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.
Also one disputing back radiation must explain how many instruments that measure CO2 concentration manage to work. The basic design of these:
15um infrared light source -> beam splitter
one side of beam splitter -> sealed sample of air with known CO2 concentration -> IR photo transister
other side of beam splitter -> sample of ambient atmosphere -> IR photo transister
CO2 concentration is obtained by comparing the output of the two photo transisters.
Pretty much the same as Tyndall’s experimental setup only tweaked for one particular gas in a narrow range of partial pressures and put into a space the size of a thimble using modern technology.
Dave Springer says:
May 9, 2011 at 5:57 am
RJ says:
May 9, 2011 at 1:41 am
“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.”
“- If back radiation is so powerful and it is a heat source, why don’t we use it?”
Good questions. Although what about this free energy oven. Does it qualify?
We do use it all the time. One example is the smudge pots used to limit freeze damage in orange and avocado groves. The heat of the smoke from the smudge pots is inconsequential. The effect comes from the black carbon particles in the smoke which absorb upwelling IR from the ground and send a portion of it downwards and sideways. It works as an insulator. This is the same mechanism by which CO2 molecules insulate. Anyone who contests this is simply wrong and needs to take an introductory class in physics.
———–
Dave, you and I structurally disagree, but end at the same conclusion. To me, and I am sure it is correct by physics, is the effect comes from the black carbon particles in the smoke which absorb upwelling IR from the ground increases the temperature at that altitiude (10 m) and by SB using delta T (LBL if you want) between the surface and these particles decreases the upward flux making it warmer than it would have been without the carbon particles in this thin layer where the smoke is.
You do not need a special kind of “back radiation” that flows from cold to hot to explain it, it only scrambles minds away from what is actually happening. If you care about people’s minds at all, stop wording it like you just did. There is no special radiation called “back radiation” or “backward radiation”.
“It takes the oceans centuries if not millenia to absorb additional CO2 ”
This does not appear correct. CO2 absorbtion at the surface of the ocean is limited by the surface area. However, the surface area of H2O in the clouds is fantasitically greater than the surface of the ocean. In addition, the water in the clouds is cold, which increases its capacity to hold CO2.
This is where CO2 is absorbed and returned to the oceans. High in the couds, not at the ocean surface. Near the equator, where the oceans are warm this CO2 will be released back into the atmosphere as the rainwater warms. In higher lattitudes where the oceans are cold this CO2 will not be released. The rain water will mix with the cold seawater and sink to the bottom of the ocean, carrying the CO2 with it. The polar oceans should be less caustic, more Ph neutral as a result, as compared to the tropical oceans. Which has been reported.
Eventually this cold water will upwell in the tropics and release its CO2. Thus the CO2 being released during La Nina years was deposited at higher latitudes many years before. This accounts for the cause and effect lag observed between warming and CO2 release, which Al forgot to mention in his movie. This is strong evidence that temperature drives CO2. There is no similar observation that temperature lags CO2 in the paleo record, which is evidence that CO2 is not a driver of temperature.
ferd berple says:
May 9, 2011 at 8:11 am
“This extra heat is generated due to gravitational contraction – the planet is slowly shrinking in diameter. This way, by compressing by only a few millimeters every year, it can generate heat by increasing the pressure of its constituent gas.”
So Ferd, is it your assertion that the earth and venus are shrinking? I already explained to you that temperature only increases during the process of compression and the earth, Venus, and Mars (unlike Jupiter) aren’t shrinking.
What part of that don’t you understand?
Let me fix that for you by adding the explanation for the extra warmth on Jupiter from the article you quote:
Robert Stevenson says:
May 9, 2011 at 2:16 am
For current CO2 partial pressure or concentration I calculate a distance of 3600 m of traverse through the earth’s atmosphere by ‘IR radiation’ before the absorbable IR is ‘filtered out’ and reduced to zero.
—-
Robert, I come up with a close conclusion, not exact, but close. However, the 3600 m is more than 36 times that is given in other conversations I have read speaking of it’s absorption very near the surface. Do you have an average absorption coefficient you are using, or a mean optical thickness for CO2 from which that is calculated? Maybe Hottel specifies emissivity direct then what equation are you using to get the 3600 m extinction distance?
Wayne
If you want a bit deeper understanding of the radiative energy flow one needs to understand that all matter above absolute zero radiates and where there are two bodies at different temperatures there’s a net transfer of energy between the two from warmer to colder. The net transfer rate is all the matters for most practical concerns but at the deeper level the radiative transfer goes two ways. The warm object doesn’t stop the cold object from radiating so energy from the cold object is indeed reaching the warm object just as energy from the warm object reaches the colder one. It’s simply a matter of the colder object receiving more energy from the warmer than the warm object receives from the colder.
That doesn’t seem like proverbial rocket science to me but you may perhaps be right that it might as well be rocket science for many people.
Explain why the surface of venus, which only receives some 2.5% of the sun’s energy due to the albedo effect of the clouds can have a temperature of 500C.
Why do we use a figure of .7 when calculating the solar energy reaching the earth’s surface? If we did this on venus, then the surface temperature should be very cold indeed.
The missing 33K comes from the assumption that only 70% of the solar radiation is available at the surface due to albedo. This is an incorrect assumption, as is clearly demonstrated by the surface temperature of venus.
97.5% of the solar radiation never reaches the surface of venus, yet it has a high temperature. Thus, the .7 figure used when calculating solar radiation at the surface is refuted by observation.
Consider 240k / 288K. This is .8. Thus, the missing 33K may not be missing at all. It may simply result from our asusmption that albedo is .7. If albedo is not what we assume it to be, for reasons that are apparent on venus, then the problem is not where is the missing 33K, but rather why temperatures are not hotter than they are.
fully available in our assumption
Please re-read my main posting above where I say:
Got it?
So Ferd, is it your assertion that the earth and venus are shrinking?
Earth’s Shrinking Atmosphere Baffles Scientists
An increase in CO2 could be one reason why a layer of Earth’s upper atmosphere went through its biggest contraction in 43 years.
http://news.discovery.com/earth/earth-atmosphere-shrinking.html
“This extra heat is generated due to gravitational contraction – the planet is slowly shrinking in diameter.”
What is the mechanism by which this is possible? Why has the planet not reached equilibrium? Why does the temperature of all the planets and the sun increase towards the center? If the temperature increase is a result of continued shrinkage, then this should long ago have ended on some, if not all planets.
If this efect is unique to Jupiter, why is it so similar to what we see on other planets. Is is reasonable to suggest that a similar observation has unique and different causes on each different planet? Or is it more reasonable to assume that these unique explantions are a result of a lack of understanding. That they are modern day epicycles.
We see a surface temperature of venus that is higher than expected if we used the same methodology for albedo as used on earth. We see a surface temperature for Earth that is higher than expected if we use .7 for albedo, but NOT higher than expected if we use for example .8 or .9. We do not have to increase this above 1, so it is possible the missing 33k is simply due to an error in our understanding about how albedo actually works.
We see a surface temperature for Jupiter that is higher than we expect. This follow a similar pattern as with venus and earth. On each of the three planets science explains this by using 3 different methods, and proposes that these are unique to each planet.
That may well be, but occam tells us that this is not the likely explanation. Since a simpler explanation exists, namely that we are not properly accounding for the effects of clouds in our calculations. The observations of venus suggest that clouds do not block solar radiation the way we think, or the surface of venus would be much cooler. When we apply this logic to earth, the”missing” 33 K is no longer missing. It is simply a result of us using .7 when a more accurate number would be .8 or .9. Jupiter is also covered with clouds. It could well be that the missing 60K on jupiter is due to the poorly understood clouds, not due to continued shrinkage.
ferd berple says:
May 9, 2011 at 8:28 am
The effective surface area is greatly increased or diminished by wind driven waves. It’s also limited by how far out of equilibrium it is. It’s also limited by how fast the surface water mixes with the deeper water which is governed by both winds and convective currents. The amount of CO2 that can be held in water increases with depth as well. In deep ocean trenches CO2 has been observed in liquid droplets. So the rate at which surface water is sequestered at depth is also very important.
It’s been a bit of a surprise for the climate boffins that no matter how much faster humans introduce CO2 into the atmosphere only about half of it remains in the atmosphere. The mechanisms that serve as carbon sinks for the atmosphere (we didn’t even start talking about biological and chemical sequestration) are diverse and not well enough understood to predict whether this will remain true going forward.
Dave Springer,
You see, I know radiation in many cases can and does radiate in any and all directions, but that depends on the temperature and radiation from the surrounding matter. To radiate all directions the matter all around must be colder than the source that is radiating. The main difference you and I have is that radiation never actually flows from cold to hot matter, it doesn’t even flow from equal temperature pieces of matter or you could burn yourself with a Fresnel lens in a dark warm room as my little experiment should show you, if you will get curious and perform it yourself. Planets and stars radiate against basically nothing so you can let the other temperature in the Stefan-Boltzmann equation be zero, but always subtracting 2.7K would be more proper. You are one tiny step from moving your rather unrealistic view into what actually happens.
Here is what happens because of the Stefan-Boltzmann equation that screws so many people up (sigma=5.6704r-8, epsilon=1):
ε σ ( 288K^4 – 280K^4 ) = 41.572 W/m^2
or
ε σ ( 288K^4 ) – ε σ ( 280K^4 ) = 41.572 W/m^2
The top one will always show you the correct and actual flow of radiation between two pieces of matter. The latter one implies that matter always radiates at all times in all directions even if the temperatures are identical and the last term gets this quirky term applied to it, “back radiation”. You will end up with the same numeric answer but it leaves you with the wrong impression that two things have occurred when in reality only one thing has occurred, radiation from the warmer to the cooler or not at all if the two temperatures are the same.
This same logic applies to your split beams and it is why such instruments must be constructed to tightly control the temperatures inside. By the second set of equations temperatures of different pieces of the instrument do not matter at all, by the top equation surrounding temperatures of the pieces of the measuring instrument matters greatly. Go lookup an operation manual and see if I am not correct.
Please, drop the “back radiation”, it really does not exist, use the top equation.
Dave Springer says “I already explained to you that temperature only increases during the process of compression ”
What you and Ira and Joel fail to consider is that there is continuous compression of cold descending air which heats that air until it becomes hot enough to then ascend, expand, and cool until the process repeats. The atmosphere thus acts as a continuous compressor (and expander).
In addition to the 4 links I provided above, here’s 2 more peer-reviewed papers that explain this as well:
http://www.climatephysics.com/PDFs/Chilingar%20-%20Cooling%20due%20to%20CO2.pdf
http://docs.google.com/fileview?id=0B74u5vgGLaWoYTAyYTc4NmUtZDFkMC00ODg3LTgwYzAtOTg3OTJhZjI5MDVk&authkey=CKyD1r8H&hl=en
ferd berple says:
May 9, 2011 at 8:48 am
Does this change air pressure at sea level significantly?
That’s what’s happening on Jupiter. Pressure at depth is constantly rising. That isn’t happening on the earth. Atmospheric pressure at sea level rises and falls to some degree as horizontal pressure ridges sweep along but the average pressure remains the same at 1 bar.
Jupiter is still undergoing gravitational contraction that began when the solar system was born. This process stopped for the earth billions of years ago. The sun stopped its gravitational contraction when temperature increase from ongoing compression lit off a sustained fusion reaction. The outward pressure from fusion counteracts the inward pressure from gravity and an equilibrium point was reached where they are equal and opposite in force and the sun has a relatively stable diameter that will persist until it starts running out of hydrogen fuel to sustain the outward pressure.
Hockey Schtick says:
We consider that…but it can’t change the result. You are talking about things that can only redistribute energy within the earth-atmosphere system. You still must satisfy conservation of energy when you look at the interaction of the Earth System with the sun and space. And, the combination of a surface temperature above the 255 K blackbody temperature and an atmosphere transparent to terrestrial IR radiation doesn’t do this: There is much more energy going out of the system than coming into it. The result of this would be rapid cooling.
Ira
I always enjoy reading your articles and the comments that they generate.
I am sceptical as to how useful it is to consider just one element of how the atmosphere may work ignoring other factors which are known to exist and which in some circumstances are definitely more important factors (I have in mind convection, evaporation etc). Leaving that aside, I have problems in envisaging that the back radiation plays any significant role in the workings of the atmosphere.
I have no problem with the argument on net energy flow and that if the atmosphere is warmer it slows down the heat loss from the warmer earth (or ocean). The problem I have is whether the atmosphere is warm simply because of the absorption of solar energy (a combination of absorption of incoming solar radiation and absorption of reflected and radiated solar energy from the bottom up) and adiabatic lapse, or whether in addition back radiation from GHGs plays a significant role.
You will see the point I made at (richard verney says) at May 8, 2011 at 8:39 pm
Smoking Frog sought to answer the point. He comments at May 9, 2011 at 5:21 am:
“Martin Mason said – If back radiation is so powerful and it is a heat source, why don’t we use it?
Because the earth’s surface is already at the temperature to which the back-radiation has raised it.”
However, with respect that explanation cannot be correct. We know as fact that solar (possibly with the help of back radiation) heats the earth’s surface to the temperature to which solar energy has raised it, yet not withstanding this we can still extract work from the incoming solar energy. We can collect and focus the 184 w/m^2 of incoming solar energy and use it to melt salts etc in solar power plants. That being the case, it begs the question why can’t we collect and focus the 333 w/m^2 of back radiation and extract useful work from it.
The fact that we cannot do this suggests that the ground is not being bomb barded with 333 w/m^2 of (back) radiation.
I have a black and white marble path. On sunny days, this path is warm to walk on. The black marble slabs are considerably warmer than the white marble slabs. Not surprising since black is a better absorber than white and therefore the black marble stones absorb more of the incoming 184 w/m^2 of solar energy. IF back radiation existed and if there was some 333 w/m^2 of back radiation beating down on the ground, the black marble slaps should be significantly warmer than the white marble slaps at night or on cloudy days. However, they do not appear to be. In particular when left over night to bask in the supposedly 333 w/m^2 of back radiation, the black marble slaps do not heat up whereas they do heat up with only 184 w/m^2 of incoming solar energy!!
Ira, I would like to see someone conduct a very simple experiment along the following lines;
1. Get two identical metal slabs (same dimensions for area and thickness) save that one is painted brilliant white and the other matt black,
2. Pre heat the slabs to the forecasted daily temperature (say picking a day when the estimated temperature is going to be 20degC).
3. On a clear sunny day (ie the day estimated to be 20 degC) place the slaps in the sun and measure there respective temperatures every half hour.
4. On a mild summer night (one estimated to be 20 degC), pre heat the slaps to the forecasted night temp of 20C and then leave them out after the sun has fully set and measure there respective temperatures every half hour.
5. Compare the results.
6. In particular does the matt black slab gain heat at night from the down welling back radiation. If it does not, why not?
Ira, I would appreciate your comments
Bryan says:
No…What I am saying is that Postma and G&T mix in a lot of correct science that is already known with some incorrect science…or just glossing over things…to reach completely incorrect and absurb conclusions. That tends to be how peddlers of pseudo-science operate.
It is sad to see that the pull of pseudo-scientific arguments are just too strong for you to resist making them again and again. The shells that we consider are blackbody shells, so yes, the S-B equation applies by definition. This is a model. Is it a good model? Well, yes, it is quite a fine model to illustrate the basic features of the greenhouse effect. When you want to do detailed quantitative calculations, you adopt a better model. Is that concept so difficult to understand?
It is not science to attack a model for being to simple when it is meant to be a simple representation and where more refined models are available and can be used to show that the qualitative predictions of the simpler models for which they are used are correct. That is instead the realm of pseudo-science, a realm that is apparently just too irresistible to you. That you cannot even distinguish the difference between scientific arguments and the pseudo-scientific nonsense that you peddle is very very sad for you, the people reading this thread, anybody who respects the scientific enterprise, and even AGW skeptics who don’t want to be considered complete crackpots. I actually pity people like Ira and David M. Hoffer for having to put up with people like you on their side of the AGW debate.
Heh, and LOL. Unless I missed it, nobody has yet tackled the “venus thing” presented above by a commenter (which suggests that the GHE theory isn’t valid):
http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html
BTW, it holds for other planetoids with an atmosphere (I can provide links if anyone cares).
Despite the Orwellian chants about “multiple lines of evidence,” the case for a GHE threat is really hurting these days, due to the total lack of any such lines of evidence. In fact the multiple lines of evidence appear to go the other way:
1. No warming for 10-15 years, despite all the increases in the terrible GHGs (and not just OCO).
2. Ice core records show no correlation between GHGs and temperature.
3. The temperature swings during the past couple of millenia indicate the climate changes naturally without changes in GHGs. (We don’t need Mann’s proxies to know what happened during the MWP and LIA; it’s recorded in the history books, for crying out loud!)
4. No “hot spot” in the mid-troposphere in the tropics, as predicted by ALL the climate models. (So much for treating their output as “data.”)
5. No laboratory demonstrations or other real-world empirical demonstrations of any GHE effects.
6. Areas with the most greenhouse gases (tropics) have maximum temperatures that are no where near as high as some desert areas with the lowest amount of GHEs (yeah, yeah, it’s the water evaporation and clouds; but that is precisely the point on Earth).
7. Articles such as the one cited above, which show clearly that temperature in a gaseous atmosphere has nothing to do with the “greenhouse effect.”
Dave Springer:
“We do use it all the time. One example is the smudge pots used to limit freeze damage in orange and avocado groves. The heat of the smoke from the smudge pots is inconsequential. The effect comes from the black carbon particles in the smoke which absorb upwelling IR from the ground and send a portion of it downwards and sideways. It works as an insulator. This is the same mechanism by which CO2 molecules insulate. Anyone who contests this is simply wrong and needs to take an introductory class in physics.”
Well, I question this. Since the backradiation is coming from cooler air above, it cannot be warming the orange grove.
The Clean Air Act killed the smudge pots, so they now just blow air through the orchards or add heat by spraying water. Maybe they didn’t ever really need that backradiation?
Hockey Schtick says:
May 9, 2011 at 9:23 am
“What you and Ira and Joel fail to consider is that there is continuous compression of cold descending air which heats that air until it becomes hot enough to then ascend, expand, and cool until the process repeats. The atmosphere thus acts as a continuous compressor (and expander).”
Not in my case. I’ve discussed it in depth many times at WUWT. The following search reveals some of it.
http://www.google.com/search?hl=&q=tunderstorm+heat+engine+springer+site%3Awattsupwiththat.com&sourceid=navclient-ff&rlz=1B3GGGL_enUS290US290&ie=UTF-8
The big picture:
The sun heats the ocean, the ocean heats the atmosphere, the cosmic void cools the atmosphere.
This thread is about radiative transfer in and out which is a detail in the big picture. Convective transfer is a different detail but also very important. The water cycle in general is exceedingly important in basic understanding of atmospheric physics. Vast amounts of energy are lifted from the surface by evaporation in what’s called “latent heat of vaporization”. It’s called “latent” because it won’t register on a thermometer. When the vapor condenses the latent heat is released. As the earth gets warmer (for whatever reason) the speed of the water cycle increases. This is a negative feedback mechanism and it’s the most glaring flaw in the whole warmist narrative. There has never been a runaway greenhouse on the earth. Never. The hypothetical amplification of anthropogenic CO2 forcing by increased water vapor is a wholesale fabrication without a shred of evidence to support it and with mountains of contrary evidence. The water cycle is a negative feedback not a positive feedback. Most of the more informed global warmists and skeptics know that this amplification is the heart of the controversy. None dispute that when everything else is equal more CO2 will result in a warmer surface and that this is would be about 1.0C for each CO2 doubling starting from a base point of 280ppm. They also acknowledge that a warming surface will speed up the water cycle. The controversy is over whether a faster water cycle is a positive or negative feedback. The evidence says it’s negative. The alarmist must have it as a positive feedback because otherwise the only warming that’s gonna happen is a modest welcome amount that is of great net benefit to the biosphere. Living things don’t tolerate ice very well so the less of it there is the more life can flourish on this third rock from the sun.
Climate boffins have pretty much conceded the debate over water vapor amplification. As this concession ocurred it manifested to the unwashed masses as “global warming” was first replaced by “climate change” and now is morphing yet again into “climate disruption”.
The climate does nothing if not change and it has been doing so since long before humans entered the equation so “climate change” failed to elicit the needed level of fear response in the masses. Climate disruption has more fear factor in it.
An inconvenient amount of climate disruption is a distinct possible result of anthropogenic activity but once again the evidence is all stacked against it. By the same token radically modifying anthropogenic activity to lessen any imagined disruption has an immediate negative consequence of slowing down the global economy which is driven in large part by fossil fuel consumption.
Thus we have a risk/reward decision to make and in my view trying to reduce CO2 emissions is essentially all risk and no reward. Real pollutants that immediately and directly effect our health and well being are a much greater concern. Heavy metals in our water, particulate pollutants in our air, ozone, and lots of other things are legitimate red flag events but CO2 is plant food and the more of it we have the better off we are.
“In deep ocean trenches CO2 has been observed in liquid droplets. So the rate at which surface water is sequestered at depth is also very important.”
That is intersting. The ocean pressure goes up 1 atmosphere per 30 feet of depth. At 300 K CO2 becomes a liquid at 100 atmospheres. The deep oceans are all below 300K and 100 atmospheres is only 3000 feet – much less the the depth of the average ocean basins.
So, what this means is that CO2 can exist as a liquid across most of the ocean bottoms. As liquid CO2 should weigh more than H2O, the question really should be why the bottom of the oceans is not all liquid CO2? Except that the oceans are not saturated, and thus liquid CO2 would be absorbed.
http://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-temperature_phase_diagram.svg
http://oceanservice.noaa.gov/facts/oceandepth.html
http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html
well worth the read, as well as the follow on explanation. what I find fascinating is that albedo has no effect on the temperature comparison between earth and venus, which accounts fully for the missing 33K in Ira’s analysis.
quote from the article:
For example, in the analysis, not only does the amount of CO2 not enter in (Earth has 0.04%, Venus a whopping 96.5%), but the albedo (from either cloud tops or the planetary surface) does not either (Venus has dense clouds that reflect much of the incident visible radiation, while Earth does not, and Earth’s surface is 70% deep ocean, while Venus is solid crust). The real atmospheres don’t care at all about these great differences in the two atmospheres and planetary surfaces, they only care, and quite precisely, about their distances from the Sun.
http://2.bp.blogspot.com/-4R16sH96XBk/TX5hIW8MADI/AAAAAAAAAD4/lhiu503gY58/s1600/venus%2Bearth%2Bcomparison.JPG
This cannot simply be coincidence. How can two planets with completely different atmospheres, albedo’s and surfaces show almost identical temperatures as a function of pressure if the standard climate model is correct? Quite simply they can’t. These observations are either false or climate science has it fundamentally wrong.