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.
Tim: I fear that you are just confusing folks (of course, it is not intentional?):
“Or think of it this way. At some point in time, an average 1 m^2 column of air will have some amount of thermal energy U (~ 30,000,000 J). During the next second, that column of air will
* give 324 J to the surface via thermal EM radiation
* give 195 J to outer space via thermal EM radiation
* get 350 J from the surface via thermal EM radiation
* get 78 J from the surface via evaporation/condensation
* get 24 J from the surface via convection
* get 67 J from the sun via sunlight
30,000,000 J – 324 J – 195 J+ 350 J + 78 J + 24 J + 67 J = 30,000,00o J”
WHY DO YOU DO THIS?
You are simply “reading” the K&T diagram, using joules, instead of watts. Doesn’t help most folks, so don’t know why you do this? Probably confuses many. Is this your goal?
Sorry, K&T is still just a nice theory, without empirical evidence. So, still no real science, so far. Just an old cartoon that attempts to explain the GHE, but which has NO empirical support that I have seen (as I am sure you know, there can be NO science without empirical evidence. And the CAGW folks have exactly NONE that I know of, to date).
But some questions about the details:
Only 24 J for convection? And only 78 joules for evaporation? (which you get back in the upper atmosphere, but that’s another subject). Come on, man! These are probably the major places where the BS is hiding.
\
A “photon-warmed” OCO molecule instantly rises and imparts energy with other molecules in the air, which then also rise. I think that climate scientists vastly underestimate the convection. Otherwise, we should be seeing a change in the lapse rate as OCO concentrations increase. Don’t think we see this.
The “wet areas” on Earth NEVER see higher temperatures, because of the effects of water. See Willis Eschenbach’s articles on this. So the “average 78 joules for evaporation” meme is complete junk science.
IF your analysis (theory) is correct, THEN we should be seeing SOME measurable effects of the additional OCO. We are NOT seeing ANY effects of which I’m aware. In fact, we are seeing things going the “wrong” way, despite NASA’s disgusting corrupt attempts at revising the data history. Therefore, we must have some reservations about the adequacy of the construct.
Amen, have a good day.
richard verney says:
I told you that this was pernicious nonsense the last time you made the statement and it doesn’t get to be less pernicious upon repetition. That is like saying that a beaver dam can’t create a pond because all it does is merely delay the flow of water.
The point is that the temperature of the earth’s surface is determined by what is needed to achieve a balance between the power it receives from the sun and the power the earth system radiates back out into space. When you reduce the flow of heat back out into space for a given surface temperature, the surface temperature must increase until the flow of heat back out into space once again equals the amount of heat being received from the sun.
This is not all that complicated to understand if one actually wants to understand science rather than to try to make the science fit one’s ideological preconceptions.
Alleyne says:
May 12, 2011 at 3:44 pm
Phil. said on Visualizing the “Greenhouse Effect” – Light and Heat
May 11, 2011 at 9:12 pm
“Strictly the equation should be:
q =(ε σ Th^4 – a σ Tc^4) Ac
however following Kirchoff’s Law a=ε
so:
q = ε σ (Th^4 – Tc^4) Ac”
As I understand it Kirchoff’s Law states αλ = ελ, but only at thermal equilibrium and does not require that the absorbtivity and emissivity of the surroundings be the same as that of the emitting object, otherwise what you are suggesting is that everything has the same absortivity and emissivity and αλ = ελ = a constant.
‘ε’ refers to the emissivity of the hot object, ‘a’ refers to the absorptivity of the hot object, it is nowhere implied that “the absorbtivity and emissivity of the surroundings be the same as that of the emitting object”
jae says:
You just make this stuff up, don’t you? The K&T diagram is based on empirical data, from satellite measurements mainly.
You do realize that once you have a reasonable estimate for the amount of precipitation that falls over the earth then it is trivial to compute how much heat is transported by the evaporation / condensation mechanism? I almost had my students do it as an exercise in an introductory physics course.
Again…You are just making stuff up. The models do predict a change in lapse rate…They predict that, overall, the lapse rate will DECREASE (mainly because of the decrease in lapse rate in the tropics…You know, the so-called “hot spot” that in a post above you claimed is missing). That’s a negative feedback in all the climate models.
If the models are underestimating convection, that would mean that the lapse rate should be decreasing even more…i.e., that the “hot spot” should be larger than the models predict. Your view of the view of the science is not even internally consistent.
jae says: May 13, 2011 at 7:07 pm
“Doesn’t help most folks, so don’t know why you do this? Probably confuses many. Is this your goal?”
There is always a possibility for being too simplistic for some and too complex for others. This assumed people know about watts and joules and heat capacity. If they don’t they can skip the analysis (but then they should also skip trying to draw scientific conclusions about the topic as well).
The point is that there is LOTS of energy around. Being able to gain or lose a few hundred joules from the atmosphere is not that amazing. In any given second, we do not need too supply all the 330 J per square meter for “backradiation” from the 168 J coming from the sun.
“Sorry, K&T is still just a nice theory, without empirical evidence. “
What sort of empirical evidence do you want? Every factor on the energy balance can be measured to fair accuracy, can be modeled to fair accuracy and can be calculated from first principles to fair accuracy.
I will admit that the exact values are not something that can be calculated/presented in a forum like this. I will admit that estimating global averages can be a challenge. I would not be surprised if some of the number are off a little. I would not be surprised if some of the numbers change significantly from year to year (for example, cloud cover & albedo). And small difference can make large differences in the overall climate.
But the general scheme seems pretty solid (keeping in mind that the energy balance diagram is a major simplification).
“Only 24 J for convection? And only 78 joules for evaporation? (which you get back in the upper atmosphere, but that’s another subject). Come on, man! “
Yes, I agree there could be significant uncertainty in the numbers. If you truly think there are major problems, then write them up and submit them to a scientific journal. Or submit them here.
The 78 W/m^2 for evaporation can be estimated pretty well from global precipitation estimates. I did it once — I challenge you to try it once.
If you just “feel” there is a problem, then I really have nothing I can say to you.
“A “photon-warmed” OCO molecule instantly rises…”
Why do you say this? Rising hot gas is a result of the bulk expansion of the gas making it less dense. A single hot molecule would know rise AFAIK.
Your question about changing lapse rate would be interesting to explore further. I don’t know if it has changed or how it should change with more CO2.
The “wet areas” on Earth NEVER see higher temperatures, because of the effects of water. See Willis Eschenbach’s articles on this. So the “average 78 joules for evaporation” meme is complete junk science.
I am completely confused by what you think is junk science here. Perhaps you could explain?
IF your analysis (theory) is correct, THEN we should be seeing SOME measurable effects of the additional OCO. We are NOT seeing ANY effects of which I’m aware.
Even most skeptical scientists seem to agree there is SOME sensitivity of temperature to CO2 and that at least SOME of the increase over the last century should be attributed to CO2. I am not in a position to know which estimates are most accurate, or how much of the warming would have occurred without CO2 increases.
See
http://wattsupwiththat.com/2011/04/26/the-climate-sensitivity-and-the-surface-temperature-record-question-answers-from-major-players/
for example for more info.
Alleyne: At this point, both Tim and I have patiently explained to you how the greenhouse effect does not violate the 2nd Law.
I’ll also point out that both of the major physics textbooks that we use in our introductory physics courses (one for the calculus-based course and one for the algebra-based course), popular texts used by hundreds…if not thousands…of colleges and universities to teach physics, contain discussions of the greenhouse effect and global warming. Don’t you think there would be an uproar in the physics community if the textbooks were teaching about things that violate the 2nd Law?
You have absolutely no credible shred of an argument left to believe that the greenhouse effect violates the 2nd Law. It is ludicrous to continue to make this argument…and, if you can’t understand why it doesn’t from our explanations, then you need to help us understand what your confusions are.
richard verney says:
May 12, 2011 at 8:39 pm
8. That Trenberth’s energy budget is wrong. It defies commonsence that DWLIR exceeds incoming solar energy given that the DWLIR can have been created only by the incoming solar energy (and energy radiated/released by the core which latter energy is said to be miniscule such that this can be ignored).
Well you know what they say about ‘commonsense’, it’s neither common nor sensible!
Try this:
You have a container into which water is flowing at 100l/min and flowing out through an overflow pipe, clearly outflow equals inflow at steady state. Now recycle 60% of that outflow back to the input, what’s the new outflow?
Answer: 250, so the recycle flow is greater than inflow, does this defy commonsense?
Tim Folkerts says:
“Even most skeptical scientists seem to agree there is SOME sensitivity of temperature to CO2 and that at least SOME of the increase over the last century should be attributed to CO2. I am not in a position to know which estimates are most accurate, or how much of the warming would have occurred without CO2 increases.”
Thank you for that. It is also my own view. CO2 has caused some warming. But it is insignificant because it is too insignificant to measure. The null hypothesis of natural climate variability has never been falsified, therefore we must assume that what we are observing is mostly natural climate cycles.
Smokey says:
That is because such a hypothesis is unfalsifiably vague. You guys often complain (without justification) that AGW is not falsifiable when in fact there are lots of tests that it has passed and lots more tests that it will continue to have to pass in the future. However, your null hypothesis really is unfalsifiable. If the global temperature shot up by 10 K in one year, you could claim it was just a natural climate cycle caused by some unspecified mechanism.
jae,
I’m going to hand you the key if have the mind to see it and recognize it, I’ll call it wayne’s “Natural Geometric Greenhouse Effect”. It only strictly applies to atmospheres with thick enough GHG’s to make it opaque at relative short distances.
Take Tim’s numbers from KT97’s diagram, just the (78 + 24) + 67 to get 169, but one of those three numbers are off by one for the only possible number is 170 Wm-2, will explain the +1 later. But we see 235 being ejected at the TOA, we are missing 65 Wm-2.
Here’s the key to this entire discussion on GHE. Take the 65 * 6 (the six sides of a cube), that equals 390 Wm-2 or the maximum possible power that the surface can ever create since it is at 288 K. But radiation from the bottom of the one meter cube cannot pass net energy to the surface from whence it came, an object cannot be affected by it’s own radiation. So forget the bottom of the six sides of that cube, no net energy can pass backwards downward.
Now concentrate on the four sides of that cube. Any radiation horizontally is totally cancelled by the homogeneous nature of our atmosphere, for ever plus there is an equal minus nearby (see Miskolczi’s papers for a better worded description). So forget energy moving through the four sides of that imaginary cube.
This is very close to the same logic of three degrees of freedom described in the derivation of the ideal gas laws and how we came to know how pressure of a gas with those 3 degrees of freedom manifests itself as pressure.
So, you are left with a maximum of 65 Wm-2 that can move and it is upward through the top of the cube.
Playback: 170 + 65 = 235 Wm-2 seen at the TOA.
Also: 390 * 5/6 = 325 Wm-2, what KT97 is colloquial calling “back radiation”. (a misnomer and once again off by one)
This one sixth’s of energy that can use the upward degree of freedom is an absolute maximum, more flux can never occur upward. The (1 – 1/6) or 5/6 is the lower limit of what is colloquial call “back radiation” must always be equal or more than this limit.
That’s it, it is all simple geometry and I will wait no longer for someone to figure it out. I have tried to hint all of the necessary connections in the past month’s but have yet to find anyone who can seem to think out of the box. It is now recorded.
See? The 169 Wm-2 above violates that principle, it must be 170 and TFK09 has it corrected. Miskolczi passes with flying colors. Their numbers though hard to extract are very close to each other. No surprise, all of the base numbers come from measurements.
It seems any atmosphere, even if the energy transfer might be slow and by conduction and convection, follows this same principle. So even a pure nitrogen atmosphere would have it’s “greenhouse effect”.
Also curious is this seems to place a lower limit on the optical thickness of any planetary atmosphere and it is:
–ln(1/6) = 1.791759469…. .
There you go fellows in science, disprove that, I can’t seem to do it.
I know I don’t write word pretty, please excuse.
Can you and anyone else who can fathom this help me to get others to see the
greenhouse IRlight?Joel Shore says:
May 13, 2011 at 9:41 pm
That is because such a hypothesis is unfalsifiably vague. You guys often complain (without justification) that AGW is not falsifiable when in fact there are lots of tests that it has passed and lots more tests that it will continue to have to pass in the future. However, your null hypothesis really is unfalsifiable. If the global temperature shot up by 10 K in one year, you could claim it was just a natural climate cycle caused by some unspecified mechanism.
============================
That is an absolutely stupid and asinine analysis.
You are arguing from the negative…or, at worse, from the absurd….so what you are saying is flawed to the core.
Nobody…absolutely nobody…is claiming the absurdities that you claim (10K in one year)…and that absurdness speaks for itself.
Chris
Norfolk, VA, USA
Joel Shore says:
May 13, 2011 at 8:54 pm
You have absolutely no credible shred of an argument left to believe that the greenhouse effect violates the 2nd Law. It is ludicrous to continue to make this argument…and, if you can’t understand why it doesn’t from our explanations, then you need to help us understand what your confusions are.
========================
Who is “OUR” in “our explanations”….and the “US” in “help us understand”?
Or you more than one person, Joel?
Or are you writing for a groupthink cluster? An amalgam? A super-individual?
Or are you using that tired and old scientific nomenclature of “we”?
Who is “we” and “us”?
Define it.
Chris
Norfolk, VA, USA
Errata, to correct paragraph above:
It seems any atmosphere, even if the energy transfer might be slow and by conduction
and convection, follows this same principle. So even a pure nitrogen atmosphere would have it’s “greenhouse effect”.Sorry, convection is one of the other two energy transfers that is singled out in KT97 diagram and is added in separately (24 Wm-2).
Dave Springer Says “G&T need to repeat the experiment with double-paned polyethylene”…….
You obviously did not read the second experiment which backs up the findings of RW Wood
Basically the project was to find if it made any sense to add Infra Red absorbers to polyethylene plastic for use in agricultural plastic greenhouses.
Polyethylene is IR transparent like the Rocksalt used in Woods Experiment.
The addition of IR absorbers to the plastic made it equivalent to “glass”
The results of the study show that( Page2 )
…”IR blocking films may occasionally raise night temperatures” (by less than 1.5C) “the trend does not seem to be consistent over time”
http://www.hort.cornell.edu/hightunnel/about/research/general/penn_state_plastic_study.pdf
You have also failed to come up with any evidence that radiative heating can produce significant effects in a volume the size of a large greenhouse
Now if you think that the “greenhouse theory” has any evidence that the radiative effects of CO2 and H2O can significantly heat a volume of air at STP please let us know.
Dave Springer says
The RW Wood real greenhsoue experiment (glass vs. rock salt) is bogus. The glass panes heat up when they absorb IR and lose it right away through conduction. The G&T experiment repeats the mistake. A kilometer’s thick layer of greenhouse gases doesn’t conduct very well at all, unlike a thin pane of glass or polyethelene.
Dave try this on the next sunny day.
Go to your car, the dashboard might be so hot that it is too hot to touch.
Touch the windows and you will find them quite cool.
So much for IR absorbers causing a large temperature rise.
For sceptics that think the IPCC “greenhouse effect” is bogus please note that none of the defenders has risen to the challenge of my yesterday post!!!!
Those advocates of the IPCC “greenhouse theory” should get real.
If the radiative effects of H2O and CO2 are supposed to “heat” the atmosphere to 33K higher than “it would otherwise be” then they need to show significant radiative heating in a volume of the atmosphere.
This they cannot do.
Instead they distort equations and say look “there’s the proof”.
If we went to the installer of our home central heating system with a complaint that it wasn’t working would we be satisfied with a couple of equations as an excuse.
Call the bluff of IPCC “greenhouse theory” advocates!
Ask for proof of radiative heating in a volume of the atmosphere.
They will be stumped!
The fact that the temperature profile of the troposphere can be derived from thermodynamics without reference to radiation sums it up.
A good place for the IPCC advocates to start would be the radiative heating of a space the size of a real greenhouse.
Lets get some real figures for say 30 cubic metres of air at STP on a KT average day.
Bryan, greenhouse gases don’t radiatively heat the atmosphere. They cause the surface to warm by shielding it from cooling it would otherwise have. The surface then causes the atmosphere to warm through convection. This is not a difficult concept.
As far as CO2 having any effect, up to about 50 W/m2 out of that 324 W/m2 back radiation is from the presence of CO2 molecules. This is measurable via the IR spectrum.
Jim D says “Bryan, greenhouse gases don’t radiatively heat the atmosphere. ”
I say …..That good we agree on that point.
This means my earlier post on R W Wood and the polytunnel experiments are vindicated
Jim D says “They cause the surface to warm by shielding it from cooling it would otherwise have.”
I say….In other words like the radiative component of insulation.
The Sun heats the surface should come next!
Jim D says “The surface then causes the atmosphere to warm through convection.”
I say …..Once a surface temperature is obtained the air next to the surface increases temperature by conduction and the laws of thermodynamics determine the temperature profile via the lapse rate.
The “greenhouse theory” seems to be missing or is it simply the radiative effect of CO2 and H2O in the IR.
I think there is not a lot of difference between our views.
Bryan, it is an insulating or shielding effect reducing cooling. The surface with more CO2 and H2O above it is warmer than otherwise. Convection distributes this extra warmth to the atmosphere. If you agree with this mechanism, you are agreeing with the basic ideas needed for AGW.
Jim D
There are many versions of the “greenhouse theory”.
A great number of them involve significant direct heating of the atmosphere.
My post was directed at the lack of evidence for such a view.
A much more sophisticated version of the “greenhouse theory” is mainly concerned with the radiation to space at the TOA.
The lapse rate going back from TOA to Earth surface gives the surface temperature.
This viewpoint is proposed by Leonard Weinstein and Nullius in Verba and seems quite plausable
Jim D says:
May 14, 2011 at 2:25 am
Bryan, greenhouse gases don’t radiatively heat the atmosphere. They cause the surface to warm by shielding it from cooling it would otherwise have. The surface then causes the atmosphere to warm through convection. This is not a difficult concept.
As far as CO2 having any effect, up to about 50 W/m2 out of that 324 W/m2 back radiation is from the presence of CO2 molecules. This is measurable via the IR spectrum.
All gases “shield” the surface from warming not just GHG’s. With 99 % N2 and O2 what part do you assign to them? Again with the back radiation. Show the temperture of the 324 W/m^2 using standard SB equation and the CO2 portion you attribute.
The TOA is the other part of the theory. CO2 reduces outgoing radiation at the top, but as explained above, the warming required to compensate it occurs via the surface warming and resulting convection through the troposphere. (Other things happen in the stratosphere). If anyone is saying adding CO2 directly warms the air, they would be wrong. I don’t think you would find any proper science sites or articles saying that.
Wayne says,
“Here’s the key to this entire discussion on GHE. Take the 65 * 6 (the six sides of a cube), that equals 390 Wm-2 or the maximum possible power that the surface can ever create since it is at 288 K. But radiation from the bottom of the one meter cube …”
A black body @ur momisugly 288 K emits 390 W/m^2 from each square meter. The phrase “one meter cube” implies a cube 1m x 1m x 1m. That cube has an area of 6 m^2. It can emit 390 W/m^2 from EACH side, not a total of 390 from all sides.
Assuming the above interpretation of your set-up is correct, either you need to
1) not divide by 6 and just use 390 W/m^2 for each side.
2) think if your cube as having an area of 1/6 m^2 on each side (length = 0.41 m, volume = 0.068 m^3).
I haven’t gone any farther through your explanation, because this needs to be addressed before any of the further analysis would make sense.
Joel Shore says:
“If the global temperature shot up by 10 K in one year, you could claim it was just a natural climate cycle caused by some unspecified mechanism.”
That is exactly right, unless you can specify the mechanism using the scientific method. The temperature has risen more than that in the past, well prior to the industrial revolution. Explain that mechanism. You crave fame, don’t you? Here’s your chance.
No wonder Trenberth wants to replace the climate null hypothesis with his own cherry-picked version. The real null hypothesis falsifies his alternative CAGW hypothesis, and he knows it. So like all climate charlatans, he wants to turn the scientific method on its head, and replace it with mumbo-jumbo.
Bryan says:
There are not different versions of the theory. There are just different degrees of sophistication in discussing what goes on in the atmosphere. At a low level of sophistication, just radiative effects are considered. In such models, there is naturally a lapse rate due to the fact that the atmosphere is heated mainly from below (because most of the sunlight makes it down to the earth’s surface or pretty close to the surface).
At a higher level of sophistication, convective effects…which lead to the actual lapse rate observed in the troposphere are considered. This is because the role of convection is basically to set a stability limit on the lapse rate that is given by the appropriate adiabatic lapse rate: Lapse rates higher than the adiabatic lapse rate lead to convection, which lowers the lapse rate back down to the adiabatic lapse rate.
Since you seem to be very concerned about using terminology correctly, I will point out that you are not using terminology very precisely here. Here is a more correct way to say things: When one considers convection, the best quantity to consider is the radiative balance at the top of the atmosphere. This is because you know that at the only heat flows between the atmosphere and space are radiative whereas within the atmosphere, especially the troposphere, there is a combination of different heat flow processes.
However, it is not really correct to say that the surface temperature is determined by the lapse rate from the top of the atmosphere. It is determined by the lapse rate from the effective radiating level, which is the level in the atmosphere from which, on average, the emitted radiation successfully escapes to space. By radiative balance, this level will have a temperature of ~255 K.