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.
Allyene – not in ‘heat is the net transfer of energy from hot to cold and cold to hot’ , and, statistically speaking or not, see Joel’s post re amount. Without giving a mechanism to stop it then statistically cold can takeover being the dominant source of heat if there’s enough of it. My cup of coffee in the Arctic should boil away.
Dave Springer says:
This was disproven by expermental physicist John Tyndall over 150 years ago. Back radiation from gases that absorb IR is quite real. Suggest you read the original work here (it’s free):
http://www.archive.org/details/heatconsideredas00tyndrich
Al Gore is always quoting Tyndall’s work in 1860 as the ‘final word’, the science is settled end of discussion its all been nailed by the great Irish bogtrotter.
Folkerts:
“It’s like someone who played a little HS football thinking he could coach in the NFL.
It’s like someone who plays video games thinking they could really fly a plane.
It’s like someone who took a first aid course thinking they are a doctor.
Sure, once or twice per game, a fan might make a better call than the coach, but day-in and day-out, my money is on the professional. It takes a pretty big ego to think that freshman-level musings are somehow new or unknown to practicing scientists and teachers.”
LOL. And just HOW are you going to reconcile these thoughts with the FACT that the whole CAGW “theory” has now been exposed as a complete scam?
I think most truck drivers probably have a better nose for reality than most climate scientists and politicians.
I think IAmDigitap has summed up the problem neatly, (/#comment-664758 May20 8:13 pm). No one who does and understands what it is they does in the applied sciences can believe any of the reasoning from the AGWScience as to how things work.
Perhaps it’s a problem of theoretical v applied, or rather, the particular theoretical we have now who think they can change the 2nd Law to fit their musings or call Light energies thermal and keep a straight face, while of course still letting the practical bods do the actual adjustments necessary, such as in the proliferation of ‘ideal’ laws, to make things work, because they know why things work.
An amusing example here: http://www.phschool.com/science/science_news/articles/hot_crystal.html
Right or wrong will come out in the testing.
Ah, Steve…
“I read it last week when you first posted the link. The article points out that a blackbody model for the moon that does not take into account the specific heat capacity of the moon generates a certain amount of error in predicting the maximum and minimum temperatures. Unfortunately the article doesn’t then explain that, once the heat capacity is known, the correct heat capacity can be plugged back into the models to generate the correct temperatures. It wasn’t a surprising problem for the Apollo mission, considering they hadn’t been to the moon yet. We know the heat capacity of the surface of the earth because we’ve been here for a while.”
So, it looks like you read the part about the moon. Now keep on reading for the most important parts of the article. The widely cited “blackbody temperature of Earth,” -18 C is the temperature that a satellite would “see.” It is the radiation at about 5 km above the surface–the altitude where more radiation goes up than goes down. BUT, because of the lapse rate, that means that the surface is much warmer. In fact it’s about 33 C warmer, a warmth that is attributed to a greenhouse effect. However, the laplse rate has ABSOLUTELY NOTHING to do with greenhouse effects, being dependent upon only the heat capacity of the air (Cp) and gravity (g).
Thus, one does not need any greenhouse effect to explain the warmer surface (and the 390 watts shown in the K&T cartoon).
The linked article shows that this same effect occurs on all planetoids with atmospheres, irregardless of how concentrated the greenhouse gases are.
It appears that the greenhouse effect in the atmosphere does not work for the same reason a greenhouse doesn’t work when all the windows are open–convection.
Then you state:
“It’s assuming an average temperature, from the temperature record. Which could be wrong. That doesn’t negate the ability of CO2 to absorb more IR radiation than N2. There is no getting around a greenhouse effect. Ira’s post seeks to quell this issue so that we can get to the matter of quantifying the response of the climate for a given increase in CO2.”
No, the diagram is trying to show how the greenhouse effect adds the 33 using radiation. What is ironic, to the point of being weird, is that the diagram is probably quite correct; the surface is at 15 C, the upward radiation is 390 wm-2, the backradiation is as shown, etc. But as I said above, it has to START with the 390 wm-2, and there is no way that can be somehow be “created” with backradiation.
So we will never get to the matter of quantifying the response (temperaturewise) of the climate to CO2, since there ain’t one. Which the real world data (surface temperature, SST, radiosonde, etc.) has now shown, anyway.
Robert Stevenson, I agree completely with your sentences I have highlighted in bold.
However, even though I am quite willing to assume that LWIR is absorbed to extinction in the first 120 meters (or some small number of tens of meters), it is quote easy to show that your statement “there is nothing left for the CO2 bands to absorb” is incorrect, as I pointed out to Wayne earlier (here: http://wattsupwiththat.com/2011/05/07/visualizing-the-greenhouse-effect-light-and-heat/#comment-661881).
Here is a short version:
1) ~15μm LWIR photons emtted by the Earth pass into the lower 120 meters of Atmosphere and all are absorbed by CO2 (and H2O) molecules. So, the original (first generation) photons from the Earth are absorbed to extinction, as you correctly claim. We are in total agreement so far.
2) The CO2 (and H2O) molecules that absorbed those first-generation photons are energized. They re-emit that energy in random directions, as second-generation photons. (They also collide with other air molecules and cause them to become energized and emit photons, but, for simplicity we’ll ignore that part of the process.)
3) About 1/2of those second-generation photons will be emitted in an upwards direction, and the other 1/2 downwards towards the Earth Surface. OK so far?
4) The second-generation photons going upwards will be absorbed by CO2 (and H2O) molecules that are in the layer of air above the 120 meter line and they will be absorbed to extinction in about another 120 meters or so.
5) The CO2 (and H2O) molecules in the layer from 120 to 240 or so will become energized. They re-emit that energy in random directions, as third-generation photons. About half will go up and the other half down where they will enter the lower 120 meter layer.
6) The downward-going third-generation photons will be absorbed to extinction in the lower 120 meter layer.
7) The CO2 (and H2O) molecules in the lower 120 meter layer will become energized by the third-generation photons and will emit that energy as fourth-generation photons. About half will go up and the other half down where they will strike the Surface and be absorbed.
8) If you consider this process with multiple 120 meter (or so) layers (and, for now, ignoring convection and so on) you should notice that the higher-generation photons will cause about 1/4 + 1/8 + 1/16 and so on photons to strike and be absorbed by the Earth, in addition to the 1/2 downward photons in step (3).
Thus, it is clear that, although your statement about the first-genration photons being absorbed to extinction in 120 meters (or so) is absolutely correct, the higher-generation photons are responsible for some considerable additional downwelling radiation towards the Surface. Thus, it is not correct to state that “there is nothing left for the CO2 bands [above 120 meters] to absorb”. They do absorb and re-emit exponentially-decreasing amounts of photon, and, since re-emission is about half upwards and half downwards, some of those re-emitted (and re-emitted, and re-emitted, …) photons will add to the downwelling radiation and therefore contribute to the Atmospheric “greenhouse effect”.
jae says: “The widely cited “blackbody temperature of Earth,” -18 C is the temperature that a satellite would “see.” It is the radiation at about 5 km above the surface–the altitude where more radiation goes up than goes down. BUT, because of the lapse rate, that means that the surface is much warmer. In fact it’s about 33 C warmer, a warmth that is attributed to a greenhouse effect. However, the laplse rate has ABSOLUTELY NOTHING to do with greenhouse effects, being dependent upon only the heat capacity of the air (Cp) and gravity (g).”
You are reading an explanation into the article that isn’t in the article. The word “lapse rate” doesn’t appear once. The article attributes a lack of accounting for the heat capacity of the mass of the atmosphere to the higher than expected temperatures. You are confusing the explanation in this article with the one given in the “No Greenhouse Effect on Venus” article, which you also cited.
No matter, the lapse rate does not negate the ability of CO2 to absorb more infrared radiation than N2. Assuming the lapse rate stays the same, exchanging CO2 for N2 will raise that 5 km altitude higher (as the temperature at the surface goes up). Removing all CO2 from the atmosphere will bring that 5 km altitude lower (as the temperature of the surface goes down). The question should be “by how many meters per unit change in CO2?”.
jae, your statement that the
lapse rate has ABSOLUTELY NOTHING to do with greenhouse effects, being dependent upon only the heat capacity of the air (Cp) and gravity (g).
is absolutely wrong. The “dry adiabatic lapse rate” is controlled by the “the heat capacity of the air (Cp) and gravity (g)“, but the actual measured lapse rate is controlled by greenhouse emissions (among other things). Without greenhouse gases, the atmosphere would actually have the same temperature at all altitudes. It is the greenhouse gases that cause the lower atmosphere to cool. It is also the greenhouse gases that help produce the morning temperature inversions where the atmosphere is much warmer than the surface.
Steve continues:
“You are reading an explanation into the article that isn’t in the article. The word “lapse rate” doesn’t appear once. The article attributes a lack of accounting for the heat capacity of the mass of the atmosphere to the higher than expected temperatures. You are confusing the explanation in this article with the one given in the “No Greenhouse Effect on Venus” article, which you also cited.”
It’s actually the “same difference,” since the lapse rate depends on heat capacity and gravity (lapse rate = g/Cp). And I note that you are not refuting either article, just restating the “consensus ho-hum.” Hmmm, is that because you cannot?
And you state:
“No matter, the lapse rate does not negate the ability of CO2 to absorb more infrared radiation than N2. Assuming the lapse rate stays the same, exchanging CO2 for N2 will raise that 5 km altitude higher (as the temperature at the surface goes up). Removing all CO2 from the atmosphere will bring that 5 km altitude lower (as the temperature of the surface goes down). The question should be “by how many meters per unit change in CO2?”.
Yeah, I know the theory, since I hear it from even many of the “skeptics.” Problem is, there is absolutely no empirical support for it, so it is dying a natural death. The effects you mention, as well as many others, are just not being observed. No hot spot in the upper tropical atmosphere, as all models predict. Not even a rise in surface temperature or sea surface temperature over the last 10-15 years. To the contrary, it seems likely we will see a notable cooling for the next few years, according to many climate scientists. Ice core records show that increases in CO2 LAG warming by about 800 years. If the GHE from OCO exists, it must be a very weak force, indeed!
FWIW, I doubt that I will ever win this battle, but I’ll wage it until someone shows me wrong with EMPIRICAL EVIDENCE. Radiation cartoons and climate models don’t count.
Ira, bless you, for you seem to have learned not one single thing in these some 800 comment. Here you are speaking again of ½ up and ½ down and that is only correct in a one dimensional world.
We live in a three dimensional world. I had to apologize to Dr. Miskolczi for stepping on his toes on that very point. the “light-bulb” that went off in my head, he had already covered that in his last paper.
It is ideally 1/6th up and 1/6th down and you have to take the components of the 3d vectors, six possible ways to move randomly in a 3d world, viewed best as degrees of freedoms. Much the same as seen when visualizing how gases create pressure with tree degrees of freedom. See the ‘3’ in the pressure equations.
That also means that 4/6th or 2/3rd of a photon random movement will always be horizontal or tangent to the surface, and, since any atmosphere is reasonably viewed as a homogeneous horizontally, these components do absolutely nothing except maintain a constant temperature. That horizontal component of any photons random emission plus the 1/6th downward component or when totaled is 5/6th and this IS THE GREENHOUSE EFFECT. It is geometric in nature and has nothing to do with radiation except that radiation and conduction transfer energy (see: equipartition across possible states).
A photon, better just a certain amount of energy, that just jumps around in the atmosphere does absolutely but to maintain equilibrium, radiative, temperature, pressure and density.
I keep saying please, but will say it again, please, even if you don’t like certain points in his papers, read them. The atmospheric physics in the equations are correct for any atmosphere, those part of his papers are not contested. Enlighten yourself before this thread ends and please retract that mumble-jumble you just fed to Robert Stevenson.
Wayne says:
“Ira, bless you, for you seem to have learned not one single thing in these some 800 comment. ”
Oh, Wayne, how can you possibly question the SELF-APPOINTED EXPERT WHO IS THE HOST? LOL! You need to keep in mind that the host has a PhD, which is loudly proclaimed and which must mean something….
jae says: “It’s actually the “same difference,” since the lapse rate depends on heat capacity and gravity (lapse rate = g/Cp).”
The “Greenhouse Gas on the Moon” article proposes that the blackbody models that explain the GHE on the earth don’t correctly account for heat capacity at all, either rocks, oceans or atmosphere. That’s why the exposition begins with the NASA error on the moon (with no appreciable atmosphere). The article disputes using blackbody modeling, in total, for calculating planetary surface temperatures.
“And I note that you are not refuting either article, just restating the “consensus ho-hum.” Hmmm, is that because you cannot?”
I stated that the NASA error was easily adjusted for once the correct heat capacity was known. Blackbody modeling can be adjusted. That directly refutes the main premise of the article. I did refute the article, you didn’t notice.
I also refuted the notion that the lapse rate “explains” the temperature at the surface. No, the lapse rate can be used to calculate the temperature at the surface after the altitude and temperature of the tropopause is known. The lapse rate does not explain why the tropopause is at a specific altitude. It is the ability of the atmosphere to absorb and emit energy that explains the temperature of the atmosphere.
“Problem is, there is absolutely no empirical support for it, so it is dying a natural death.”
Gases like H2O and N2 absorb more infrared than N2. A 15 degree surface beneath a 9 degree gas will cool slower than a 15 degree surface beneath a 7 degree gas. This is empirical support for the GHE that cannot be refuted by hand waving about bad models getting this or that wrong about climate predictions.
What can be refuted is that (shocker) the models are correct about a given change for a given increase in CO2. But there will be a change, and it will be due to more energy within the earth atmosphere than before. Energy can be expressed as heat, but it can also be expressed as work.
“Not even a rise in surface temperature or sea surface temperature over the last 10-15 years. To the contrary, it seems likely we will see a notable cooling for the next few years, according to many climate scientists.”
We see cooling every night of every day, every winter of every season. The GHE does not trump solar forcing, it supplements it.
“Ice core records show that increases in CO2 LAG warming by about 800 years.”
Ice age cycles are due to solar forcing cycles, no doubt. It is to be expected that as the oceans warm the CO2 content of the atmosphere increases.
“If the GHE from OCO exists, it must be a very weak force, indeed!”
At present concentrations, I am in the “weak force” camp. Well, weak compared to the standard models. I believe that most of the 20th century warming was due to natural, solar variations that are not entirely understood.
As a so called greenhouse gas, CO2 pales into insignificance when compared with water vapour. To be as effective as water vapour in absorbing land LWIR the concentration of CO2 would need to increase 900 times ie from its present 380ppm to 42000ppm. Yet governments in the EU, US, Canada etc insist on spending huge sums to reduce CO2 emissions and in the process closing down a large part of our almost wholly CO2-dependent economies. This is a ludicrous and futile waste of resources.
Steve says:
“If the GHE from OCO exists, it must be a very weak force, indeed!”
At present concentrations, I am in the “weak force” camp. Well, weak compared to the standard models. I believe that most of the 20th century warming was due to natural, solar variations that are not entirely understood.
This is entirely true Steve and I would add that as a so called greenhouse gas, CO2 is very weak and pales into insignificance when compared with water vapour. To be as effective as water vapour in absorbing land LWIR the concentration of CO2 would need to increase 900 times ie from its present 380ppm to 42000ppm. Yet governments in the EU, US, Canada etc insist on spending huge sums to reduce CO2 emissions and in the process closing down a large part of our almost wholly CO2-dependent economies. This is a ludicrous and futile waste of resources.
R Stevenson says:
May 22, 2011 at 6:23 am
As a so called greenhouse gas, CO2 pales into insignificance when compared with water vapour. To be as effective as water vapour in absorbing land LWIR the concentration of CO2 would need to increase 900 times ie from its present 380ppm to 42000ppm.
Not true, what do you base that on?
jae says:
May 21, 2011 at 8:43 pm
Wayne says:
“Ira, bless you, for you seem to have learned not one single thing in these some 800 comment. ”
Oh, Wayne, how can you possibly question the SELF-APPOINTED EXPERT WHO IS THE HOST? LOL! You need to keep in mind that the host has a PhD, which is loudly proclaimed and which must mean something….
Patronise as much as you like but Ira talks a lot more sense than either of you two.
Heat is transferred by conduction, convection and radiation and heat losses are often computed using a combined convection and radiation coefficient hc + hr. Heat loss:
Q = (hc+hr)*A*deltaT
Heat from the land surface is transferred by conduction through a boundary layer and also by radiation to the immediate atmosphere. Considerable heat is then transferred by natural convection from the lower reaches to the upper reaches clearly radiating in three dimensions as well before finally leaving for space. The transfer of heat from the surface is not just dependent on the mechanism of radiation and re-radiation to cool the heated thin (120m) boundary layer as so many contributors have pointed out.
Phil says:
R Stevenson says:
May 22, 2011 at 6:23 am
‘As a so called greenhouse gas, CO2 pales into insignificance when compared with water vapour. To be as effective as water vapour in absorbing land LWIR the concentration of CO2 would need to increase 900 times ie from its present 380ppm to 42000ppm.’
Not true, what do you base that on?
This is based on the increase in CO2 concentration needed to make the gas as effective as water vapour in absorbing LWIR ie based on equivalence:
For a product term PwL of 0.0231*(4*3.281) ft.atm a water vapour absorptivity of o.2 absorbs 84Wm-2 of land LWIR in 4m.
The equivalent for CO2 requires a product term PcL of 0.0004*900*(4*3.281) ft.atm giving a CO2 absorptivity of 0.2 absorbing 84Wm-2 of land LWIR in 4m.
NB a partial pressure of o.ooo4*900 atm is 380ppm *900.
Phil says:
‘ False because you’re wrong about where in the energy spectrum CO2 absorbs.’
It is apparent from whatyou say that you are not familiar with ‘Wien’s law of displacement’ judging by your comment that the spectral band from 12 to 18 microns includes the peak emission of the Earth’s emission spectrum.
Recourse to Wien’s law shows that a wavelength of maximal emission λ_max of 15μm yields a temperature of minus 80C; whilst 15C gives a maximal emission λ_max of 10μm.
CO2 absorbs infrared emissions from the Earth’s surface only minimally in the range 7 to 13μm and it is within this range where the greatest proportion of radiation emitted by the Earth is found. This range is called ‘open radiation window’, because it is here that the least amount of absorption by water vapour and CO2 takes place
Ira, I apologize. didn’t mean to use to strong of words and your example of the integration using 1/4 + 1/8 + 1/16 and so on … was basically correct, but it has become apparent that this only applies to the vertical movement, the vertical axis of radiation transfer, where you also have two more horizontal axises involved in three dimensions. So, the 390 Wm-2 up and down should always be spoken properly as 130 Wm-2 going up and down just as you described it. I just thought you should have pointed out that only one-third of the radiation participates in this vertical dance. That was my only point. I’ll try to not get so emotional when seeing misleading expalnations are made.
Five or six of your posts ago I also thought it was exactly as you were explaining it above, explaining that this happens to all radiative movement from the surface and in the lower atmosphere, but I have learned that is not so
R Stevenson says:
In other words, it is based on extremely naive approximations and yet you expect us to believe it over actual line-by-line radiative calculations?!? The magnitude of the effect produced by CO2 is well-understood and accepted by even skeptical scientists like Richard Lindzen and Roy Spencer.
Stop talking nonsense.
Wayne, Robert Stevenson and others have made the point that, given current concentrations of CO2 and H2O and other so-called “greenhouse gases”, the first-generation photons from the Surface up into the Atmosphere are absorbed to extinction in 120 meters or some other relatively small distance compared to the total height of the Atmosphere. I accept that.
I have claimed that, despite the 120 meter extinction, the layers above the 120 meter distance also contribute to the downwelling radiation that ultimately reaches the Surface such that, if about 1/2 are due to the first-generation photons being absorbed and re-emitted, then about 1/4, 1/8, 1/16 and so on are due to higher-generation photons due to emission and absorption, and re-emisson, and so on and on.
An objection was raised that, since a re-emitted photon may go in any direction, we might better consider that it may go not only in the two vertical directions (up/down) but also in the four horizontal ones (east/west, or north/south) such that only about 1/6th of the first-generation photons cause downwelling radiation, and so on for the remaining layers.
Well, there is something to that claim. Certainly, a photon re-emitted horizontally will not reach the Surface. On the other hand, there are only two exits from the Atmosphere for radiative energy, 1) out the Top of the Atmosphere (TOA) to Space and 2) out the Bottom of the Atmosphere (BOA) to the Surface. Thus, the second- and third- and higher generation photons will engage in energy transactions that ultimately result in more than half the upwelling energy from the Surface to the Atmosphere ultimately coming out the BOA and back to the Surface.
I am not going to insist on the 1/2 + 1/4 + 1/8 + 1/16 calculation because it is most likely an over-estimate. On the other hand, based on measurements (for example the Perry curves in this posting as well as others in his book), I am quite certain that a substantial portion of the LWIR energy emitted from the Surface ultimately, after a number of absorption and re-emission transactions, does make its way back down and that some of that downwelling LWIR is due to layers above the initial, first-generation extinction level.
Steve continues with more arm waving:
“I also refuted the notion that the lapse rate “explains” the temperature at the surface. No, the lapse rate can be used to calculate the temperature at the surface after the altitude and temperature of the tropopause is known. The lapse rate does not explain why the tropopause is at a specific altitude. It is the ability of the atmosphere to absorb and emit energy that explains the temperature of the atmosphere. ”
LOL, you refuted nothing, you just waved your arms AGAIN (do you know the diff?). It seems that you don’t even understand my comments or the article I linked! Please explain why all of the planets with atmospheres (including Earth) have a surface temperature that is much higher than their blackbody temperatures. Is it the greenhouse effect, or a more simple physical explanation, like the lapse rate and pV=RT?
I don’t think that you radiation freaks truly understand Local Thermodynamic Equilibrium. You seem to simply ignore heat capacity and thermalization–and prefer to look at radiation, in vacuuo. That is simplistic, to say the least.
It boggles my mind that actual physicists and other scients are not noticing the misleading crap portrayed in the K&T radiation cartoon. But then it took me about 5 years to finally discover the problem, so maybe there is hope for the others, too. While all the numbers in the cartoon may well be close to reality, it is interpreted (probably even by the authors) as demonstrating that a magic “greenhouse effect” keeps Mother Earth at an average temperature of 15 C, which would irradiate at a rate of 390 Wm-2. The cartoon only works IF the surface is at 15 C due to factors OTHER THAN the GHE (which Siddons, et. al. have adequately explained). Most people looking at that cartoon will be led to believe that the 324 wm-2 “backradiation” is SUSTAINING the 390 wm-2 surface radiation by ADDING energy to the surface. THAT, folks, is pure baloney, because it is suggesting that a cold atmosphere (about 5C average) can warm a warmer surface which is really, really bad physics (yeah, yeah, there are still some folks out there that believe that, but they will eventually learn….). The diagram is correct ONLY if the surface is maintained at 15 C by phenomenon other than some impossible backradiation magic. Which, of course, shows that the GHE theory is nonsense.
Don’t know how to express this more clearly….
The GHG theory is baloney. No wonder it cannot be demonstrated empirically.
Ira Glickstein, PhD says:
May 22, 2011 at 6:41 pm
I have claimed that, despite the above fact, the layers above the 120 meter distance also contribute to the downwelling radiation that ultimately reaches the Surface such that, if about 1/2 are due to the first
I do agree with you on most points. If talking of absorption in a given length, that never means all is absorbed in that distance. It is a logarithmic function. it just means most is absorbed in that length and the ratio is normally termed as the mean free path and that seems to be 1-1/e portion or 63.2% is absorbed, 36.8% being transmitted, each mean free path length. For the next length 63% of what is left from the first length will be absorbed, and so on. Just take 1−0.368^lengths to get the statistical chance of that happening, in any direction. This is not the same as total extinction.
So radiation has a chance if directed downward to reach the surface no matter how high in the atmosphere it is emitted, it’s just that the chance fades quickly as you count lengths or shells. Same applies no matter which direction you are speaking of. That is why it is so easy to be misconstrued and sure hope it hasn’t been done to you.
Probably numerically a photon ever has a chance to pass from the surface of the sun down to the core without absorption but you probably would require arbitrary precision math to calculate the answer, for 10^327 might not be enough exponent.
The only problem as you keep speaking of this photon logic is the temperature lower is always warmer so the reverse always trumps and will have even more flowing upward. Many find it easier to accept that SB with a delta T properly used makes tracing individual photons rather irrelevant and of course so much easier for all to follow.
I hasten to add that the infrared active gases DO play an important role in the atmosphere: they facilitate rapid thermalization and radiation to space. It is possible that LTE would not exist without a certain amount of those “GHE gases.” However, it appears that only a certain amount of these gases is necessary to effect thermalization and LTE. So, unfortunately, we cannot test the concept of an atmosphere without “GHEs,” since we have none to observe. Even Jupiter, with its massive predominance of Helium and Hydrogen contain plenty of IR-active gases to facilitate LTE through thermalization reactions (collisions).
So, the “what if the atmosphere had no GHEs and contained only N2” concept cannot be addressed with empirical data. Still mere conjecture…