Guest Post by Ira Glickstein
This series began with a mechanical analogy for the Atmospheric “Greenhouse Effect” and progressed a bit more deeply into Atmospheric Windows and Emission Spectra. In this posting, we consider the interaction between air molecules, including Nitrogen (N2), Oxygen (O2), Water Vapor (H2O) and Carbon Dioxide (CO2), with Photons of various wavelengths. This may help us visualize how energy, in the form of Photons radiated by the Sun and the Surface of the Earth, is absorbed and re-emited by Atmospheric molecules. 
DESCRIPTION OF THE GRAPHIC
The animated graphic has eight frames, as indicated by the counter in the lower right corner. Molecules are symbolized by letter pairs or triplets and Photons by ovals and arrows. The view is of a small portion of the cloud-free Atmosphere. (Thanks to WUWT commenter davidmhoffer for some of the ideas incorporated in this graphic.)
- During the daytime, Solar energy enters the Atmosphere in the form of Photons at wavelengths from about 0.1μ (micron – millionth of a meter) to 4μ, which is called “shortwave” radiation and is represented as ~1/2μ and symbolized as orange ovals. Most of this energy gets a free pass through the cloud-free Atmosphere. It continues down to the Surface of the Earth where some is reflected back by light areas (not shown in the animation) and where most is absorbed and warms the Surface.
- Since Earth’s temperature is well above absolute zero, both day and night, the Surface radiates Photons in all directions with the energy distributed approximately according to a “blackbody” at a given temperature. This energy is in the form of Photons at wavelengths from about 4μ to 50μ, which is called “longwave” radiation and is represented as ~7μ, ~10μ, and ~15μ and symbolized as violet, light blue, and purple ovals, respectively. The primary “greenhouse” gases (GHG) are Water Vapor (H2O) and Carbon Dioxide (CO2). The ~7μ Photon is absorbed by an H2O molecule because Water Vapor has an absorption peak in that region, the ~10μ Photon gets a free pass because neither H2O nor CO2 absorb strongly in that region, and one of the 15μ Photons gets absorbed by an H2O molecule while the other gets absorbed by a CO2 molecule because these gases have absorption peaks in that region.
- The absorbed Photons raise the energy level of their respective molecules (symbolized by red outlines).
- The energized molecules re-emit the Photons in random directions, some upwards, some downwards, and some sideways. Some of the re-emitted Photons make their way out to Space and their energy is lost there, others back down to the Surface where their energy is absorbed, further heating the Earth, and others travel through the Atmosphere for a random distance until they encounter another GHG molecule.
- This frame and the next two illustrate another way Photons are emitted, namely due to collisions between energized GHG molecules and other air molecules. As in frame (2) the Surface radiates Photons in all directions and various wavelengths.
- The Photons cause the GHG molecules to become energized and they speed up and collide with other gas molecules, energizing them. NOTE: In a gas, the molecules are in constant motion, moving in random directions at different speeds, colliding and bouncing off one another, etc. Indeed the “temperature” of a gas is something like the average speed of the molecules. In this animation, the gas molecules are fixed in position because it would be too confusing if they were all shown moving and because the speed of the Photons is so much greater than the speed of the molecules that they hardly move in the time indicated.
- The energized air molecules emit radiation at various wavelengths and in random directions, some upwards, some downwards, and some sideways. Some of the re-emitted Photons make their way out to Space and their energy is lost there, others back down to the Surface where their energy is absorbed, further heating the Earth, and others travel through the Atmosphere for a random distance until they encounter another GHG molecule.
- Having emitted the energy, the molecules cool down.
DISCUSSION
As in the other postings in this series, only radiation effects are considered because they are the key to understanding the Atmospheric “Greenhouse Effect”. I recognize that other effects are as important, and perhaps more so, in the overall heat balance of the Earth. These include clouds which reflect much of the Sun’s radiation back out to Space, and which, due to negative feedback, counteract Global Warming. Other effects include convection (wind, thunderstorms, …), precipitation (rain, snow) and conduction that are responsible for transferring energy from the Surface to the Atmosphere. It is also important to note that the Atmospheric “Greenhouse Effect” and a physical greenhouse are similar in that they both limit the rate of thermal energy flowing out of the system, but the mechanisms by which heat is retained are different. A greenhouse works primarily by preventing absorbed heat from leaving the structure through convection, i.e. sensible heat transport. The greenhouse effect heats the earth because greenhouse gases absorb outgoing radiative energy and re-emit some of it back towards earth.
That said, how does this visualization help us understand the issue of “CO2 sensitivity” which is the additional warming of the Earth Surface due to an increase in atmospheric CO2? Well, given a greater density of CO2 (and H2O) molecules in the air, there is a greater chance that a given photon will get absorbed. Stated differently, a given photon will travel a shorter distance, on average, before being absorbed by a GHG molecule and be re-emitted in a random direction, including downwards towards the Surface. That will result in more energy being recycled back to the Surface, increasing average temperatures a bit.
Many thanks!
The archive Webcitation URL for the Newworldencyclopedia quote: http://www.webcitation.org/5y6Any4VA
“Infrared radiation and heat
..
Many physics teachers traditionally attribute all the heat from the Sun to infrared light. This is inexact – visible light from the Sun accounts for 50% of the heating, and electromagnetic waves of any frequency will have a detectable heating effect if they are intense enough.”
So, prove Visible light is even capabable of heating the Earth to produce half the outgoing Thermal IR claimed in the AGWScience Energy Budget KT97, without artificially intensifying it…
..I don’t see anyone walking around with redeye.
Myrrh, I’d love to hear more specifically about your understandnig of “heat”. Which of these is closest to your thinking.
* “Heat” and “thermal IR” are one and the same. Any time the term”heat” comes up in science, one could just as well use the term “thermal energy”.
* “Heat” is a subset of “thermal IR”. All heat is thermal IR, but some thermal IR is not heat.
* “Thermal IR” is a subset of “heat”. All is thermal IR heat , but some heat is not thermal IR.
* “Thermal IR” and “heat” overlap, but there is some heat that is not Thermal IR, and there is some thermal IR that is not heat.
Myrrh,
Entropy is defined within statistical mechanics as
S = k_B ln(Ω).
Or within classical mechanics, entropy is
S = δq/T
How does anything I wrote lead to any situation where S is destroyed?
Tim, is this what’s stopping you from answering my question?
Don’t worry about it, since you haven’t picked up from what I’ve said, but concentrate on answering the question as from the KT97 and we can work through it.
It says, that the Solar energies of Visible plus UV plus Nr IR that reach the surface of the Earth and then convert to heat and then the Earth radiates out the amount of Thermal IR it says.
You tell me what that means, exactly, as I’ve asked. How and how much. These are not Thermal, they are not hot we do not feel them as warmth, they are therefore not heat on the move so they cannot of themselves transfer actual heat, which would be themselves, to organic matter to change its temperature. How does each of these three Solar actually convert to heat in the organic matter of the Earth, how much heat does each of these produce?
It’s not my hypothesis; it’s not for me to tell you what I think heat is, it’s for you to explain it to me because I’m questioning what you mean by it (as a defender of this AGWScience Energy Budget at least in your mode of ‘99% of the heat generated is by these Solar energies’).
Tim – re your post on entropy. I don’t read maths. Explain it in English so that I can understand.
And p.s. re the Solar energies, please stick to the KT97.
And I’ll come back to this later. Good night.
Myrrh says:
April 20, 2011 at 7:13 pm
Tim, is this what’s stopping you from answering my question?
Don’t worry about it, since you haven’t picked up from what I’ve said, but concentrate on answering the question as from the KT97 and we can work through it.
It says, that the Solar energies of Visible plus UV plus Nr IR that reach the surface of the Earth and then convert to heat and then the Earth radiates out the amount of Thermal IR it says.
You tell me what that means, exactly, as I’ve asked. How and how much. These are not Thermal, they are not hot we do not feel them as warmth, they are therefore not heat on the move so they cannot of themselves transfer actual heat, which would be themselves, to organic matter to change its temperature. How does each of these three Solar actually convert to heat in the organic matter of the Earth, how much heat does each of these produce?
From about a century ago it has been well known that the energy carried by a photon is given by Planck’s constant times the freqency. Therefore a UV photon carries more energy than a visible and that more than an IR photon. When any of these photons is absorbed it gives up all the energy it carries to the absorbing medium.
Seventy percent of the Earth’s surface is covered with water which absorbs ~90% of all the radiation incident on it.
It’s not my hypothesis; it’s not for me to tell you what I think heat is, it’s for you to explain it to me because I’m questioning what you mean by it (as a defender of this AGWScience Energy Budget at least in your mode of ’99% of the heat generated is by these Solar energies’).
It’s nothing to do with ‘AGW Science’ it’s an established part of basic physics for about a century.
I have taken Tim’s suggestion and have re-written my program that calculates any slice of the Planck energy curve between any two frequencies, wavelengths, of wavenumbers with a specified source temperature and destination’s temperature at a given emissivity.
That has so opened my eyes.
If you take the segment of carbon dioxide absorption at 288 K and between 575/cm and 720/cm wavenumbers (13.89µm & 17.39µm) at an emissivity of one and radiated to a zero K surface, you find that the total absorption/emission in this band, if totally absorbing all radiation within this segment, to be 60 W/m^2. This is 60/390 or approximately 15% maximum absorption per molecule by CO2 if it is the only greenhouse gas present at toal absorption. However, water molecules are about 40 to 60 times more prevalent in the lower atmosphere so this has to be respected. But if you look at any spectrum of CO2, you will find that the absorption is not anywhere close to total absorption, it is more like 0.25 or 25% absorption in the lower atmosphere which gives an absorption of 15 W/m^2 in this band, and remember this on a per molecule basis per this narrow band.
The absorption of CO2 starts at the surface with close to 1 to 2% absorption and ends up with an absorption of ~50% in that band at 100,000 meters in this narrow band above the surface. That is where the average of 25% came from that occurs at some lower level in the atmosphere.
See:
http://i53.tinypic.com/21ay9zn.png
http://i53.tinypic.com/14t39ma.png
By KT97 paper 102 W/m^2 / 235 W/m^2 (or 43%) of the upward transfer of heat is by conduction/thermals or evaporation/convection. But there is also an amount of solar absorption that is absorbed by the atmosphere and that also makes it way to space (never downward against a temperature gradient) that is about 67 W/m^2 / 235 W/m2 (28%). The total is now (102+67=169)W/m^2 / 235 W/m2 or 72% of the heat transferred from the surface to space, always from upward from warmer layer to cooler layers by Stefan-Boltzmann relationship of flux = ε•σ• (Ta^4 –Tb^4) from the matter with temperature of Ta to the matter with a temperature of Tb. That leaves about 28% that could possibly by affected by CO2 absorption, all other can be ignored for it merely follows Stefan-Boltzmann’s Plank integration.
But we are missing about 28% of the flux or 0.28 * 235 = 66 W/m^2, where does that come from? Well, the surface is warmer that the air above so let’s roughly integrate the transfer by Stefan-Boltzmann equation upward from the surface to cooler layers above of a few kilometers. Looking at the standard atmosphere at 2 km you see that the temperature is then about 288K – 6.5 K/km^2 * 2 km or 275K. Using Stefan-Boltzmann transfer equation you get ε = 1 and σ = Stefan-Boltzmann constant and then flux = ε•σ•(288K^4 – 275K^4) = 66 W/m^2.
To me that is the end to this AGW discussion of some 17 months! End of story! I now see it all, and this matches so well what Miskolczi has been saying all along, that CO2 plays, not a little, but zero effect in the flow of energy from the surface, for water vapor will immediately compensate to maintain the flow of energy upward,. it’s concentration is limitless. If CO2 increases, then the 2 km used in this example will increase slightly to a lower temperature to compensate, to let’s say 2.02 km, so that the missing 66 W/m^2 is always balanced, so that, in the end, input from the sun equals the upward flux from the atmosphere and the surface.
We live in a very small band of temperatures that cannot be either too cold nor too hot on the average. We can look millennia backwards to see that this world balances mostly, in the warm non-glacier periods, between these goalposts. I now see how that is achieved.
Now the explanation by ‘chjoaygame’ at physicsforums needs to be read a few times until you thoroughly understand what is said, for he expains it more clearly than I can:
http://www.physicsforums.com/showpost.php?s=912234afa1f8662b1eb57ce49b6f7e22&p=1972705&postcount=34
Hope I made that clear enough, for I so want to give everyone here at least the chance to see the real physics involved.
Those here should realize: (part one of four)
wayne says:
April 20, 2011 at 10:18 pm
Thanks, wayne, excellent, well written and logical quote that you provided from physicsforum.
Now the explanation by ‘chjoaygame’ at physicsforums needs to be read a few times until you thoroughly understand what is said, for he expains it more clearly than I can:
http://www.physicsforums.com/showpost.php?s=912234afa1f8662b1eb57ce49b6f7e22&p=1972705&postcount=34
I don’t understand this paper. But I’m confused by this section
“The land-sea surface is partly warmed by the back radiation downwards through the window from the clouds.”
How can this occur. If the clouds are a lower temperature and a colder body can not warm a hotter one?
“Consequently, the overwhelming varying, and nearly the only, flow, of back radiation from atmosphere to land-sea surface is from the lower surfaces of clouds. Because it arises from clouds which are cooler than the land-sea surface, …”
Myrrh says:
…….”I don’t read maths. Explain it in English so that I can understand.”…….
Myrrh you have a very good grasp of the ‘nuts and bolts’ of the radiative interactions in the atmosphere.
Phil says
……” Therefore a UV photon carries more energy than a visible and that more than an IR photon. When any of these photons is absorbed it gives up all the energy it carries to the absorbing medium.
Seventy percent of the Earth’s surface is covered with water which absorbs ~90% of all the radiation incident on it.”…….
Now the implication of this he says is that all this radiation is converted into thermal energy of the Earth surface molecules almost immediately.
Myrrh is quite right to point out that dependent on the wavelength, different outcomes are realised.
The most obvious example being photosynthesis.
Another trend you have noticed is the corruption of normal science to fit in with an IPCC driven agenda hence your concern for the NASA Infra Red information rewrite.
If you’ve been following my exchange with Joel about the new edition of
University Physics by Young and Freedman it will confirm your concerns.
My edition, the ninth (1995), in which they say nothing about the “greenhouse theory”.
However in the latest (13th edition) they have about a page on the greenhouse theory in which they feel compelled to add ;
Molecules of CO2 in the atmosphere have the property that they absorb some of the infrared radiation coming upward from the surface. They then re-radiate the absorbed energy, but some of the re-radiated energy is direct back down toward the surface instead of escaping into space. In order to maintain thermal equilibrium, the earth’s surface must compensate for this by increasing its temperature T and hence its total rate of radiating energy (which is proportional to T^4). This phenomenon, called the greenhouse effect, makes our planet’s surface temperature about 33 C higher than it would be if there were no atmospheric CO2. If CO2 were absent, the earth’s average surface temperature would be below the freezing point of water, and life as we know it would be impossible.
It then goes on to talk about the burning of fossil fuels, the increase in CO2, and the increase in temperatures, ending with these two sentences:
The resulting temperature increase will have dramatic effects on climate around the world. In the polar regions massive quantities of ice will melt and run from solid land to the sea, thus raising ocean levels worldwide and threatening the homes and lives of hundreds of millions of people who live near the cost. Coping with these threats is one of the greatest challenges facing 21st-century civilization.
Now the added content, most will see as primitive hyper alarmist rubbish, that even Skeptical Science would be too embarresed to print.
Why did they feel compelled to pollute a good standard physics textbook?
The “gesture paragraphs” stick out like a sore thumb.
What kind of pressures does the IPCC political ideological collosus bring to bear in publishers and university department to fit in with consensus settled science.
We already know from the Climategate e-mails how concerned the’ team’ were with the BBC and peer reviewed Journals and how the ‘team’ determined the agenda.
Has the ‘thought police’ reached down to standard text books?
It appears they have.
Johnny Ball the popular science presenter (now banned for his views on climate science) illustrates this with a new edition of a elementary school chemistry textbook(GCSE standard) where almost the entire book as devoted to global warming , pollution and in which Carbon Dioxide is described as a pollutant.
Phil says:
April 20, 2011 at 9:11 pm
From about a century ago it has been well known that the energy carried by a photon is given by Planck’s constant times the frequency. Therefore a UV photon carries more energy than a visible and that more than an IR photon. When any of these photons is absorbed it gives up all the energy it carries to the absorbing medium.
BUT, what kind of energy? What are these energies capable of doing? What effect do they have because of their particular characteristics in reacting with other matter? What are each actually doing when they give up their energies?
The assumption here pushed by AGWScience that this means ‘more energy means greater power to heat’ is ludicrous. A photon of blue light does not give up its energy in heat to a plant in photosynthesis. I’ve been through all this. What other characteristics does it have? It is highly reflective off surfaces, all the colours of the world you see around you are from those visible colours not being absorbed but reflected back to the viewer. Why are these so reflective? Because they’re tiny and the real world is solid and so they bounce off. Blue light is so lightweight in this regard that it bounces off every oxygen and nitrogen molecule in the Gas Air as it passes through. Because it is highly energetic, which means only that it is moving more rapidly in the same time and distance that a less energic wave is moving, it bounces off faster than slower moving photons of say Green light, that’s why the sky is blue – because these supposedly more powerful photons are more easily reflected and scattered in our atmosphere the Gas Air. Size matters. It only takes a tiny molecule of oxygen or nitrogen to scatter blue light. Our atmosphere is, rounded up, 100% oxygen and nitrogen, the Gas Air, it has weight, volume it’s an ocean of gas above us and blue light has great difficulty in getting through it as can be understood because it is so easily scattered. That it carries more energy cannot be equated with having more power to work. Just how much heat is it creating high in the cold blue sky, there’s a lot of it.
All this hot object giving off higher and higher more energetic frequencies shows is that it takes a lot of heat to create these finer photons. They are effects given off, they cannot be assumed to be therefore more powerful to effect change in the world by creating heat than the cause creating them.
UV is even more energetic than Visible, but we cannot feel it because all that energetic movement is inconsequential in comparison with the longer bigger photons of thermal IR. See the NASA page, even Near IR is microscopic compared with the bigger pinhead sized photons of thermal IR. UV cannot even get through the first layer of our skin. In intensity, less dense mountain air or high noon at the equator, it’s very highly energetic form can drill our skin and burn it, but Visible light can’t even do that. It penetrates a little further before being reflected or absorbed, not creating any heat in giving up its energy. How then is this blue light creating heat in the KT97? It isn’t. All that energy has therefore to be taken out of the KT97 budget which claims Solar is converting to Heat, because it is not contributing to it. Ditto the rest of those shortwaves. UV is the only one capable of creating heat, converting to heat, and that is limited to degree of intensity in conditions. Near IR is not hot either and as short wave higher energetic movement it is more apt to be reflected, (back or through whatever organic medium), than the longer bigger thermal IR which penetrates deeper, etc. etc. Near IR is used in photosynthesis.
The KT97 is nonsense based on this impossible scenario that planckian carrying more energy means carrying more power in organic matter which is the Earth, let alone carrying more power to heat. Energy exchanges do not always mean creating heat, see my posts above.
So, still my question. How much heat do these Solar KT97 photons actually create? From which…, how much of it, these Solar energies, is necessary to heat up the Earth to produce the amount of Thermal IR claimed in KT97 in upwelling from this creation of heat?
Bearing in mind, for example, that Blue light does not heat naturally, but by artificial concentration in intensity, such as a laser, can burn, just how intense would these have to be in our real world to create that amount of Thermal IR?
Light energies are not hot, they are not carrying any heat to effect change claimed so heat transfer is not applicable, we’re talking only of these photons’ actual ability to create heat in absorption in the claimed reaching the Earth balance.
I say it’s insignificant. As insignificant as in an incandescant bulb giving off 95% of its energy in heat, Thermal IR, compared with the 5% in Visible light which is not hot. The Visible light is adding zilch to heating the room the lightbulb is in.
It’s nothing to do with ‘AGWScience’ it’s an established part of basic physics for about a century.
What light from the Sun is capable of doing in different wavelengths is now far too well known to get confused, or be fobbed off by, the idea of ‘carrying more power’ meaning power to do what it says on the AGWtin. As real gases are affected by real world conditions and a molecule of CO2 cannot stay up in the Gas Air defying gravity and pressure and its own weight relative to Air, without work being done, so too are photons of light affected by real world conditions. They cannot then be claimed to do whatever it is someone wants them do if it is physically impossible, they cannot heat organic matter if they are actually physically incapable of doing so and it is well established science that energy transfer is not limited to creating heat. They are limited by their own real properties and the properties of the real world in which they move and have their being; in relationship, in reaction, relative to.
It is AGWScience that has twisted meanings to give the impression that these molecules and photons are something other than what they are and can do things which the real molecules and photons can’t do.
And there are various ways in which this has been done to create an alternative physical universe of impossible things. Here it seems it’s enough to first blindside ‘everyone’ with the idea that photons carrying more energy means carrying more power to effect change, and added to that by taking out references to other possibilities from their properties the idea is pushed that their only effect upon absorption is creating heat, to bolster the idea that ‘carrying high energy means more power to create heat’. It’s a con. A very clever manipulation achieved by taking bits from real world science out of context, by misrepresenting laws and by applying them in physical contexts not applicable to them. Those doing the manipulating are well aware that this is how and what is being done to manipulate thinking.
The very sad thing is that this is manufactured and promoted by those who know the real science thoroughly and this deliberate confusion is now well on its way to being spread into the education system, undoing all the advances in understanding the physical world gained by real science and capable of being appreciated by everyone to some extent or other. The deliberate creation of global ignorance.
So, I’m still asking, where is the proof that these shortwave energies are physically capable of and actually able to convert to heat to give off that amount of Thermal IR?
They can’t answer it because such proof does not exist because the properties of these energies are physically unable to effect this.
So, for example, is Tim one of the manipulators or one of the manipulated in his reasoning as shown here in this discussion? Is he a manipulator who has the, what would seem to such, ‘bright’ idea that when unable to counter solid fact the best course of action is to incorporate it and create an alternative scenario and then stick in something equally physically impossible to continue the meme that is being promoted, or is he one of manipulated who simply can’t think logically? For example, unable counter the given evidence that Visible light has other possible effects besides ‘creating heat’, as in photosynthesis and the examples from healing I gave, he counters with ‘but of course, but when photosynthesis isn’t happening it’s creating heat’… A desperate believer trying to make sense of the deliberately twisted logic of the manipulators, or a manipulator congratulating himself on creating another get out ‘reason’ to counter the real world science, because again without any accompanying proof/science logic explanation that such a thing can happen? Again without any accompanying proof/examples yet he claims he is extremely well educated in these matters. What do you think? Do you think he didn’t know what I meant in my paragraph re entropy and NET?
Bryan – thank you re ‘good grasp’. I have to say it’s been quite an enterprise for me having to dredge up half remembered stuff from school days and having to read up on this as best I’m able without the maths language. I’ve learned an awful lot of stuff I didn’t know..
I didn’t see your post before I submitted mine which also touches on the manipulative aspect, so I’ve been interested in your exchanges with Joel. I’m as concerned as you are about the effects this is having in education by changing standard science to AGW brainwashing and the text book example is so incredibly blatant, but only if you have an old copy of the text.. This ‘re-education’ begins from infants up and always with the just enough real science to make the following false claim believable or by simply excluding certain things that would give a rounded appreciation, at whatever level. I find it interesting that they haven’t yet managed to change everything on-line, sheer volume of the stuff available probably, but there it’s easier to make things disappear and make-believe that it never existed.
However, I have been wondering of late how far this re-education goes in its reach within society. Is there a cut-off point and where, at what schools or universities? If the creation of science ignorance means there’s eventually no-one left who can actually come up with new stuff for those now doing the manipulating..?
Bryan,
You’ve come up with a great way to never have to accept any fact that is inconvenient to your ideologically-driven worldview: When a textbook says something that you like, then you take it as evidence that your position is correct. When it says something that you don’t like, it is all part of a grand conspiracy and can thus be safely ignored.
RJ:
“I don’t understand this paper. But I’m confused by this section”
and
“How can this occur. If the clouds are a lower temperature and a colder body can not warm a hotter one? ”
I wish ‘chjoaygame’, who ever he/she is would not have brought ‘back radiation’ into their comment, but I do see that concept. Clouds do not act the same, in a radiative sense, as the atmosphere. They contain tiny liquid droplets, and a liquid surface radiates much more with a gray body spectrum than gases, placing more radiation back into the radiative ‘window’ frequencies, both on the bottom of the clouds radiating downward and on the top of the clouds radiating upward (and on the sides also but by homogeneity cancels). But radiation in the window has such a small chance of being absorbed this does decrease the net energy leaving the surface. And, in some rare cases the low clouds are, in fact, warmer that the surface itself in the winter from a warm front and, in that case only, do radiate more downward than the surface is radiating upward and do warm the surface.
A better way would for him to have expressed this simply as a decrease in the temperature gradient (smaller lapse rate) underneath clouds, now that is well documented in any book on meteorology as the lapse rate decreases. Then you can stay with the same logic of just using Stefan-Boltzmann with two temperatures and the emissivity between the layers without even needing the complexities of tracing individual photon flows.
I had to integrate this just to prove to myself that it really doesn’t matter when you are using the SB equation (emissivity set to 1) the correct way with two temperatures as a delta of the T’s to the fourth:
AltitudeRange (m) — T Range (K) — Flux (W/m^2)
0000-1000 m — 288.2K – 281.7K — 34.115 (always upward)
1000-2000 m — 281.7K – 275.2K — 31.834
2000-3000 m — 275.2K – 268.7K — 29.656
3000-4000 m — 268.7K – 262.2K — 27.580
4000-5000 m — 262.2K – 255.7K — 25.604
5000-6000 m — 255.7K – 249.2K — 23.724
6000-7000 m — 249.2K – 242.7K — 21.938
7000-8000 m — 242.7K – 236.2K — 20.245
8000-9000 m — 236.2K – 229.7K — 18.641
9000-10000 m — 229.7K – 223.3K — 16.871
10000-11000m — 223.3K – 216.8K — 15.713
11000-12000m — 216.8K – 216.7K — 0.2309
12000-13000m — 216.7K – 216.7K — 0.0
.
.
Sum of above individual fluxes above = 266.152 W/m^2
.
As whole in one SB calculation:
0000-12000 m — 288.2K – 216.7K — 266.152 W/m^2
See, you can calculate as many layers as you want to prove some point but it really doesn’t matter at all, if you have the two temperatures and the correct emissivity then the sums of layer-by-layer will be the same as the whole taken in one big jump.
I wish davidmhoffer, and even Ira, could grasp this part of physics and so much of the back and forth comments above would have vanished.
Joel Shore says:
“…your ideologically-driven worldview…”
Classic pot/kettle statement. Are there no mirrors in Joel Shore’s basement?
wayne
,,,,,,”I have taken Tim’s suggestion and have re-written my program that calculates any slice of the Planck energy curve between any two frequencies, wavelengths, of wavenumbers with a specified source temperature and destination’s temperature at a given emissivity.”……
Sounds an interesting project.
Do you have a link to this program?
I would like to compare the KT Earth surface up value of 390W/m2 from a continues source to the 324W/m2 backradiation from a filtered atmospheric source.
Myrrh says:
“A photon of blue light does not give up its energy in heat to a plant in photosynthesis.”
It is certainly true that a blue photon absorbed by a plant will not heat the plant — instead it will initiate some chemical reaction — perhaps to creates some sugar. (Of course, many blue photons do NOT get absorbed for photosynthesis, but instead simply get absorbed, for example by a rock or the ocean. The energy from these photons will get turned directly into thermal energy.)
But back to the photon absorbed by photosynthesis. The K&T diagram is an average over the whole earth over a significant period of time — lets assume it covers 1 year. Let’s imagine the photon was absorbed by some grass. By the end of the year the chemical energy that came from that absorbed blue photon will be released when the grass is digested by and animal or decomposes. Storing the energy of that photon as chemical energy for a day or a year or a century only delays when it gets converted to thermal energy.
In equilibrium, the energy will be balanced. Unless there is a net increase in organic matter, the energy released by digested plants will equal the energy absorbed by growing plants. During the spring and summer, there will be a net conversion from EM energy to chemical energy; in the fall and winter there will be a net conversion of chemical energy to thermal energy.
A tree that is growing today is converting EM energy to chemical energy. A tree that was growing 100 years ago but died this year will be converting a similar amount of chemical energy back to thermal energy. (In fact, since people tend to be clearing forests (with lots of organic matter) and replacing it with crops (with only a little organic matter), the chemical energy from blue photons 100 years ago is actually ADDING net thermal to the system now.)
SUMMARY: Ultimately the blue photon DOES give up its EM energy to thermal energy EVEN IF it gets absorbed by a plant.
Smokey says:
So, Smokey, can you come up with an example where I have approvingly cited a respected textbook and then when it was pointed out to me that a later edition of the textbook said something that conflicted with my ideologically-driven worldview, I came up with a dramatic conspiracy theory to explain why the textbook was lying to the students because I refused to believe that perhaps it was my worldview that was wrong?
I didn’t think so.
RJ says:
Welcome out of the realm of the pseudo-science preached by “Slayers”, G&T, Bryan, and others and into the realm of science! I hope you will now refuse to naively believe anything said by those people who have deceived you into believing that the greenhouse effect might violate the 2nd law!
The speed of light is irrelevant. The rate at which thermal energy leaves an object (measured in W or W/m^2 ) is determined by its temperature.
Now, all of a sudden, you are throwing in a variety of new issues. Let’s take them one at a time –
CO2’s role: If you are talking about CO2’s radiative role in the total natural greenhouse effect, this is something that has to be calculated using line-by-line radiative transfer codes. The result is that water vapor & condensed water vapor (i.e., clouds) is the bigger contributor to the effect; however, CO2 still contributes on the order of 10 to 25% to the total 33 C temp difference attributable to the greenhouse effect. (The reason for that broad range is that things are not additive, so you get one result if you start with an atmosphere without greenhouse gases and add CO2 and another result if you start with the current atmosphere and remove CO2.)
However, there is an important caveat to all this – The above assumes we are talking about changing the level of CO2 while keeping everything else the same. However, water vapor is a condensable gas. What that means is that if you reduce the level of CO2 in the atmosphere, you reduce the temperature and, as a result of this, you reduce the amount of water vapor in the atmosphere. Hence, the non-condensable greenhouse gases like CO2 and methane play the important role of increasing the temperature so that more water vapor goes into the atmosphere. As a result, climate models say that if you remove the CO2, you would end up basically losing almost the entire greenhouse effect.
Conduction & convection: First of all, conduction plays a very small role in heat transport in the atmosphere although it does play some role in the transfer of heat from the earth’s surface to the atmosphere in direct contact with the surface. Convection and the associated mechanism of evaporation and condensation of water vapor play much more important roles.
So, if you want to consider what happens in AGW…i.e., the effect of increasing levels of non-condensable greenhouse gases like CO2, the easiest thing to do is to first look at the effect on energy balance at the “top of the atmosphere”. The reason for doing this is that the communication with space is only via radiation. It turns out that a doubling of CO2 levels produces about 3.8 W/m^2 of forcing at the top of the atmosphere, a number that, give or take ~5%, is agreed to by everybody from the IPCC to Richard Lindzen and Roy Spencer. The way this happens is that the additional CO2 essentially raises the “effective radiating layer”, i.e., the height from which IR radiation can escape to space without being absorbed again. Since the temperature decreases with height in the troposphere, that means the radiation comes from a colder part of the atmosphere and hence, via the T^4 law, the intensity in W/m^2 is less.
What has to happen in response is that the atmosphere has to heat up enough that the new effective radiating layer has the same temperature as the old effective radiating layer did. To a first approximation, one can assume that this happens by the troposphere warming uniformly with height. This means that the “lapse rate” (the temperature change with height) remains the same…and the reason to assume this is that this lapse rate is essentially set by convection.
However, a better approximation is that, at least in the tropics, the lapse rate will actually decrease somewhat when the atmosphere warms…due to the dependence of lapse rate on temperature when the air is saturated with water vapor. This leads to what is called “the negative lapse rate feedback”, something included in all the climate models, which lowers a bit the prediction of how much the surface has to warm.
I know that this explanation is a little long…but the sum total is, yes, the effect of convection is taken into account.
No…The highest temperature is determined by a balance between energy in and energy out. There is no highest temperature set by the sun independent of understanding the energy out part of the equation. (Well, okay, there is the limitation that the earth’s temperature can’t possibly exceed that of the sun….but clearly that is something we don’t need to worry about.)
Myrrh says:
The statistics of large numbers. Entropy is a macroscopic concept. The whole point of the 2nd Law is that it is a statement of irreversibility (the world looks different if you run forward in time rather than backward in time) that arises from reversible interactions at the microscopic level. I suggest you get a physics textbook and read about it…It is, I think, one of the deepest pieces of physics and it can at least be motivated to students in an introductory course with simple analogies like balls in two different bins.
Understanding this is an important part of transitioning from the “Magical 2nd Law of Thermodynamics” that you seem to believe in to the actual 2nd Law of Thermodynamics as understood by physicists.
I didn’t think
so.FIFY