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.
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Ira,
” 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.”
Could you give more details as to what shifts the energy into the ~10μ window. Is this due to net out from the surface of the absorbed back radiation or are there other effects??
Really good post. Really good questions in some comments. The questions take us exactly to the crucial issue: what are the physical hypotheses which explain what CO2 does to increase climate sensitivity. There will be several such physical hypotheses, of course. What seems best understood is that changes caused in clouds by the additional CO2 will have an impact on climate sensitivity. However, we also understand that there are no physical hypotheses which explain the expected or imagined change in cloud behavior. There will be some day, after the needed scientific work is done. The other needed physical hypotheses are in worse shape. We do not have so much as good hunches about the phenomena in question, unlike the case of clouds. The science is in its infancy. Any Warmista who denies this surely must be challenged to produce the relevant physical hypotheses. Short of those hypotheses, the claim that someone has scientific reasons for attributing warming to manmade CO2 are as empty as the claim that straw can be spun into gold.
George E. Smith says:
February 28, 2011 at 3:23 pm
The only function of the GHG molecules is to heat the atmospheric gases; along with all the other mechanisms that are heating it. After that, the GHG molecules serve no function in the climate process whatsoever.
—–
George, are you positive of including the word “only” in your statement and not “one of”. I read from those words that you don’t think thermalization can run in reverse the way the equatuion reads with symmetry. Like when the atmosphere is warmer than it should be compared to the surface and at dusk or night. I have always viewed GHGs can either heat or cool depending on the exact conditions. Any clarification?
Bill Illis,
” Once the sun sets, the atmospheric temperature should fall to -220C within a second.”
Even without GHG’s we would still have stored energy in the water and surface of the earth.
Bill
almost everyone believes the non-GHGs absorb and emit no IR radiation at all
Bad textbooks. It seems that way. Because otherwise how would say Nitrogen release energy. Some would be by convection by surely not all. Otherwise it would have to collide with water vapour or CO2. Which might not happen. And then what as it rises higher and higher.
I’ve been trying to think of the perfect experiment to demonstrate the effects of “back radiation”. Here’s what I came up with.
Put a pot on the stove. Fill it with a couple of gallons of water. Put in a thermometer. Heat it up to boiling. Turn off the heat. Every 10 minutes, make a note of the temperature as the water cools back toward room temperature.
Refill the pot to get the same volume of water. Heat to boiling. Turn off the heat. Slowly move a cookie around the room–put it anywhere you like, but not over the pot because you don’t want to restrict convection in any way (we want to measure the influence of radiation, not convection). The cookie will “back radiate” into the water. Every 10 minutes, make a note of the temperature as the water cools. Voila! The difference between the two temp series as the water cools will be your radiation effect.
The mass of the water and the mass of the cookie are supposed to represent the relative thermal capacities of the earth’s surface and rarefied CO2.
It might be more appropriate to use a Cheerio or a speck of dust, I don’t know.
Katherine 4:26
So, when the Earth warms, it radiates less longwave radiation in the bands absorbed by CO2 and when it cools, it radiates more longwave radiation in the bands absorbed by CO2?
I think you are right except that the longwave radiation that would subsequently move beyond the shorter end of the 10um atmospheric window would be absorbed / re-radiated by H2O instead. What we can say is that, all other things being equal, as the earth warms CO2 becomes a less significant GHG.
James Sexton 4:20 pm
Eyes evolved by pure chance, doubtless along with a whole load of other “useless” sensors and probably at all sorts of different sensitivity / frequency ranges. Natural selection favoured those who could see. See?
(It is interesting to speculate on what other senses could be close to mutating into something useful)
Ira, can you explain this to me. Approximately 6% of the energy spectrum, hard uv, is absorbed by the upper atmosphere, mostly by Ozone.
Now this heat must be reradiated, so half must go down. I never see this heat in any of the box figures, but it can’t just disappear.
So where does this heat go and in what form does it leave or enter the Earths atmosphere?
I think your counter analogy is missing a few elements. During the day, the black ball absorbs “high grade” heat and tranfers it to the water by convection/conduction. At night, “low grade” heat is transferred to the ball from the water by convection/conduction and is radiated out to “space.” All things being equal, add more balls to the pool and you can heat the water to a higher temperature. In point of fact, people actually do this to help their pools warm up in early spring. You just add a pool cover to reduce re-radiation at night.
Now, I’m not claiming that bumping the CO2 from 350ppm to 1,000ppm is going to roast us alive. Far from it. But if someone could point me to a post on the logarithmic behavior of GHG’s in the atmosphere, I’d appreciate it.
The main thing to correct in this explanation is that the CO2 and H2O will not emit in wavelengths that they don’t absorb, so none of the 10 micron photons reaching space will have been emitted by the CO2 or H2O gas. Clouds can emit at all wavelengths, but not these gases. I believe Miskolczi has a similar misconception that the window region will somehow show increasing GHGs, when it can’t because they don’t emit there.
The other quibble is related to the idea of these photons heating the atmosphere. In fact, the troposphere is mostly heated by convection from the surface with radiation having a net cooling effect, so the atmosphere as a whole emits more photons to space than it gains from the ground.
Ira, with respect, a comment;
You wrote (in part);
Regarding the incoming (mostly) visible radiation;
“On the left side:
….. (portions omitted for brevity)
The remainder is absorbed by the Surface of the Earth, warming it.”
Regarding the outgoing IR radiation;
“On the right side:
(1) The warmed Earth emits longwave radiation towards the Atmosphere.”
Both of these are entirely correct. But you are missing one small detail, if I might be so bold as to supply a minor edit;
“On the right side:
(1) The warmed Earth emits longwave radiation towards the Atmosphere.” This subsequently causes the Earth to COOL by an amount EXACTLY equal to the energy contained in that packet of emitted IR radiation.
And then of course the reemitted radiation from the gas may return to the Earth thereby warming it again. But this warming must be less than the cooling when the IR radiation left. Thus, no “net energy gain” and no ”higher equilibrium temperature”.
You cannot simultaneously retain energy and also emit it. You can accumulate energy and emit it later thereby de-accumulating it.
I know it is hard to believe that 30 years of very hard work by climate scientists could have such a major flaw. But sometimes folks get so far into the details of the work that the forest is no longer visible since they have been staring at the tree bark.
Nice graphics.
Cheers, Kevin.
If I understand rightly, while to our eye air is transparent, in the longwave earth’s atmosphere is a very murky and foggy kind of thing. I also believe that the greenhouse effect is due to the stairstep kind of transit that longwave radiation coming up from the earth has to go through to reach the surface from which it can be emitted to space. What I have yet to see is how the calculation is done that figures the transit time. To me this would be an important calculation because the longer the transit the greater the heating of the atmosphere should be. Is this something that is dealt with in the field of statistical physics? It would also be interesting to understand in microscopic detail what happens when shortwave radiation hits a solid surface – or for that matter a liquid surface since the earth is 71 % sea.
Bill Illis says:
February 28, 2011 at 4:40 pm
Fortunately we don’t have to work through the theoretical quantum physics for every particle in the atmosphere. All we have to do look is look at the surface with a thermal spectrometer from a high altitude and observe the result.
The following is what you see in the infrared spectrum looking upward and downward:
http://www.sundogpublishing.com/fig8-2.pdf
It’s from the 2006 textbook “A First Course in Atmospheric Radiation” by Grant Petty.
Looking downward from 20km over the arctic ocean you can see how much energy is missing in the CO2 absorption band. In the IR window you can “see” right down to sea level which follows the curve of a 265K blackbody. At CO2 absorption frequency of 15um the curve at 265K suddenly drops down sharply to follow the 225k blackbody curve. Using the dry adiabatic lapse rate of 1 Kelvin per 100 meters this gives us an emission altitude of 4 kilometers or about 12,000 feet. At that point absorption and thermalization (transfer of energy to other atmospheric gases) of 15um upwelling radiation by CO2 ceases and it is transmitted directly out to space and follows a colder blackbody curve.
Now, if you reduce the surface temperature of 265K by an amount that’s enough to fill in the hole at 15um (and the other smaller holes in CO2’s lesser absorption bands) to make a smooth blackbody curve at a lower temperature the downward difference is the amount of greenhouse effect by all atmospheric CO2.
CO2 greenhouse effect isn’t linear except for the first 50ppm or so and then it turns into a log curve where additional CO2 has less effect. This is also determined empirically by taking actual measurements of absorption in a laboratory column of gas so it doesn’t rely on theory. I can look up that curve too and have posted a link to it before but don’t have it handy and don’t feel like searching for it again.
The bottom line when the numbers are crunched on the empirical data is a 1.1C increase in surface temperature per doubling of CO2 starting from a baseline of 280ppm with about half of that already a done deal in going from 280ppm to 390ppm today. That 1.1C is the IPCC low end “sensitivity” estimate which isn’t a scary number at all and in fact is a great number because if that’s all it is then the slight warming, mostly in the winter in the higher latitudes, is a great boon to agriculture especially when the biological effect of higher CO2 on green plant growth rates and water consumption is taken into consideration. It’s actually moving the earth closer to an optimum climate where I define optimum as that climate which dominated the earth’s history and in which green plants evolved. Naturally we would expect plants to be best adapted to the environment in which they spent the most time evolving and adapting over hundreds of millions of years. Even if you don’t believe in macro-evolution just about everyone accepts micro-evolution and that’s all we’re talking about is micro-evolution.
In order to sex up CO2 greenhouse warming to a point that might make it scary the climate boffins invented, out of whole cloth with no empircal data to back it up, an imaginary “amplification” where a little CO2 warming increases greenhouse warming by water vapor by twice as much. Following that out to its logical end, since warming is warming no matter the source, water vapor warming will cause even more water vapor warming through positive feedback and we get a runaway greenhouse. In the almost sure knowledge that the earth never experienced a runaway greenhouse even with ancient CO2 levels 10 to 20 times greater than today, these anti-science scoundrels insist with a “high level of confidence” that this amplification is real and it’s based on nothing more than faster than expected surface temperature rise in the past few decades which can be TOTALLY explained by multi-decadal cyclic behavior in ocean currents, trade winds, and/or solar magnetic activity causing small global average albedo changes. There isn’t a lick of evidence that water vapor amplification is more than a figment of fevered imaginations. But CO2 greenhouse effect alone IS real and empirically established.
When looking at http://www.skepticalscience.com/images/infrared_spectrum.jpg link given by Tim Folkerts above, and looking at the spectrum of the surface looking up there appears that the all-atmosphere radiation is somewhere around 5% radiance. You see that 5% especially in the window frequencies between about 8 and 12.5 µm.
That seems to imply that most of the transfer in Ira’s animation after initial absorption is still via thermalization and re-excitation, both directions and is keeping most of the radiance in the GHG absorption/emission lines. Would you roughly agree with that?
The mass of the earth is one trillion, that’s 1 followed by 12 zeros, greater than the mass of carbon dioxide in the atmosphere. There is no way that an infinitesimal amount of gas could contain enough energy to significantly change the earth’s temperature. Any heating of the earth is by direct absorption of energy from the sun.
Ken Coffman:
“I’ve been trying to think of the perfect experiment to demonstrate the effects of “back radiation”. Here’s what I came up with.”
Well, to repeat myself at least 100 times, here’s another “experiment” to consider:
Atlanta has at least three times as much GHGs as Phoenix in July (both cities are at virtually the same elevation and latitude, so solar energy is not a factor, at least on clear days). Yet it is virtually always MUCH cooler in Atlanta than Phoenix. EVEN AT NIGHT, I keep wondering, WTF?
Now, this can be explained “simply” by the heat lost through evaporation of moisture in Atlanta, which cools their world. BUT, the question still remains: does evaporatative cooling negate/minimize/marginalize the radiative effects of GHE? If so, who gives a damn about the putative increase in CO2???
It is really weird that I have never got a sensible answer to this question, despite asking it for about 4 years now…
Bryan says:
February 28, 2011 at 2:52 pm
“Your graphs are completely misleading. They show that the intensity of the Solar Radiation as being equal to the Earth surface IR upward radiation.”
The curve seems to depict atmospheric transmissivity rather than quantitative energy transfer, despite its label.
“Further the colder atmosphere cannot heat or “warm” the warmer Earth Surface.”
The colder atmosphere still radiates IR back down, contributing to the total inflow. It’s the net transfer that should be considered.
“All it can do is to slow to some extent the heat loss from the surface.”
Yes, that’s how it works. But the warmists would rather sell you a tipping point with catastrophic thermal runaway, when in fact CO2 is already so close to its maximum effectiveness (critical mass if you like) that increasing it will have negligible further effect.
This is what theoreticians are really good at. I know, I have had to deal with them, as a pragmatic, applied scientists for years. Once they almost talked me out of one of my best inventions, that now saves lives worldwide. Not boasting, just saying. We found out much later, after I put my career on the line, what the key neglected variable was.
What modelers are good at is simplification, actually oversimplification. The goal is to eliminate as many variables that are unknown, or that compete with the model. We have all seen this in action. Once these are accepted, then the rest plays out like clockwork.
I found, at a cursory glance, a few major omissions and simplifications. By ignoring these, the model simplifies, and seems reasonable. To keep this short, I will mention the first. It is a type of misdirection, as a magician would use. Theoreticians are like magicians—they must oversimplify in order to describe a chaotic and heterogeneous system.
Here goes. Did anyone pick up that the “average” incoming radiation is “centered around” 1/2 µ? That is true sometimes, but remember that our sun is a variable M star. What that means is that it has bursts of very short wavelength (very high energy) radiation, like X-rays. Other times, when it gets quiet, the output is switched to lower energy radiation. Including infrared, up to 15000+ nm.
The sun puts out some X-rays—it also generates some infrared.
Defining the solar output range to be between 100 nm and 3000 nm is an arbitrary range, based on averages (as Gaussian distributions). There is an infrared component of incoming solar radiation that is not only reflected, but also absorbed by CO2 and other molecules, and then reradiated as lower energy radiation. The higher in the atmosphere this happens, the more is lost back to space.
CO2 absorbs light primarily in the IR wavelength, but it is not totally transparent to other wavelengths. So the model has another assumption.
Other energy from the sun, such as plasmas, and particles are very important. Especially protons. Protons can protonate CO2, and other molecules to form formic acid and other species.
Etudiant mentions water. Water vapor also reacts with CO2 to form carbonic acid, that can go on to do other chemistry, besides being the king at absorbing almost all wavelengths of incoming and outgoing radiation. Water is the boss, not the secondary actor.
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. Remember that Mars has 970,000 ppm of CO2 in its atmosphere. But there is not much atmosphere, so there are fewer molecules to absorb. If we halved the CO2 concentration on Mars, it would have a minuscule effect.
BTW, most organisms on the planet are adapted to “seeing” in the ultraviolet. Humans are pretty rare that they cannot. Many animals “see” also in the infrared, so Ira’s argument in that regard has little impact with me. His purpose, it seems, was to for us to focus on the visible range of light to the exclusion of the other incoming wavelengths, in order to help us apprehend his model.
The relationship between the earth and sun is involves the relationship of two variable, chaotic and heterogeneous systems. I like to think of the atmosphere like the Jovian or Saturnian atmospheres, where we see banding and concentration of clouds and compounds, flowing countercurrent to one another. Our atmosphere is invisible to us. The situation with ozone teaches us that gases can be more or less concentrated in different areas of the earth, varying in response to unidentified variables, in a fluid, dynamic interaction.
Notwithstanding these caveats to the models assumptions, Ira does a great job describing the consensus model of the greenhouse effect.
Oh, no!
I did it again, misspelled my /unbolding. It was only meant for one word.
Sorry.
Phil’s Dad says:
February 28, 2011 at 5:32 pm
James Sexton 4:20 pm
Eyes evolved by pure chance, doubtless along with a whole load of other “useless” sensors and probably at all sorts of different sensitivity / frequency ranges. Natural selection favoured those who could see. See?
(It is interesting to speculate on what other senses could be close to mutating into something useful)
======================================================
lol, It’s all too clear now! Now I can see! Evolution means something was whispering in our soon to be ears that there was something to see out there! Now I’m coming to an understanding! That d.a. Newton……what could he ever logic?
I must disagree with the comments to the effect that N2 & O2 radiate (or absorb) any important amount of IR.
Look at a somewhat similar and more familiar idea – visible light emitted by a Hydrogen atom (the Bohr model covered in freshman chem & physics around the world). It is easy to observe that H only emits very specific energies of light which are “easily” predicted by the quantum mechanics of the orbiting electrons and the allowed transitions between energy levels of those orbits. Photons of other energies are simply not emitted by H atoms. And photons of other energies are simply not absorbed either. Different atoms and molecules will absorb and emit at their own characteristic visible frequencies due to their own electron orbital energies. If you know the energies of the allowed orbits, you can find the energies of photons that can be absorbed or emitted by other gases.
For thermal IR (above a few micrometers), the quantum mechanics is different. This is not taught in freshman chemistry. Here the energies are not related to electrons jumping to other orbits (that takes too much energy), but instead it is related to rotations and vibrations of the molecules (which can happen at the energies associated with IR photons). However, it is an observed fact (supported by theory) that monatomic gases (like argon) or symmetric diatomic gases (like N2 and O2) do not have vibration modes or rotation modes that would allow them to absorb (or emit) IR photons. Just like yellow light is not absorbed or emitted by H atoms, IR is not absorbed or emitted by N2 & O2. (There are some unimportant exceptions – for example O2 or N2 with different isotopes can absorb IR weakly for example. But it is my understanding that this is a very small effect, even given that N2 is MUCH more common in the atmosphere.)
Thanks for a very clear explanation of the “greenhouse” radiative effect. As someone who is just beginning to learn about the radiative modeling of the atmosphere, it is greatly appreciated. I’m sure that to many of the WUWT regulars this is very elementary, but to those of us who are just learning, the graphics made it very understandable. It goes in my hardcopy file for sure.
One question. I never see Rayleigh or Mie scattering mentioned, although it is my understanding that, in the atmosphere these equations govern the absorpsion and scattering of electomagnetic radiation from the sun, and the “long wave” radiation of the earth back to space. I am only just aware of Mie theory, having run across it in a project to measure jet engine exhaust particle size.
Can’t these eqations be used to settle some of the arguements of just how much electromagnetic radiation is absorbed and scattered?
PS: Because of Robert Woods 1909 experiment with two miniature “greenhouses”, one with a “rock salt” (i.e., transparent to the longwave IR material) window and the other with a glass window, showing NO MEASURABLE DIFFERENCE in the final equilibrium temperatures in both boxes, we’ve known SINCE 1909 that to ascribe the warming of greenhouses to the allegation of a “one way valve” due to the regular sodium silica glass, is in error.
Real “Meteorological” textbooks for many years have noted this and used the prefered term: “Atmospheric Effect”.
I think the WUWT crowd needs to realize this fact and steadfastly refuse to use the terms “Greenhouse gases” or “Greenhouse Effect”.
Truth needs to win!
Max
HankHenry says:
February 28, 2011 at 6:15 pm
“If I understand rightly, while to our eye air is transparent, in the longwave earth’s atmosphere is a very murky and foggy kind of thing.”
Yes.
“I also believe that the greenhouse effect is due to the stairstep kind of transit that longwave radiation coming up from the earth has to go through to reach the surface from which it can be emitted to space.”
Yes,
“What I have yet to see is how the calculation is done that figures the transit time.”
Don’t need to do that. We lofted infrared spectrometers with high altitude balloons in clear dry air over the arctic ocean and measured the energy level across the spectrum looking downward.
“To me this would be an important calculation because the longer the transit the greater the heating of the atmosphere should be.”
Yes.
“Is this something that is dealt with in the field of statistical physics?”
Classical (statistical) mechanics and quantum mechanics both. The scale is classical since the wavelength of thermal IR spans billions of molecules at once in the troposphere where all the action takes place. Quantum explanations get truly bizarre. But again there’s no need to use theory when you have empirical observations. It’s like trying to calculate the acceleration of gravity by theory and just measuring how fast a lead ball falls by dropping it from the Leaning Tower of Pisa.
“It would also be interesting to understand in microscopic detail what happens when shortwave radiation hits a solid surface – or for that matter a liquid surface since the earth is 71 % sea.”
Interesting yes but again it’s an easy empirical measurement. The ocean absorbs practically every bit of sunlight that reaches the surface and penetrates to a depth of about 300 meters give or take depending on turbidity. At low angles it begins to reflect a significant portion of incident light but low angles only occur when the sunlight is weak to begin with (near dawn and dusk and at very high latitudes).
Clouds however also cover an average of around 70% of the earth’s surface and they can reflect anywhere between 15% to 85% of the sun’s light directly back out into space. Average albedo of the earth isn’t known to an acceptable margin of error with estimates ranging a few percent above and below 35%. Every percentage point difference is a few degrees warmer or colder surface temperature if the difference is lasting across a number of years. With a marginal exception for seasonal NH/SH difference due to snow cover it’s assumed to be a constant value in the models and different models just pick a number that works out best for fitting hindcast global average temperature with measured past global average temperature. In other words albedo is not just a fudge factor in the climate models but rather a damn big fudge factor that dwarfs any change that anthropogenic CO2 can possibly bring about.
This is why the hypothesis that galactic cosmic ray intensity changes result in more or fewer clouds and changing albedo. GCRs are modulated by both solar magnetic field, which is largely unpredictable in strength except for generalities associated with 11-year sunspot cycle and is also modulated by unpredictable events like nearby supernovas, and by more predictable very very long slow changes in intensity due to the solar system traversing spiral arms of our galaxy and wandering above and below the galactic plane in cycles lasting tens and hundreds of millions of years.
Quite frankly it really appears GCR intensity is The Big Kahuna when it comes to global average temperature variations. The latter half of the twentieth century saw the most intense solar magnetic field (by sunspot number proxy) in the past 400 years since sunspot records began. This would have resulted in fewer GCRs, fewer clouds, lower average albedo, and surface warming from the lower albedo.
Oops. Saw a mistake in my last comment. Sunlight penetrates the ocean to roughly 300 feet not 300 meters. That would be 100 meters (give or take depending on turbidity) before it gets inky black. It sucks to be one of those strange people (Americans and Brits) who learnt English units of measure in our youths and has had the rest of the world pressuring us into going metric. I try. Sort of.