Guest post by Ira Glickstein
The Atmospheric “greenhouse effect” has been analogized to a blanket that insulates the Sun-warmed Earth and slows the rate of heat transmission, thus increasing mean temperatures above what they would be absent “greenhouse gases” (GHGs). Perhaps a better analogy would be an electric blanket that, in addition to its insulating properties, also emits thermal radiation both down and up. A real greenhouse primarily restricts heat escape by preventing convection while the “greenhouse effect” heats the Earth because GHGs absorb outgoing radiative energy and re-emit some of it back towards Earth.
Many thanks to Dave Springer and Jim Folkerts who, in comments to my previous posting Atmospheric Windows, provided links to emission graphs and a textbook “A First Course in Atmospheric Radiation” by Grant Petty, Sundog Publishing Company.
Description of graphic (from bottom to top):
Earth Surface: Warmed by shortwave (~1/2μ) radiation from the Sun, the surface emits upward radiation in the ~7μ, ~10μ, and ~15μ regions of the longwave band. This radiation approximates a smooth “blackbody” curve that peaks at the wavelength corresponding to the surface temperature.
Bottom of the Atmosphere: On its way out to Space, the radiation encounters the Atmosphere, in particular the GHGs, which absorb and re-emit radiation in the ~7μ and ~15μ regions in all directions. Most of the ~10μ radiation is allowed to pass through.
The lower violet/purple curve (adapted from figure 8.1 in Petty and based on measurements from the Tropical Pacific looking UP) indicates how the bottom of the Atmosphere re-emits selected portions back down towards the surface of the Earth. The dashed line represents a “blackbody” curve characteristic of 300ºK (equivalent to 27ºC or 80ºF). Note how the ~7μ and ~15μ regions approximate that curve, while much of the ~10μ region is not re-emitted downward.
“Greenhouse Gases”: The reason for the shape of the downwelling radiation curve is clear when we look at the absorption spectra for the most important GHGs: H2O, H2O, H2O, … H2O, and CO2. (I’ve included multiple H2O’s because water vapor, particularly in the tropical latitudes, is many times more prevalent than carbon dioxide.)
Note that H2O absorbs at up to 100% in the ~7μ region. H2O also absorbs strongly in the ~15μ region, particularly above 20μ, where it reaches 100%. CO2 absorbs at up to 100% in the ~15μ region.
Neither H2O nor CO2 absorb strongly in the ~10μ region.
Since gases tend to re-emit most strongly at the same wavelength region where they absorb, the ~7μ and ~15μ are well-represented, while the ~10μ region is weaker.
Top of the Atmosphere: The upper violet/purple curve (adapted from figure 6.6 in Petty and based on satellite measurements from the Tropical Pacific looking DOWN) indicates how the top of the Atmosphere passes certain portions of radiation from the surface of the Earth out to Space and re-emits selected portions up towards Space. The dashed line represents a “blackbody” curve characteristic of 300ºK. Note that much of the ~10μ region approximates a 295ºK curve while the ~7μ region approximates a cooler 260ºK curve. The ~15μ region is more complicated. Part of it, from about 17μ and up approximates a 260ºK or 270ºK curve, but the region from about 14μ to 17μ has had quite a big bite taken out of it. Note how this bite corresponds roughly with the CO2 absorption spectrum.
What Does This All Mean in Plain Language?
Well, if a piece of blueberry pie has gone missing, and little Johnny has blueberry juice dripping from his mouth and chin, and that is pretty good circumstantial evidence of who took it.
Clearly, the GHGs in the Atmosphere are responsible. H2O has taken its toll in the ~7μ and ~15μ regions, while CO2 has taken its bite in its special part of the ~15μ region. Radiation in the ~10μ region has taken a pretty-much free pass through the Atmosphere.
The top of the Atmosphere curve is mostly due to the lapse rate, where higher levels of the Atmosphere tend to be cooler. The ~10μ region is warmer because it is a view of the surface radiation of the Earth through an almost transparent window. The ~7μ and 15μ regions are cooler because they are radiated from closer to the top of the Atmosphere. The CO2 bite portion of the curve is still cooler because CO2 tends to be better represented at higher altitudes than H2O which is more prevalent towards the bottom.
That is a good explanation, as far as it goes. However, it seems there is something else going on. The ~7μ and ~15μ radiation emitted from the bottom of the Atmosphere is absorbed by the Earth, further warming it, and the Earth, approximating a “blackbody”, re-emits them at a variety of wavelengths, including ~10μ. This additional ~10μ radiation gets a nearly free pass through the Atmosphere and heads out towards Space, which explains why it is better represented in the top of the Atmosphere curve. In addition, some of the radiation due to collisions of energized H2O and CO2 molecules with each other and the N2 (nitrogen), O2 (oxygen) and trace gases, may produce radiation in the ~10μ region which similarly makes its way out to Space without being re-absorbed.
There is less ~15μ radiation emitted from the top of the Atmosphere than entered it from the bottom because some of the ~15μ radiation is transformed into ~10μ radiation during the process of absorption and re-emission by GHGs in the atmosphere and longwave radiation absorbed and re-emitted by the surface of the Earth.
Source Material
My graphic is adapted from two curves from Petty. For clearer presentation, I smoothed them and flipped them horizontally, so wavelength would increase from left to right, as in the diagrams in my previous topics in this series. (Physical Analogy and Atmospheric Windows.)
Here they are in their original form, where the inverse of wavelength (called “wavenumber”) increases from left to right.
Source for the upper section of my graphic.
Top of the Atmosphere from Satellite Over Tropical Pacific.
[Caption from Petty: Fig. 6.6: Example of an actual infrared emission spectrum observed by the Nimbus 4 satellite over a point in the tropical Pacific Ocean. Dashed curves represent blackbody radiances at the indicated temperatures in Kelvin. (IRIS data courtesy of the Goddard EOS Distributed Active Archive Center (DAAC) and instrument team leader Dr. Rudolf A. Hanel.)]
Source for the lower section of my graphic.
Bottom of the Atmosphere from Surface of Tropical Pacific (and, lower curve, from Alaska).
[Caption from Petty: Fig. 8.1 Two examples of measured atmospheric emission spectra as seen from ground level looking up. Planck function curves corresponding to the approximate surface temperature in each case are superimposed (dashed lines). (Data courtesy of Robert Knutson, Space Science and Engineering Center, University of Wisconsin-Madison.)]
The figures originally cited by Dave Springer and Tim Folkerts are based on measurements taken in the Arctic, where there is far less water vapor in the Atmosphere.
[Fig. 8.2 from Petty] (a) Top of the Atmosphere from 20km and (b) Bottom of the Atmosphere from surface in the Arctic. Note that this is similar to the Tropical Pacific, at temperatures that are about 30ºK to 40ºK cooler. The CO2 bite is more well-defined. Also, the bite in the 9.5μ to 10μ area is more apparent. That bite is due to O2 and O3 absorption spectra.
Concluding Comments
This and my previous two postings in this series Physical Analogy and Atmospheric Windows 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 (clouds, rain, snow, etc.) that transfer a great deal of energy from the surface to the higher levels of the Atmosphere.
For those who may have missed my previous posting, here is my Sunlight Energy In = Thermal Energy Out animated graphic that depicts the Atmospheric “greenhouse effect” process in a simlified form.
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 Emissions Spectra 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 ones 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.
What’s the electric blanket plugged into, again? What is this external source of energy pumping the system up? I got lost somewhere in the bouncing frequency stuff.
What is also misrepresented is the minusculeness of the bounce-back. I refer you to Noor van Adler: http://climategate.nl/wp-content/uploads/2011/02/CO2_and_climate_v7.pdf
All these posts about backradiation towards quantum mechanics made me go back to the basics, looking at it using the old thermodynamics and I ended with a result where there is backradiation but without any resulting effect. I dissected the first basic steps where radiation hits the surface and this seems enough to get answers.
In the radiative solution, the non-GHG surface temperature is found by using E = sigma T^4 (SB) where E comes only from the sun. If then T could go up because of GHG, this would mean more energy input would be needed. So where does this come from, are GHG capable of generating energy? Many people found a justification for this, but think of the following?
If we look at the CO2 idea as a plate with T2 above earth, you have something like the
classic radiation between two plates here, where the sun would heat the lower one which is T1.
So sure radiation will go both ways, there is backradiation and I go with that.
But read that in an end state (equation 19.2) where both plates would be T1, Qnet will be zero. Surface1 will never get any warmer by the (back)radiation from above, despite the accumulated (heat)energy in plate 2 and radiation going everywhere. Radiation is energy but is never heat.
So you can do this calculation with multiple radiation layers (like CO2 layers) and the
result will be the same. T1 will not get any warmer with Qnet getting zero, and all the
layers acting as insulation (like some people think CO2 does) and all plates actually
permanently getting radiation from both sides.
(Earth atmospheer would also be forced to become T1 everywhere form the surface up if it was’nt for gravity)
So what are the tricks with radiation that many people don’t see?
For starters I want to say that the photons of EM radiation can be regarde as cold, only interaction with matter gives any thermal energy (to get a temperature) which is taken away (partly) when a(nother) photon leaves.
Ideas where the delay of escaping photons by GHG causes heat accumulation have no basis, heat comes from a surface (matter) and cold energy went with the photons that took off. It does’nt matter how long it takes before the photon gets out to space (in the sun it takes up to 170.000 years)
Most greenhouse effect statements/sites claim that the radiative balance of earth must be because of the First law, the greenhouse theory makes fame by using energy in-out balances etc. convincing 99.99 percent of the people. But this is all dead wrong, the Second law rules here and this means simple energy conservation is not the whole story.
Earth could conserve it’s energy by accumulating it until it would be as hot as the sun,
nothing against the First law this way.
Is’nt it strange to say at first: well, because of energy conservation earth must
radiate away what it receives and that way we can calculate what the temperature must be by using SB and so we know for sure it must be -18C (not mentioning atmosfeer, and what is actualy measured).
Then secondly: listen, we also have GHG and this makes earth +15C because bla bla. So in fact saying: it’s wrong, earth does not simply radiate away what it receives and SB does not apply, but we can calculate the greenhouse effect using it.
Or: GHG introduces new physics, if one places multiple layers between two radiative
surfaces the old laws of physics don’t work anymore. Extra energy will turn into heat and raise the original surface temperature (think of the plates, it won’t happen).
So then in the GHG physics T of earth surface is supposed to go up with still the same
amount of energy coming from the sun. Now we know the Second law wants to establish a dynamic radiative equilibrium at the surface with a certain temperature but also T = dE/dS, so this means that for T to be able to go up by backradiation up entropy must decrease?? Strictly looking at this step.
Looking closer it must look like this:
Why does the sun heat the earth to T? Because HQ radiation from the sun can leave earth as LQ IR radiation (to the cold space) in the process gaining entropy by leaving WASTE HEAT on the surface (and they don’t call this irreversible for nothing, the downgraded (photon)energy won’t be able to do the same trick at this place again).
Some LQ IR returns (backradiation), but can never get rid of more heat. Because in that case it would have to leave as even lower quality IR, and hey …… this can only happen at a LOWER surface temperature (think of the BB-spectra of earth next to the sun, all the energy flows from the high spectrum to the low one).
See the contradiction, that’s the mighty second law of thermodynamics in action that says: it’s all wrong with this heating by backradiation philosophy.
So backradiation will simply leave in a reversible proces (like reflection does) with NO
waste heat, and with the same frequency as it had and bounce whatever way it wants with no effect on the surface. It’s like in the Qnet = zero situation between the two plates (lotsa radiation, no more heating by the cold photons).
So what is ‘the heat’ that can’t go from low to high temperature, and warming the earth surface and what’s all the confusion?
Sadi Carnot who laid the foundations of the Second law meant it to be like this: heat =
entropy (read here), but Clausius later changed the definition.
Maxwell’s classic Theory of Heat states: heat is something which may be transferred from to another, according to the Second law of thermodynamics.
In any case, heat needs matter which has a temperature (as kinetic energy) and other
matter at lower T. Radiation has no temperature and can never ever represent heat. And so the photons of radiation can be regarded as cold.
Heat is the waste from the irreversible radiation phenomena happening due to what the Second law dictates and is equivalent to the entropy gained and what is called
dissipation.
Heat is released when a photon interacts with matter. Almost everybody thinks ‘the
heat’ has to do with all the energy (E= h x v) related to the cold travelling photon. So
we have seen that this is not the case, this is imaginary heat (which is not heat but
energy) that is never released as long as matter is’nt involved. Energy is only released
when the photon disappears in the matter and after that heat from this matter may flow if other colder matter is there, but this heat is not equivalent with the photon energy but is a function of the temperature difference between surface temperature and colder matter above it (Q = k*A*dT). If there is no colder matter, there is no heat (dT=0).
If earth had no atmosfeer, the photons would warm earth surface to SB temperature but no heat would ever emerge or be exchanged. Then if there was a layer of CO2 around it at 10 meters or 10 km, this would create backradiation, but the vacuum inbetween would be as cold as in space, and the backradiation would not make the surface warmer, and there would be no heat despite all the radiation.
Now because heat is flowing from earth surface we know we have an irreversible process (waste heat, making entropy rise) then we also know for sure the new lower energy photon can never release waste heat at this temperature where it came from ever again, so to think backradiation can go beyond that and even create a higher temperature is impossible by the laws of thermodynamics.
This IR photon can release energy to matter at a higher colder level, and this energy
could flow as heat to matter at an even higher colder level, but that than is in fact
where this heat is. At a higher colder level, and this is the only direction heat can go.
So the heat coming from the surface is the part of the solar radiation that did’nt get
radiated away (directly) as IR (and the total energy of this IR is thus lower than the LWR that hits the surface). Heat is the part that has nothing to do with radiation, and the IR that left has nothing to do with heat.
And so the balance becomes: IR = LWR – HEAT. So the IR that leaves the surface does’nt only have a lower frequency, but the total energy of it is also lower than the incoming LWR. This is the second blow for the backradiation.
It is this HEAT that warms the lower atmosfeer and gives the temperature’s measured (in air, so does not even have to be representing the surface), and it can only take place by conduction from surface to air(surface), (or the process in the top ocean layer) it must be transported from matter at T1 to matter at T2 and it finds its way up to space dissected from the photons that gave up their energy.
As I Googled on the photons in the sun, the radiation from core to surface passed by on many pages and since these are not infected with the greenhouse virus the discriptions go along the lines of my view. Photons jiggle in the ‘random walk’ for tenthousands of years from layer to layer, and they do not heat the core. And also found; this degradation of high quality X-ray photons to relatively low quality optical photons, is only to be expected from the Second law of thermodynamics.
And look at this: a photon can only travel a tiny distance before running into another
hydrogen nucleus. It gets absorbed by that nucleus and the re-emitted in a random
direction. If that direction is back towards the center of the Sun, the photon has LOST
GROUND! It will get re-absorbed, and then re-emitted, over and over, trillions of times. The path it follows is called a "random walk"
— Sir Arthur Stanley Eddington:
"The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation."
Good examples, Phil and Richard Verney. Prior to my bouncing balls analogy, I considered and partially drew up a similar idea, using a half-silvered mirror.
1) In a dark room, point a narrow beam flashlight or laser pointer at an angle towards a mirror on the floor. Notice the lighted oval in the dust on the mirror. The beam will reflect off the mirror and head for the ceiling.
2) Now, take a half-silvered mirror and mount it horizontally above the floor in the path of the upward beam of light. Half will pass through, but the other half will reflect back to the mirror on the floor, creating another lighted oval in the dust on the mirror. The second oval will be about half as bright as the first.
3) The light from the second oval will head back up to the half-silvered mirror. Half will pass through, but the other half will reflect back to the mirror on the floor, creating yet another lighted oval in the dust on the mirror. The third oval will be about a quarter as bright as the first.
4) Depending upon how large your half-silvered mirror is, there will be an unlimited number of lighted ovals in the dust on the mirror.
5) The half-silvered mirror is an analogy to the Atmosphere with GHGs that, in effect “reflect” (actually of course they absorb and re-emit) half the IR radiation both upwards and downwards (actually of course in all directions so the radiation is dispersed and will not remain confined to an oval).
6) Get a light meter, such as that used by photographers, and measure the light reflected from the floor both before and after installation of the half-silvered mirror. The second reading will be nearly twice the first. That is the point of the examples proposed by both Phil and Richard Verney.
I especially like the idea of Phil to change the half-silvered mirror from 50% reflected to 66%, as an analogy to increasing Atmospheric GHGs (Not just CO2 but also H2O !!!). When this is done the light meter will register higher.
Commie Bob (March 10, 2011@5:41am)
Your point no. 5 is completely wrong. Lets dissect. You say “For those who doubt that back radiation exists, consider this: Infra-red radiation is electromagnetic radiation. It is the same as radio waves and light. While infra-red, radio and light may propagate similarly and be subject to the same law (inverse square) you have forgotten about wavelength. The obscure rays from an incandescent solid are vastly superior in their ability to heat than the luminous rays. You go on “Here are two examples of radiation from a weaker source going toward a stronger one:” Radiation commieBob is not heat. Radiation produces heat, and heat produces radiation but the radiation in and of itself is not heat, it is a byproduct. Radiation propagates without difficulty in space where there is no effective temperature(forget the 3k). I can even generate and emit emr without heat as the cause simply by plugging a transmitter into the wall and hooking up an antenna. Simply put the 2nd law does not apply to radiation at all. If it did all electromagnetic radiation emitted from the antennas of radio, tv, etc. would automatically head for colder climes like the interior of antarctica. The coldest would win(net flow). I won’t bother with your flashlight as it’s only vague misdirection. Just like agw. Backradiation as claimed is an energy absorption(conversion to heat)/reemittance towards the surface from some fictitious emitting altitude and raising surface temperature through fake amplification is clearly Bogus.
5b is vacous nonsense. “If I stand near a strong radio transmitter, I can still tune in weaker transmitters. Nothing about the stronger transmitter’s signal prevents the weaker signal from getting to me. Of course not! A strong 30 meter wave doesn’t care what a weak 20m wave does! They don’t interact because their wavelength’s or frequencies are different so the stronger signal has no possible way to prevent the weaker signal from getting to you. “The net energy flux will still be from the stronger source toward the weaker one.” Here you are implying some form of energy transfer between a 30m wave and a 20m wave or vice versa. Do you have a magic wand?
“It is a net flux though, in other words, the net flux is the difference between the two signals.” Oh, please commieBob do not emit any more pseudoscience as the net result is I can only laugh out loud.
I advise all here to read through Hans’ post above, a few times. The English is weak, but the point about the nature of entropy and ‘waste heat’ is not to be missed.
Phil.
you say :Yes provided that hν for the photon matched the energy difference between the two higher energy levels (in a Q branch for example).
Aha! Eureka moment, maybe? This makes perfect sense! The photon does not exist between points, but instantaneously communicates information (in its reference frame) between the point where it is emitted and the point where it is absorbed. Of course the photon energy must match perfectly where it is absorbed (and emitted). This also explains why photons are made up of the same “stuff” as matter. They merely communicate the state of the matter, which is governed by expectation probabilities that are predicted by quantum mechanics. When one “decay” or energy level drop happens that emits a photon, the other state shift elsewhere is necessary and already mapped by the photon. That would explain the “spooky” experiments we learn about in quantum mechanics that involve photons with equal energies and opposite momentum. By observing the polarization of one, we “influence” the polarization of the other instantaneously at any distance. Of course, the photons must “know” instantly the properties of the other because they are the vehicles of communication relaying the change of states, and the photons already “know” of their destination, as they are not under the influence of time. The properties of the photon, the energy and momentum, are the communications between states of matter separated by a distance. This feels like a logical connection between spec. relativity and quantum mechanics.
Now, how does gravity fit in with all this?…
Need more help, Phil.
Folks, re-radiative shells (excuse my made-up lingo) and their ability to indirectly raise the temperature of the radiating object (via reduction of the rate of heat loss) is real. NASA has been using this for decades to keep their space vehicles from freezing. Its easy to look this up… it’s not a mystery. Stop arguing that it isn’t real. You’re missing the point. It’s definitely real… but the far better question is “how much of an effect would it be in an atmosphere?” When NASA uses it on their satellites, they maintain a vacuum between the readiative layers (to eliminate conduction). The atmosphere would behave much differently.
I think all this discussion of thermodynamic, quantum theory, etc. is way off base. The question can be answered much more simply. Do what scientist used to do back when they were doing science. Measure.
Go out 1 hour after sunset. Point a spectrometer straight up and measure the spectrum. Whatever you measure is being emitted by the atmosphere (mostly). Its either being emitted because of its inherent temperature, or from absorption and reemission from the upwelling IR of the planet.
You could obtain measurements every hour, and watch the change. 1 hour after sunset may not be long enough… depending on the amount of solar radiation that scatters sideways in the atmosphere from the sun just over the horizon.
Regardless… what you measure will be reality. Clearly, we can probably all agree, you will definitely measure some amount of IR. To make the analysis even more precise, obtain temperature readings of the atmosphere at different altitudes, and subtract out how much inherent IR that temperature of air would naturally radiate, etc.
You may even be able to calculate or measure the upwelling IR from the ground. By carefully combining all this data, it shouldn’t be that hard to determine… not theorize… how much radiation is backscattered to the planet from the atmosphere.
I suspect the answer will not be zero (I believe there is at least some GHG re-radiation), but I also suspect that the answer will not be enough… not nearly enough… to account for the alarmists claims.
Anyways, all this discussion isn’t going to convince anyone… there are too many variables… to many unknowns. What fraction of heat transfer is re-radiation and what fraction is convection? No one knows. Does re-radiated IR from excited CO2 molecules make it back to earth, or does it somehow get taken up by the atmosphere along the way? No one knows. How much downwelling IR is from re-radiation of upwelling IR, and how much is due to scattered (and absorbed-reradiated) downwelling radiation from the sun? No one knows.
But if we stop theorizing and start measuring, we can determine how much IR is emitted from the atmosphere towards the earth (even if we don’t know the exact mechanism). This will be the only real way to get a handle on this issue.
Gary P. (March 10, 2011)
Here’s a better explanation for your “experiment”. The radiation being emitted by your filament where previously was allowed free escape is now being reflected by the interior surface of your metal cylinder. Reflection is not absorption/reemission. Energy reflected is not energy absorbed. To invoke backradiation your filament needs to heat the cylinder hot enough to radiate sensibly back to the object. This is clearly not happening. Your cylinder was “relatively cold”. In fact by placing a round reflector around a centered filament you have created a rudimentary cavity whereby radiation formerly lost is now harnessed and focused centrally. The metal of the cylinder did emit no sensible radiation of its own. There is technically no hot to cold flow at all since you have removed air. Oh, and your emergency reflective blanket does reflect the small amount of heat a body produces but it does a far more important thing to keep one warm. Normal blankets are porous and allow easy convection and consequent air exchange. A reflective blanket is far less porous and much better at trapping the air mass around the body reducing the level of air exchange. This allows your body to warm the water vapor in your cocoon. No backradiation needed thanks!
tallbloke says:
March 10, 2011 at 4:26 am
Ira Glickstein
“the “greenhouse effect” heats the Earth because GHGs absorb outgoing radiative energy and re-emit some of it back towards Earth.”
No, No and a thousand times No.
Re-emitted radiation does not and cannot heat the Earth significantly, because downwelling IR does not and cannot penetrate the surface of the ocean beyond its own wavelength. The amount of energy from back radiation mixed into the ocean by wind and wave action is negligible and extra co2 therefore cannot account for the additional warming of the ocean bulk in the late C20th.
The greenhouse effect works by *SLOWING DOWN THE RATE THE EARTH COOLS AT*, by raising the altitude at which the atmosphere radiates to space . There is more than a semantic difference. Understanding it this way enables you to understand that it was reduced albedo 1979-1998 allowing more Solar energy to enter the oceans that caused the majority of the global warming at the end of the last millenium.
————————————————————————————–
I find it hard to follow the logic of this post. If “downwelling IR does not and cannot penetrate the surface of the ocean beyond its own wavelength” (which I do not believe is true anyway) it is because it is being absorbed. That means the energy is retained by the oceans. The alternative is that it is being reflected in which case the sea would be red. If you look at a swimming pool the deep end always looks bluer. That is because the light reflected off the bottom has had the red light removed by absorption. Infrared is even more strongly absorbed by water molecules a fact that is exploited by microwave ovens.
You also write “he greenhouse effect works by *SLOWING DOWN THE RATE THE EARTH COOLS AT*, by raising the altitude at which the atmosphere radiates to space” . This I sort of agree with but would prefer to use the statement “changes the radiation balance” Although it is only a different way of coming to the same conclusion you cannot reduce the energy going into space in the 14 to 18 micron band without saying where the rest goes. The fact is that the remainder is back radiated to earth in exactly the way Ira describes. These descriptions are not in conflict with one another.
For all those others who come up with spurious reasons why there is no downward radiation, what does it take to convince you when you see graphs showing actual measurements of the energy being received. Where is this radiation coming from if it is not from the atmosphere? It cannot be the sun because the sun’s spectrum is insignificant beyond 3 micron.
Ira,
I follow your logic, but the electric blanket analogy was still a bad idea.
On the other hand I’m amused that half the criticism comes from either complaints about nomenclature, or the “cold things can’t warm up warm things” argument.
For the cold things can’t heat up warm things crowd, please stop with the complicated explanations and torchered arguments. Just ask yourself, do igloos work or don’t they? You can quote as many definitions of laws of thermodynamics as you want, construct as many analogies as you wish, with plates, bowling balls, flashlights, coats….but the fact is that igloos work. They’re made of cold stuff like ice and snow, and a person can survive very severe cold weather inside of one because “back radiation” keeps them warm. Someone dumb enough to sleep outside the igloo instead of inside is just a cryogenic experiment.
do the inuit build fires in their igloos.
nighttime says:
March 11, 2011 at 12:33 am
do the inuit build fires in their igloos.>>>
sigh. i suppose they just might sometimes which has what to do with anything?
If you insist I exclude the possibility of fire keeping them warm….
An igloo, constructed of only snow and ice, containing no additional heat sources of any sort other than what is generated by the human being(s) within them, works.
The dope sleeping outside next to a fire on the other hand will still be a cryogenic experiment with a cooked spot opposite the fire.
Brian H says:
I advise all here to read through Hans’ post above, a few times. The English is weak, but the point about the nature of entropy and ‘waste heat’ is not to be missed.
I would like to second this comment.
Hans also highlights the” quality” factor of the radiation or of energy generally.
A number of people think that once the quantity of energy is known that all there is to it.
The “quality” of the energy or radiation is perhaps even more important.
What does “quality” mean.
It means how easy it is to convert that energy into another type or for it to do work.
The classic example is high quality Solar radiation(short wavelength) arriving on Earth and an approximately equal quantity of degraded Long wavelength radiation leaving.
Now the first law of thermodynamics would not be violated if the whole process were reversed.
Its the second law of thermodynamics that states that this is impossible to convert low quality radiation into an equal quantity of higher quality radiation.
@ur momisugly Dave Springer says:
March 10, 2011 at 4:30 pm
Hi Dave,
About your reply to my post, I agree with your explanation of what is seen at the arctic.
I would like to know your opinion about the small emission peak in the middle of the CO2 15um absorption pit.
It is my opinion that that could be the only real backscattered photon emission of CO2, and that the other emissions could be due just to temperature of the IR active gases in the atmosphere.
Maybe I’m wrong with that, but I believe that because the “peak” is always positive at ground and at the TOA, and looking down at the tropical atmosphere that peak appears only over the 19-20km where the CO2 became the predominant IR active gas.
I repeat, I could have wrote a very silly thing, I’m not an atmospheric physicist just an electronic engineer.
Thanks to Hans for this information (and other that counter what to me seems like fiction but I’m never sure).
Radiation leaving the surface then returning to heat the earth seems like nonsense. Even for reason of logic
http://slayingtheskydragon.com/images/stories/freeoven.jpg
but it helps that posters like Hans and other explain why in this way.
davidmhoffer says:
March 11, 2011 at 12:15 am
David, this is an interesting point but you are wrong about how igloos work. They do not work by back-radiation.
Igloos maintain a higher temperature than the outside environment in the same way that all enclosures, including greenhouses, do.
This is quite simple and holds for all internal 3 dimensional environments enclosed by two dimensional barriers.
It is the result of the reduced probability of all three modes of energy transfer from a three dimensional gaseous environment towards and absorption through the two dimensional solid barrier (wall, glass or in the case of igloos, ice). The further from the two dimensional surface, the lower the probability is that the energy will be able to leave the enclosed atmospheric environment.
Historically, traditional dwellings tended to be constructed around a central fireplace for this very reason.
I live in a house high on the Sussex Weald which dates back more than 200 years. The are 4 fireplaces on the ground floor built into one central brick stack in the centre of the house. The external walls are merely 25 mm weather boarded with a 50 mm cavity and the internal skin is just 15 mm plaster board. There is no cavity wall insulation whatsoever and no double glazing. Thats just 2″ inches of wood and plasterboard between me and the elements 600 feet above sea level high on the Sussex Weald.
In the winter it is evident that the above holds true in that the closer you are to the external walls on a cold night, the colder it feels. The same is true for greenhouses. Ask any horticulturalist which plants are his smallest and lowest yielding and he will tell you it is the plants nearest the glass. Ask any Eskimo which part of the igloo he prefers to sleep in and I guarantee he will tell you, “the middle”.
This is what the “greenhouse effect” is. The greenhouse effect is simply the reduced probability of energy loss from all three modes of transfer, towards and through an external two dimensional surface from a three dimensional gas.
This fact holds true for all internal environments from glass houses to timber clad houses and even to igloos.
It does not hold true for the open atmosphere and therefore there is no “greenhouse effect” in the atmosphere.
The two dimensional barrier, be it timber, brick, glass or even ice, simply inhibits all three modes of energy transfer. This is the so called “greenhouse effect”.
That is why humans have evolved to construct and reside in dwellings.
There is no “greenhouse effect” in the atmosphere.
Can someone please comment on the post by DavidM re igloo’s
“They’re made of cold stuff like ice and snow, and a person can survive very severe cold weather inside of one because “back radiation” keeps them warm.”
If David is serious isn’t this fiction (I’m not an expert). Don’t igloo’s keep people warm because the air is warmer due to conduction. It has nothing at all to do with back radiation.
For a start wouldn’t most of the heat leave the body by conduction not radiation. And the point that Hans raised above.
RJ;
but it helps that posters like Hans and other explain why in this way.>>>
I am not just a skeptic, but a raging skeptic. There is so much hooey in IPCC AR4 that they should replace the 4 with an S. Which is why it drives me crazy when people go to great lengths to explain why there is no backradiation or it defies the laws of thermodynamics, or it creates energy… simple things like an igloo show that there IS backradiation, cold things CAN radiate heat to warm things, and NONE of it breaks any laws of physics.
Here’s my oversimplified explanation on a photon by photon basis. Frankly it p**sed me off to no end to figure out that the surface does in fact get warmer (thought by darn little and maybe even cooler when all interelated effects are included) but as for the concept of backradiation, there is nothing wrong with the basic ghg explanation other than presumed order of magnitude:
http://knowledgedrift.wordpress.com/2011/02/27/co2-exactly-how-does-it-warm-the-planet/
Hans:
Brian H:
Brian:
Yes, I totally agree with Hans explanation, it is correct. There are others here saying many correct statements. I have tried many times, in somewhat words, different analogies, trying to get others to see reality. But fellows, don’t get your hopes up. There are some here are firmly stuck in the AGW-IPCC-Trenberth mentality, as this post highlights, and since they have yet to see the reality, they probably never will. If I could say two thing I see keeping them confused, is that they consistently either speak instantaneously and not averaged over time and they fail to separate sun-earth-to-space system level energy flows with the inter-Earth system energy flows. And, heat does always flows from warmer to cooler, never backwards.
davidmhoffer:
I don’t mean to cross you, I mean that, I respect many of things you have said but can I try one last time for you to critique your thoughts on this “back radiation” and warming?
All of this talk of igloos, quinzees, coats, blankets, layers of GHGs being insulators and increasing warmth by “back radiation” has one big flaw as my physics sees it. In the case of your body, the heat source is within your body and any of these insulators are wrapped around the energy source itself. In the sun-earth-to-space system’s case, when wrapping the Earth with blankets or layers of GHG’s, you do not have the energy source within, but instead, outside that system. Physics is a bitch, every time you try to fool it with ‘trapped heat’ you will find there is one big factor left out that in the end violates you whole concept.
GHG layers will keep the same amount out of the Earth system as it can ever keep within, since the ultimate energy source is outside that system (ignoring radioactive decay in the soil). That’s it. Don’t have papers in my hand proving that albedo/reflection will increase *equally* with any insulation wrapped about the Earth but I do know it is true from what I have learned over the years. As I always try, keep an open mind and critique your own thoughts, you should see something in what I just said.
Phil and Ira
Phil, I found your comments (March 10, 2011 at 7:52 pm) very interesting. Is this based upon an actual experiment or only a theoretical calculation?
What I am getting at is whether this reflected (back) radiation has genuine power to do work.
Consider the attached power plant:. http://www.solar-green-wind.com/wp-content/uploads/2009/12/largest_solar_power_station-1528.jpg
Consider the Earth’s energy budget:
http://www.klimaatfraude.info/images/EnergyBudgetNew.jpg
The power station is using mirrors tuned to collect and focus 184 w/sqm (i.e., 161 + 23) of solar bandwidth energy. Of course, during a sunny day, these mirrors are also receiving some (or all) of the 333 m/sqm back radiation. However, they are not focused to collect that nor are they tuned to the wavelength of downwelling long wave radiation. They are of course, tracking the elevation of the sun and therefore are effectively tuned to collect and focus the 184 w/sqm solar bandwidth energy. I presume that this power station produces no power at night and presumably only modest amounts on cloudy days and may be none on heavy dark rain cloudy days. It can effectively only work in a sunny climate such as California, Spain, Affrica (although of course, the illustrated station appears to be in Germany but Germany are beginning to realise that the country is not well suited to solar power generation).
My question is: If there was real power in the 333m/sqm longwave back radiation, why isn’t the power station designed to collect and focus this longwave radiation? There is nearly twice as much energy (viz 333 cf 184 m/sqm) and this longwave energy is available 24 hours a day come rain or shine. This eliminated the storage issue which has always beset green energy projects.
If there was real power (ie, the ability to do work) in this backradiation it is inconceivable that someone would not be collecting it, or that there would not be mainstream research designed at collecting this. For the vast majority of countries solar radiation is a non starter (due to cloudiness and latitude) but these countries have plenty of backradiation.
I guess I am raising a question on the point made by Hans (Hans says:
March 10, 2011 at 8:00 pm) in that the radiation may be there but it does not have any energy/ability to do work.
Phil and Ira your further views/comments would be appreciated.
If, as so many people seem to claim, the atmosphere radiates like a blackbody than how come we can see landmasses sharply defined in the infrared satellite pictures that get beamed down every 6 hours. Would the land/sea boundary in local places not get fuzzy and streaky by either an onshore (cooler) wind or an offshore (warmer) wind. But no, the coastline remains sharp everywhere and at all times. These pictures are taken in the 8.3μm – 14.4μm band which is exactly the open infrared window WITH NO ATMOSPHERIC RADIATION.
Check it out for yourself at http://www.sat.dundee.ac.uk/geobrowse/geobrowse.php. You will have to register, but it costs nothing.
Phil. says:
March 10, 2011 at 4:32 pm
“If you use Wien’s Law to determine the maximum there are two forms, a frequency form and a wavelength form, the peak frequency does not correspond to the peak wavelength using c=λν.”
The superimposed dashed line blackbody curves don’t correspond to the frequency/wavenumber on the horizontal axis. If you plug in the peak frequency indicated on the horizontal axis to Wien’s Law formula you get a very different temperature in Kelvin from that labeled on the dashed curves. Interestingly the labeled values correspond to degrees Rankine!
You can find it with calculator below which gives results in F, C, K, and R.
http://www.ajdesigner.com/phpwien/wien_equation_t.php
Something is definitely whacked in those plots but I can’t quite figure out what it is.
wayne says:
March 11, 2011 at 3:17 am
“GHG layers will keep the same amount out of the Earth system as it can ever keep within”
No. The energy enters the system in short wavelengths (visible light) which is not absorbed by GHGs. The shortwave energy is absorbed by the ocean. The energy leaving the system, radiated from the ocean surface, is longwave which is absorbed by greenhouse gases. The insulation effect of the GHGs works only in one direction. They do not insulate the earth from the sun but rather insulate the earth from the frigid cold of the cosmic void (which is 3 Kelvins and is called the cosmic microwave background radiation).
The net effect is the GHGs don’t slow the warming of the ocean from the sun they slow the cooling of the ocean into the cosmic background. This causes the surface temperature to rise higher than it would be otherwise. The greater temperature differential between the surface and the cosmic background causes heat to move through the insulation faster which reestablishes equilibrium (energy in equals energy out). The insulating effect of the GHG raises the surface equilibrium temperature.
davidm
I don’t think people have said there is no back radiation. What I think they have said is this back radiation does not result in a colder body warming a warmer body from this back radiation.
Cold things can radiate to hot things. But it will not warm the hotter thing when the radiation arrives is how I understand this process.
Its like a brilliant teacher passing knowledge to a student. The student can pass knowledge back to the teacher but this will not improve or add to the teachers knowledge (heat). But the student can improve the knowledge of younger child. The same with the sun earth CO2 relationship.
And I see you as a luke warmer not a true sceptic. You are sceptical of the overstated alarmists predictions not the GHG science itself.
Even though the GHG science could lead to the chicken in the oven situation. Or a person in a CO2 container cooking themselves due to back-radiation.
@wayne (con’t)
The one-way insulating effect of GHGs is why, in my blanket example, I use two black rocks which are both exposed to the sun during the day so they can heat up (equally) then just one rock has a blanket thrown over it at night. The next morning they are uncovered and the temperature of the blanketed rock will be higher than the unblanketed rock. The next day, since one rock is warmer in the morning than the other yet both will be exposed to the sun again getting the same amount of daytime heating, the rock that is blanketed at night will reach a higher daytime maximum temperature. This temperature increase will continue until a new (higher) daytime equilibrium temperature is reached. The hotter the rock is when the blanket is thrown over it at night the quicker it will lose heat through the blanket. Heat flow rate through the insulating barrier is proportional to the temperature difference between the warm and cold sides. As the difference increases heat is lost faster. It is that which prevents the blanketed rock from just getting hotter and hotter until it melts.