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.
I have just read through Nasif’s thread on Jennifer Marohasy’s blog and I haven’t had such an interesting and informative read or learned more about AGW issues in years. It will prompt me to read more too as there it would seem to show a possibility that not only is AGW not significant but that the whole greenhouse effect is not like it is viewed by the majority. The responses from the warmists sound like even they don’t believe it any more.
I’m genuinely sorry that Nasif doesn’t get better coverage, he’s a bit eccentric but an excellent and thought provoking read
Ira Glickstein,
Thank you for your efforts to bring out the science of one isolated aspect, which I call the earth’s ‘atmospheric effect theory’. It is one out of many interacting aspects of our earth’s atmosphere. I understand you are doing so when there are many aspects (including the one you are discussing) of our atmospheres which do interact and which are not isolated in the actual complex atmospheric dynamic.
The single isolated aspect (out of many interacting aspects) which you are presenting for discussion was purposely selected and isolated by you to aid in a clear presentation of just the one aspect that I call the earth’s ‘atmospheric effect theory’. I support your efforts to that extent with the understanding that what is not being presented by you is the total net effect (negative or positive) of the single isolated aspect you are discussing on the total complex earth dynamic system.
This latest post is much better, in my view, than the previous posts in your series that used analogy. It is best to just present the science rather than use analogy. Analogies are always limited and have some misleading attributes.
Things I find not at issue wrt the earth’s ‘atmospheric effect theory’ from the so-called consensus focused IPCC science:
a) The gases in our atmosphere interact by collision with each other and in doing so transfer energy.
b) Some of the gases in our atmosphere have the ability to absorb electromagnetic radiations of certain wavelengths. And in certain conditions re-emit it.
c) Some of the gases in our atmosphere have varying interaction with the incoming solar electromagnetic radiation and in doing some energy is transferred to some of the gases.
d) Some of the gases have varying interaction with the blackbody (or near blackbody type) radiation generated by all the surfaces of the earth and in doing so some energy is transferred to some of the gases.
e) Some of the gases have varying interaction with the blackbody (or near blackbody type) radiation generated by the atmospheric gases themselves and in doing so energy is transferred to some of the gases and also sometimes to the earth’s surface.
f) The electromagnetic radiation from the sun and also from the gases in our atmosphere has varying interaction with each of the earth’s various types of surfaces and in doing so some energy is transferred to the surfaces.
g) Some of the electromagnetic radiation from the earth’s surfaces go directly to space.
h) The electromagnetic radiation from all the gases in our atmosphere can, under certain conditions, go directly to space.
Things I find at issue wrt the earth’s ‘atmospheric effect theory’ from the so-called consensus focused IPCC science:
a) I would like to see the formal theory for what I call earth’s ‘atmospheric effect’. Show me the integrated formal theory. Has it been only premised that there is one, not shown that there is one? It cannot be uncoupled from other aspects of the climate system and remain meaningful.
b) I would like to see the actual comprehensive /unbiased /multiple /corroborating observations that demonstrate that a theory of earth’s ‘atmospheric effect’ has a significant net effect on meaningful climate parameters. OK, on average GST too.
Ira Glickstein,
John
@ur momisugly Steve
I’ll read those links if I can get to them. Thanks.
One thing you might consider is that just because nitrogen by itself does not radiate it doesn’t mean nitrogen can not cool by radiation in the real atmosphere. It will do it through greenhouse gases by re-exiting them by a high enough collision and that greenhouse gas molecule will then radiate the energy away. I have also found that even though most references will show pure nitrogen with only a small band in the near IR and oxygen having bands in the microwave region, they both do radiate a small amount in the mid-infrared just above and below 20 µm due to N2-O2 collision electron interactions together. So, just because a pure nitrogen atmosphere might actually not be able to cool alone, it can once other species of molecules are put in the mix. Just found the paper last week describing that very combo with spectrums included. Well, that’s about where I stand at this point. And that is why I still think a pure nitrogen atmosphere with the same sea level pressure would be hot for sure, you have then taken away all of the ways that nitrogen can possibly lose IR heat. Two month’s ago I would have said exactly the same thing you said.
Martin
Thanks for posting this.
What this GHG theory shows is how people will hold onto their beliefs no matter what. They are not acting as scientists should but hold onto their theory based on faith not science.
The killer for me is that logically the GHG theory does not stand up. It leads to absurd possible outcomes. Like for example heating the house with CO2 in the roof space. Or ice in a Igloo heating the body by backradiation.
Or an oven that heats a chicken without any outside power source.
http://www.slayingtheskydragon.com/en/blog/111-a-pictures-worth-a-1000-words
The GHG theory is flawed IMHO and its time to either move on or at least acknowledge the issues with this theory.
Hans asks
…..”Lets slice a blackbody cavity which is at a equilibrium temperature of 288 Kelvin in half and replace the other half with a mirror. How much warmer will this cavity become?”…..
Ira Glickstein replies
…..”With longwave IR it would not be a mirror, but an absorbing/re-emiting thin, black-painted metal shell surface that would return about half the energy it absorbed”…..
My comment to Ira;
This sounds as if you think that IR radiation cannot be reflected!
When I was at school we did experiments to show that all EM radiation including Infra Red radiation exhibit the full range of wave properties of;
Reflection, Refraction, Interference and Diffraction.
Surely you did not mean to imply the opposite to what every school level physics pupil should know?
I said
Joel Shore’s simple world consists of an earth without oceans and a land surface that does not retain heat.
Joel replies
No…Retention of heat is not relevant to the considerations that I mentioned. The way that it comes into it is that the ocean helps to keep the temperature more uniform.
My reply;
The Oceans, covering 70% of planet surface, absorb solar radiation.
Some shorter wavelengths penetrate the water to a considerable depth.
In other words the effect is to increase the temperature of the water.
Ocean currents(and tides) distribute the hotter water.
E.g. the Gulf Stream effect keeps the west coast of UK much warmer than without it.
Glasgow is at the same latitude as Moscow.
The atmosphere, in particular clouds, help insulate the Earth surface.
The gross error of IPCC dogma is to attribute a 33K increase effect as due solely to the radiative properties of CO2 and H2O in gaseous form.
The early climate models did not even include clouds although some attempts are now being made to rectify this gross defect.
Nah. You’ve all got it “wrong on the internet”!
Here’s the Real Deal:
Way back in Hypothetical History, the Earth had no CO2 and was in thermal and radiative equilibrium with Sol. But then one day the Three-Handed God of Gasses wiggled his middle pinkie and ~~BAZOWIE~~ CO2 joined the fun.
This interrupted the normal escape routes and timing of surface radiation in a few LW slots, delaying it by hundreds, or even thousands, of microseconds, and it consequently warmed the air and surface slightly. But then the leading edge of the delayed LW escapee photons made it to the TOA, and fled the trap. Ever since, the surface and air temps have been nice and stable at the new minutely higher temperature.
But, someday, the above-mentioned God of Gasses will wiggle his middle big toe, and ~~EIWOZAB~~ the CO2 will vanish! Then the “excess” will directly blow the joint and temperatures will return to pre-Pinkie levels.
And now you know!
~~~~~~~~~~
We Believers in the Gospel of the God of Gasses are called “The Laggards”! Join us now, even though it may already be too late.
Or not.
😉
Exegesis;
The sequence above is actually slightly more complex and interesting. When the CO2 first appears, a drop in OLW occurs until the lagged photons hit TOA and the exit doors there. The energy they represent, as a function of flux times the lag duration, is the measure of the “excess” which hangs around and keeps temps a smidge above normal. When the CO2 vanishes, that drains away, and so does the temperature anomaly vis-a-vis the Pinky Event.
Hans asks
…..”Lets slice a blackbody cavity which is at a equilibrium temperature of 288 Kelvin in half and replace the other half with a mirror. How much warmer will this cavity become?”…..
The cavity will remain at the same temperature! The phrase “at equilibrium” means “the photons in the cavity are at equilibrium with the walls of the cavity, all of which are at 288 K..” Putting a mirror down the center won’t change the temperature of either the photons or the walls. The left half of the cavity and the right half of the cavity will still be at 288 K.
Hans says:
March 30, 2011 at 7:01 pm
Ira Glickstein, PhD says:
March 30, 2011 at 2:02 pm
“Having made that error, the author continues:
One might think that, because the blackbody is now absorbing more light, even if it is its own infrared light, then it should warm up. …
Yep, it should warm up and (if it is a true blackbody in the longwave region) it will absorb that reflected longwave energy and, all else being equal, will warm up.”
Ira, so when will this cycle of selfheating stop?
Lets slice a blackbody cavity which is at a equilibrium temperature of 288 Kelvin in half and replace the other half with a mirror. How much warmer will this cavity become?
Good question. But I do not think the answer is what you think it is.
If the total system is at equilibrium with its surroundings ( there is no other source of heat ) then it is at equilibrium and so the nature of the surfaces will have no effect on temperature.
But let us take the more interesting example where the cavity has a power source. It does not matter how big but say it is 100 watts. Assume also that it is in vacuum so that it has no conduction losses and has a highly polished external surface so that it has no external radiation losses. If this is in dynamic equilibrium (that is it is losing heat at a constant rate but has a constant temperature) then the 100 watts will be dissipated through the opening of the cavity with a near black body spectrum characteristic of that constant temperature. Lets say for argument’s sake that this is 800K. If you silver the inside of part of the cavity it will be a slightly poorer black body so its spectrum will not be perfect and and therefore a small rise in temperature will have to occur in order to dissipate the same 100 watts. However the effect will be very small and there is of course no conflict with the conservation of energy.
However an even more interesting experiment would be to take a sphere blackened on the outside with lamp black which, although not a perfect black body, is very close to perfectly black. Now heat this with 100 watts. Let us say that the sphere has a surface area of 100 units. The dissipation is therefore 1 watt per unit area (still in a vacuum so no conduction losses). If the surface area of this sphere was the same as the area of the apperture in the original black body cavity then the temperature would be close to but a little more than 800K because it is not quite perfectly black. Now place a semispherical shell a small distance from one half of the sphere. This shell has a black internal surface and a perfectly silvered outside. Energy dissipation on this side of the sphere is therefore absorbed by the shell but can only be radiated back to the sphere since the silvered external surface cannot radiate. Therefore, if we take the sphere and shell system as a whole, all the 100 watts has to be radiated from the 50 units of surface that is not covered. For this to happen the temperature has to rise to a level where the heat loss per unit area is double. If this temperature is T the fourth power of T is equal to 2 times the fourth power of 800. Thus T is 800 times the fourth root of 2. The shell will also be at this new temperature since the two facing surfaces must be in equilibrium if there is no nett heat flow (no dissiptation from the shell’s external surface).
“The killer for me is that logically the GHG theory does not stand up. It leads to absurd possible outcomes. Like for example heating the house with CO2 in the roof space. Or ice in a Igloo heating the body by backradiation. ”
The killer for me is that people could actually concluded that the GH effect predicts that you could heat a house with CO2 in the roof! No competent scientist would say that nor support that – the relative size and relative temperatures are wrong! Only poorly informed skeptics ever seem to come to this flawed conclusion (although poorly informed warmists can make it seem like a plausible conclusion based on their own faulty understanding of the GH effect).
Since you are claiming the GH theory predicts that a house will warm up from C02 in the roof, perhaps you could explain the logic behind that prediction. How specifically would the GH theory lead to the conclusion that you could heat your house (or even limit cooling) simply from a layer of GHGs inside the roof space?
Tim
Why don’t you go to Jennifer’s blog and read Nasif’s work and the responses. It may surprise you and answer your question. It didn’t actually say you can heat your house with an attic full of CO2 but go and read and be ready to be surprised even.
Tim
I know no competent scientists would say this. But its what scientists seem to be saying with the GHG theory.
CO2 supposedly adds heat to the earth due to backradiation. Why would the same not apply in a house (or if a person was enclosed in a container of CO2).
Or as per the chicken in the oven example above.
Or do you believe CO2 and backradiation can operate at higher levels but not at ground level. If so why not. If CO2 reflects back radiation to increase the temperature of the surface why can this not also apply at ground level.
Common glass Mirrors that reflect visible light generally reflect near-IR (what we’ve been calling shortwave) at a fairly high level of reflectivity. However, their reflectiity generally falls off considerably in the Far-IR (what we’ve been calling longwave). But, you are correct, specially coated metal mirrors are available that reflect very well out to 10μ or even 20μ. For example:
The point I was making was that a black-painted metal shell was all you needed, and that that was more like the Atmospheric “Greenhouse Effect” than more expensive, damage-prone, special far-IR mirrors.
wayne says:
March 31, 2011 at 3:24 am
“And that is why I still think a pure nitrogen atmosphere with the same sea level pressure would be hot for sure, you have then taken away all of the ways that nitrogen can possibly lose IR heat.”
There is still adiabatic cooling. The nitrogen gas will rise and cool, and then radiate it’s heat away at whatever wavelengths that cooler nitrogen gas radiates at, be it far infrared or microwave.
RJ says:
March 31, 2011 at 6:53 am
Tim
I know no competent scientists would say this. But its what scientists seem to be saying with the GHG theory.
CO2 supposedly adds heat to the earth due to backradiation. Why would the same not apply in a house (or if a person was enclosed in a container of CO2).
Or as per the chicken in the oven example above.
Or do you believe CO2 and backradiation can operate at higher levels but not at ground level. If so why not. If CO2 reflects back radiation to increase the temperature of the surface why can this not also apply at ground level.
CO2 in your loft space would be warming but the effect would be tiny since your ceiling and your roof already do a very good job of absorbing radiated heat and re radiating it back. Any downward radiation from CO2 would warm the floor of the loft and upward radiation would warm the roof. Since the CO2 would be at a slightly higher temperature than the roof my guess is that this warming of the floor would be slightly greater than it would have been if it were left to the roof alone to backradiate to the floor. Therefore there would be a slight drop in roof temperature and so a slight drop in total heat lost through the roof but it would be tiny. Silver foil would be more effective!
Furthermore the scale is different. Energy radiated from the earth’s surface in the 14-18 micron band is initially radiated at around 290K and if there were no greenhouse gases this energy would be directly lost to space (just like the energy around the 10 micron band). The absorption by CO2 means that radiation to space can only take place at an altitude where there is little chance of further absorption. This is just below or within the tropopause ( around 8km at the poles and 16km at the equator). The temperature here is about 220K. At this temperature the energy radiated is about 10 times less than the original energy at the surface. This difference has to be made up because the incident radiation from the sun is fixed. There is no option but for the surface to warm in order to increase the radiation at the other wavelengths to compensate.
In the case of your loft there is no radiation into space and even if there were the height of your loft would induce a temperature difference of about 1/50th of a degree.
cal says
…”The absorption by CO2 means that radiation to space can only take place at an altitude where there is little chance of further absorption. This is just below or within the tropopause ( around 8km at the poles and 16km at the equator). The temperature here is about 220K. At this temperature the energy radiated is about 10 times less than the original energy at the surface. This difference has to be made up because the incident radiation from the sun is fixed. There is no option but for the surface to warm in order to increase the radiation at the other wavelengths to compensate.”……
Cal has given a good outline of the more sophisticated version of the Greenhouse Theory.(GT)
This is quite a contrast to the cruder; …. atmosphere “toasts” the Earth Surface version favoured by Joel and others.
In this version the famous experiment by R W Wood is not contradicted as the radiative effect of CO2 and H2O can still be very small for that particular volume.
Ira likes analogies and the best one here is of a bath with an small open drain hole being filled with a bigger water supply from the tap.
I’m not saying I agree with this version of GT, but at least its more plausable.
martin mason says:
You mean the thread that starts out with this statement?
Since that statement is utterly wrong, I don’t really see why you would get anything out of his post. He then goes on to do a calculation for “total emissivity” of CO2 without even defining what he means by “total emissivity” (of an entire atmosphere’s pathlength?) … or to what wavelength his calculations apply.
If you want to read about the science of calculating radiative transfer in the atmosphere, pick up a book on the subject or at least find a blog post by someone who has a clue what he is talking about.
Bryan says:
March 31, 2011 at 9:10 am
cal says
…”The absorption by CO2 means that radiation to space can only take place at an altitude where there is little chance of further absorption. This is just below or within the tropopause ( around 8km at the poles and 16km at the equator). The temperature here is about 220K. At this temperature the energy radiated is about 10 times less than the original energy at the surface. This difference has to be made up because the incident radiation from the sun is fixed. There is no option but for the surface to warm in order to increase the radiation at the other wavelengths to compensate.”……
Cal has given a good outline of the more sophisticated version of the Greenhouse Theory.(GT)
This is quite a contrast to the cruder; …. atmosphere “toasts” the Earth Surface version favoured by Joel and others.
In this version the famous experiment by R W Wood is not contradicted as the radiative effect of CO2 and H2O can still be very small for that particular volume.
Ira likes analogies and the best one here is of a bath with an small open drain hole being filled with a bigger water supply from the tap.
I’m not saying I agree with this version of GT, but at least its more plausable.
————
Thanks Bryan I have never been called sophisticated before!
However I would point out that there is nothing contradictory about the two ways to describe the effect. I prefer this one (but have used both on this thread) because systems with many positive and negative feedbacks are difficult to predict. One can describe the greenhouse effect from bottom up, so to speak, as Ira has done, but it is hard to calculate the nett effect of small changes. However the top down approach (puns definitely intended) allows one to look holistically at the system and apply solid rules like energy balance equations to predict change on the basis of actual measurements. These are available at the macro level such as the temperature and position of the tropopause and radiation at different wavelengths leaving the atmosphere. It is because these measurements are readily available that I am sceptical of the warmists’ claims. The satellite data does not seem to provide evidence of the macro changes theory would predict. I can’t help feeling that if they had such data it would be spread all across the media. My conclusion is that rather than adapt their theory they are desperately trying to come up with an explanation. The issue is not whether the previous 10 doublings have had an effect. The issue is will this one. It is not obvious that it will because the effective level at which CO2 radiates into space is already at the coldest point in the atmosphere. For further reductions in radiation to occur the whole upper atmosphere has to cool. I will wait and see. I am sceptical, but everything is possible. I just think we would have seen at least a trend by now.
Bryan says:
I am not in favor of the cruder one. I have often pointed out that the picture described by cal is necessary for a fuller understanding. See for example, this post: http://wattsupwiththat.com/2011/03/10/visualizing-the-greenhouse-effect-emission-spectra/#comment-625057 and in general the discussion we had when I tried to explain to you why Wood’s experiment did not disprove the atmospheric greenhouse effect. I am glad to see you belatedly coming around to me point-of-view.
However, the cruder picture is not without merit for getting some of the basic ideas down. Yes, it neglects some things like convection that eventually should be included in a more refined picture. But, simple models are always limited.
“martin mason says: March 31, 2011 at 6:33 am
Tim
Why don’t you go to Jennifer’s blog and read Nasif’s work and the responses. It may surprise you and answer your question. It didn’t actually say you can heat your house with an attic full of CO2 but go and read and be ready to be surprised even.”
Well, the very first paragraph is off to a bad start
http://jennifermarohasy.com/blog/2011/03/total-emissivity-of-the-earth-and-atmospheric-carbon-dioxide/#more-7739
There is no such “central assumption” that “every one of its subsystems behaviors as if they were blackbodies.”
The bulk of the paper deals with a rather involved equation that appears to be some empirical fit to CO2 absorption data. Without access to the original paper, it is very difficult to comment on the accuracy of the equation or Nasif’s application of of the equation.
However, the conclusion states “the potential of the carbon dioxide to absorb and emit radiant energy is negligible”. His calculations clearly contradict various experimental results (http://www.skepticalscience.com/images/infrared_spectrum.jpg or http://brneurosci.org/spectra.png for example) which clearly show CO2 having a clear and significant impact on IR in the atmosphere. I have to go with experimental evidence and reject his calculations.
Furthermore, Nasif’s comments in the discussion following the paper do not particularly impress me.
RJ;
The killer for me is that logically the GHG theory does not stand up. It leads to absurd possible outcomes. Like for example heating the house with CO2 in the roof space. Or ice in a Igloo heating the body by backradiation. >>>
What is absurd is taking the explanations, which are based on 200 years of documented physics theory verified by thousands of experiments, and instead of learning how to understand the equations and the physics, instead make wild accusations that are completely out of proportion. Instead of responding with the ludicrous “so why can’t I heat my house by putting CO2 in the attic” as a proper question.
Q; If I put CO2 in my attic, according to the laws of physics, would it heat my house?
A; It would provide an amount of insulation so small that you likely could not measure it without some very expensive and accurate instruments, but it would have some effect compared to a vacuum for example. However it would still be positive compared to vacuum. A foot of fibre glass insulation would have a measurable effect, and by the way, works on the same physics. Does it generate “new” heat? No. It just slows down the escape of IR resulting in a warmer house for a given amount of heating input from the furnace, stove, people, etc. And BTW, if you take the temperature of the fibre glass insulation on a very cold day, you’ll find that it is indeed colder than the ceiling of the house it rests on. Despite which, it keeps the house warmer.
Stop extrapolating actual physics to orders of magnitude higher claims than the physics actually makes, and the absurdity will go away with it.
Joel
I certainly do not believe you ever advanced a version of the greenhouse theory that explained it as being almost totally confined to above the tropopause.
R W Wood and G&T are correct in saying that the radiative effects of CO2 are very small at atmospheric temperatures and pressures.
In response to Hans, Ira Glickstein claimed that a radiating body would heat itself up with its own reflection.
“Yep, it should warm up and (if it is a true blackbody in the longwave region) it will absorb that reflected longwave energy and, all else being equal, will warm up.”
Bang go the laws of energy conservation then.
If you believe in back radiation, then try this suggestion of Alan Siddons. Shine a beam of light on a surface which reflects some of the light, such as a wall. Shine the light at 45 degrees so that the part which is reflected bounces off at the same angle. Now take a mirror and position it so that it reflects back to the illuminated part of the surface the light that is reflecting off the surface. You will see that it makes absolutely no difference to the brightness of the surface. (It will, of course, illuminate the wall where it is not already illuminated by the beam.)
Ira claims that the laws of thermodynamics are not broken because the energy exiting from inside his reflective shell is the same as that entering. But inside the shell (which in theory could be as large as a room, or a furnace) you are producing two units of energy out of one. This is energy creation, not conservation.
@Steve
If the entire pure nitrogen atmosphere could radiate sufficiently to overcome the cloudless sky daytime irradiance transferred by conduction, then you are, or course, correct. Just wish I could get some definitive proof and the answer to why professors in physics and spectrometry at various universities disagree with each other on that very point. Some would say that the ones saying “all matter always radiates if over zero K” are only referring to liquids and solids.
I guess you do know what that would mean if you could prove that. That would mean that not only does nitrogen absorb and radiate adequately by itself but also oxygen and argon at 101325 Pa and there is no special attribute of GHGs at all over the atmospere as a whole, for the entire atmosphere then would be acting in exactly the same manner as they do. It’s just that the spectrums don’t seem to show that, or, possibly that their radiance is just so incredibly tiny and the hot atmosphere I mentioned above is still probably true though a bit cooler than with zero radiance.
But I still would ask you on that hypothetical situation, if I could: If there was zero radiation from a pure nitrogen atmosphere, heck, lets make it pure argon as dense as ours, no oceans, no clouds, would it be cold or hot? What do you think?
BigWaveDave says:
Yes, when you pressurize gas, it warms. However, if you pressurized some gas and then let it sit in equilibrium with its surroundings for billions of years, it will equilibrate with its surroundings. The earth’s atmosphere is not undergoing continual gravitational collapse.
It is also true that the lapse rate, i.e., the decrease in temperature with height in the troposphere is determined by understanding what would happen if a parcel of gas rises up in the atmosphere and undergoes adiabatic expansion or sinks down and undergoes adiabatic compression. So, yes, the fact that the temperature decreases with height in the troposphere is due to this fact (coupled with the fact that the atmosphere is primarily heated from the bottom…since the adiabatic lapse rate only sets a stability limit on the lapse rate, which is why the temperature actually increases with height in the stratosphere).
However, in the absence of an IR-absorbing atmosphere, the temperature at the surface would be set by the condition that the earth system must be in radiative balance with its surroundings. And, the temperature of the rest of the atmosphere would have to adjust accordingly.