Guest post by Ira Glickstein
A real greenhouse has windows. So does the Atmospheric “greenhouse effect”. They are similar in that they allow Sunlight in and restrict the outward flow of thermal energy. However, they differ in the mechanism. A real greenhouse primarily restricts heat escape by preventing convection while the “greenhouse effect” heats the Earth because “greenhouse gases” (GHG) absorb outgoing radiative energy and re-emit some of it back towards Earth.
The base graphic is from Wikipedia, with my annotations. There are two main “windows” in the Atmospheric “greenhouse effect”. The first, the Visible Light Window, on the left side of the graphic, allows visible and near-visible light from the Sun to pass through with small losses, and the second, the Longwave Window, on the right, allows the central portion of the longwave radiation band from the Earth to pass through with small losses, while absorbing and re-emitting the left and right portions.
The Visible Light Window
To understand how these Atmospheric windows work, we need to review some basics of so-called “blackbody” radiation. As indicated by the red curve in the graphic, the surface of the Sun is, in effect, at a temperature of 5525ºK (about 9500ºF), and therefore emits radiation with a wavelenth centered around 1/2μ (half a micron which is half a millionth of a meter). Solar light ranges from about 0.1μ to 3μ, covering the ultraviolet (UV), the visible, and the near-infrared (near-IR) bands. Most Sunlight is in the visible band from 0.38μ (which we see as violet) to 0.76μ (which we see as red), which is why our eyes evolved to be sensitive in that range. Sunlight is called “shortwave” radiation because it ranges from fractional microns to a few microns.
As the graphic indicates with the solid red area, about 70 to 75% of the downgoing Solar radiation gets through the Atmosphere, because much of the UV, and some of the visible and near-IR are blocked. (The graphic does not account for the portion of Sunlight that gets through the Atmosphere, and is then reflected back to Space by clouds and other high-albedo surfaces such as ice and white roofs. I will discuss and account for that later in this posting.)
My annotations represent the light that passes through the Visible Light Window as an orange ball with the designation 1/2μ, but please interpret that to include all the visible and near-visible light in the shortwave band.
The Longwave Window
As indicated by the pink, blue, and black curves in the graphic, the Earth is, in effect, at a temperature that ranges between a high of about 310ºK (about 98ºF) and a low of about 210ºK (about -82ºF). The reason for the range is that the temperature varies by season, by day or night, and by latitude. The portion of the Earth at about 310ºK radiates energy towards the Atmosphere at slightly shorter wavelengths than that at about 210ºK, but nearly all Earth-emitted radiation is between 5μ to 30μ, and is centered at about 10μ.
As the graphic indicates with the solid blue area, only 15% to 30% of the upgoing thermal radiation is transmitted through the Atmosphere, because nearly all the radiation in the left portion of the longwave band (from about 5μ to 8μ) and the right portion (from about 13μ to 30μ) is totally absorbed and scattered by GHG, primarily H2O (water vapor) and CO2 (carbon dioxide). Only the radiation near the center (from about 8μ to 13μ) gets a nearly free pass through the Atmosphere.
My annotations represent the thermal radiation from the Earth as a pink pentagon with the designation 7μ for the left-hand portion, a blue diamond 10μ for the center portion, and a dark blue hexagon 15μ for the right-hand portion, but please interpret these symbols to include all the radiation in their respective portions of the longwave band.
Sunlight Energy In = Thermal Energy Out
The graphic is an animated depiction of the Atmospheric “greenhouse effect” process.
On the left side:
(1) Sunlight streams through the Atmosphere towards the surface of the Earth.
(2) A portion of the Sunlight is reflected by clouds and other high-albedo surfaces and heads back through the Atmosphere towards Space. The remainder is absorbed by the Surface of the Earth, warming it.
(3) The reflected portion is lost to Space.
On the right side:
(1) The warmed Earth emits longwave radiation towards the Atmosphere. According to the first graphic, above, this consists of thermal energy in all bands ~7μ, ~10μ, and ~15μ.
(2) The ~10μ portion passes through the Atmosphere with litttle loss. The ~7μ portion gets absorbed, primarily by H2O, and the 15μ portion gets absorbed, primarily by CO2 and H2O. The absorbed radiation heats the H2O and CO2 molecules and, at their higher energy states, they collide with the other molecules that make up the air, mostly nitrogen (N2), oxygen (O2), ozone (O3), and argon (A) and heat them by something like conduction. The molecules in the heated air emit radiation in random directions at all bands (~7μ, ~10μ, and ~15μ). The ~10μ photons pass, nearly unimpeded, in whatever direction they happen to be emitted, some going towards Space and some towards Earth. The ~7μ and ~15μ photons go off in all directions until they run into an H2O or CO2 molecule, and repeat the absorption and re-emittance process, or until they emerge from the Atmosphere or hit the surface of the Earth.
(3) The ~10μ photons that got a free-pass from the Earth through the Atmosphere emerge and their energy is lost to Space. The ~10μ photons generated by the heating of the air emerge from the top of the Atmosphere and their energy is lost to Space, or they impact the surface of the Earth and are re-absorbed. The ~7μ and ~15μ generated by the heating of the air also emerge from the top or bottom of the Atmosphere, but there are fewer of them because they keep getting absorbed and re-emitted, each time with some transfered to the central ~10μ portion of the longwave band.
The symbols 1/2μ, 7μ, 10μ, and 15μ represent quanties of photon energy, averaged over the day and night and the seasons. Of course, Sunlight is available for only half the day and less of it falls on each square meter of surface near the poles than near the equator. Thermal radiation emitted by the Earth also varies by day and night, season, local cloud cover that blocks Sunlight, local albedo, and other factors. The graphic is designed to provide some insight into the Atmospheric “greenhouse effect”.
Conclusions
Even though estimates of climate sensitivity to doubling of CO2 are most likely way over-estimated by the official climate Team, it is a scientific truth that GHGs, mainly H2O but also CO2 and others, play an important role in warming the Earth via the Atmospheric “greenhouse effect”.
This and my previous posting in this series address ONLY the radiative exchange of energy. Other aspects that control the temperature range at the surface of the Earth are at least as important and they include convection (winds, storms, etc.) and precipitation that transfer a great deal of energy from the surface to the higher levels of the Atmosphere.
I plan to do a subsequent posting that looks into the violet and blue boxes in the above graphic and provides insight into the process the photons and molecules go through.
I am sure WUWT readers will find issues with my Atmospheric Windows description and graphics. I encourage each of you to make comments, all of which I will read, and some to which I will respond, most likely learning a great deal from you in the process. However, please consider that the main point of this posting, like the previous one in this series, is to give insight to those WUWT readers, who, like Einstein (and me :^) need a graphic visual before they understand and really accept any mathematical abstraction.
http://wiki.answers.com/Q/What_percentage_of_the_electromagnetic_spectrum_is_visible_light
some answers..
“”””” kuhnkat says:
March 1, 2011 at 5:04 pm
George E. Smith,
“Did the classical EM radiation laws of Maxwell not run up against the ultraviolet catastrophe and hence the modification by Planck and Einstein introducing the quantised photon?”
One of the misconceptions that even good scientists fall prey to is believing that mathematics drive science. Mathematics is a tool that can be used to DESCRIBE the real world and allow us to manipulate ideas about it and make projections if we do a good enough job of the description. “””””
I have no idea what your point is; do you have one you’d care to state ?
And there is NO mathematics that can describe the real world or even attempts to. Mathematics can be used to describe the expected behavior of our theoretical modles of the real world; which are every bit as fictional as the mathematics is; we made all of it up, so none of it is real.
We do try to construct our fictional models to try and mimic reality; but that is all they do; they do not explain reality.
Wayne wrote:
“So you are saying that if you had a large clump of warm nitrogen in empty space held together by gravity that it could not radiate in a black body manner at all, zero, none, zip? Maybe check some good astronomy books on that matter that cover quantum aspects.”
and
“Ira placed no numbers on exactly how much was split between those 7, 10, and 15 µm band portions. Just that those interactions do occur.” … That is how I see it from my years in studying physics.”
Wayne, maybe you need to continue study physics for some more years and learn how to put numbers on magnitude of effects. I am sure you heard about “pressure broadening” and “collision-induced absorption” during your studies. Now consider that we are not living on a star. Please open your reference book and compare gas pressures and temperatures of stars with Earth atmosphere.
Then try to comprehend the the difference between numbers. It is called “Physics”.
Please also do understand that “greenhouse effect” does not occur because 1/1,000,000 fraction of 15um band energy gets re-distributed and re-emitted from 10-13um band.
But of course you are formally correct. Instead of saying “hot air cannot possibly generate any photons in that range” I should have said “hot air cannot generate any remotely considerable amount of photons in that range”.
Dave Springer says:
March 1, 2011 at 3:54 pm
CO2 IS INSULATION.
IT DOES NOT HEAT ANYTHING. IT SLOWS DOWN HOW FAST THE SURFACE COOLS.
I WONDER IF ALL CAPS WILL HELP. GOD KNOWS I’VE TRIED EVERYTHING ELSE TO GET THIS SIMPLE CONCEPT ACROSS.
Errr, NOPE, it don’t help, YOUR the one missing the point.
(I hope the capitals help)
Here is a more realistic way to “visualise” the “greenhouse effect” as commonly (and incorrectly) explained and viewed at present.
from,
http://www.globalwarmingskeptics.info/forums/thread-855.html
Could someone please explain to me (understandably) why
a thermal image of a greenhouse shows it radiating more than it’s surroundings. ?
(I know the greenhouse radiates more because it is warmer than it’s surroundings, but
it is supposed to trap radiation, yet (somewhat inconveniently) greenhouses, as far as I’m aware, radiate according to the Planck curve)
I thought a greenhouse was supposed to “trap” radiation.
Is Plancks law wrong, surely not.
So, would the better question be. Why are the greenhouses surroundings so much cooler than the greenhouse, although
the surroundings do not actually “trap” radiation, they do appear to be radiating far less than the greenhouse.. ?
What then is cooling the surroundings. ?
I am assuming the best explanation would be because the surroundings are cooled by something far more powerful than radiation looses,
namely conduction and convection of sensible and latent heat.
A greenhouse “works” because it reduces conduction and convection to it’s surroundings.
It would appear reasonable to say observation of a thermal image of a greenhouse and it’s surroundings indicates that
conduction and convection (of sensible and latent heat) is far more powerful than radiation looses, and
is responsible for cooling the surroundings mostly.
Is this a correct series of assumptions, or rather statements of the blitheringly obvious.
I too am bored with the way “climate discussions” seem to be either circular, or descend into mud slinging.
Maybe, just maybe, present discussions are discussing the wrong “things”..
End of quote.
The above has recently been misquoted on this blog by someone else.
In the end, the REAL QUESTION, that is avoided, is simple.
It is,
Why do physicists using closed, isolated, far higher concentrations than are realistic, to suggest (and supposedly observe that) CO2 has a high specific heat capacity,
YET,
CHEMISTS USING THEIR MASS BALANCED EQUATIONS SHOW CO2 HAS A LOW SPECIFIC HEAT CAPACITY.
(Hey, this caps thing is quite good isn’t it..)
Maybe, just maybe, CO2 reacts differently in an open and mixed system, at far, far, far lower concentrations than a closed, isolated, at far, far, far, far, far, far, higher concentration of CO2 system.
Dam, the EPA never thought of (or understood) that, AND niether did most “climate sceptics” either apparently.
(brackets are quite good as well.)
Increased CO2 in the upper atmosphere increases global cooling , obviously,
BECAUSE,
it increases (the planet’s ability to loose, or rather emit) radiation of energy to space.
AND,
CO2 helps move energy about FASTER in the lower atmosphere,
BECAUSE,
conduction and convection (of energy AND latent heat) is increased,
BECAUSE,
of the physical properties (which “we” really are not sure of) of CO2.
But this is all irrelevant, CO2 is dwarfed into insignificance by H2O and
it’s nefarious abilities, most undeniably including change of state,
which at atmospheric temperatures, CO2 just can not touch.
CO2 AIN’T INSULATION.
It is the staff of life, this planet is almost entirely, carbon based life forms.
(as James T Kirk noted, way back when, when Star Trek was young)
Nowhere near enough people (and almost ALL politicians + bureaucrats ) understand how little “climate science” actually does know.
Lines 2 and 3 of the infamous Rumsfeld quote describe the current state of the “settled science” of AGW and “climate science” best at present, in my opinion.
ie,
“Known, unknowns, and
unknown, unknowns.”
“”””” Bryan says:
March 1, 2011 at 2:31 pm
George E. Smith
Did the classical EM radiation laws of Maxwell not run up against the ultraviolet catastrophe and hence the modification by Panck and Einstein introducing the quantised photon?
I have always understood that continuous spectra are associated with radiating solids.
For gases that radiate a line spectra is what I’d expect.
You can flick between absorption and emission spectra for H2O
http://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC
Same also for CO2
http://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC “””””
So that CO2 infrared spectrum for example, is the absorption spectrum for 390 ppm of CO2 in dry standard air, I take it; or am I presuming too much. You did check that the spectrum is for the system of primary interest; namely earth’s lower tropospheric atmosphere; didn’t you ??
Your spectra look nothing at all, like the spectralcalc ones that Phil has pointed us to; can you explain that ?
“”””” Myrrh says:
March 1, 2011 at 5:26 pm
http://wiki.answers.com/Q/What_percentage_of_the_electromagnetic_spectrum_is_visible_light
some answers.. “””””
So now we go from the sublime to the ridiculous. That wiki answer to the question it total BS; and you can use your own non wiki dictionary explanation of BS.
The proposed standard Solar spectral irradiance (w/m^2/micron) contains 8.725% of the energy below 400 nm (UV) and 56.023% below 800 nm (visible, so that means 47.3% of the total solar spectrum is visible, and only 44% is in the IR from 0.8 micron to infinity. So there is more visible than IR
Was just thinking I’ve long since lost track of how many physicists, engineers, chemists, scientists of who knows how many stripes with credentials, real world experience, text books, articles and studies galore at their finger tips, having a raging argument about how photons interact with CO2 molecules. Such a tiny simple question about just that.
But the climatologists at the IPCC with thousands of factors to consider, plus all the combinations of those factors… they’ve got a consensus. Wow, they must be really smart 😉
Dave Springer shouted: “I AM SORRY BUT YOU ARE WRONG. COLD DENSE GASSES ALL EMIT A CONTINUOUS BLACKBODY SPECTRUM. SEE KIRCHOFF’S FIRST LAW OF RADIATION WHICH I POSTED EARLIER.”
You should be sorry, because you didn’t get the meaning of “dense gas” as it is used in astronomy and web articles about “continuous spectrum”. When astronomy talks about “dense gas”, they mean “optically non-transparent gas”, like star’s atmosphere or some other non-transparent object. Earth atmosphere is not optically dense, not in the 10-13um band at least. In climatology-speak it is called “IR transparency window”, for that very reason. As such, air does not absorb 10-13um EM waves, and does not emit any “remotely considerable amount of radiation” in that band, at least for any practical reasons.
Domenic says:
March 1, 2011 at 11:43 am
to Phil and Cal
Nope. The full characteristics of N2 and O2 in the long wavelength IR have never been actually tested.
Indeed they have, as shown above they are exceptionally weak, it would require incredibly dry air to make the measurement since the spectrum of water is millions of times stronger. Probably very long path length FTIR spectroscopy.
There is something very fishy in the spectral graphs bandied about from calculations regarding the emittance and reflectance of N2 and O2. They are not metals.
Indeed they are not, perhaps you should realize that gases have very well known molecular structures and correspondingly well known spectra.
Both N2 and O2 must be tested thoroughly in the long wavelengths and not guessed at.
No one’s guessing at them, except perhaps you.
Bill Illis submitted a CERES OLR image
http://img132.imageshack.us/img132/1866/renderdata.jpg
and stated:
“one should be able to see the hot parts of the continents, or the cold parts of the continents. Or something.”
Where did you get this picture? Is it possible that the signal was filtered to show absorption CO2 bands only, and not 10-13um? Could it be possible that ground emission in “atmospheric transparency window” is spotty and does not resemble land, so it is hard to recognize? Please keep in mind that 70% of surface are clouds that are blackbodies in IR, so it will not improve visibility either.
Theo Goodwin says:
February 28, 2011 at 7:51 pm
bubbagyro writes:
“CO2 is generated on the earth’s surface. It becomes more dilute as it diffuses upward. The models, similar to Ira’s, assume it is a narrow band. This is not true. The very dilute CO2 and water even in the stratosphere absorb radiation. The higher that occurs, the more is lost to space.”
Please expand on this. My understanding is that the modelers assume that concentrations of CO2 are the same wherever they occur in the atmosphere – all the way up. In addition, they assume that the behavior of CO2 molecules regarding radiation is the same throughout the atmosphere. It has always seemed to me that these “uniformity” assumptions were just evidence of an unwillingness to do the necessary empirical research. In plain and simple terms, I would like someone to address the linked questions of “where are the CO2 concentrations and how does radiative behavior change depending on where they are?”
Your assumption is not correct, concentration is not constant, mole fraction is to a good approximation. They do not assume that the radiative properties are the same through the atmosphere, line broadening changes with pressure and temperature.
Very good article (and graphics). Most lay people have no idea that CO2 absorbs only a small fraction of the IR spectrum. Those of us who took undergraduate organic chemistry remember the use of IR absorption analysis and the fact that CO bonds absorb only certain wavelengths.
Slightly OT, but VUK said:
There is also possibility of a half way house:
Solar input is constant,
I don’t think that is assumption is a half-way house, I think that position is full on nut house. We have been studying solar output for such a short time, that making any statements about solar output being constant is, IMHO, ridiculous. Based on observations of many other stars, variable output of stars is certainly well known. Our star may be relatively constant in output, or may be in a relatively constant phase. But assuming that solar output is constant over thousands of years is a pretty big assumption that is based on nothing (once again, IMHO) other than wishful thinking.
Certainly, with no convincing explanation for the major climate variations we know have occurred over 10K to multi-M year periods, I would be very hesitant to assume that changes in solar output could not be a contributor.
We should study all aspects of climate, including the most important source of energy into our world climate system (the only other being radioactive decay heat, I believe) a little longer before we make simplifying assumptions that lead us to stupid answers (such as CO2 is the only thing that affects world climate–which is effectively what the IPCC and green lobby asserts today regardless of how much they weasel word it if pressed.)
mkelly says:
March 1, 2011 at 12:24 pm
Phil. says:
March 1, 2011 at 10:15 am
“As stated above absolutely wrong, the only way that N2 and O2 molecules can shed energy is by collisional exchange with CO2, H2O etc. molecules which can then radiate.”
Thanks for the information Phil. Your photo while nice does not answer the question of N2 and O2 at the same temperature. Since temperature drives the emittion frequency will they both be the same? I math (Weins Law) says yes, but I have found no info on the subject.
No, why do you think that the N2 and O2 spectra shown are at different temperature?
For two different gases the emission will depend on the transition concerned BB only provides the potential maximum, the line strength will have the dominant effect.
By the way by your statement above you are in the camp that says without GHG we would be a very hot world indeed. Not at -18 C. Once a N2 or O2 molecule was heated via conduction with the ground it would stay heated for a very long time with no H2O or CO2 to reduce its energy. Correct?
No, how do you propose that the atmosphere gets hotter than the surface?
Derek says:
March 1, 2011 at 5:40 pm
“Could someone please explain to me (understandably) why
a thermal image of a greenhouse shows it radiating more than it’s surroundings. ?
(I know the greenhouse radiates more because it is warmer than it’s surroundings, but
it is supposed to trap radiation, yet (somewhat inconveniently) greenhouses, as far as I’m aware, radiate according to the Planck curve)
I thought a greenhouse was supposed to “trap” radiation.
Is Plancks law wrong, surely not.”
——————————–
You didn’t show your thermal image, but, if it’s showing the greenhouse hotter than the tree adjacent, it’s because the greenhouse is hotter.
If the greenhouse skin is polyethylene, the interior of the greenhoue will be what is seen for the greater part. If it’s glass, it will be the glass that is emitting.
On a clear day, the greenhouse will not be much hotter than adjacent objects with similar exposure to the sunshine. It will be hotter than the air outside. The other objects would be as warm but some heat was convected away.
On a clear night, it will be hotter than adjacent objects and hotter than the air. Once again, it’s about the heat loss on the outside, not heat gain on the inside.
I have just taken readings with an IR thermometer from the outside of my greenhouse, looking in. It is nighttime There is a broken pane that is covered with polyE. The wall of an adjacent shed is 0C. The single-glazed pane of glass shows 7C, the poly shows 15C and through the open window, it shows 16.5C.
Obviously, that only speaks to IR transmission of the materials, since the inside temperature arises from thermal mass or internal heat source.
In practice, a poly greenhouse works about as well as a glass one, in spite of the difference in IR transmission. Conduction/convection cools much faster than radiation in these circumstances. And in many others!
That’s my version!
Bill Illis, that satellite picture looks like a water vapor channel. It is not total OLR, nor is it a window wavelength. It is very easy to see the surface diurnal cycle when you don’t look at the water vapor channel. The WV channel has other uses, but not to see the surface. Find other IR images. Typical ones are reversed so that clouds appear white (cold) and the day-time surface is black (hot), going grey at night.
I reiterate, the atmosphere has no way to emit in the 10-micron window region. Its molecules are incapable of producing such wavelengths.
Al Tekhasski says:
March 1, 2011 at 5:29 pm
[snip the ad hominem]
But of course you are formally correct. Instead of saying “hot air cannot possibly generate any photons in that range” I should have said “hot air cannot generate any remotely considerable amount of photons in that range”.
—–
Better. And no, I don’t have the numbers or even a rough estimate. Also I was not speaking of stars or star’s atmosphere but instead warm IR emitting gas clouds so you never see these in visual measurements or photographs. But, you can look at all of the spectrums of Earth’s atmosphere and see the imprint of the overall black, or better gray, body absorption and/or transmission low at the bottom.
Do you have the numbers instead of pulling 1/1,000,000th from the top of your mind? Many here would like to have such knowledge, or do you prefer it to stay hidden?
Alan McIntire says on March 1, 2011 at 6:40 am
Hmmm, so outgoing radiation at all wavelengths increases as temperature, but since the peak goes to lower wavelengths, it just does not increase as quickly at long wavelengths?
Umm, if outgoing radiation increases at all wavelengths, how can that be a negative feedback? It seems that the amount of extra outgoing radiation decreases with each temp increase, so it is logarithmic or something.
In any case, since the CO2 absorption bands are saturated, does it matter if CO2 increases. Also, does pressure broadening depend on partial pressure or total atmospheric pressure?
Dave says
“Enough already with the argument that certain gases that don’t absorb infrared can’t emit it…. The kinetic energy gained by the nitrogen molecules will be lost in a continuous blackbody spectrum characteristic of the temperature of the gas.”
OK, enough with theory and arguments! Let’s study the data that you touted — the data looking up at downward IR. You postulate a continuous BB spectrum from the N2 & O2 in the atmosphere. Where is that BB radiation in the data?
Looking up into the sky, it is clear that SOMETHING is emitting close to a BB radiation curve @ur momisugly ~265 K (the atmospheric temperature near the surface), but only above ~14 um or below ~ 8 um (which happens to be where H2o & CO2 emit well). That radiation we can attribute to GHGs near the surface.
Between 8-14 um, the energy is typically around 5% of the BB radiation levels that would be expected for ~265 K atmosphere. EVEN IF we attribute ALL that radiation between 8-14 um to N2 & O2, the much more common N2 & O2 molecules are emitting much less energy. At best, they are very poor radiators.
No theory. No Kirchoff’s Laws. No models. Just data.
I don’t know, but I suspect, that even the radiation between 8-14 um is not due primarily to N2 or O2, but rather to GHGs (possibly CO2 or H20, but potentially also O3, CH4 …). That would make the downward contribution from N2 & O2 molecules as even less. So that would make them very very poor radiators.
Wayne remarks snidely: “Do you have the numbers instead of pulling 1/1,000,000th from the top of your mind? Many here would like to have such knowledge, or do you prefer it to stay hidden?”
Glad to oblige. The number of six orders of magnitude can be seen from this picture, courtesy of “Phyl.:
http://i302.photobucket.com/albums/nn107/Sprintstar400/CO2N2O2.png
– intensity of lines in 10um area are about six orders of magnitude smaller than 15um band.
davidmhoffer said:
“Richard Smith;
You enjoy having your rants cut to shreds in one thread after another? Well at leat you’ve finally given in on the igloo… now if we can just get you past trying to define absorption and re-mission in a random direction as inventing perpetual motion…”
David – you are referring to a different Richard Smith who was ‘ranting’ on WUWT a few days ago. It is a case of mistaken identity. I deprecate any ranting from either side. I have now re-registered as Richard E Smith to avoid confusion.
P. van der Meer, Al Tekhasski, Phil – you all get it! I completely concur with your clear thinking.
I’m sorry Ira, but someone has convinced you to believe in a concept that violates the basic laws of thermodynamics. Unless you can convince me that this model does not violate both the first and second law of thermodynamics, I will have to conclude that you have drunk some of the kool-aid. I am not trying to insult you, I respect you, and would like to convince you of the truth, but to do that you will have to get back to the basics, and admit this is just plain wrong!
There is so much wrong I would have to spend an inordinate amount of time writing, so I will focus on just one aspect of it. Your animated illustration at the far right shows the atmosphere absorbing energy radiated up from the earth at 15μ . Think about this carefully now. To do this which body has to be hotter? Earth right? OK so how can the atmosphere with only 15μ radiant energy warm up so hot that it exceeds the earths temperature and radiates back at two wavelengths 7μ and 10μ!? It can’t! The only way you can create a black body radiator at 7μ or at 10μ is to heat a body up to the hotter temp that corresponds to that wavelength. IF it radiates at any black body energy at all, to obey the first law of thermodynamics, it MUST radiate at energy equal to or longer than 15μ. So your illustration and explanation violate both the first and second law since 1) to be true it illustrates that energy in the atmosphere must have been created from nothing, and 2) it illustrates that a cooler body is capable heating up a warmer body.
If I am wrong on this one point then please correct me, and teach me how this can be true. If not admit the mistake and correct the illustration. Then we can go on and correct the other things that are wrong with this “Trenberth” like illustration. While you are at it correct the mistake that shows 10μ radiation from a gas that is not even capable of producing this wavelength as well!
mkelly asks:
“What difference is there between the spectrum of N2 and O2 both at the exact same temperature and radiating? I have not found anything on that.”
The HITRAN (high-resolution transmission molecular absorption) database contains the spectra of all the important gases that absorb in the infrared. Some of the N2 and O2 isotropologues (those with 2 different isotopes) do have measurable spectra in that range, but the 2 most common isotropologues don’t. This has been measured in the lab. Neither molecule has been observed to absorb or emit radiation at the frequencies associated with the temperatures of interest. However, if either molecule gets hot enough, it will emit visible light.
Latter, mkelly continues:
“By the way by your statement above you are in the camp that says without GHG we would be a very hot world indeed.”
That is exactly correct – without greenhouse gases, the atmosphere would be above the boiling point of water both day and night, and the surface would freeze every night.
Philip Peake (aka PJP) says:
“the effect is, indeed, logarithmic in nature (Log base e, not Log base 10).”
What? The only difference is a multiplicative constant! Except for a constant, ALL log relationships are identical. The base makes no difference at all.
Dave Springer says:
March 1, 2011 at 4:06 pm
Tim Folkerts says:
March 1, 2011 at 2:38 pm
“For 400 ppm it clearly takes less than the height of the atmosphere, but how much less?”
APPROXIMATELY 12,000 FEET OVER THE ARCTIC OCEAN. SEE THE GRAPH OF IR SPECTRUM FROM 20,000 FEET LOOKING DOWN THAT IRA POSTED IN THE COMMENTS TODAY.
No, The spectrum from 20,000 feet (6 km) shows the energy emitted by CO2 from about 70 meters below the sensor.
For your estimate, you should use the environmental lapse rate (6.5 K/km), not the dry adiabatic lapse rate (9.8 K/km). That produces a CO2 emission height of 20,177 feet (about 35 meters above the reported altitude).
At the surface, 400 ppm Co2 absorbs 63% of the 15um band in less than 20 meters, 99% in 100 meters. Water vapor requires even less.
In other post, you keep talking about “dense gases” without defining what “dense” is. As the pressure increases, the existing vacuum emission lines get broadened. At the surface of the Earth, these are merged into bands with significant gaps between them. At the surface of Venus (92 atm), the CO2 emission spectra is identical to the expected blackbody emission with no gaps.
In truth, at the surface of the Earth, the spectra is continuous, but with ups and downs. As a result, an insignificant amount of energy is emitted (or absorbed) in the “gaps”.
George E. Smith
Thank you for your replies above.
I agree with the general content but I have a different interpretation of the historical development of radiative physics.
The classical Rayleigh-Jeans Law was developed in line with classical electromagnetic theory.
Its departure from reality necessitated the quantum Planck radiation formula. Experiment confirms the Planck relationship.
This lead gives I hope some hopefully uncontroversial background.
Work through to the Planck formula and pick the wavelength option.
There is a clear departure between the two formulas for wavelengths shorter than 3um.
However for wavelengths longer than this the two formulas give the same result.
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html