Guest post by Ben Herman and Roger Pielke Sr.
We have received a further question on our post:“The Greenhouse Effect” by Ben Herman and Roger Pielke Sr.
The question is summarized by the following text
Anyway my question refers to the common example of taking away the atmosphere and observing a cold surface. But as I understand it, the mean daytime surface temperature on the moon is over 100 C, with no greenhouse effect. The mean nighttime temp drops to -150 C. http://www.solarviews.com/eng/moon.htm
This is important to note, because encouraging a popular picture in which the presence of the atmosphere only warms the surface takes all the convection and fluid dynamics out of the discussion, and that’s where all the important complexities are.
Isn’t it more the case that the atmosphere both warms and cools the surface, depending on circumstances? The IR absorption of H2O and other GHG’s warms the surface relative to what it would otherwise be, but as the lunar case shows, convection and turbulent mixing cools the surface relative to what would happen without an atmosphere. Take away the atmosphere and you take away both warming and cooling mechanisms.
We have reproduced the substance of our follow up answer below.
Predicting the surface temperature indeed involves the interaction of the atmospheric and ocean turbulent sensible and latent fluxes, long- and short- wave radiative fluxes and interfacial fluxes between the surface and the atmosphere. I have been urging for years to move away from the surface temperature to characterize global warming and cooling (and replace with ocean heat content changes in Joules) because the surface temperature is such a limited sample of the heat content changes of the climate system as well as involving these complicated feedbacks.
On the Moon, there is, of course, no atmosphere, so its surface temperature results from the difference between the surface long wave radiative emissions, the amount of solar radiation absorbed and reflected, and the conduction of heat into and out of the surface. The effect of the atmosphere on Earth is to mute the diurnal (and seasonal) temperature range as a result of the turbulent fluxes, and other effects (such as clouds and precipitation). These atmospheric effects, for example, result in lower daytime and higher nighttime temperatures from what they otherwise would be. I presume this is the cooling and warming effects that you refer to. However, even with these effects, the surface is clearly warmer than it would be without the CO2 and water vapor IR absorption bands.
But the reasons are that the atmosphere scatters back to space some sunlight, and takes up some of the surface heating through conduction, and mixes it it by convection and turbulence. Also, the relatively rapid rotation of the earth on its axis does not permit the daytime side to reach equilibrium before it starts nighttime cooling. As a result, daytime temperatures on earth are cooler than they would be with no atmosphere, and warmer at night than with no atmosphere.
Of course, the Moon, with no atmosphere, still has to have basically the same effective radiating temperature as does the Earth. This should be
[sigma *Tmd**4 + sigma* Tmn**4]/2 = sigma*Te**4 where Tmd is the daytime temperature of of the Moon, Tmn is the night time temperature of the Moon, and Te is the effective radiating temperature of the Earth.
The fact that the daytime time temperature is warmer than the Earth’s temp is simply a result of the fact that the Moon is not in an equilibrium state – it warms up during the daytime and cools down at night, just as does the Earth. However the warming during day and cooling at night must balance each other or the Moon ( and the Earth) would be steadily heating up or cooling down over time. The daytime warming occurs because the outgoing IR cannot balance the absorbed solar during the day. The nighttime cooling occurs because the outgoing IR is greater than the non-existing solar at night. The existence of a partially absorbing atmosphere does, as you stated, keep days cooler and nights warmer.
Also, the length of a day on the Moon is 29.5 earth days, almost a full Earth month. Therefore the daylight side of the Moon heats due to solar radiation, for half a month. Then when it’s night, it cools for another half month. Thus the daytime and nighttime temperatures are much more extreme. There is no greenhouse effect on the Moon, of course, and if the Moon’s day was the same 24 hours as an Earth day, its day and night temperatures would not vary as much but its radiative equilibrium temperature would be the same.
Update #2 John Nielsen-Gamon has alerted us to more information on the Moon’s radiative temperature. John e-mailed
I read your blog post on Greenhouse Part 2. I also recently came across the Science of Doom web site; it seems to be of very high quality. You might want to link to http://scienceofdoom.com/2010/06/03/lunar-madness-and-physics-basics/ [on] your post to direct the reader to further details on the radiative temperature of the Moon.
Update – corrected text (underlined) h/t to Gerald E. Quindry
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http://hyperphysics.phy-astr.gsu.edu/hbase/electric/diph2o.html
I simplifies how a dipole moment can appear , and also that H2O has a dipole , in contrast to what Phil wrote some posts above.
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
the following explains why classical statitistical mechanics was not enough to describe black body radiation:
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
Note that at low frequencies, i.e. infrared, classical and quantum mechanical (Planck) forms coincide.
anna v says:
August 3, 2010 at 9:56 pm
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/diph2o.html
I simplifies how a dipole moment can appear , and also that H2O has a dipole , in contrast to what Phil wrote some posts above.
It appears in addition to your ignorance of the physics that you can’t read! I did not say that H2O doesn’t have a dipole I said that “nitrogen, oxygen, and water vapor do not radiate as blackbody spectra”. Which is of course true, your protestations to the contrary notwithstanding.
anna v,
You seem to think gases are black bodies, when actually they are far from it. They cannot radiate at unpermitted wavelengths, and are only seen by their lines where they can radiate. Gases in space likewise are only visible by lines if they have them. Isolated matter that does not radiate easily (like O2 molecules) carry their kinetic energy until they collide with something. If they are in a dense enough gas, this can reach thermal equilibrium by collisions (when gas laws apply). Maybe O2 has some exotic quadrupole behavior, but these lines must be millions of times weaker than the vibrational bands of CO2 etc., since we don’t see these in a normal atmosphere.
Phil and Εd
You need to study a bit of physics, particularly thermodynamics, classical electromagnetism and statistical mechanics.
The physics you know is propaganda tools for AGW. The world we see and touch and measure is not just quantum mechanical. Quantum mechanics smooths over to classical theories for the distances we see and measure everyday. Hbar is a very small number and that is why quantum mechanics took so long to be established, it is so esoteric.
Every matter radiates and the black body formula is an approximation of the spectrum. It is true that gases have gray body constants and spectrum variations, but still they radiate heat away in a continuum of soft radiation that comes from what really “collisions” mean. Collisions are electric and magnetic fields bumping into each other. Read a bit on Maxwell’s equations. When that happens radiation comes out.
Stop parroting mantras you do not really understand and trying to correct people who do know their physics.
RE:Phil: (July 29, 2010 at 12:49 pm) [‘ice-locker’ gas atmosphere] “It’s called the stratosphere, the gas is oxygen.”
You are quite right. I thought it might be useful to visualize a hypothetical atmosphere that blocked nearly 100 percent of the incoming short-wavelength, solar-radiation, but still allowed the ground to radiate infra-red directly to outer space. It would take a *very* special cocktail of gases to do that.
Of course, convection is possible as long as a significant amount of solar heating can take place at the surface.
anna v says:
August 4, 2010 at 9:01 pm
Here!! Here!!
Kindest Regards
anna v,
O2 and N2 gas molecules have elastic collisions, and a well-defined temperature by virtue of their kinetic energy alone (thermometers work by collisions, not radiation). Their collisions conserve momentum, energy, and their rotational counterparts (in mechanics as also in quantum mechanics). Quantum mechanics predicts very low probabilities for emitting photons, and that is why their emission lines are negligible compared to CO2 and H2O that are “IR active” (a term in spectroscopy that distinguishes these molecular behaviors for good reason). A gas made of O2 and N2 would have no greenhouse effect. Your argument is suggesting it should, and by that logic we would be toast by now regardless of CO2 and H2O. Is that really what you want to say? Think it through.
Jim D says:
August 4, 2010 at 10:10 pm
O2 and N2 gas molecules have elastic collisions, and a well-defined temperature by virtue of their kinetic energy alone (thermometers work by collisions, not radiation). Their collisions conserve momentum, energy, and their rotational counterparts (in mechanics as also in quantum mechanics). Quantum mechanics predicts very low probabilities for emitting photons, and that is why their emission lines are negligible compared to CO2 and H2O that are “IR active” (a term in spectroscopy that distinguishes these molecular behaviors for good reason). A gas made of O2 and N2 would have no greenhouse effect. Your argument is suggesting it should, and by that logic we would be toast by now regardless of CO2 and H2O. Is that really what you want to say? Think it through.
Please Jim, you have to think through. Read a bit of thermodynamics and classical electromagnetism and statisctical mechanics. Quantum mechanics too.
There are elastic collisions and continuum inelastic collisions that have nothing to do with the fine lines of the excited spectra of the atoms and the excited rotational and vibrational spectra.
There exists a continuum of radiation in the infrared to microwaves also in quantum mechanics, though it is cumbersome to carry all the paraphernalia of state functions to show that. Classical electrodynamics is sufficient.
An inelastic collision between molecules could transfer energy to vibrational and rotational modes and also radiate a photon in the asymmetric distorted fields coming from the collision.
It is as simple as that and you do not know the basics of what we are discussing.It has to be like that because all matter composed of molecules radiates away in some sort of black/gray body formula.
Parroting “quantum mechanics says” is really not very meaningful. Quantum mechanics says there is very high probability of emitting soft photons if two molecules collide.
anna v,
I see we disagree, and I can’t do much about that except to say look for observations of oxygen lines, or even a continuum due to it, in the atmospheric spectrum. In the end observations count to prove and disprove theories. Having seen these spectra, I am sure you won’t find O2 doing much of anything to them. O3 does, but not O2. When you have found such spectra, which are routinely measured, get back to me because there is no point in this discussion without the observations, much as I like the physics theory part.
If there is a flaw in the Greenhouse Effect theory, and from what I can dig up, there are quite a few, I suspect that the most important flaws are the simple ones. The ones that you can see by stepping back and looking at the really big picture. That’s when specialized scientists who rarely consider the big picture, and lay people can agree.
Theo, good questions. About CO2 concentrations in the ‘atmosphere’. I asked this too a while ago. Helium is lighter than ‘air’, it rises. CO2 is heavier than ‘air’ it generally sinks. When in high concentrations in certain water wells or low lying vallies around volcanoes and the like, it lingers there apparently – which is a known health hazzard. CO2 obviously has a choice to rise up like helium, or sink. The fact that it mostly stays at ground level is quite convenient for the greenery that feeds on it. If it rose we’d have trouble living on the planet. Where the heck this greenhouse effect is supposed to occur, I don’t know, because at ground level heat rises.
Dave Springer says:
July 28, 2010 at 10:11 pm
Moon’s average temp as recorded by two different Apollo missions is negative 23C or close enough to not be worth arguing about at mid latitudes. Thermocouples were placed on the surface and at intervals up to 3 meters deep in the regolith in the one they could bore that deep. Data was returned over a period several years. At a depth of around 1 meter IIRC (raw data is buried but accessible somewhere on Nasa web site as I found it and read it several months ago) temperature reading became constant over days and seasons.
To sum up, whatever is keeping the earth warmer appears to be keeping it a lot more than 33c warmer to offset the big difference in albedo betwixt the earth and moon.
~
I think AnnaV touched on this above at 9:17, Aug 1st. But, (correct me if I’m wrong) do we measure the Earth temperature on the ground and at 3m depths when coming to the conclusion that average Earth (air) temperature is 15 degrees C?
Is the assumption above made by Dave Springer that if the Earth had no atmosphere it’s temperature would be roughly -23 degrees C, hence a 38 degree greenhouse effect that we really must be ‘experiencing’… a correct assumption?
Our atmosphere is obviously an insulator that shields us from extreme solar radiation during the day. The phenomena of a warmer Earth night than the Moon night is consistent with an atmosphere acting as an insulator. The question then for me is: is it also an insulator that adds ‘greenhouse’ heat energy at the same time? Can insulators ever really ‘add’ energy?
LaymanAlert says:
August 28, 2010 at 9:58 pm
” Can insulators ever really ‘add’ energy? ”
Definately not, but they sure can absorb energy / heat and then
release it (mostly) back at varying rates over varying timescales..
In a cycle upon cycle sort of way, that may appear to the casual glance as sometimes adding more or less (back).
For example, PDOs, AMOs, and loads more (on numerous timescales – some not repeating) we don’t know about yet.
Something I been trying to get across for several years now….
ie,
http://i53.photobucket.com/albums/g43/DerekJohn_photos/stuff/Dailywaterjacketsized.jpg