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.
RJ says:
March 11, 2011 at 4:33 am
“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”
Correct. But it causes the warmer body to cool at a slower rate.
Radiative transfer between two objects of different temperature is a two way street.
Say the warmer body is radiating at 2 w/m^2 and the cooler body is radiating at 1 w/m^2. The net flow is, of course from warmer to colder, at exactly 1 w/m^2.
The warmer body is adding energy to the cooler body but the cooler body is also adding energy to the warmer body. The cooler body is simply adding less energy to the warmer body than the warmer body is adding to the cooler body. This will always be the case. In most situations we only talk about the net flow of energy which always goes from warmer to colder but in reality there is flow in both directions and one flow is larger than the other. This smaller flow is “back radiation” and it is real beyond dispute.
Dave S
“or perhaps recycled back down to earth where the result is a warmer earth surface that generates photons at a higher rate to compensate”.
If two heat sources are in a vacuum. One is 20 degrees and one 10 degrees.
Option 1. Both heat sources have a power source to maintain their heat at 20 and 10 degrees. I assume the 10 degree source would rise slightly but the 20 degree source would not change.
Option 2. The power source is switched off. Would the 10 degree source slow the cooling rate of the 20 degree source
With conduction I assume it would as the air would be slightly warmer. But what about in a vacuum when there is only radiation energy loss.
richard verney says:
March 11, 2011 at 3:55 am
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.
This was a theoretical example but for it not to work as outlined you have to overturn basic physics. In fact the approach is used in practical light bulbs, a dichroic coating is applied to the bulb envelope to reflect the IR back to the filament and thus heat it so you get more output from the same current (or the same output in the visible from a lower current).
http://www.bulbs.com/blogs/light_source/post/2010/12/03/Cooler-Than-Ever-Halogen-IR-Bulbs.aspx
The only way I could ever even partially accept the blanket analogy would be if the blanket in question were something like a water filled rubber duvet and you were attempting to get a good nights sleep, perched on an overhanging precipice at the top of Mount Everest.
Give it a go, I guarantee you will be stone cold dead by the morning.
Blankets, electric or otherwise, its pure pseudo-science. The atmosphere bares no resemblance to a blanket. It has many properties and they all must be considered.
Yet in the “greenhouse” hypothesis most of the atmospheres properties are ignored. This is a fact that we all know to be true.
See my first post as an example of exactly that: http://wattsupwiththat.com/2011/03/10/visualizing-the-greenhouse-effect-emission-spectra/#comment-617396
Dave Springer
……”In most situations we only talk about the net flow of energy which always goes from warmer to colder but in reality there is flow in both directions and one flow is larger than the other. This smaller flow is “back radiation” and it is real beyond dispute.”……
There is radiation both ways but the radiation from the colder surface has fewer photons of every wavelength than is leaving the hot surface.
Also the QUALITY of the radiation is less as Hans pointed out and is restricted to the temperature profile of the colder surface.
This means that the colder surface radiation from say 300K can only effect a cancellation of that part of the output profile of say a 400K warmer surface.
That why it’s a misuse of language to say that the colder surface “heats” or “warms” the hotter surface.
To say that the cold surface insulates the warmer surface is a more accurate description of the process.
It also agrees better with your two rocks illustration
In this thread arguing about greenhouse gases and how they lead to a warmer earth, it occurs to me that clouds have the same effect, but more so. If the earth has a roughly 60% cloud cover, and those clouds act roughly like the surface and absorb most of the short wave radiation and reradiate at longer wavelengths, we get 60% of incoming sunlight absorbed by clouds, 30% radiated back to space, 30% to the earth’s surface.
40% of incoming sunlight directly reaches the surface, for a total of 70%, or roughly 240 watts out of 342.
The ground radiates energy back to space, 40% gets through, and 60% is absorbed by clouds, half radiated to space, half radiated back to earth. That would result in
a net warming to 10/7 *240 = 342 watts. You’ve got a significant fraction of the warming already without even considering greenhouse gases.
I realize there is plenty of reflected light in the daytime so the actual figures would be reduced somewhat, but obviously zero reflected light at night.
Thanks Dave Springer for clearly explaining how “back radiation” from the Atmosphere to the surface of the Earth reduces the net flow of energy from the Earth to Space. This flow reduction causes the Earth to warm until, at the resultant higher temperature, the surface emits more longwave radiation such that energy in = energy out, and average temperatures stabilize.
The Petty graphs (from his textbook that you turned me on to – thanks again) clearly show that a sensor on the surface, looking upwards towards the bottom of the Atmosphere, detects longwave radiation coming down. That is actual, measured evidence, not simply based on theory and models.
Looking at these measurements confirms that the main peak is in the 14μ to 18μ region, exactly where CO2 has its major absorption and, consequently, where it re-emits most generously. The other peaks are where H2O and O2/O3 have their major absorption and emission. The main valley is in the ~10μ region where neither H2O nor CO2 absorb/emit strongly, again confirming the role of GHGs.
RJ and others seem to accept the existence of “back radiation” but doubt that it can warm the surface of the Earth because it comes from a cooler source, the bottom of the Atmosphere. Thanks for setting them straight by reiterating that radiation goes both ways, with the Earth heating the bottom of the Atmosphere and the bottom of the Atmosphere heating the Earth, with the net flow of energy going from the Earth to the Atmosphere.
Others in this thread seem to doubt the very existence of “back radiation”, despite the actual measurements reported by Petty. It seems these good folks are so sure it is dark that they refuse to open their eyes to see the light!
Hi Fred Souder,
Sorry for the late reply, I missed your post. Your question about photons is interesting. I have no clue about the general case but I can answer for the case where I am confident that I know what I’m talking about. 😉
When a photon strikes a surface or a molecule, a variety of things can happen:
1 – It can promote something to a higher energy level. http://en.wikipedia.org/wiki/Infrared_spectroscopy
2 – It can have an elastic collision. (that’s how we see light reflecting from a surface) 3 – It can impart kinetic energy.
We are taught, and can practically confirm, that a photon can not cause something to jump to a higher quantum level unless it has enough energy to make it do so. In other words, if I want a gas to emit green light, I have to excite it with blue light. Red light won’t work.
On the other hand, low frequency (long wavelength) photons can cause a surface to heat without having to promote molecules to higher quantum levels.
I think the answer to your question (as I understand your question) is this: Promoting molecules to higher quantum levels is not the only way a photon can impart energy.
I have found a good lecture note on the subject: http://galileo.phys.virginia.edu/classes/252/black_body_radiation.html
Ira
RJ does not know re back radiation. I am just trying to understand this issue nothing more. Is the GHG theory flawed or not.
Re evidence of radiation. What are your views on this
http://slayingtheskydragon.com/Latest-News/climate-follies-encore.html
Lord: “Back radiation can be simply demonstrated by pointing a simple infrared detector at the underside of a cloud. Try it.”
Chorus: “My IR detector only cost $60! Simple! Agreed! Agreed!”
Slayer: “Clouds do not absorb and re-radiate heat back to Earth. Clouds add THERMAL MASS which takes longer to heat and cool. Warmists ‘support’ this false hypothesis with IR thermometer readings, but the IR readings of a hot Barbie is the same from any distance; ENERGY is not. Your $60 REMOTE thermometer is not measuring the radiant energy you are receiving, it is measuring the resonance of the Barbie.”
We know that this was the final act of the follies for there has been no reply in 36 hours from the Lord or the Luke Chorus.
At this point from what I have read I do not believe that a colder body can heat a warmer body. Otherwise we get a ridiculous situation where a chicken above zero could be cooked by nothing more than back radiation.
My views at this point are
That most of the energy leaves earths surface by conduction not radiation
The amount of CO2 is far to small to heat earth even if back radiation does occur and does heat the earth. (Which I doubt)
Colder bodies can not heat a warmer one. So CO2 might slow the rate of cooling but can not warm earth.
Dave Springer says:
“The insulation effect of the GHGs works only in one direction.”
—
The no belongs to you.
I have never come across a “one-directional insulator”. Have you?
You are imaginating out of what in physics has been proven over and over again.
There are spectral bands in CO2 where the solar specrum crosses and those will keep the same outside the Earth system. But, if you can ever invent a one-directional insulator, you will be a rich man. Go for it, you seem tho think CO2 is it.
cal says:
March 10, 2011 at 11:53 pm
tallbloke says:
March 10, 2011 at 4:26 am
…
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.
Hi Cal, and thanks for your reply.
I didn’t say there was no downward radiation, I said it doesn’t heat the bulk of the ocean. Now some say it must or the oceans would freeze, because of the amount of radiation measured as upwelling from the ocean surface, compared to the amount of solar shortwave entering it. This misses the point. Downwelling IR at the wavelengths found in nature doesn’t penetrate the ocean beyond it’s own wavelength. Microwave ovens are tuned to used wavelengths that cause water molecules to vibrate, and so heat up. Different wavelengths. The small amount of IR generated heat which is mixed into the near surface is not enough to account for the increase in ocean heat content, and the extra height of the space radiative atmosphere has not been elevated sufficiently by extra co2 or any water vapour feedback to account for slowing down the cooling of the ocean enough to cause the OHC increase either.
Therefore the most likely cause is the reduction in albedo over the tropics measured by the ISCCP cloud data from 1980-1998 allowing more insolation at the surface. Sunlight penetrates into the ocean many tens of meters. This is why you can see all the way to the bottom in clear tropical waters. It looks blue because the blue end of the spectrum penetrates the deepest of all, so it is blueish light which is being reflected off the white sand on the seabed or back out of the deep.
The downwelling IR is not just coming down vertically. over 95% of downwelling IR is emanating from molecules which are less than a kilometer above the Earth’s surface and the photons are travelling in all directions from straight down to horizontal. This means a significant portion get reflected by the sea surface anyway. This means a proportion of the radiation measured as coming off the sea surface is reflected radiation not absorbed and re-emitted radiation. Additionally, as Stephen Wilde says on my blog:
“What happens in practice is that increased DLR heats the ocean skin and thereby increases the rate of evaporation. The enthalpy of vapourisation (at current atmospheric pressure) dictates that for every unit of energy that provokes an evaporative event four more units oif energy are taken from the surrounding environment.
So, the increased evaporation from more downwelling IR is self limiting. One fifth of the DLR provokes extra evaporation but when the evaporation occurs it soaks up the other four fifths of the extra DLR and once the extra DLR is used up it cannot provoke any more evaporation.”
So it looks like the ocean maintains the atmosphere-ocean balance despite increased co2 and this is bourne out by the fact that satellite measurements of surface temperature show that the lower troposphere stayed at a pretty even temperature from 1980-1998 until the ocean belched out a big wad of energy in the super el nino. This then caused an upwards step change in global temperature. See Bob Tisdale’s posts on this
The key point is that this was sequestered solar energy from a more active than average sun shining through less than average tropical cloud amounts, penetrating deep into the oceans, where longwave radiation from clouds and co2 doesn’t reach.
Dave Springer said:
“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.”
I think that needs slight refinement.
I don’t think that GHGs slow the cooling of the OCEAN into the cosmic background because all they do to the ocean is increase the rate of evaporation and radiation from the ocean skin with, I think, a zero effect on the energy flow from ocean bulk to air for reasons that I have set out elsewhere.
However they do slow the cooling of the AIR into the cosmic background so the rest of the comment is correct but then one has to put the effect into proportion.
Due to the ocean bulk temperature not being affected the necessary adjustments all have to be made in the air alone and that is achieved by shifting the speed of the hydro cycle and the air pressure distribution. The latitudinal position of the jetstreams is a good proxy for that.
However the scale of natural changes in the hydro cycle and the air pressure distribution is already huge over periods of say 500 years such as the time between MWP and LIA or LIA and the present. The jets appear to have shifted by up 1000 miles latitudinally between such peaks and troughs.
I have difficulty envisioning the effect of more CO2 contributing more than a mile to such shifts and possibly less than that when the full negative effects of a faster hydro cycle are factored in.
In other words, wholly inconsequential.
Dave Springer says:
March 11, 2011 at 4:30 am
Dave Springer,
Your reply to wayne regarding the oneway insulating effect of GHG’s would only be valid if the Incoming EMR were entirely or even mostly SW.
But this is not the case as it is mostly LW. Some say 50-50 but that is not the whole picture.
Your point only has validity if incoming EMR is mostly SW. It is not and therefore you are as far from reality as it is possible to be.
The SW EMR (light) emitted by the sun is a by product of the suns extreme temperature, not the other way round. Which is why there is a 600 km high bulge in the atmosphere under the solar point covering 25% of the atmospheres surface area, tracking the solar point around the Earth 24/7 called the Diurnal Atmospheric Bulge.
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1966SAOSR.207…..J&db_key=AST&page_ind=0&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES
What happens when radiation from cold surface reaches hotter surface?
One hurdle that the “cold” radiation suffers from.
It flows “up hill.”
The respective blackbody spectra of the hot and cold objects will be centred around different maxima characteristic of their temperature.
I will invent magnitudes rather than calculate accurate ones to save time.
Lets say that initially there is only the colder object present.
Lets say that some way out from the cold object placed in a vacuum, 100 Joules of IR centred radiation of wavelength 15um pass through one metre square area in one second.
Now place a hotter object radiating at 250 Joule/s of 5um centred radiation at that squaremetre.
So what happens to the radiation from the colder object?
Three viable solutions.
1. Classical wave theory approach.
A single Pointing vector of magnitude 150W/m2 with direction hot to cold.
2. Subtraction of photon streams will result in heat flow of resultant 150W/m2
(The insulation option)
3. Absorption of 100Joules/s of 15um centred radiation and emission of 100 J/s of 5um centred emission. (The “heating up” option)
I consider that options 1 or 2 give the correct solution
Whats wrong with option 3?
The consequence for that square metre of having the hotter object there is the up-conversion of 100J of 15um centred radiation into 100J of 5um centred radiation.
This also raises the possibility of increasing the temperature of the hotter object.
If so this would also contradict the Stephan Boltzmann Equation as shown below.
The increase in the “quality” of the radiation appears to violate the second law.
Option 2 gives the correct answer using Stephan Boltzmann Equation without speculating about quantum mechanical effects of photon absorption.
What do the textbooks say.
University Physics Young and Freedman Pg 484.
“If a body of absolute temperature T is radiating and its surroundings (at temperature Ts )is also radiating and the body absorbs some of this radiation.
If it is in thermal equilibrium with its surroundings then
T = Ts .
For this to be true the rate of absorption must be
= AεσTs^4 ”
If however T > Ts
Flow of heat from body = AεσT ^4 – AεσTs^4
H = Aεσ(T ^4 – Ts^4 )
“In this equation a positive value for H means heat flow out of the body.
The equation shows that for radiation as for conduction and convection the Heat current depends on the temperature difference between the bodies.”
So it looks like option 2, mirrors the equation above.
.
” wayne says:
March 11, 2011 at 3:17 am
Hans:
Brian H:
Brian:
Yes, I totally agree with Hans explanation”
Thanks Wayne, Brian, and RJ. I hoped there would be at least some readers here making it to the end of my bad English analysis.
“Ira Glickstein, PhD says:
March 11, 2011 at 6:23 am
RJ and others seem to accept the existence of “back radiation” but doubt that it can warm the surface of the Earth because it comes from a cooler source, the bottom of the Atmosphere. Thanks for setting them straight by reiterating that radiation goes both ways, with the Earth heating the bottom of the Atmosphere and the bottom of the Atmosphere heating the Earth, with the net flow of energy going from the Earth to the Atmosphere.”
Ira,
radiation goes both ways but radiation is not heat. Radiation is cold and is able to create heat and that heat is not related to the photon energy. It happens only if there is matter, and there must be matter at Thot and at Tcold. Only then heat emerges as the energy flow from hot towards cold. This heat is a function of the surface temperature not of the photons as I pointed out here.
Bryan says:
March 11, 2011 at 7:16 am
What happens when radiation from cold surface reaches hotter surface?
One hurdle that the “cold” radiation suffers from.
It flows “up hill.”
A fundamental error in the first line, radiation doesn’t involve gradients, no such thing as ‘up hill’.
Small correction
The consequence for that square metre of having the hotter object there is the up-conversion of 100J of 15um centred radiation into 100J of 5um centred radiation.
Should read
The consequence for that square metre of having the hotter object there is the up-conversion of 100J of 15um centred radiation into 100J of 5um centred radiation to add to the effect of the hotter surface.
Dave Springer says:
March 11, 2011 at 4:18 am
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.
Nothing wrong with the plots, you’re using the wrong formula for Wien’s Law, you can’t use the wavelength formula and convert to wavenumber. You copied that statement from me and then ignored it and tried to do just that!
Try looking here:
http://www.wolframalpha.com/input/?i=Wien%27s+displacement+law&a=*FS-_**WiensDisplacementLaw.lambda-.*WiensDisplacementLaw.T–&f2=5780+K&f=WiensDisplacementLaw.T_5780+K&a=*FVarOpt-_**WiensDisplacementLaw.nu–
For a temp of 270K the peak frequency is 15.9 THz corresponds to 18.9 microns.
Bryan says:
March 11, 2011 at 7:16 am
The increase in the “quality” of the radiation appears to violate the second law.
What on earth is the ‘quality’ of radiation? What are its SI units?
Bryan says:
March 11, 2011 at 7:16 am
What happens when radiation from cold surface reaches hotter surface?
Lets say that initially there is only the colder object present.
Lets say that some way out from the cold object placed in a vacuum, 100 Joules of IR centred radiation of wavelength 15um pass through one metre square area in one second.
Now place a hotter object radiating at 250 Joule/s of 5um centred radiation at that squaremetre.
So what happens to the radiation from the colder object?
Three viable solutions.
1. Classical wave theory approach.
A single Pointing vector of magnitude 150W/m2 with direction hot to cold.
2. Subtraction of photon streams will result in heat flow of resultant 150W/m2
(The insulation option)
3. Absorption of 100Joules/s of 15um centred radiation and emission of 100 J/s of 5um centred emission. (The “heating up” option)
I consider that options 1 or 2 give the correct solution
Whats wrong with option 3?
None of the above, the cooler object will warm up until it is in equilibrium with the incoming radiation from the hotter object resulting in more radiating reaching the hotter object which will also increase in temperature until it is in equilibrium too.
Ira Glickstein said:
“Thanks Dave Springer for clearly explaining how “back radiation” from the Atmosphere to the surface of the Earth reduces the net flow of energy from the Earth to Space. This flow reduction causes the Earth to warm until, at the resultant higher temperature, the surface emits more longwave radiation such that energy in = energy out, and average temperatures stabilize.”
So now we have a new, sceptic, version of greenhouse warming. Backradiation does not directly add heat to the Earth but by reducing the rate of radiative cooling “it causes the Earth to warm”. Forgive me for not being able to distinguish between these two fallacies.
A heated body’s molecules are vibrating in accordance with the energy it is absorbing. A cooler body emitting towards the hotter body cannot heat it up any more because the emissions (backradiation) are not at the energy level to make the molecules vibrate any faster. Likewise the radiative cooling version of greenhouse theory cannot make the hotter body’s molecules vibrate any faster. Of course there is such a thing as radiative cooling, but in a constant irradiance model (such as Kiehl & Ternberth’s) the Earth is not cooling down so cutting off the flow of radiant energy cannot add any heat as it cannot make the incoming energy vibrate the molecules any more. Reduction in radiative cooling may have an effect at night (and if so the Earth will be less cold than it otherwise would be) but this is not the basis of the ‘greenhouse effect’ which is about a build up of additional heat below a radiation barrier until it is breached and a fictitious radiative equilibrium is arrived at. Further, the net flow argument which is used to demonstrate compliance with the laws of thermodynamics in this theory is a fraud. On this argument you could have any amount of backradiation – a million watts for example – but as the flow out would still be greater than the flow in (1 million plus the 66 watts of solar) then there would be compliance.
Phil. says:
March 11, 2011 at 7:41 am
A fundamental error in the first line, radiation doesn’t involve gradients, no such thing as ‘up hill’.
Well its a reasonable analogy
Shorter wavelengths are characteristic of higher temperature sources .
Shorter wavelength photons have higher energy than longer wavelength ones
Bryan says:
March 11, 2011 at 8:50 am
Phil. says:
March 11, 2011 at 7:41 am
“A fundamental error in the first line, radiation doesn’t involve gradients, no such thing as ‘up hill’.”
Well its a reasonable analogy
Shorter wavelengths are characteristic of higher temperature sources .
Shorter wavelength photons have higher energy than longer wavelength ones
Not reasonable at all because it has no relevance to the transport of radiation.
It amazes me that so many are still chasing around the canard tossed out by the AGW people.
Just like “Hide the decline!”
“Hide the nitrogen, oxygen and water!”
They tell you to disregard the N2, O2 and H2O in the atmosphere.
They tell you to disregard the HUGE heat capacity and HUGE thermal mass represented by N2, O2 and H2O in the atmosphere.
Disregard the 99.05% of the atmosphere. It has no effect.
Focus only on the 0.05% CO2 that we tell you to.
Because CO2 is a magical molecule and it controls the atmosphere.
And like sheep, many do so.
This is a far more accurate picture of what is truly going on:
http://slayingtheskydragon.com/Latest-News/omgmaximum-co2-will-warm-earth-for-20-milliseconds.html
“Thermodynamics will provide exact, repeatable quantities for energy flows or resultant temperature based on equations with three main variables. These variables are the difference in temperature, the mass of the bodies and the specific heat of the bodies. The greater the temperature difference, the greater the energy movement, which is the ‘delta T’ component.
A pound of water is easier to heat than ten pounds of water, which is the ‘mass’ component. A pound of Aluminum is easier to heat than a pound of Lead, which is the specific heat component. Carbon Dioxide has a specific heat of 0.8J/Ks K, which means it gains or losses heat faster than standard air. This coefficient actually reduces the mass values we will now discuss, but we will assume this to be 1.0 J/Ks K to simplify discussion.
In determining the heat flow of the planet we must place the ‘human produced’ atmospheric component in perspective with the total system. Humans produce 28 Giga-tons of atmospheric carbon annually. For comparison, 28 G-tons of ocean would be 5.93 cubic miles or 28 G-tons of Earth would be 2.96 cubic miles.
What the Warmists are trying to tell you is that YOUR 6 cubic mile portion of the ocean controls the temperature of the entire 310,000 million cubic miles of ocean. Or alternatively, YOUR 3 cubic miles of dust controls the temperature of the 259 trillion cubic miles of Earth. As absurd as this assertion is, the actual particle physics is an equal distortion.
It’s a Small World After All
Carbon Dioxide is a benign molecule that is required for life and is currently less than 390 parts per million (PPM) of the atmosphere. Prolonged exposure to concentrations of up to 80,000 PPM, have shown no adverse side effects. All federal registries listed CO2 as ‘non-toxic’ until the recent EPA reclassification. Calling a substance a ‘toxin’ does not make that substance a toxin, except in the toxic mind of bureaucrats.
All substances absorb and emit electromagnetic energy in discrete spectrum bands. The Earths outgoing Infrared energy is in a narrow band and can be absorbed by CO2 only in the 5 and 15 micron wavelength range. There is a finite amount of this IR energy, so the absorption is not directly connected with the amount of CO2. The term ‘absorption’ is misleading also, for the amount of time that this IR flow is ‘interrupted’, called the lapse rate is a fraction of a millisecond.
The majority of the space around an atom is void. Most IR energy passes through the CO2 molecules with no impact. The further you go above the surface of the Earth, the less air and the less CO2 you and outgoing IR waves will impact. Professor Nasif Nahle of the UA de Nuevo Leon has done the ‘mean free travel’ calculations on the IR escape rate. Outgoing IR energy is delayed by at most 22 milliseconds.
That is the total extent of ‘global warming’. All of the Planets CO2, the 97% from natural and the 3% from man delay temperature change by an immeasurably small amount of time. And this ‘delayed’ heat transfer is NOT radiated back to Earth. It is leaving a ‘hot’ Earth at the speed of light for a ‘cool’ outer space and is only delayed momentarily.” end quote
CO2. In reality, in the overall scheme of things, an obscure bit player. Hardly worth looking at. A nothing. Just like the major AGW players: Keeling, Mann, Jones, Gore, Schmidt, Hansen….in reality they are nothing but bit players. Nothings. Not even worth a glance.
Soon, many more people will come to realize that.
Phil. says:
What on earth is the ‘quality’ of radiation?
The ‘quality’ of radiation or energy generally is its ability to do work or in other words turn into other energy forms.
If you google the appropriate words you will find plenty of hits particularly from solar energy capture systems.
In the meantime here are two sources
http://www.scribd.com/doc/31017446/The-Second-Law-of-Thermodynamics
http://www.ijoticat.com/index.php/IJoT/article/viewFile/185/171