Guest Post by Ira Glickstein
Solar “light” radiation in = Earth “heat” radiation to Space out! That’s old news to those of us who understand all energy is fungible (may be converted to different forms of energy) and energy/mass is conserved (cannot be created nor destroyed).
My Visualizing series [Physical Analogy, Atmospheric Windows, Emission Spectra, and Molecules/Photons] has garnered almost 2000 comments, mostly positive. I’ve learned a lot from WUWT readers who know more than I do. However, some commenters seem to have been taken in by scientific-sounding objections to the basic science behind the Atmospheric “Greenhouse Effect”. Their objections seemed to add more heat than light to the discussion. This posting is designed to get back to basics and perhaps transform our heated arguments into more enlightened understanding :^)
As I’ve mentioned before, during my long career as a system engineer I’ve worked with many talented mathematical analysts who always provided precise results, mostly correct, but some precisely wrong, usually due to mistaken assumptions. I got into the habit of doing a “back of the envelope” calculation of my own as a “sanity check” on their results. If their results matched within reasonable limits, I accepted them. If not, I investigated further. In those days my analysis was really done using a slide rule and scrap paper, but I now use spreadsheets.
The graphic above is based on an excellent spreadsheet from http://serc.carleton.edu/files/introgeo/models/mathematical/examples/XLPlanck.xls. It uses Planck’s Law to calculate the black body radiation spectrum from the Sun, as observed at the top of the Earth’s Atmosphere. It also may be used to calculate the radiation spectrum from the Earth System (Atmosphere and Surface, see below for explanation) at any assumed temperature. (I will refer to this spreadsheet as “Carleton” in this posting.)
I modified the Carleton spreadsheet to compute the mean Solar radiation per square meter absorbed by the Earth System, which turns out to be 240 Watts/m^2. I then used the spreadsheet to determine the effective mean temperature of the Earth System that would emit an equal amount of energy to Space, and that turned out to be 255 Kelvins (-18ºC which is 1ºF).
Since the mean temperature at the surface of the Earth is 288 Kelvins (+15ºC which is 59ºF), that leaves 33 Kelvins (33ºC which is 58ºF) to be accounted for. Guess how we acount for it?
The yellow curve (above left) shows that Solar radiation is in a tall, narrow “shortwave” range, from about 0.1μm (microns, or millionths of a meter) to about 4μm, which we call ultra-violet, visual, and near-infrared. The vertical axis is Intensity of the radiation, measured in Watts/m^2/μm, and the horizontal axis is Wavelength, measured in μm. If you divide the area under the yellow curve into vertical strips, and add up the total area, you get 240 Watts/m^2.
Since we humans sense the visual portion of this radiation as “light”, that is the name we give it, and that has led to the false assumption that it contains no “heat” (or “thermal”) energy.
The violet curve (above right) shows that, assuming a mean temperature of 255 K, Earth System radiation to Space is in a squat, wide “longwave” range, from about 5μm to beyond 40μm, which we call mid- and far-infrared. If you divide the area under the violet curve into vertical strips, and add up the total area, you get the same 240 Watts/m^2 as is under the yellow curve.
DETAILED EXPLANATION
The graph on the left shows the actual observed Solar radiation spectrum (in red) as measured at the top of the Atmosphere. It is superimposed on a black body model (in blue) showing very good correlation. Thus, while the Sun is not exactly a black body, it is OK to assume it is for this type of “sanity check” exercise.
If you calculate the area under the curve you get about 1366 Watts/m^2. That means that a square meter of perfect black body material, held perpendicular to the Sun, would absorb 1366 Watts.
However, the Earth is not a perfect black body, neither is it a flat surface perpendicular to the Sun! So, to plot the yellow curve at the top of this posting, I had to adjust that value accordingly. There are two adjustments:
- The Earth may be approximated as a sphere, with the Sun shining on only half of it at any given time. The adjustment factor for this correction is 0.25.
- The albedo (reflectiveness) of the Earth system, primarily clouds and light-colored areas on the Surface such as ice, causes some of the Solar radiation to be reflected back out to Space without contributing any energy to the Earth System. The adjustment factor for this correction is 0.7.
After applying these adjustments, the net Solar energy absorbed by the Earth System is 240 Watts/m^2.
The graph on the right shows the black body model for an Earth System at a mean temperature of 255 K, a temperature that results in the same 240 Watts/m^2 being emitted out to Space.
Of course, the Earth System is not a perfect black body, as shown by the graph in the upper panel of the illustration below, which plots actual observations from 20 km looking down. (Adapted from Grant Petty, A First Course in Atmospheric Radiation, Figure 8.2, http://www.sundogpublishing.com/AtmosRad/Excerpts/index.html.)
The actual measured radiation is the dark squiggly curve. Note that it jigs and jags up and down between the topmost dashed curve, which is the black body spectrum for a temperature of 270 K and a lower dashed curve which is the black body spectrum for 230 K. This data was taken over the Arctic, most likely during the daytime. The Petty book also has a graph looking down from over the Tropical Pacific which ranges from 300 K down to 210 K. Observations will vary by tens of degrees from day to night, summer to winter, and Tropical to Polar.
However, it is clear that my result, based on matching 240 Watts/m^2, is within a reasonable range of the true mean temperature of the Earth System as viewed from Space.
NOTE ABOUT THE ABOVE ILLUSTRATION
WUWT readers will notice some apparent inconsistencies in the graphs above. The top and bottom panels, from Petty, peak at 15μm to 20μm, while the purple, blue, and black curves in the middle panel, and the Earth System curves from the Carleton spreadsheet I used (see above) peak in the 9μm to 11μm range. Also, the Petty black body curves peak at a “Radiance” around 100 mW/m^2/sr cm^-1 while the black body curves from Carleton peak at an “Intensity” of around 14 W/m^2/μm. Furthermore, if you look closely at the Petty curves, the labels on the black body curves are mirror image! What is going on?
Well, I know some of the reasons, but not all. (I hope commenters who are more fluent in this than I am will confirm my explanations and provide more information about the differences between “Radiance” and “Intensity”.) I have Googled and Wikied the Internet and am still somewhat confused. Here is what I know:
- The horizontal axis in Petty’s plots are what he calls “Wavenumber”, increasing from left to right, which is the number of waves that fit into a cm (centimeter, one hundredth of a meter).
- This is proportional to the frequency of the radiation, and the frequency is the inverse of the wavelength. Thus, his plots are the mirror image of plots based on wavelength increasing from left to right.
- The spreadsheet I used, and my previous experience with visual, and near-, mid-, and far-IR as used in military systems, always uses wavelength increasing from left to right.
- So, when I constructed the above illustration, I reversed Petty’s curves, which explains why the labels on the black body curves are mirror image.
- Fortunately, Petty also included a wavelength legend, which I faithfully reproduced, in non-mirror image, at the top of each plot.
But, that still does not explain why the Petty black body curves peak at a longer wavelength than the Carleton spreadsheet and other graphics on the Internet. I tried to reproduce Petty’s blackbody curves by multiplying the Carleton values by the wavelength (μm) and that did not move the peak to the right enough. So, I multiplied by the wavelength again (μm^2) and, voila, the peaks agreed! (I hope some WUWT reader will explain why the Petty graphs have this perverse effect. advTHANKSance!)
ANSWERING THE OBJECTIONS TO BASIC ATMOSPHERIC “GREENHOUSE EFFECT” SCIENCE
First of all, let me be clear where I am coming from. I’m a Lukewarmer-Skeptic who accepts that H2O, CO2 and other so-called “greenhouse gases” in the Atmosphere do cause the mean temperature of the Earth Surface and Atmosphere to be higher than they would be if everything was the same (Solar radiation, Earth System Albedo, …) but the Atmosphere was pure nitrogen. The main scientific question for me, is how much does the increase in human-caused CO2 and human-caused albedo reduction increase the mean temperature above what it would be with natural cycles and processes? My answer is “not much”, because perhaps 0.1ºC to 0.2ºC of the supposed 0.8ºC increase since 1880 is due to human activities. The rest is due to natural cycles and processes over which we humans have no control. The main public policy question for me, is how much should we (society) do about it? Again, my answer is “not much”, because the effect is small and a limited increase in temperatures and CO2 may turn out to have a net benefit.
So, my motivation for this Visualizing series is not to add to the Alarmist “the sky is falling” panic, but rather to help my fellow Skeptics avoid the natural temptation to fall into an “equal and opposite” falsehood, which some of those on my side, who I call “Disbelievers”, do when they fail to acknowledge the basic facts of the role of H2O and CO2 and other gases in helping to keep temperatures in a livable range.
Objection #1: Visual and near-visual radiation is merely “light” which lacks the “quality” or “oomph” to impart warmth to objects upon which it happens to fall.
Answer #1: A NASA webpage targeted at children is sometimes cited because they say the near-IR beam from a TV remote control is not warm to the touch. Of course, that is not because it is near-visual radiation, but rather because it is very low power. All energy is fungible, and can be changed from one form to another. Thus, the 240 Watts/m^2 of visible and near-visible Solar energy that reaches and is absorbed by the Earth System, has the effect of warming the Earth System exactly as much as an equal number of Watts/m^2 of “thermal” mid- and far-IR radiation.
Objection #2: The Atmosphere, which is cooler than the Earth Surface, cannot warm the Earth Surface.
Answer #2: The Second law of Thermodynamics is often cited as the source of this falsehood. The correct interpretation is that the Second Law refers to net warming, which can only pass from the warmer to the cooler object. The back-radiation from the Atmosphere to the Earth Surface has been measured (see lower panel in the above illustration). All matter above absolute zero emits radiation and, once emitted, that radiation does not know if it is travelling from a warmer to a cooler surface or vice-versa. Once it arrives it will either be reflected or absorbed, according to its wavelength and the characteristics of the material it happens to impact.
Objection #3: The Atmospheric “Greenhouse Effect” is fictional. A glass greenhouse works mainly by preventing or reducing convection and the Atmosphere does not work that way at all.
Answer #3: I always try to put “scare quotes” around the word “greenhouse” unless referring to the glass variety because the term is misleading. Yes, a glass greenhouse works by restricting convection, and the fact that glass passes shortwave radiation and not longwave makes only a minor contribution. Thus, I agree it is unfortunate that the established term for the Atmospheric warming effect is a bit of a misnomer. However, we are stuck with it. But, enough of semantics. Notice that the Earth System mean temperature I had to use to provide 240 Watts/m^2 of radiation to Space to balance the input absorbed from by the Earth System from the Sun was 255 K. However, the actual mean temperature at the Surface is closer to 288 K. How to explain the extra 33 K (33ºC or 58ºF)? The only rational explanation is the back-radiation from the Atmosphere to the Surface.
Thank you Hockey Schtick !!…
William C. Gilbert’s words are much better than the ones I have been using and now I have someone to attribute them to. He’s right, it is merely not so simple, but understandable, physics.
wayne says:
It is clear that Gilbert has never actually read any elementary textbook on atmospheric physics or climate science or he would be aware that the argument about adiabatic lapse rate that he presents is not new to anyone in the field…It is discussed in all of these books. (Alternatively, maybe Gilbert is aware of this but is confident that the readers who he wants to convince have not.)
However, far from his claim that this temperature profile explains the 33 deg temperature difference between what is observed and what radiation balance requires, the fact is that it alone doesn’t explain any of it. You need to consider not only how the temperature varies with height but what then sets the constant that tells you what the absolute temperature is at some height in the troposphere. In the absence of absorption of terrestrial radiation by the atmosphere (and with the other caveats about still having the same albedo and such), that average temperature would have to be 255 K at the surface because of radiative balance and then the temperature would decrease with height at the lapse rate from there.
jae says:
The errors in your explanations have now been explained to you multiple times in this thread. There is no excuse for you to continue to cling to them.
WOW, another great question that I hope those more knowledgeable than I can answer. THANKS Anton Eagle – sometimes the right questions can lead to deeper knowledge.
Here is my take:
1) The Perry curves in this posting are based on NASA measurements taken in the Arctic, where the water vapor content of the Atmosphere is less than in regions closer to the Tropics. My earlier posting in this series at here reproduces more Perry curves in their full glory (and not mirror-imaged), including curves from the Tropics.
2) The Perry curves plot what he calls “Radiance” and that seems to differ from “Intensity” (in the Carleton spreadsheet plots) in that the amplitude of longer wavelengths appears to be multiplied by the wavelength squared for reasons I do not yet understand. Thus, any readings we take in the ~15μm region are shown about four times higher than comparable readings in the ~7μm region, for example (because 15^2 is over four times 7^2).
3) In comparing the amplitudes I think the best bet is to judge where they are with respect to Perry’s plot of the black body curves. Although it is not clear in the small versions I included in this posting, the full-resolution plots show that the topmost dashed curve in both plots represents a 270 K black body.
4) As I understand it, the ~15μm radiation from the Surface to the Atmosphere is absorbed by H2O and CO2 molecules which, when excited, bump into nitrogen and oxygen and other air molecules, and heat the air. The result is emission of long-wave radiation at a range of wavelengths (not just in the ~15μm region, but including the ~7μm and ~10μm regions) in random directions, some of which finds its way back down to the Surface and is re-absorbed. That conversion of a portion of the ~15μm radiation into other wavelengths may explain why there is a “bite” out of the ~15μm radiation that seems to be missing from the radiation out to Space.
5) In particular, notice that the ~10μm region (from around 8μm to 12μm) is very close to the highest black body curve, except for the little “bite” near 9.5μm which is where there is an oxygen/ozone absorption effect. In addition to the ~15μm “bite” that corresponds to the CO2 absorption region, notice that the H2O absorption areas, namely the ~7μm region and the part of the ~15μm region that extends from 18μm to 25μm and above is also somewhat below the highest black body curve.
6) Thus, if we assume, as a first approximation, that the Surface approximates a blackbody at 288 K, with a spectrum something like the smooth blue curve in my illustration above, we see that the Atmosphere passes the ~10μm region (except for part of the ~9.5μm oxygen/ozone “bite”) and, from the Perry plot of Surface looking UP, re-emits much of the ~7μm and ~15μm region back down to the Surface. From the Perry Space looking DOWN plot, we see that the ~10μm region is the highest (except for the oxygen/ozone “bite”) and that the two H2O and the one CO2 regions are depressed. My take is that the radiation in the H2O and CO2 absorption bands shuttles back and forth between being absorbed and re-emitted by the Surface and Atmosphere (where about half heads in the direction of Space), all the while transforming a bit to the ~10μm region, which gets a free pass to Space, with each transaction.
7) So, BOTTOM LINE, the readings taken from the Perry curves need to be interpreted properly to answer your question. There is no extra energy.
Joel:
“The only way that adiabatic compression could possibly explain the earth’s surface temperature would be if the atmosphere (and / or the earth itself) were undergoing continual gravitational collapse, which we know is of course not the case.”
Thank you! I’ve had big trouble trying to explain this to people before. I tried using the example of a bike tire, which heats up when you compress the air but then doesn’t stay hot (even though it stays compressed, but the elasticity of the innertube, analgous to gravity, is not reducing the volume of gas). Success rate with this explanation is surprisingly low.
Joel:
“The errors in your explanations have now been explained to you multiple times in this thread. There is no excuse for you to continue to cling to them”
?? Can you please point me to those explanations, sir? I must have missed them, or else, perhaps, probably, most likely, they were balogne? Come on, fella, provide some tangible thing that I can relate to, instead of your Orwellian insistance that there is, “out there,” something that proves your case/argument/status/being/etc..
WTF?
“The only way that adiabatic compression could possibly explain the earth’s surface temperature would be if the atmosphere (and / or the earth itself) were undergoing continual gravitational collapse, which we know is of course not the case.”
Typical CAGW-practitioner gobbledygook
And the atmosphere does not behave as an enclosed bicycle tire. No wonder the “success rate” with that explanation is so low.
Here’s Dr. Jelbring’s more detailed explanation:
http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBYQFjAA&url=http%3A%2F%2Fruby.fgcu.edu%2Fcourses%2Ftwimberley%2FEnviroPhilo%2FFunctionOfMass.pdf&ei=9V3HTbH4IIP4sAOLzuTqAQ&usg=AFQjCNHTux_zuvY-oHVCehfC6OOmfzUafQ&sig2=p-LjGfmce1A-Vqk5ybrjZg
Show me the exact error’s you claim, citing specific excerpts from his paper.
ferd berple says:
May 8, 2011 at 2:24 pm
The solar radiation hitting the earths surface is 184 W/m^2 per Trenberth 2009 or 198 W/m^2 per Trenberth 1997. The surface albedo must be applied to this to get the net gain. Back radiation adds another 333 or 324 W/m^2 respectively.
There seems to be a whole lack of common sense going around these days.
So, according to T, the earth receives 184 w from the sun, radiates some of this back outwards, where some of it is absorbed by the atmosphere and re-radiated back to earth, where it provides 333 w.
In other words, 184 w ends up as 666 w, because the back radiation is omni-directional at at most 50% reaches the earth……………………………………
///////////////////////////////////////////////////////
There does appeart to be a complete lack of commonsense in these figures.
If these figures were correct (ie., back radiation is approximately twice the power of solar), why are we wasting time with trying to capture solar energy rather than back radiation energy?
Why don’t we construct a large array of mirrors collecting and focusing this back radiation much like the Californian Solar power station: see
http://greenwombat.files.wordpress.com/2010/01/esolar-power-plant.jpg
This not only would produce more energy (viz about 330 cf about 190 W/m^2; back radiation cf solar), it would additionally solve the storage problems inherent with present day green energy projects since back radiation is available day and night etc.
The answer is simple, either this back radiation does not exist, or if it does exist it is incapable of doing any sensible work (ie., it lacks sensible energy).
The lack of any serious research into collecting and utilising the back radiation energy source strongly suggests that leading energy scientists regard the back radiation set out in Trenberth’s energy diagrams to be complete and utter nonsence!
Anyone who supports Trenberth’s diagram and considers that the back radiation theory is correct should be asked to explain why we are not utilising this fanastic energy source. After all, if it existed it should be the main focus of green energy projects.
“The only way that adiabatic compression could possibly explain the earth’s surface temperature would be if the atmosphere (and / or the earth itself) were undergoing continual gravitational collapse, which we know is of course not the case.”
Typical CAGW-practitioner gobbledygook
And the atmosphere does not behave as an enclosed bicycle tire. No wonder the “success rate” with that one is so low.
Here is a more detailed explanation from Dr. Jelbring:
http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBYQFjAA&url=http%3A%2F%2Fruby.fgcu.edu%2Fcourses%2Ftwimberley%2FEnviroPhilo%2FFunctionOfMass.pdf&ei=9V3HTbH4IIP4sAOLzuTqAQ&usg=AFQjCNHTux_zuvY-oHVCehfC6OOmfzUafQ&sig2=p-LjGfmce1A-Vqk5ybrjZg
Show me exactly where he is in error, citing exact quotes from the paper, without any hand waving.
Luuuucy?????? Ira?????? we are missing some comments here. WTF? Are you THAT desperate????
A courteous, well-bred person will not insult me, and none other can. [Paraphrasing William Cowper, ca 1763]
While you’re at it, Dr. Noor van Andel’s paper also explains the “GHE” based upon the adiabatic lapse rate. Again, show me exactly where he is in error, citing exact quotes from the paper, without any hand waving.
http://climategate.nl/wp-content/uploads/2011/02/CO2_and_climate_v7.pdf
Wow. Once again, misconceptions abound on both sides.
Ira, just because it is the only seemingly rational suggestion that has been posited publicly does not mean that it actually describes the physical process accurately. If it did, the term “backradiation” would not have had to have been coined in the first place.
It is a simple matter to increase the absorption in a gas above the level of the incident energy, without ever having to increase the relative concentration of the gas, and is done on a daily basis in my field, and has been for many decades, but we do not call it “backradiation”.
Some (no, I don’t know exactly how much) of the reflected solar energy has already been absorbed by the atmosphere before being reflected. The statement that it contributes nothing to the atmospheric temperature profile is thus at least partly incorrect.
So Ira, if you really are sincere about wanting to know where the 33K difference comes from, you could start by calculating the Mie backscatter cross section of a 10um dielectric sphere, and I would suggest calculating it with a 9.25um or 10.59um em wave incident on it. I suggest those 2 wavelengths because measurements have already been done with them, and you will have something to compare the calculated values to, although the measured values were normally given in steradians, which can also be calculated.
You might also consider how it is possible to treat two entities that are physically coupled (think about it) as if they were two separate “blackbodies” radiating “at” each other.
Cheers.
BTW, N2 DOES have resonance lines in the solar UV region.
A warm atmosphere will emit radiation. Some of it will be backradiation.
Even without IR absorption the atmosphere will warm.
http://earthobservatory.nasa.gov/Features/EnergyBalance/page6.php
Convection.
Evaporation.
Incoming energy absorption (visible light).
With this in mind, and accepting the backradiation mechanism, how can the “greenhouse IR” component be ascribed the full 33 C difference?
Surely it can’t be?
From what I see the proponents of the Greenhouse theory simply keep stating it as fact without explaining the observed phenomena that seemingly falsify it such as.
– You cannot heat a hot body from a colder body which you have to be able to do.
– The temperature at the surface and at height can be explained without recourse to radiative theory which to me means that the temperature is determined by the fact that we have an atmosphere not necessarily because we have an atmosphere with GHGs. The atmospheric column is nothing like a bicycle tyre in physical terms, that is a red herring.
– In the past when we have had multiples of current CO2 levels we have not had runaway warming.
– There is patently no runaway warming now while CO2 levels ramp up inexorably. There is no runaway warming on venus.
– If back radiation is so powerful and it is a heat source, why don’t we use it?
It’s the answers to the simple things that are important not the circular academic arguments. The consensus view is that AGW is happening because of a trace GHG, the only problem is that there is no unequivocally correct theoretical or observational data that supports it.
John of Kent says:
May 8, 2011 at 3:09 am
Ira Glickstein does not seem to understand how matter interacts with radiation.
On the contrary he seems to understand it fairly well, you however appear not to!
Wayne,
“The air above the cloud tops will be cooler than normal shielded by the water mass in the clouds and the air between the surface and the cloud base warmer than normal.”
The problem is for those doubting back radiation to explain the greater night time head loss in dry clear skies vs humid clear skies. You don’t seem to be able to do it without clouds, are you doubting the humid vs dry clear sky difference exists?
BTW, no huge lens covering a wide enough range of the infrared spectrum exists to conduct your hypothetical experiment.
How does this fit in with the Holographic Universe theory?
According to the more reasonable reconstructions of past temperature (Moberg, Loehle) the surface temperature has been rising since 1700. This is 230 years longer then co2 has been rising to any great degree.
What is Ira’s explanation for this earlier warming?
The Earth is a big heat engine. Most of the effective solar heating of the ocean occurs in the tropics, whereas most of the effective radiation of heat to space occurs near the poles. Most of the energy between the equator and temperate latitudes is shifted by the ocean. From the temperate latitudes to the poles, most of the energy is shifted by the atmosphere. This movement of energy is achieved mainly by convection of one sort or another, and since the temperature of the ocean is little affected by back radiation, changes in co2 concentration can’t have much effect.
Why does Ira refer simply to the Earth’s surface as an amorphous entity instead of taking into consideration the fact that 70% of it doesn’t absorb much energy from back radiation?
over 90% of downwelling radiation striking the ocean surface has been emitted a kilometre or less above it, because of re-absorption and re-emission. Since this re-emitted radiation is travelling at any random angle wrt to the ocean surface, most of it is travelling at angles which will either miss the surface or be reflected by it. The back radiation which is entrained into the ocean bulk by wave action is minimal, because wave action subducts water which is well below the level back radiation can penetrate to (little more than its own wavelength). Most of the radiation measured as coming from the ocean surface is actually either been reflected or is being emitted by molecules evaporated from the ocean surface.
Since the ocean surface temperature changes precede surface air temperature changes by several months, and since the top two metres of ocean contain as much heat capacity as the entire atmosphere above it, it is clear that surface temperature and atmospheric temperature is strongly influenced by the ocean, which is heated by the sun, not by back radiation.
Solar variation affects albedo, and that affects how much solar energy the ocean absorbs. This is why the number of sunshine hours correlates with surface temperature over the last 130 years much more closely than co2 level.
http://tallbloke.files.wordpress.com/2010/06/soon2009.jpg
In my opinion, surface temperature variation is due to the variation of the Sun. Co2 is along for the ride.
Why is “the Petty black body curves peak at a longer wavelength than the Carleton spreadsheet”?
As dr.bill said, this is because the Planck equation is actually an integral. When you change the x-axis, the peak actually does shift. I have written a full explanation at
http://mc-computing.com/Science_Facts/Blackbody/Blackbody_Equations.html
There is also a plot showing the difference in the shape of the two 300K curves and their peaks.
biological evolution has “tuned” our visual system to be most sensitive where the light energy is maximized
Not quite, that is where the intensity per wavelength interval is brightest, not where the energy per frequency interval is largest.
This demonstrates why people who believe in Global Warming always plot spectra versus wavelength. When you want to analyze the energy in the system, all plots should be versus frequency (normally expressed as a wavenumber) to show an honest plot. In that case, most of the energy from the Sun is in the IR. When plotted versus wavelength, the plots incorrectly imply that most of the energy is in the visible and UV spectra.
The one big attractive feature of the “greenhouse theory” is its amazing elasticity.
The climate getting warmer is a sure proof of CAGW
But then so is the climate getting colder, say some IPCC advocates.
Joel Shore has refined this even further to say Postema is a believer, only Postemo hasn’t quite realised it.
Perhaps with the same elasticity Joel will prove that Gerlich and Tscheuschner also are really IPCC advocates.
Joel goes on to say of me;
…..”He has absolutely no serious desire to discuss the science”…..
Quite the opposite Joel;
On page 9 of your co-written Halpern et al comment paper you state that the Stephan Boltzman Law can be used to work out the thermal energy between atmospheric shells.
I brought your attention to it in my post above;
….. ” 3. Has the Stephan Boltzmann equation applying to gases.”……
Its no good trying to weasle your way out of it.
Your comment was printed in a specialist Journal with readership almost entirely of Physicists.
They would have no problem understanding your point.
Do you still maintain this position or will this be your third major repudiation of this notorious document.
In fact you should perhaps repudiate the document in its entirely!
Ira, I’d really like some of the “back radiation” now. Just stepped outside my house in Kamloops BC and pointed an IR thermometer straight up into the sky and got a temperature reading of -10 F. When I pointed the thermometer horizontally down the street, got 34 F. Pointing it at the outside of my house gave a temperature of 44 F as did pointing it at my driveway. The airport temperature now is given as 48 F. The altitude of the airport is about 200′ lower than where I live. I should note that the sky is perfectly clear at this time with no clouds in sight (just wish it would do this in the daytime).
The surface of the earth heats up considerably during the day and this heat is released during the night. Of course having heat buffers of variable capacity greatly complicates models. The -10 F temperature that I’m seeing with my IR thermometer is the average temperature of the atmosphere from 1600′ above sea level to space. What portion of this would be related to “greenhouse gasses” and what portion is the result of heat flux from sun-warmed surface and air to space?
Martin Lewitt, you are right, I do not “believe” in “back radiation”, just plain radiation as taught in physics.
Clouds make warmer nights because the clouds are usually warmer than the normal air temperature at that altitude and therefore the surface’s rate of loss by radiation upward will be less leaving you with a warmer than normal night. It is also that same radiation keeps those clouds warmer than te air at that altitude would normally be. Just using Stefan-Boltzmann will get you very close if you know the temperatures and emissivities involved. There are even rare cases when the clouds are actually warmer than the surface and then the clouds are radiating downward to the surface and also to space but as you should see, this condition is short lived since it has cooler on both sides unless continually replenished with warmth to maintain the temperature differential.
BTW, that experiment does not require all frequencies to be valid. I’ll just leave it for each here to decide it’s merits, sounds like most here can handle high-school science correctly.
From the comments here, a lot of people seem to believe that the greenhouse effect cannot exist because it violates the 2nd law of thermodynamics. To my shock, I am finding myself agreeing with Joel Shore on the elementary physics. I have just finished reading the Postma essay, and it contains the same strawman argument that crops up every time this matter is discussed.
Postma described a black body warmed by a heat source and claimed that you cannot make it warmer by reflecting that emitted radiation back. Whilst acknowledging back radiation exists, he asserts that this energy cannot cause the black body to increase in temperature. He states that a body cannot raise its own temperature. Well of course not. The reason this is a strawman fallacy is because nobody is making that claim. The claim is that the back radiation reduces the rate of cooling of the earths surface because the net outflow in watts is slightly less than it would have been without the back radiation. It is the sun that causes the warming because energy is now coming in faster than it is leaving, so the temperature will rise until a new equilibriumis reached.
An analogy is a tub with a ‘V’ cut near the top. The higher the water level is above the ‘V’, the faster it flows out. This is an analogy of the SB law of blackbody radiation. Suppose the sun is represented by a running tap. The water will rise above the ‘V’ just enough so that the rate of input is equal to the rate of overflow. Let us now represent the back radiation by blocking some of the ‘V’ which represents the reduced outflow of radiation from the earths surface. The water level (temperature) will now rise such that the outflow increases to balance the inflow. If you turned the tap off (remove the sun from the climate system), the water level (temperature) would start to decline just as you would expect from thermodynamics.
Ira,
Here is a schematic from a search, nothing special, merely from the first site that had a lapse curve, month of June, 45 degrees North latitude.
http://i260.photobucket.com/albums/ii14/sherro_2008/Lapse.png?t=1304929624
Source was Bigg 2005, blog was http://scienceofdoom.com/2010/04/24/tropospheric-basics/
The coldest temperature measured on earth is about -89 deg c at Vostok. This is colder than any part of the lapse curve below about 75 km above Earth.
How can it get so cold? What stops heat getting to Vostok?