Guest post by Reed Coray
The following example illustrates the issues I have with reasoning often used to argue that increasing the amount of CO2 in the Earth’s atmosphere will increase both the Earth’s surface temperature and the Earth’s atmosphere temperature. Immediately following is a direct quote from URL
http://www.school-for-champions.com/science/heat_transfer_earth.htm
“The present situation is that there has been an increase in infrared-absorbing gases in the atmosphere, such as carbon dioxide (CO2) and methane (CH4). Energy that would normally escape into space is absorbed by these molecules, thus heating the atmosphere and spreading through convection currents. The average temperature of the atmosphere has increased 0.25 °C since 1980, mainly attributed to an increase in infrared-absorbing gases in the atmosphere.”
Although the above statement makes no direct reference to Earth surface temperature, I believe it carries the implication that greenhouse gases in the Earth’s atmosphere increase the Earth’s surface temperature.
I make two comments: the first is relevant only if the above implication is valid, the second is relevant independent of the validity of the implication. First, placing matter adjacent to a warm surface such that the matter is capable of absorbing/blocking radiation to space from the warm surface can lead to a decrease in the warm surface’s temperature. Second, increasing the amount of the absorbing/blocking matter can lower the temperature of the absorbing/blocking material.
Take for example an internal combustion engine whose metal surface is exposed to a vacuum. In addition to doing useful work, the engine produces thermal energy (heat). That thermal energy will produce a rise in the temperature of the engine’s surface such that in energy-rate equilibrium the rate energy is radiated to space from the engine’s surface is equal to the rate thermal energy is generated within the engine. By attaching radiating plates to the engine’s surface, some of the energy radiated to space from the engine’s original surface will be absorbed/blocked by the plates; but because thermal energy can be transferred from the engine to the plates via both radiation and conduction, the temperature of the engine’s original surface will be lowered. This is the principle of an air-cooled engine[1]: provide a means other than radiation of transferring heat from an engine to a large surface area from which heat can be removed via a combination of conduction, convection and radiation, and the engine’s surface temperature will be lowered.
If plates at a temperature lower than the original engine surface temperature are attached to the engine, it’s true that the temperature of the plates will increase to establish energy-rate equilibrium. Once energy-rate equilibrium is established, however, increasing the plate radiating area (adding additional matter that blocks more of the energy radiated from the original engine surface) will likely lower the plate temperature.
Thus, blocking the amount of surface radiation escaping to space does not necessarily increase the surface temperature; and increasing the amount of radiation blocking material does not necessarily increase the temperature of that material. In both cases (the Earth/Earth-atmosphere and the internal combustion engine in a vacuum), the heat eventually escapes to space–otherwise the temperature of the Earth’s surface and the engine would continue to rise indefinitely. The difference isn’t that the energy doesn’t eventually escape to space (it does in both cases), the difference is in the path the energy takes to reach space. The amount of generated thermal energy in conjunction with the path the thermal energy takes to get to space determines temperatures along the path; and adding more material may increase or decrease those temperatures. To say that “Energy that would normally escape into space is absorbed by these molecules, thus heating the atmosphere…” by itself is unwarranted; because an equivalent statement for the case of adding extra plate material to the engine would be “Energy that would normally escape to space from an engine with small attached plates is absorbed by additional plate material, thus heating the plates…” For air-cooled engines, this statement is not true—otherwise the plate surface area of air-cooled engines would be as small as possible.
It’s fairly easy to visualize why (a) adding thermally radiating plates to an air-cooled engine might decrease the engine’s surface temperature, and (b) increasing the area of the radiating plates might decrease the plate temperature. It’s not so easy to visualize, and may not be true, why (a) adding greenhouse gases to the Earth’s atmosphere decreases the Earth’s surface temperature; and (b) increasing the amount of atmospheric greenhouse gases lowers the temperature of the Earth’s atmosphere. I now present one possible argument. I do not claim that the argument is valid for greenhouse gases in the Earth’s atmosphere, but I do claim that the argument might be valid, and can only be refuted by an analysis more detailed than simply claiming “Energy that would normally escape into space is absorbed by these molecules, thus heating the atmosphere.”
If we assume that (a) matter cannot leave the Earth/Earth-atmosphere system, and (b) non-greenhouse gases radiate negligible energy to space, then for a non-greenhouse gas atmosphere the only way thermal energy can leave the Earth/Earth-atmosphere system to space is via radiation from the surface of the Earth. The rate radiation leaves the surface is in part a function of both the area and temperature of the surface. For a greenhouse gas atmosphere, energy can leave the Earth/Earth-atmosphere system to space both via radiation from the Earth’s surface and radiation from greenhouse gases in the atmosphere. Suppose it is true that the density of greenhouse gases near the Earth’s surface is such that radiation emitted from low-altitude greenhouse gases does not directly escape to space, but is in part directed towards the Earth’s surface and in part absorbed by other atmospheric greenhouse gases. As the atmospheric greenhouse gas density decreases with increasing altitude, radiation emitted from high-altitude greenhouse gases can directly escape to space.
Now it’s not impossible that since (a) in addition to radiation, heat is transferred from the Earth’s surface to greenhouse gases via conduction, and (b) convection currents (i) circulate the heated greenhouse gases to higher altitudes where energy transfer to space can take place and (ii) return cooler greenhouse gases to the Earth’s surface, that the process of heat transfer away from the Earth’s surface via greenhouse gases is more efficient than simple radiation from the Earth’s surface. Many engines are cooled using this concept. Specifically, a coolant is brought into contact with a heated surface which raises the coolant’s temperature via conduction and radiation, and the coolant is moved to a location where thermal energy transfer away from the coolant to a heat sink is more efficient than direct thermal energy transfer from the heated surface to the heat sink.
One way to realize increased thermal transfer efficiency would be to use a coolant, such as greenhouse gases, that efficiently radiates energy in the IR band (i.e., radiates energy at temperatures around 500 K). Another way would be to spread the heated coolant over a large surface area. Since surface area increases with increasing altitude, thereby providing expanded “area” (in the case of a gas, expanded volume) from which radiation to space can occur, it’s not clear to me (one way or the other) that greenhouse gases won’t act as a “coolant” reducing both the temperatures of the Earth’s atmosphere and the Earth surface.
[1] It’s true that for most air-cooled engines the main transfer of heat from the engine plates is via a combination of (a) conduction of heat to the air near the plates, and (b) convection that replaces the warm air near the plates with cooler air. To aid this process, a fan is often employed, or the engine is located on a moving vehicle and the vehicle’s motion through an atmosphere provides the flow of air across the plates. Although conduction/convection may be the primary means of heat dissipation from the plates, radiative cooling also dissipates heat.
George E. Smith; says on July 27, 2012 at 4:26 pm:
“So I decided to take a look at Tim’s Wiki reference in detail to see for myself their “rather elegant proof” ?
but I also noticed on wiki, that they do actually have a reference to “Thermal Radiation”, and what it is, so all you folks in Myrrh’s club, can stop pretending, that you have never heard of it.”
==============
I do usually read your comments and, mainly, find nothing that pops out worth screaming about. In this comment however there is just one small thing, which may be important, therefore:
I too have typed “Thermal Radiation” into my search engine and looked up Wikipedia as I do like elegant explanations or even better still elegant proof.
– Well I did not find any of that there, as when we talk about “Thermal Radiation” – here on WUWT, I always assume that it is radiation from the Earth’s surface where T = (or averages) 288K we do discuss, unless, of course, Solar or any other form of “radiation” is specifically mentioned.
As you know, according to the “correct script”, there is an “Atmospheric Window” that lets a certain amount of “IR radiation” from the surface pass straight through the GHGs on its way to outer space. Therefore I recon IR radiation (from T = 288K) at ground level must be powerful stuff.
Or that idea may be completely wrong.
Well, I am not exactly in “Myrrh’s club”, but I have never been able to prove by experimentation that IR radiation from an object even with a temperature (T) = 440K, or say 150K above T ambient is significant enough to take into consideration. (Temps. mentioned here are approximates and do not really matter as long as they are not hot enough for visible light to be emitted)
Take “radiation” from a thermostatically controlled hotplate, which, when set on low has a T range of, say 125 – 150 deg. Celsius, can not reach much further than a few centimeters through, or into, the air. (Invert the hotplate and measure T just below the hot surface, convection is then bypassed and “Thermal air expansion” and radiation is all you are left with). – The heat just gets absorbed by the air, or possibly mainly by the atmospheric water vapor content.
The heat then, as I see it, is conducted and convected away.
– IMHO it is a fact that those “Atomic/Molecular vibrations” that produce EM waves do not change one iota just because two, or more, solid and gas molecules are in “Thermal Contact” with each other and the “radiation” for that reason turns into “conduction”
I could bring in “The Zeroth Law of Thermodynamics” here, but this posting is getting long enough as it is.
Wiki shows a diagram and explain:
“This diagram shows how the peak wavelength and total radiated amount vary with temperature according to Wien’s displacement law. Although this plot shows relatively high temperatures, the same relationships hold true for any temperature down to absolute zero. Visible light is between 380 and 750 nm.”
Did you omit to look at that particular diagram?
It is interesting that their highest T is 5500K and the curve, of course is red, and quite steep. As T is lowered so the accompanying curve looses its “steepness” all the way down to 3500K which is the lowest T involved. The curve for T = 3500K is quite flat.
Therefore I feel it is only fair to ask you: ”What do you estimate the curve from T = 288K will look like?” – Should extrapolate down to “very flat indeed”.
I think. I may check it out one day though.
I believe the term “radiation” used in these discussions is short for “electromagnetic radiation” so that “thermal radiation” is short for “thermally induced electromagnetic radiation” where thermal or vibrational energy is converted to the photons that actually leave a surface. When those photons are absorbed by another surface, they will yield their energy to that surface even if it is warmer than the surface that emitted them. The laws of thermodynamics only apply to mutual exchanges of photons, not to the individual photons themselves.
If you and and a friend had a pointless arrangement for each to send the other a $100 check every month, neither of you would profit by this deal but your banks would still have to process the transactions. The individual checks would be equivalent to the photons emitted in ‘thermal radiation.’
Spector says:The laws of thermodynamics only apply to mutual exchanges of photons, not to the individual photons themselves.”
That is very wrong. I see that someone made such a statement on lofi.forum.physorg.com/Information-Carried-By-A-Photon_2
but this is a very misleading statement, but am not attacking you for the mistake, but just providing the necessary correction.
I think you maybe thinking of temperature not applying to a single particle.
O H Dahlsveen says:
“Well I did not find any of that there, as when we talk about “Thermal Radiation” – here on WUWT, I always assume that it is radiation from the Earth’s surface …
You should include radiation from the air and clouds, etc. but otherwise I agree. Spector said it pretty well in his previous post.
“Therefore I recon IR radiation (from T = 288K) at ground level must be powerful stuff.”
“Strength” is the wrong way to think about it. Visible light gets thru the atmosphere pretty well; some IR gets thru pretty well; some radio gets thru pretty well. It is not a question of “strength” but rather a question of the properties of the air.
Would you say that blue light has to be strong to get thru a blue piece of glass, but the red photons are weak? Or red light has to be strong to get thru a red piece of glass, but the blue photons are weak? No — those particular photons are simply “lucky enough” no to be absorbed by those particular materials.
Some wavelengths of IR are simply “lucky enough” not to get absorbed by the molecules in the atmosphere.
“Take “radiation” from a thermostatically controlled hotplate, which, when set on low has a T range of, say 125 – 150 deg. Celsius, can not reach much further than a few centimeters through, or into, the air.”
IR photography refutes this claim. Google “thermal images” to see lots of photons that traveled feet (or miles) from the hot source to the camera. It may no longer be intense enough for you to “feel” the heat, but the photons can indeed travel long distances.
”What do you estimate the curve from T = 288K will look like?”
In many ways, it will look the same as the curve at any other temperature. The curve will rise rapidly, then fall off slowly as you increase the wavelength. Of course, you would have the “rescale the axes” to get it to look similar, but the general shape stays the same.
http://en.wikipedia.org/wiki/Planck%27s_law#Percentiles
Spector says:
“Here, again, is a curve showing almost no difference between the calculated energy (or power) escaping the Earth’s troposphere (‘Radiative Forcing’) for CO2 concentrations of 300 PPM and 600 PPM.”
True enough, but there is also “almost no difference” between 288 K and 289 K. Indeed, that 1 K temperature change is about what the doubling of CO2 would produce (absent feedbacks). If there was a bigger difference in the curves, there would be a bigger difference in temperature.
” That is why the surface absorption plot shown in the main article can be very misleading as only (390-324)=66 of the 235 joules per second per square meter shown escaping the troposphere on the classic Kiehl-Trenberth diagram actually is radiated directly from the surface.”
You are, I am afraid, comparing apples and oranges. Think in terms of your cash analogy.
* Mr Surface “pays” Miss Atmosphere $350 (in IR radiation, and $78 + $24 in other forms). Mr. Surface pays only $40 directly to Mrs. Space. Any money Atmosphere pays to Surface doesn’t (directly) change the Surface–>Space exchange.
Only 40 W/m^2 escaping from the earth as a whole is radiated directly from the surface.
* Indirectly, you could say Miss Atmosphere receives $350 from Surface IR, $78 from Surface Evaporation, $24 Surface Thermals, and $67 from Mr Sun. So you could say 350/519 = 67% of any outgoing flow from Atmosphere came from Surface IR — ie $132 out of $195 leaving to Space came indirectly from from the the Surface IR (or $170 total came indirectly from the surface (counting thermals & evaporation)).
* For the surface when we focus on IR only, there is $390 coming in, and $324 heading out, so the $66 you mention in has nothing to do with space, but relates only the surface/atmosphere exchange of IR. The 66 W/m^s is the net IR flow of 66 W/m^2 thru the boundary between the Surface and the Atmosphere. It is NOT energy “escaping from the troposphere”.
BOTTOM LINE: the 66 W/m^2 you calculated and the 235 W/m^2 that you compare it to are not directly related.
“””””…..Tim Folkerts says:
July 27, 2012 at 10:17 pm
“The constant that Planck introduced (h) is of course nothing more than the energy contained in any single cycle of any frequency of the waves of classical physics.”
Not even close. Classically “any single cycle ” of EM waves could have any conceivable energy by having arbitrary large or small E&B fields.
Tim we are talking about the (h) that occurs in the E = h (nu) ” F” Planck revolution that started off “Quantum mechanics”.
So if a “black body” emits a photon of energy E and frequency = (nu) then since by Planck which you agree with (as do I), the photon energy is hnu so if I divide the Total photon energy hnu, by the number of cycles of the EM wave in one second which is (nu), I get
Energy per cycle = hnu / nu = h Joules per cycle.
Remember that (h) is the quantum of “action” ; it is NOT the quantum of “energy”; and its units are Joule.seconds.
So now tell me again how I’m “not even close”.
I wonder why you don’t consider the start of “Quantum Mechanics” to be back when the alchemists discovered that matter (stuff) was “quantised” and that the quanta, of stuff, the smallest units it could come in were atoms and molecules; so of course chemistry must also be Quantum Mechanics , and not simply applied Physics. Matter would seem to be even more quantized than Black Body radiation, since matter quanta consist of only a handful of allowable vaues; 92 or so; well until they discovered the stuff fine structure of isotopes; whereas the photon quanta of the black body radiation are allowed to have ANY value of energy whatsoever without restriction, as is the frequency (f or nu) so long as that energy is hnu.
Blackbody radiation is somewhat like a string of sausages; I’m a sausage knitting expert. You can have ANY amount of sausage you want, so long as you twist it up into individual connected “links”, and you can make smaller links and make more of them and still have the same amount of sausage, in that case h is the amount of sausage per link; well actually sausages are sort of the inverse of blackbody radiation in thathat the total amount of sausage is fixed, rather than the energy per cycle as in BB radiation.
But I’m still waiting for someoe to give the frequencies of some of the best known quantised frequencies of black body radiation ; or any sort of thermal radiation.
wikipedia.org/wiki/Thermal_radiation is the first wiki reference to thermal radiation I found; didn’t have to look far. And I’m the very worst giggler on the planet; well I use Bing anyway.
I’m quite happy to accept your assertion Tim, that Black Body Radiation was the beginning of quantum mechanics; that’s not the same as saying BB radiation IS quantum mechanics, any more than atoms and molecules are quantum mechanics. Yes QM is useful in explaining the properties or behavior of atoms and molecules; but the alchemists/chemists who discovered them weren’t quantum mechanics experts.
And my compliments to jcbmack; I often need all the help I can get. After only 52 years as a paid working Physicist, I sometimes forget stuff, and sometimes totally goof, and when I do, I tend to admit it, rather than dig the hole deeper.
And no I DON’T have a PhD; which is why as I said, I know VERY LITTLE about quantum mechanics.
Also the expression for The Stefan Boltzmann law is not quite correct, since it has a (c^2) term in it The correct expression should have the velocity of light in the particular medium, and the c^2 is only true for the vaccuum case. So c^2 needs to be replaced by (c/n)^2; where n is the refractive index of the medium in which the emission or absorption occurs. ( a classical Physics concept.). So it would seem that the BB energy depends more on the wavelength than the frequency, since the frequency is unchanged, when you change them medium, but the energy or power is not.
that is ow Roland Winston made a solar image that was brighter than the sun, because his image was in a YAG crystal.
“””””…..Did you omit to look at that particular diagram?
It is interesting that their highest T is 5500K and the curve, of course is red, and quite steep. As T is lowered so the accompanying curve looses its “steepness” all the way down to 3500K which is the lowest T involved. The curve for T = 3500K is quite flat.
Therefore I feel it is only fair to ask you: ”What do you estimate the curve from T = 288K will look like?” – Should extrapolate down to “very flat indeed”……”””””
I think. I may check it out one day though……”””””…..O H Dahlsveen says:
July 26, 2012 at 1:19 pm
George E. Smith; says on July 25, 2012 at 4:28 pm:
“I might come back to see who wants to join you.”
============
George E, will you come back to join us even if I am not going to join Tim?…..”””””
Why is it that some like to assume than anything not mentioned is something not klnown.
I don’t need to look at ANY black body radiation spectrum graph; because I already know what it looks like. ALL BB radiation spectra curves look the same, because they ARE all the same.
If you plot the spectrum (hopefully on log scale paper) with an x scale of wavelength divided by the spectral peak wavelength, and a y scale of the spectral radiance divided by the peak spectral radiance, you get a universal spectrum with a peak (y) of 1.000, and an x scale centered on 1.000, perhaps going from 0.1 to about 50.
The Planck formula is a function of a single variable: wavelength x Temperature (lambda.T)
And if you plot it the way I said, the one graph serves for any situation. It is common to plot the vertical axis, as both a linear 0 —> 1 scale, and a log scale perhaps 1E-4 (or -5) to 1.000. Not a lot of point going outside a 0.1 to 50 range on the x axis. The linear y scale is only readable for x from about 0.3 to 8, and the y log scale is down to 10^-5 at x = 0.2 and 40.
I don’t need to ping wiki to find out ANYTHING about BB radiation.
If you want a universal BB spectrum go look up Warren J Smith (the late, sadly) “Modern Optical Engineering,” page 218 in the second editionMcGraw Hill. A really great book if you want to learn anything about Optics.
Konrad: The long and the short of it is that while you may be able to imagine alternate bodies with weird spectral emission patterns such that increasing CO2 can cool it, the surface of the Earth that we live on is pretty close to being a blackbody emitter. For such an Earth and a lapse rate so that temperature decreases with altitude, the effect of increasing CO2 is to decrease, not increase, emission because as CO2 is added, the emissions that escape to space move to higher altitudes where it is colder and hence less radiation is emitted.
The approximately-logarithmic dependence of radiative forcing on CO2 concentrations is the net effect of additional CO2, i.e., the fact that CO2 both absorbs and emits. There is additional linear cooling effect…That is simply a figment of your imagination.
Of course, this picture accepted by all serious scientists in the field including Richard Lindzen and Roy Spencer and in accord with the modern radiative transfer calculations that are well-verified by an entire technical field (remote sensing), is verified by spectra of the Earth’s emissions as seen from space by satellites.
George E. Smith:”I wonder why you don’t consider the start of “Quantum Mechanics” to be back when the alchemists discovered that matter (stuff) was “quantised” and that the quanta, of stuff, the smallest units it could come in were atoms and molecules; so of course chemistry must also be Quantum Mechanics , and not simply applied Physics.”
I must admit I don’t understand the point of your most recent lines of discussion with Tim. Apparently, you are quite concerned with whether blackbodies are classical or quantum physics. I personally cannot see how this matters one bit except to say that the conception of how blackbodies function is different under classical and quantum frameworks(again see the ultraviolet catastrophe) and the view informed by QM is held to be the *correct* one. I don’t believe that you will disagree with this and I can’t see the point of trying to argue that blackbodies are 85% classical and 15% quantum or whatever.
IMO, you will be better served by focussing on what, if any, differences you may have with current GH theory.
Cheers, 🙂
I said:
Of course, that should read:
Shawnhet, I think you are right when you say ‘IMO, you will be better served by focussing on what, if any, differences you may have with current GH theory.” Partly George & I have a challenge with terminology (eg “energy per cycle” vs “energy per (cycle per unit time) ); partly I think different levels of understanding of QM is making the discussion difficult. I find the underlying physics fascinating, but it is not a simple topic. In any case, you are right that this doesn’t matter much other than for academic interest.
* Theoretically, blackbodies are ideal radiators that can only be adequately explained by QM
* Experimentally, blackbodies can be approximated extremely well by an opening to a large cavity.
* Practically, many parts of the land, the oceans, and the clouds are quite close to BBs (with respect to thermal IR). GHGs are close to BB *for specific wavelengths* but are close to “white bodies” or “clear bodies” for other wavelengths.
At this level of discussion, that is all that really needs to be said. The details matter for detailed calculations, but that is way beyond the scope of this discussion.
“””””…..Shawnhet says:
July 31, 2012 at 9:35 am
George E. Smith:”I wonder why you don’t consider the start of “Quantum Mechanics” to be back when the alchemists discovered that matter (stuff) was “quantised” and that the quanta, of stuff, the smallest units it could come in were atoms and molecules; so of course chemistry must also be Quantum Mechanics , and not simply applied Physics.”…..”””””
Well to each his own I guess. I believe that Quantum Mechanics, and its offspring QED, and QCD are generally regarded as the current best description of how the REAL world works; made of REAL materials, that have REAL electron structures, and arrays of energy levels.
It is beyond me to see how that relates to a very UNREAL notion, that has no REAL existence, and requires NO knowledge of ANY real world materials, or of the properties of any REAL materials.
In fact knowledge of ANY real materials immediately negates the possibility of a REAL black body existing, since ANY real material has a refractive index (possibly complex) which means that ANY such surface MUST have a polarised Fresnel reflection coefficient that is wavelength dependent, so NO REAL surface can absorb 100% of ALL wavelengths of EM radiation that falls on it, which is the very essence of a Black Body.
So that leaves the “Cavity Absorber/Radiator” that Tim referred to; which I am quite familiar with.
Here again reality sets in; since the cavity must be at a single (any one) Temperature > 0 and must NOT lose ANY energy from anywhere save the cavity aperture. So that requires that the walls of the cavity must be made of some material , that has a ZERO thermal conductivity; or an infinite thermal insulation property; again not anything in the REAL universe.
And the whole point of my initial comment, was the enormous importance to Physics of the investigations of the ultimate thought experiment; the non-existent hypothetical black body.
Yes Planck suggested that EM radiation must consist of discrete “quanta”; same as the alchemists realized that the simple numerical ratios of chemicals reacting in a chemistry experiment, were easiest to explain by assuming that there must be a dscrete quantum of matter for each of the “elements” of their knowledge.
A little contemplation of the notion of matter or anything else being infinitely divisible, with no minimum size for any sample of anything, is clearly even sillier, than the idea of them all being a collection of quanta.
The difference between atoms and BB photons (or THERMAL RADIATION PHOTONS), is that the former only have a very limited set of quantum sizes and compositions, while the BB/Thermal photons have no such constraint and can have ANY energy at all, so long as it is given by hF. (h) is fixed in value, but (F) is NOT, and also can have any value. This distinguishes BB or Themal radiation (Plasmas also) from the spectrally discrete lnes, of either atomic or molecular absorptions/emissions, that are the main factors in the GHG atmospheric theories. Those discrete spectral line/band spectra ARE the consequence of quantized energy levels in REAL MATERIALS.
As for current Green House theory; I’m not much interested in it, since (a) I don’t believe the data sampling regimen is valid, in the light of modern information theory, including sampled data theory, so I don’t believe the purported “data”, and Anthony’s new paper tends to bear out the glaring problems of present weather data gathering. Furthermore, I believe that negative feedback by absorption or scattering/reflection of INCOMING solar energy by H2O in all three phases, has far more control of earth’s Temperature, than the “greenhouse” effects.
Let me say categorically, I do NOT dispute the so-called green house effect; although some totally stupid experimental “demonstrations” of it are performed by idiots who deserve to be tarred and feathered; such as substituting a 2800 K 100 Watt lamp as a LWIR radiation source, that is 10,000 times as bright, as the REAL earth surfaces (or a bottle of water) at 288 K, that is the ACTUAL source of the LWIR that is intercepted by GHGs such as H2O and CO2.
But you and ANY reader are quite free to believe whatever you want. Here in the 21st century, people on earth still have some odd beliefs.
George:”It is beyond me to see how that relates to a very UNREAL notion, that has no REAL existence, and requires NO knowledge of ANY real world materials, or of the properties of any REAL materials.”
I agree that a BB is an unreal entity but it seems to approximate certain portions of the real world relatively well. To quote Tim above who says it better than me: “* Practically, many parts of the land, the oceans, and the clouds are quite close to BBs (with respect to thermal IR). GHGs are close to BB *for specific wavelengths* but are close to “white bodies” or “clear bodies” for other wavelengths.”
If what Tim says above is valid (and it seems to me to be), then that answers your question, doesn’t it? Only if someone disagrees that some portions of the real world are pretty close to BBs would it make sense to say that BB behavior has no relevance to the real world.
“And the whole point of my initial comment, was the enormous importance to Physics of the investigations of the ultimate thought experiment; the non-existent hypothetical black body.”
Yes, I agree. This is why I am having trouble with your argument. If the unreal BB doesn’t relate at all to the real world(your first comment), how can it also be of “enormous importance” to physics?
Cheers, 🙂
Well Shawn, I think we generally think of our scientific theories and models, as being our best or at least a useful description of how we believe the real world behaves; whereas, these models and their descriptions are actually all made up; as is the mathematics we use to describe the behavior of the models. The point is we can quite accurately (in most cases) describe how the model will work, because we endowed it with properties which ar under our control. The trick is to try and construct our models so that they EMULATE the real world, as closely as we know how. When they deviate from that, then we alter, reconstruct or abandon the models in favor of something that is a closer image of reality.
WUWT readers might be convinced that in “climate science” we make our computer models, and then we try to construct the data to match what our computers tell us is the behavior we want; well I exaggerate of corse.
The thing about a Black Bodyis that it was well known and realized that no such thing could exist; yet it was a contrivance about which we could say: This is how it would work if there was such a thing. And as you And Tim Folkerts too point out, we can make very good approximations to that fictitious animal, and they do behave closely like the BB, Planck theory describes, which makes them of great use. As Leif Svalgaard has pointed out several times TSI is commonly measured using such a cavity “radiation trap”. The reason that BB approximations are of such use, is that we know that ony 1% of the total energy, lies beyond each end of a 0.5 to 8.0 times the peak wavelength range, so for many purposes, the faux BB only has to be a good absorber over that restrcted range.
Just think the 6,000 K sun surface radiation peaks circa 0.5 microns wavelength, while the about 300 k earth surface emissions peak at about 10 microns. The mysterious 2.7K big bang echo, being 1/100th the temperature of the earth, is radiating around 1 mm peak wavelength.
So all of our radio and TV and other comunications traffic, must be truly cold when viewed as BB emissions. Just calculate what the Temperature would be for a BB that is radiating at 60 Hertz frequency, like our power transmission lines are.
I pretty much agree with your post above, George. Sometimes in these discussions you will run into people who use the fact that “the Earth is not a real blackbody” as an argument against the GH effect. Regardless of the truth/magnitude of the GH effect, Earth is reasonably close to a blackbody over the relevant “GH” range of wavelengths.
Cheers, 🙂
joeldshore says:
July 31, 2012 at 8:41 am
—————————————–
Joel, I was interested enough in Tim Folkerts responses to my questions to take the time to design and build an empirical experiment to test Reed’s hypothesis. Tim Folkerts is partially correct, REED CORAY IS RIGHT and you are wrong. My graph ( http://i48.tinypic.com/2pp0hed.jpg ) while dimensionless is correct.
Instead of relying on the BS (blackboard scribblings) of Pierrehumbert I would suggest you design and build your own experiments. NO. Don’t run to the web to find someone else’s work. Design it and build it yourself. An ancient Chinese proverb may be relevant here – “Tell me, I’ll forget. Show me, I’ll understand. Let me do it, I will KNOW.”
And for future reference I have empirically confirmed that the answer to my original question on this thread was both B and “ D. The spherical chicken found in the same region of space has “Property of Pierrehumbert” tattooed on its butt.”