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.
[[[Ira said:
“Mars is a lot further from the Sun than is the Earth, which is the main reasion it is too cold to support life as we know it, despite all the CO2 in its Atmosphere.”
Steve says:
March 1, 2011 at 7:38 am
No, Mars isn’t at a “beyond supporting life” distance from the sun. The Martian atmosphere would be warm enough to support life if it wasn’t so thin , at about 1% the density of Earth’s atmosphere. The density of the atmosphere ties in directly with it’s heat capacity. Mars has little to no magnetosphere, so the solar wind stripped much of the atmosphere away over billions of years. ]]]
kbray asks: How much atmosphere on Mars do you need to produce the “runaway greenhouse effect”(think Hansen) to get Venus-like temperatures ? Mars already seems to have enough CO2 in the atmosphere being measured in the high 90%. Maybe at high concentrations CO2 has a “protective effect” and actually reverses the greenhouse effect. After all, as per Hansen’s ideas, it should be hotter than blazes on Mars shouldn’t it ?… Maybe we can reverse “global warming” by producing MORE CO2 ? /sarc.
“”””” Dave Springer says:
March 1, 2011 at 7:53 am
Enough already with the argument that certain gases that don’t absorb infrared can’t emit it. This is not true for dense gases. The troposphere is a mixture of cold dense gases. Please review Kirchoff’s Laws:
http://www.physics.rutgers.edu/~matilsky/documents/kirchoff.html
Radiation Laws
Kirchoff’s Laws
First Law: A hot solid, liquid, or dense gas emits radiation at all wavelengths (“a continuous spectrum of radiation”). For example, a perfect blackbody does this. If the light were passed through a prism, you would see the whole rainbow of colors in a continuous band.
Second Law: A thin hot gas in front of a cooler background emits radiation at a discrete set of isolated wavelengths. These discrete, isolated wavelengths are called the “emission lines” of the spectrum, because if you were to pass the radiation through a prism, you would see isolated lines of different colors. The whole spectrum is called an “emission-line” spectrum. The wavelengths of the emission lines are unique to the type of neutral atom or ionized atom that is producing the emission lines.
Third Law: A thin cool gas in front of a hotter solid, liquid, or dense-gas background removes the radiation from the background source at special wave lengths. If the resulting radiation were passed through a prism, there would be dark lines superimposed on the continuous band of colors due to the background. These dark lines are called “absorption lines.” The wavelengths of the absorption lines are unique to the type of neutral atom or ionized atom that is producing the emission lines.
If a certain type of gas produces absorption lines at certain wavelengths when it is in front of a hot background, then when that same type of gas is seen in front of a cooler background, it produces emission lines at the exact same wavelengths.
Explanation of Kirchoff’s First Law
Kirchoff’s First Law boils down to blackbody radiation, since solid objects and dense gases emit radiation like blackbodies.
Explanation of Kirchoff’s Second and Third Laws
Thin gases don’t emit or absorb radiation like blackbodies. To understand their emission and absorption, we must consider the structure of atoms, as described by Quantum Mechanics. “””””
Well I found this citation from Dave Springer; about “Kirchoff’s Laws”.
Would people please read what Rutgers University says about those laws; and please take note of all of the words, in their explanation.
Notice their reference to THIN HOT GASES and THIN COLD GASES. Note the “”””” THIN “””””
Those nice Balmer spectra and the like from Mercury vapor lamps or Sodium lamps and the like are observed in VERY LOW DENSITY gases, where the mean time between molecular or atomic collisions is much longer than the lifetimes of the excited states, so that spontaneous emission can occur; only then do you get the bright line spectra as seen in those HOT gases.
But the earth’s lower troposphere is neither low density nor hot; it is 288 K on average worldwide (so they tell us), and the molecular collision rates are thousands of times faster than the excited state lifetimes, so spontaneous emission almost never occurs in the lower troposphere.
But the molecular velocities of thermal motion of atoms or molecules; and especially molecules being more massive, are way lower than the vibrational mode velocites of the excited state resonances, so the resulting electron accelerations in intermolecular collisions, are much lower, hence the magnitude of the thermal radiation fields is way down in the mud, which is why it is so hard to observe.
But the fact remains, that the spectrum which is supplying the GHG resonance energies , is akin to that radiated by an ordinary yard brick or a bottle of water, at room Temperature. That radiation is 10,000 times lower in radiant emittance, than the radiation form an ordinary 100 Watt “heat lamp”, that emits radiation that is absorbed by human tissue and registers itself as what we call heat; and it does so, because we are mostly water, and absorb strongly at the 1 micron wavelength of the heat lamp emissions.
Humans do NOT perceive 10 micron 288 K radiation as producing heat, because it is only 400 W/m^2, and not 4 million W/m^2 that the heat lamp emits.
But jsut because we don’t sense it, does not mean the atmospheric gases are not emitting it.
Izen
A good question. How would O2 and nitrogen lose energy if there were no GHGs in the atmosphere.
I assume this means that nitrogen and oxygen molecules can in fact lose energy by conduction (that mostly occurs at lower attitudes) or by radiating IR energy out into space at high attitudes.
Richard Smith,
You say “But the greenhouse effect according to climate ‘science’ is not the insulation of a blanket or a reduction in the rate of cooling, but a positive addition of heat (33C or more) because of ‘backradiation’. If this theory were true it would mean that the Earth emits more energy than it receives. This is a contravention of the laws of thermodynamics.”
Surely, if temperatures are rising, (as posited by the GHG hypothesis) it must mean the exact opposite – namely that the Earth emits LESS energy that it receives. Therefore this is not a contravention of the laws of thermodynamics as you assert.
You then say “It is based on the fallacy that if the escape of heating is blocked, then the temperature will continue to rise until a ‘radiative equilibrium’ is reached . . ”
If a proportion of escaping IR is radiated back down to Earth then temperatures must increase. As this happens, then more energy is radiated from the Earth at a flux density that is proportional to the fourth power of the increase in temperature. The idea you suggest where “the heat bursts through the barrier,” although meant to be a derisive dismisal of the GHG mechanism, actually misunderstands the issue. It is a simple application of the Stefan-Boltzman equation for blackbody radiation that gives an increase in radiative emissions from Earth, until it once again equals the radiation coming into the Earth.
Your final remark “If it were true we could generate huge amounts of energy from a small input simply by placing an infra-red barrier around a radiator – just tap some of the heat off at regular intervals – free energy,” is completely false. There is nothing about a mechanism that radiates energy back to the Earth and resulting in a temperature increase, that lends itself to the notion that this can in any way lead to free energy. If you try to drain energy from the atmosphere all that would happen is the atmosphere would cool down and the Earth would radiate faster and cool down more quickly. I suggest the same thing will happen with your ‘infra-red barrier around a radiator.’
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
kbray in california says: March 1, 2011 at 1:23 pm
How about this…..
1) Chill 1 bottle of distilled water and 1 bottle of CO2 injected mineral water …
One problems with this experiment is that it is missing “outer space”. CO2 (or H2O) limits the ability of the IR to “escape” from a warm area (the earth) to a cool area (the rest of space). Without the cold surroundings, you really can’t model the “greenhouse effect”.
You really need:
1) a warm object (perhaps with a light shinning onto it)
2) a cold enclosure around the object (so that the net IR flux will flow from the object to the enclosure). Perhaps a deep freeze.
3) controllable atmosphere (CO2, humid air, dry air etc) between the two that is significantly warmer than the walls of the enclosure.
If the greenhouse effect is true, CO2 or H2O would be radiating IR back to the object. The object will cool more slowly (controlling of course for conduction & convection).
Even this will be tough to see because it takes many meters of CO2 to absorb/emit much IR.
(hmmm … as a side thought, does anyone know just how far IR of various wavelengths would penetrate thru CO2? Eg how far it takes to attenuate 50% or 99% the intensity of the IR light? For 400 ppm it clearly takes less than the height of the atmosphere, but how much less?)
Vince
I still can not see how a small amount of CO2 can heat a much larger warmer earth. Its a bit like a very small heater heating a massive room for one. And secondly I do not accept that a colder body can heat a warmer one.
If a person was enclosed in a container of CO2 would their temperature rise due to the greenhouse effect. Or would the CO2 just slightly reduce the rate of cooling. I would say it would only reduce the rate of cooling. Is this correct or not a very good example as a comparison.
Vince Causey said in response to my comment:
“Surely, if temperatures are rising, (as posited by the GHG hypothesis) it must mean the exact opposite – namely that the Earth emits LESS energy that it receives. Therefore this is not a contravention of the laws of thermodynamics as you assert.”
No. Look at the Kiehl and Trenberth global energy flows diagram, for example. Earth receives 64wm2 (after deduction of thermals and evapotranspiration from insolation of 161 wm2) which somehow backradiation magnifies to an emission of 396wm2. This is more energy out than in.
Vince then says:
“There is nothing about a mechanism that radiates energy back to the Earth and resulting in a temperature increase that lends itself to the notion that this can in any way lead to free energy. If you try to drain energy from the atmosphere all that would happen is the atmosphere would cool down and the Earth would radiate faster and cool down more quickly. I suggest the same thing will happen with your ‘infra-red barrier around a radiator.’”
Well according to the radiation equilibrium theory, I could get a huge amount of energy with an infra-red barrier. But if that example does not impress you, how about a furnace with an infra-red barrier. A much cheaper way of melting steel. Why is it that nobody has patented this yet?
[[[ Tim Folkerts says:
March 1, 2011 at 2:38 pm
kbray in california says: March 1, 2011 at 1:23 pm ]]]
Tim,
Have you ever put a sheet or glass in front of an Infra Red heater ? The IR goes right through the glass. The heat will escape through the glass. And the cold? The room is purposely kept colder in the experiment to simulate the colder surroundings of outer space.
Increased heat should still show up in the mineral water bottle if CO2 has that ability.
Your model is unlikely to create any meaningful data, it has too many variables and just the staging of your experiment sounds impossible… besides, I am only testing CO2 not the whole shabang. I go by KISS – keep it simple son.
Tim Folkerts says:
March 1, 2011 at 5:55 am
Myrrh says: March 1, 2011 at 2:45 am
“Ira says that Visible is the largest part of the Sun’s spectrum, wrong, it’s actually the smallest, and compared with the others, very very small. Light is not hot, it is Reflective not Absorptive, and your use of “absorbed by matter of one form or the other” is misleading. The radiation that penetrates to heat the Earth is Thermal IR. And that is not in the Chart.”
The issue here is the “size of the energy”, not the wavelength. There is a handy table at http://en.wikipedia.org/wiki/Planck%27s_law that shows the energy distribution of sunlight (above the atmosphere).
* A little over 10% of the ENERGY is in ultraviolet photons or shorter wavelengths.
*Close to 40% of the ENERGY is visible light photons
*Over 40% is “near IR” (from 0.7-3um). (So Ira’s claim that visible is the biggest is not quite right, but it is not far off. On the other hand, the atmosphere is still mostly transparent to these wavelenghts, so his arguments still hold).
*Only a few % is above 3 um (“thermal IR”) so it cannot possibly be the main source for heating the earth.
It doesn’t show any such thing, missing bits. See http://ds9ssl.berkeley.edu/lws_gems/e/espec.htm
I think I’m going to start calling this AGWplanks law since its use has resulted in that Chart which made incoming Thermal IR from the Sun walk the plank out of our physical Earth and it’s now become practically impossible to find anything rational about this subject. Visible light is a tiny sliver of the electromagnetic spectrum, as you can see from the above link, it may be highly energetic, but it’s not the highest of that either.
Planck’s law “In physics, Planck’s law describes the spectral radiance of electromagnetic radiation at all wavelengths from a black body at temperature T. As a function of frequency v, Planck’s law is written as: …….Note also that the two functions have different units – the first is radiance per unit frequency interval while the second is radiance per unit wavelength interval.” http:www.worldlingo.com/ma/enwiki/en/Planck’s_law
All Planck’s law shows as graphs depict is that the hotter an object the higher the peak in Visible light. How does the Radiance peak here mean it has a greater AMOUNT of the ENERGY of that produced by a heated body?
That’s how steel workers can tell the temperature of steel they’re working on, from the degree of radiance as it goes into colour. It doesn’t mean anything else. It takes very hot to produce white light. The Sun’s heat certainly hot enough to produce white light.., but it’s a peak of radiance into Visible, it hasn’t stopped producing Thermal Infrared, nor has it stopped producing any of the other wavelengths which you haven’t included.
http://m.plantengineering.com/index.php?id=2831&tx_ttnews%5Btt_news%5D=33209&cHash=db4db9479b
“Not as widely recognized is the fact that incandescent objects emit a tremendous amount of invisible infrared radiation. For example, the radiance of a steel billet at 1500F is 100,000 times greater in the infrared spectrum than in the visible spectrum.”
The real “peak amount” then between the Visible and Thermal IR is not in the Visible. Planck’s peak frequency into visible does not equal peak amount given off by a heated object.
A bog standard lightbulb gives 95% of its energy in Heat, which is Thermal Infrared (Near Infrared included in “Solar”, is not hot, it’s a cold light.) If you drew a graph showing this relationship, where would the peak be?
……………………………………..
izen says:
March 1, 2011 at 6:45 am
Re: the same quote of mine, above.
The vast majority of the energy direct from the Sun that heats the Earth is in the visible spectrum, NOT the IR. If you doubt that visible light can heat things consider the car on a sunny day. The glass of the windows blocks IR but lets through visible light that is absorbed by the (usually) dark plastic/leather interior. The hot steering wheel and seat are warmed by the visible light not any IR.
Glass does not block IR. Visible light is REFLECTIVE. It bounces off things. IR is ABSORPTIVE in organic stuff, the car is absorbing IR Heat all over.
You are correct of course that the surface is ALSO heated by the 7um and 15um IR emissions from the H2O and CO2 in the atmosphere that has been warmed by the IR emissions from the surface..
Well you have to say that don’t you, because you’re following AGWScience which can make up any number of impossible things for you to believe before breakfast. The heat we feel from the Sun, DIRECTLY, is Thermal IR. Regardless of whatever else amount is coming to us, from the heated things around us for example, to exclude this direct Thermal IR from the Sun is just plain ludicrous. I’m finding it impossible to phrase it any other way.
…………………………………………..
Ira Glickstein, PhD says:
March 1, 2011 at 6:11 am
Re: Myrrh says: I’m really at a loss to understand any of this. How on earth does Visible light and near short wave heat the Earth?
Myrrh, you really need to get outside more and sit in the Sunshine and feel the warmth! That is how visible and near-visible (“shortwave”) light warms the Earth.
If you don’t or cannot get outside, turn on an old-fashioned incandescent light bulb and hold your hand near it (not too close you will get burned). Feel the heat? That is shortwave light because the filament is heated to temperatures similar to the Sun’s surface. You can tell it is shortwave because you can see the light.
Well, again with the intellectual disdain from the so-calling themselves experts..
Ira, please take note of my replies above. I am determined to get to the bottom of this because this is a KEY premise on which AGW energy is based and all other energy arguments depend, and it’s simply nonsense.
For lightbulb information – http://www.newton.dep.anl.gov/askasci/eng99/eng99505.htm
& especially:
Physics 101: http://science.hq.nasa.gov/kids/imagers/ems/infrared.html
“Infrared light lies between the visible and microwave portions of the electromagentic spectrum. …The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are the size of cells, or are microscopic.
Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat! The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared. The temperature-sensitive nerve endings in our skin can detect the difference between inside body temperature and outside skin temperature.
Shorter, near infrared waves are not hot at all – in fact you canot even feel them. These shorter wavelengths are the ones used by your TV’s remote control.”
So, WE CANNOT FEEL VISIBLE LIGHT – it is not hot. It does not carry HEAT. The Radiation we feel from the direct from the Sun which is HOT, is Thermal IR.
You have excluded this in your Chart. We can all feel you’re wrong to do so..
This AGW premise defies REAL Science, it is already FALSIFIED. Nothing that AGW calculates thereafter from this premise has any credibility whatsoever.
Has it?
Now, as I said, I’m finding it really difficult to find anything discussing this sensibly at all, most of what’s on line has been so thoroughly trashed by AGWScience propaganda in its utter mangling of basic science concepts. Here it is attributing to Visible light and near neighbours (Solar of AGW), that which is rightly only applicable to Thermal IR.
But, I did find this just now: http://ishangobones.com/?p=509
Which appears to be explaining the actual process I’ve been thinking of as Reflective v Absorptive.
Thermal IR’s absorption method I’ve seen described as Conversion in those areas which deal with its absorptive energies, capacities, spectroscopy, medical and such, (as in a heat pad delivering Thermal IR to aching muscles, etc.), but I wasn’t concentrating on it, and I seem to recall a description similar to what’s being said here. Encyclopedia of planetary sciences says “Absorption is the conversion of electromagnetic energy to another form of energy through interaction with matter. The process can be viewed at several levels, but the end result is usually heat.”
Anyway, Thermal IR is absorptive and Visible and Near IR are not, but are reflective in all general descriptions of the difference.
Al Tekhasski says:
March 1, 2011 at 12:01 am
I am sorry, but for the sake of accuracy, CO2 in air does not have any states that interact with 10-13um band. Therefore, hot air cannot possibly generate any photons in that range. Therefore the following statement is also wrong, nothing gets “transferred” into 10-um band from “heated air”:
—-
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.
Its radiation as a black body would be much lower (low emissivity at a frequency) than the few large emissivity emission lines in N2’s spectrum but the much smaller BB radiation would still be there per the temperature. And you cannot have a temperature without there being many, many molecules or atoms (LTE). All matter (not a single isolated molecule) radiates in a black body manner except at zero K. Now if you are talking of one isolated warm N2 molecule moving isolated in empty space you would be correct, it could not radiate except at it’s emission lines and once it reached it’s ground electron, vibration and rotational state it could not radiate at all, zero, zip, none. It is the collisions and interactions between multiple molecules (between the electrons really) that create the much smaller BB background radiation. That is how I see it from my years in studying physics.
Do you see, 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.
The same is for CO2 molecules or any atoms or molecules when not in isolation (much like in the solar wind of particles or inter-galactic gases).
If you have some good books or references countering this please leave them in a comment before leaving.
George E. Smith says:
March 1, 2011 at 2:08 pm
Thanks for the further explanation between cold/hot and thick/thin gases. The Rutgers statement of Kirchoff’s First Law of Radiation was not clear about the distinction and I thought further clarification would probably be needed.
Cold dense gases emit a continuous blackbody spectrum characteristic of their temperature. “Cold” means below the ionization energy threshold. “Thin” is a little more ambiguous but your description was good i.e. thin enough so that collisions are rare. In the earth’s atmosphere “thin” would begin beyond the mesopause at 90 kilometers where the temperature starts increasing with altitude and can rise to thousands of degrees F.
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.
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.
IN THE IR WINDOW YOU SEE A 265K BLACKBODY CURVE. IN THE 15UM CO2 ABSORPTION WINDOW YOU SEE A 225K BLACKBODY CURVE. THIS IS A TEMPERATURE DROP OF 40K. DRY ADIABATIC LAPSE RATE IS 1K PER 100 METERS SO THE POINT WHERE THE SPECTROMETER NO LONGER INDICATES ANY 15UM ABSORPTION IS 4000 METERS.
THIS WILL VARY SOMEWHAT DEPENDING ON THE TEMPERATURE AND ALTITUDE OF THE SURFACE. AT HIGHER SURFACE ALTITUDES THERE IS LESS TOTAL CO2 IN THE COLUMN ABOVE IT AND IT WILL TAKE MORE THAN 12,000 FEET OF AIR TO GIT ‘ER DONE. THE TEMPERATURE OF THE SURFACE WILL SHIFT THE PEAK SURFACE EMISSION FREQUENCY AWAY OR TOWARDS 15UM WHICH MEANS LESS OR MORE, RESPECTIVELY, 15UM ENERGY TO ABSORB.
Dave Springer;
ALL CAPS – LOL
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…
Al Tekhasski says:
March 1, 2011 at 12:01 am
“I am sorry, but for the sake of accuracy, CO2 in air does not have any states that interact with 10-13um band. Therefore, hot air cannot possibly generate any photons in that range. Therefore the following statement is also wrong, nothing gets “transferred” into 10-um band from “heated air”:”
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.
Ira Glickstein, PhD says
I have two statements/observations with respect to this radiation:
1.) Forget thermo for a moment and let’s talk heat transfer. Two infinite planes separated by a distance in equilibrium (the earth being one and some height in the atmosphere being the other) – the radiosity of the one equals the emissivity of the other. The radiative heat transfer from the warmer to the colder is in proportion to the fourth power of the temperature difference. So the CO2 issue would necessarily raise the atmosphere temp, but where the temp difference between the earth and atmosphere is small, the difference between the atmosphere and space is large, so the fourth power factor of the temp would greatly lessen any lasting heating.
2.) All this back scattering and stuff only works when the light is on. It is like shining a light in a mirror lined room, it bounces around good, but turn off the light and nothing. Once the sun goes down the only heat retained in the atmosphere is the latent heat of water vapor, all that radiation goes poof into space. Take the water vapor out of the air and I don’t care how much CO2 you have in the air, when night comes it is going to get real cold.
Thanks Brian H for having a look at my free online novel. It was written over two years ago, prior to my learning about: 1) Climategate, 2) The official climate Team’s over-estimate of CO2 sensitivity, 3) Svensmark’s cosmic ray theory of cloud formation, and 4) How mistaken NASA’s (Hathaway) was in predictions regarding SC#24. Considering all that, I think I got an amazing amount correct, including the dominance of natural cycles and processes over GHG, when I wrote [Emphasis added]:
If I were to modify the above, I would add Svensmark’s GCR stuff and reduce the sea level rise by 50%. I still believe that CO2 levels are rising largely due to human activities and that they contribute to net mean warming, though not anywhere near the amount estimated by the official climate Team, and far less than natural processes not under human control. Sadly, I still think human-caused accidents are likely over the coming decades, and that the premise of the novel, Stephen Hawking’s prediction, will come true. He said: “I don’t think the human race will survive the next thousand years. Unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.” [Stephen Hawking, Physicist and Cosmologist, 2001]
What do you predict?
There were a number of comments in the thread asking questions about, or proposing various lab experiments with cylinders of artificial atmosphere, or other approaches. They are invalid.
They just don’t scale to reality and the reasons are well known. Even putting aside the existance of other kinds of molecules in the atmosphere, the cylinder in the lab with CO2 in it isn’t even close. For starters, it is at pretty much the same temperature from one end to the other. In the atmosphere, temperature declines with altitude. So the frequency range of photons that can be absorbed or emitted changes with altitude. And time of day. And latitude. And season.
PLUS, the pressure in the lab cylinder is stable. In the atmosphere, pressure declines with altitude, so while the CO2 concentration may be stable in terms of parts per million, in terms of molecules per cubic meter, it declines.
If that hasn’t completely discredited the lab cylinder experiment yet, let me continue by adding JUST water vapour to the picture. If we were to add H2O molecules to the equation, unlike CO2 which is evenly distributed throughout the atmosphere, the H2O molecules would be clustered at the bottom of the atmosphere near earth surface. In the real world, the holding capacity of the air declines with temperature, so the water vapour concentration may be as high as 40,000 ppm or less than 1,000 depending on temperature. And temperature varies with…altitude, time of day, latitude, and season. So down at earth surface 40,000 H20 vs 390 CO2, there’s not much point even doing the math to calculate the effect from CO2, it is meaningless. But as we move in altitude, latitude, season and so on to cooler temperatures and lower levels of water vapour, CO2 becomes more and more significant.
Sorry, not done yet. What else goes on in the atmosphere? Convection! As air is heated at the equator, it rises, pulling in cooler air from the temperate zones. As the hot air rises, it cools. How? By on average emitting more photons than it is absorbing. And as it cools, the wavelength of photons that is released changes… the percentage chance that an emitted photon from a rising molecule of CO2 will escape increases as the molecule gains altitude because the path to space is shorter. And the cooler air being sucked down from the poles is doing the opposite.
Then consider all of THOSE factors in terms of what wavelength of photons are being release and what wave length are being absorbed at any given point in time based on all of those factors and map that against the atmospheric window….
Just like Ira’s physical model or the explanation of the atmopsheric window in this article, a lab experiment simplified down to a cylinder with air in it is fine for evaluating certain aspects of CO2 and IR, but for drawing any conclusions about the climate? Inadequate.
As it “re-radiates” in all directions, then it also must be said that it speeds up how fast the surface cools. Right?
“”””” 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. “””””
So I take it you are implying that the near Black Body radiation Spectrum from a radiating solid, is NOT a continuous spectrum; whiel also saying that it is.
Was it not the introduction of quantization that led from the “ultraviolet catastrophe” that is quite unrelated to Maxwell’s equations for electromagnetic radiation to the highly successful BB radiation formula of Planck.
If you reread your history, you will find, that what was quantized to turn the unsuccessful Raleigh Jeans formula into the successful Planck formula was not the quantization of radiant energy levels but of the average energy per degree of freedom of vibrating molecules due to their Temperature.
The Jeans derivation assumed that the energy per degree of freedom (three for a translating only body) could have any continuous value. Planck’s breakthrough came in requiring the energy per degree of freedom to be quantized. The radiated frequencies are not quantized, and depend only on the Temperature.
Remember that the theory of black body radiation is a purely hypothetical one since no such object actually exists; and as a consequence it is connected in no way to the actual physical properties of any material; just the Temperature; so it cannot possibly be related to any energy level structure, all of which are properties of real materials.
And Planck’s derivation takes no account of the actual phase of the material doing the radiating; just its Temperature.
(atomic )Gases emit both line spectra; that are a consequence of the electron structure of those atoms; but when ionised, they can also emit a continuum radiation that is in the Ultra-Violet beyond the infinity end of the series like Balmer series and others; and they are a continuum, since the electron that is captured by the ion to radiate the photon energy, can have any energy at all while it is a free electron, so the energy differnece of the transition from a free electron to a bound state can have any value. such atomic continuum spectra are observed in the spectra of many stars.
The BB radiation spectrum arises not from discrete energy levels of any atoms or molecules, but from the acceleration of the electrons of the atoms or molecules as a result of Molecular collisions, ie Temperature.
Einstein’s quantisation of photon energies, came about as a result of his work on the Photo-electric effect, which is what he got his Nobel Physics Prize for.
Classical theory calculated the energy density of the EM field from Maxwell’s equations. From that energy density, and the crossection of a photoelectric effect material atom, such as Cesium for example, one could calculate how long it would take to intercept enough energy to release a bound electron from the material. So it was assumed that if one lowered the intensity of the “light”, it would take longer to collect enough energy from the EM field, so delaying the release of the Photo-electron.
Instead, Einstein found that no matter how much the light was attenuated; the emission of the electron was alwqays instantaneous; there was no delay to accumulate enough energy (no delay in the technology of those days). But he also discovered by selecting individual wavelengths, that no matter how bright the illumination might get; some times there was no photo-electron emitted at all. Th3e longer wavelength illuminations failed to release photo-electrons, the shorter wavelength illumination no matter how dim, released electrons instantaneously, and the kinetic energy of those electrons increased for shorter wavelength light.
He reasoned that the light must come in packets each containing a certain energy (E= h.nu), and all that happened when you attenuated the light, was the number of packets was less so you got fewer photo electrons emitted, but the KEs of those emitted were still the same no matter how dim the light. So far as I know to this day nobody has successfully explained the Photo-electric effect in terms of any classical theory of Physics.
But all that did not send Maxwell’s equations to the dustbin of history; it is enshrined forever, in the velocity of light as c = 1/sqrt( mu-naught x Epsilon-naught). Those three fundamental constants are about the only fundamental Physical constants whose values are exact with zero error (by definition).
So Maxwell still reigns supreme; just not over everything, and in particular Maxwell’s equations are not inconsistent with the Planck formula or the Stefan-Boltzmann formula (which is simply the integral of the former.)
One can find excellent treatments of the various Radiation laws, in various Handbooks of Optics such as the one sponsored by the Optical Society of America and edited by Walter G. Driscoll. The section on BB-radiation is authored by Jay F Snell at Tektronix. One can also check “Applied Optics, and Optical Engineering” Vol IV by Rudolph Kingslake (Eastman Kodak).
Snell incidently cites Kichoff’s law thusly:-
“Kirchoff’s Law is a consequence of the necessary existence of an energy balance between emission qnd absorption for a body in an isothermal black enclosure, and in Temperature equilibrium with the enclosure.”
Such conditions exist nowhere in nature; but we can actually build quite good approximations to such enclosures. Notice it says “black enclosure” meaning black in the black body sense, of total absorption of all radiation incident on the walls of that enclosure. Kirchoff’s law requires a wavelength specific balance. That is the absorption and emission of every single possible wavelength must match; but not it is a condition only of total equilibrium of a closed system.
Earth’s atmosphere is NOT a closed system, and it is never in thermal equilibrium with anything. So Kirchoff’s law simply does not apply; no matter how hard people try to make it so.
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 can draw a picture of something and easily transfer a number of data points to tohers through a picture with absolutely no understanding by wither of us of what we are seeing. Mathematics can do the same for the real world in physics.
Sadly climate science has latched onto a few data points and algorithms and think it covers EVERYTHING while still struggling with how poorly their models do. At a much higher level quantum physicists do the same. It really is all RELATIVE!!
HAHAHAHAHAHAHAHAHAHAHAHA
Here is the outgoing longwave radiation map on Feb 20, 2011 from the CERES satellite.
Can you see the continents? Can you pick out the oceans?
Well, if the emission to space went right through the atmospheric windows, right through the spectra which are not intercepted by the GHGs, one should be able to see the hot parts of the continents, or the cold parts of the continents. Or something.
What the map is really showing is that emission to spaces occurs at various heights in the atmosphere and cloudiness is a very important factor in this and that the atmospheric windows are not really apparent. Maybe this a bit esoteric, but it is telling you what is really happening in the atmosphere. It is not a AGW global warming map. It is reality. [This is always my default position, what really happens versus what the theory says should happen].
http://img132.imageshack.us/img132/1866/renderdata.jpg
Ira, I mostly praise the way you presented this post, much clearer, but the only thing I will complain about of you post is in this statement:
There you need to lose the statement “heats the Earth”. That is nonsense. You might say “keeps Earth warmer that without” or “slows the cooling of the Earth”, both implying the action of an insulator, but anything but what you said.
For myself, I have now move on the scale from ‘warmist’ to ‘skeptic’ and now just a tad before ‘denier’ so I think both of those statements are also most likely incorrect, but still that’s a better way for you to state it. It’s just that “warms the Earth” breaks core thermodynamic principles and it unqualifiedly wrong. Best to admit it and restate.
But I know you’ve already gotten an earful on that same matter.
The room temperature (300K) band gap of silicon is 1.106 eV Einstein’s constant is 1.23980 electron Volt microns.
So any photon of shorter wavelength than 1.121 microns, can be absorbed in bulk silicon, and release carriers, to be transported across a PN junction; to create a photocurrent flow. Well that assumes that the carrier lifetime is long enough for them to propagate to the junction and cross it, before they recombine.
So silicon diodes can absorb sunlight shorter that 1.121 microns wavelength, down to at least 400 nm and create a photocurrent in a “solar cell”.
But don’t try to get that same silicon junction to reverse its behavior when you pass a forward current through it, and emit any photons.
Silicon is an indirect gap semiconductor, and the reversal of the absorption transitions are prohibited, so silicon does not form Light Emitting Diodes.
So there’s a simple case of a solid that simply cannot radiate the same photon energies that it can easily absorb. Neither can Germanium which also makes good (low Voltage) solar cells.
But GaAs with its 1.47 eV bandgap readily emits 844 nm photons, which is the bandgap photon energy, because it is a direct gap semiconductor, and that transition is allowed, without any momentum discrepancy, requiring a phonon interraction as well.
So no Kirchoff’s law simply doesn’t apply to very many real world situations.