. Failing to do so, the argon atmosphere being not transparent will stand – as in all the basic atm. radiation text books.
Caballero: “…the total amount of extinction (i.e. the difference in intensity between outgoing and incoming beams) turns out to be proportional to the amount of matter …. and to the intensity…”
Argon gas is matter, IR has a radiant intensity. Argon lasers work by emitting and absorbing radiation and are used in medical applications. You really need to do your own research to learn this basic stuff.
“..argon is incapable of absorbing any frequencies of thermal IR..”
Quote my words, I didn’t write “absorbing”. Please read & learn the sec 5.8 citation and its ref.s, it is fairly short.
http://people.su.se/~rcaba/teaching/PhysMetLectNotes.pdf
Stephen 4:12am: ”Obviously, that conducted energy is initially derived from absorbed radiation at the surface.”….Radiative gases are not necessary for any part of that purely mechanical process.
Stephen needs to explain radiation being part of a step but then at same time being not any part of the steps.
Mario 10:55am: “Trick’s response is wrong on so many levels.”
Please explain exactly; best for me is use the cite I gave. Or a modern text book cite of your own.
Trick: I was responding to this:
Two argon atoms traveling in earth’s atm., one behind the other from POV of an incoming IR photon from sun. The photon slams into the nearest atom and suffers annihilation, the Ar atom still exists. The photon behind is in the “shade” of this process.
+++++++
I apologize. I thought you used vaporized, my bad for not reading what you wrote carefully.
So I though you were talking about latent heat of vaporization.
But your comment also sounds like you are talking about smashing atoms with photons to release atomic energy. It’s hard to tell what you’re trying to say that proves Argon is not invisible in the sense used in this post. So, are you positing that Argon is in fact not invisible to radiant energy 93 million miles away from the sun, and/or that its lack of invisibility to radiant energy causes it to warm directly from the sun?
Mario
Mario 4:33pm: “So, are you positing that Argon is in fact not invisible to radiant energy 93 million miles away from the sun, and/or that its lack of invisibility to radiant energy causes it to warm directly from the sun?”
Yes, basic text book radiative science, no difference if photon is from sun or is terrestrial.
“..sounds like you are talking about smashing atoms with photons to release atomic energy.”
The photon is annihilated not the Ar atom. Same as a photon when it slams into surface dirt – photon is annihilated and its energy transformed into the dirt. Both Ar gas and dirt are matter, have mass.
Stephen Wilde says:
December 31, 2013 at 10:41 am
Dear heavens, it’s called a “thought experiment” for a reason, Stephen. Einstein used them a lot, “gedanken” experiments, like imagining an elevator in space. And while everyone else was learning something from the thought experiment, you’d be the guy turning your nose up and saying “but there are no elevators in space, Mr. Einstein, so I cannot help you” …
w.
Mario 4:33pm: “So, are you positing that Argon is in fact not invisible to radiant energy 93 million miles away from the sun, and/or that its lack of invisibility to radiant energy causes it to warm directly from the sun?”
Yes, basic text book radiative science, no difference if photon is from sun or is terrestrial.
++++++++++++
So we’re back to Argon, because it has mass, will abosrb radiant energy. And this is in text books? I’ve never seen anywhere that dipole atoms can attain energy from IR radiation, which is what we are talking about right? Could you help by pointing to a source?
Since a planet can never be evenly heated so as to satisfy Willis’s thought experiment it must follow that conduction will lead to convection even for an Argon atmosphere around a real planet.
Thus,inevitably, kinetic energy is converted to gravitational potential energy as air rises and is converted back again as air descends.
Mario 2:31am: “Could you help by pointing to a source?”
It is ok to use the on-line source I posted for Willis; click on the link in 1:58pm post. Everyone welcome. See Sec. 5.8 p. 115 “Extinction and Optical path” for your help.
”Consider a beam of photons all having the same wavelength and direction. Imagine we point the beam perpendicularly at a slab of atmosphere. As the beam passes through the slab, some of the photons will be absorbed and some scattered away from their initial direction. Thus the intensity of the beam will diminish…total amount of extinction (i.e. the difference in intensity between outgoing and incoming beams) turns out to be proportional to the amount of matter in the slab and to the intensity itself.”
All that is needed is mass and intensity for the attenuation of the beam. More basically, all matter radiates in the IR. Doesn’t matter if monatomic like Ar or polyatomic like CO2 though polyatomic molecules have added vibrational, rotational absorption modes as Willis points out, repeatedly.
Willis chose Ar as a thought experiment, not me. Still, it is a good one to learn, there is like 23x as much Ar as CO2 for Earth.
Trick says:
January 1, 2014 at 5:54 am:
I see the lecture notes, and thank you for saving me the time by clipping the text of the lecture notes.
I was asking if there was a source to a text book, since you said this was basic text book knowledge. Since this is obviously a point of contention, I cannot let a lecture note solve my curiosity of what is correct. I never remember in any textbook where it stated that all gases are greenhouse gases. I’ve seen elsewhere that Ar is not like Greenhouse gases.
Are you saying all gases are Greenhouse gases now?
Mario 1:52pm: “I’ve seen elsewhere that Ar is not like Greenhouse gases. Are you saying all gases are Greenhouse gases now?”
As Willis writes and graphs above, the polyatomic gas molecules (e.g. CO2, CH4) are more infrared band active than monatomic gas like Ar since polyatomics have added vibrational, rotational absorption modes in IR range.
Greenhouse gas is an ill-defined term – better to use IR active gas; it is good science to write the monatomic gases like Ar are not as active in IR bands as IR active polyatomic gases. Every object that has mass radiates in IR. Mario can confirm this rummaging around in any radiation text book.
Quote from text book on Atm. Thermo. by Dr. Bohren 1998 p. 356: “All objects at all temperatures at all times radiate (emit) electromagnetic energy and absorb electromagnetic energy from their surroundings.”
You will be able to solve curiosity & find basic Caballero note’s work out on extinction and optical path in any modern text book on the subject at hand as a building block to further atm. science study.
Trick says:
January 1, 2014 at 2:31 pm
Mario 1:52pm: “I’ve seen elsewhere that Ar is not like Greenhouse gases. Are you saying all gases are Greenhouse gases now?”
As Willis writes and graphs above, the polyatomic gas molecules (e.g. CO2, CH4) are more infrared band active than monatomic gas like Ar since polyatomics have added vibrational, rotational absorption modes in IR range.
Greenhouse gas is an ill-defined term – better to use IR active gas; it is good science to write the monatomic gases like Ar are not as active in IR bands as IR active polyatomic gases. Every object that has mass radiates in IR. Mario can confirm this rummaging around in any radiation text book.
Quote from text book on Atm. Thermo. by Dr. Bohren 1998 p. 356: “All objects at all temperatures at all times radiate (emit) electromagnetic energy and absorb electromagnetic energy from their surroundings.”
You will be able to solve curiosity & find basic Caballero note’s work out on extinction and optical path in any modern text book on the subject at hand as a building block to further atm. science study.
++++++++++++++
Cogent response, makes sense.
Trick says:
January 1, 2014 at 2:31 pm
True for all objects … but not for all gases.
w.
I don’t understand. You guys agree that say oxygen, over most of the IR spectrum, doesn’t absorb any IR at all. It absorbs exactly zero in those frequencies. Why not?
Because it’s the wrong frequencies to resonate with their physical configuration. At those frequencies, oxygen is totally transparent to thermal IR. It’s only in a couple of narrow frequencies bands that thermal IR can affect the simple bond of the diatomic oxygen molecule, and can thus convert its energy to mechanical energy. All other thermal IR frequencies are neither absorbed nor emitted by oxygen. It has only a narrow band because it is the simplest kind of molecule, just two identical atoms. So only the frequency that can stretch the bonds can affect oxygen.
CO2 and H2O, on the other hand, have a whole host of ways to interact with IR—stretching, twisting, scissoring, flexing … and as a result, there are a whole host of IR frequencies absorbed by those molecules.
But argon doesn’t have even the single bond of oxygen, it’s monoatomic … so it’s just like the oxygen only more so. Oxygen neither absorbs nor radiates thermal IR over maybe 97% of the IR spectrum shown above. You all seem to accept that.
And yet, you can’t seem to accept that argon neither absorbs nor radiates thermal IR over 100% of the spectrum. You fight endlessly against the fact that argon is even simpler than oxygen, and so is even less affected by thermal IR than is oxygen. Argon is a single spherical molecule, and there’s nothing for the IR to shake or stretch or vibrate, so the IR can’t interact with the argon at all.
Puzzling …
w.
PS—As someone pointed out above, all solid objects radiate and absorb thermal IR. This is because they have an entire forest of different kinds of bonds between their atoms for the IR to interact with. As a result, solid objects can generally not just absorb and radiate thermal IR, but do so at a host of frequencies.
Gases are different, because they only have certain specified bonds between their atoms. In general, the more atoms that make up the gas molecule, the more effective it is at absorbing thermal IR.This is because there are more modes of flexing, twisting, scissoring, and combinations of the above, so it can absorb more frequencies of IR.
In part, that’s why methane (CH4) is a stronger GHG than either H2O or CO2. It’s also one reason why the chlorofluorocarbons are strong GHGs.
And going the other way, the simpler the molecule the fewer thermal IR frequencies it can absorb. O2 and N2 only absorb in very narrow IR frequency bands.
And at the end of the scale, the simplest gases, monoatomic gases like argon, have no bonds to stretch, shake, scissor, flex, or bend. So they don’t absorb in any thermal IR frequency, not even the narrow bands that are the only frequencies absobed by O2 and N2.
Willis 11:06pm: “True for all objects … but not for all gases.”
The Queen’s English defines gas is an object. All objects attenuate photon beams at any freq. as all objects have mass (are tangible) and therefore will always annihilate, scatter and/or absorb photons in a beam thus physically attenuate that beam. This is basic physics – available for your study in the text book cites I provided and many others.
Willis 11:31pm: “I don’t understand.”
I made an attempt to make it simple and no simpler for you to understand at 12/31 8:28am. You have not provided counterargument that I find except for polyatomic case. The links you posted 12/28 11:39pm cover just the polyatomic case.
Again, those charts you posted do not go to exactly 0.0 at any freq. upon expanding their scale. A photon beam of any freq. has a probability of its constituent photons being annihilated or scattered in any gas – even in a monatomic gas (meaning the beam is always attenuated) – depending on the gas’ experimentally determined non-zero mass scattering coefficient proportional to the probability that a photon will be scattered when meeting a particle. The angle of photon scattering and effect on particle KE is the phase function in classical electromagnetism.
This monatomic gas treatment is in text book physics Willis, available for your study simply by looking it up. I entirely agree with your discussion & links for polyatomic molecules with added vibration/rotational absorption modes.
Your assertion “..monoatomic gases like argon,…don’t absorb in any thermal IR frequency” meaning physically no (i.e. 0.0) IR photon beam attenuation is just not supported in any classical electromagnetism text I can find.
If I have missed the classical electromagnetism physics, please provide a monatomic gas applicable text book cite.
Willis Eschenbach says, December 30, 2013 at 10:56 pm:
On the Earth, you are right when you say “of course it can”. This is because the GHGs can absorb some of the radiation.
But in my thought experiment, with a transparent argon atmosphere … well, no, it can’t.”
Yes, Willis. Also with an argon atmosphere. This is not about radiation. This is about conduction/convection.
Read and address the entire comment, Willis. Not just your carefully extracted quote. You’re doing here exactly what you’re accusing other people of doing with your words. You cherry-pick a small and convenient section out of an argumentative context and in answering that pretend to have addressed the argument as a whole. Quite a transparent evasion tactic.
Willis’s thought experiment has another defect.
We all accept (I think) that if one can suppress convective overturning completely then the only way that energy can move upward is via conduction from one stationary molecule to another and then one could achieve an isothermal atmosphere with the temperature from top to bottom equalling that at the surface below. Normally to achieve that one would need a solid medium and not a mobile gaseous medium.
To get to that point for a mobile gaseous medium Willis suggests a perfectly smooth surface, perfectly evenly illuminated by an infinite number of suns all around the circumference.
Then he introduces a perfectly non radiative atmosphere so that the effective radiating height must remain at the surface.
His problem then is that the planet in nearly all cases is still rotating.
If there is ANY rotation, however small, then since rotation is in only one plane the friction between solid surface and gaseous atmosphere will be greater at the equator than at the poles.
Those friction irregularities will introduce pressure variations which will lead to density variations at the surface and convection will start.
The Coriolis force will spread the density variations latitudinally and climate zones will develop with a similar pattern of circulation as for a GHG atmosphere.
In reality that thought experiment adds nothing to the debate because it can never happen.
The basic facts are:
i) Conduction to and fro between a surface and the mass of a gaseous atmosphere warms the surface and lifts the S-B height off the surface proportionately to the mass of the atmosphere.
ii) Radiative capability within the mass of an atmosphere raises the effective radiating height off the surface.
iii) Due to the above two heights being different, density variations occur which results in convection and that convection shuttles energy to and fro between the two heights to ensure that enough energy is available at the effective radiating height to maintain radiative balance with space.
To illustrate the principle consider this:
i) For no atmosphere both the S-B height and the effective radiation height are together at the surface.and with no atmosphere there would be no circulation.
ii) For an atmosphere with 100% radiative capability the S-B height and the effective radiating height would be together at the top of the atmosphere with no circulation despite there being an atmosphere. The atmosphere would be behaving as if it were a solid with the radiating surface at the top.
Only if the two heights are separated will circulation begin and the sole purpose of that circulation is to prevent the separate heights from destabilising the system.
The two heights are separated by the inevitable movement that occurs within a gaseous medium as a result of uneven surface heating leading to density variations at the surface followed by a convective circulation and the decline in temperature with height that then results from the work done moving mass against gravity.
Convection both up and down in variable proportions is the physical process whereby the system adjusts the internal energy flows to negate the thermal effect of those two heights differing for whatever reason.
Conduction from a solid surface to the gaseous atmosphere and the ability of a gaseous medium to move internally both with and against the force of gravity is what causes the two heights to separate.
Willis, careful not to sound like myrrh about water not absorbing light, at all… Trick is giving you the proper viewpoint, maybe listen. All matter absorbs and emits infrared, even all gases, at all frequencies under the pertinent Planck curve, it is only a matter of how stronly it is absorbed/emitted and how much mass it passes through. Maybe think of looking unprotected at the sun near the horizon and why all frequencies are attenuated irregarless of just rotation and vibration lines, IR is similar. Our atmosphere’s maximum transmittance is only about 90% when zenith and that is only between 3 and 4 μm and looking at a transmittance plot the vast majority (including in the window at 8-14 μm) is only about 80%. This is the underlying gray body absorption and emission from collision induced and temporary dipole moments mainly from the nitrogen and oxygen due to the high concentrations and only extremely rarified gases show little of this gray body effect for then the collisions are so rare, but not at our troposphere pressures. The vibrational and rotational spectrums you normally see seem to be just that, of rarified samples, short path lengths, to basically zero out the gray body from the gas and the equipment itself I suppose. All of that is my current understanding after digging into this subject.
Maybe look at http://en.wikipedia.org/wiki/File:Atmospheric.transmittance.IR.jpg for a few minutes and ask why this data look as it does. (from: Transmittance page, orig. source http:/ewhdbks.mugu.navy.mil/transmit.gif)
You are correct that the rotational and vibrational modes, if present, are magnitudes stronger in certain lines and bands driving the transmittance to near zero but you cannot say because of this that an argon, or nitrogen, or hydrogen atmosphere does not absorb and emit isotropically if the atmosphere is thick. Over a couple of years ago I too was almost led astray by the likes of Phil. and Shores that there was zero interaction but found it is they that are incorrect, probably by design and selling their AGW story line. But in saying what you are saying all of those highest readings should be at 100% transmittance and not vary even down to the horizon where the attenuation is about 34 times that of zenith and all of that is not actual.