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.
JAE says:
May 9, 2011 at 10:02 am
Well, I question this. Since the backradiation is coming from cooler air above, it cannot be warming the orange grove.
Even without knowing about the exact situation you are discussing, I can tell you don’t understand the concept or the reality of back radiation.
The air above is not warming the orange grove but slowing the heat loss by radiating some of the LW radiation back. If no more energy enters the grove from the outside it will continue cool over time. It is only the law of conservation of energy at work, so the back radiation is not extra energy but only energy that has had it’s ability to leave the system delayed.
“”””” JT says:
May 7, 2011 at 8:34 pm
Ira, the basic bookkeeping of the simplest greenhouse calculations assumes that the re-emission of infra-red radiation by the greenhouse gas molecules is spatially symmetrical. I am well aware that spontaneous emission is equally likely to be in any direction so that approximately 1/2 will head downward to the surface. However, there is another kind of emission – stimulated emission – and it is massively biased in the same direction of travel as the direction of travel of the stimulating photon. Thats what creates laser light, but stimulated emission can occur without lasing. “””””
I don’t believe that is true. Stimulated emission is still isotropic. The highly directional output of a laser beam, is a consequence of the resonant Optical cavity that the emission takes place in. Only wave modes, that are aligned with the axis of the resonator, can continue to propagate in the system. The off-axis modes are suppressed. The concept is quite simple. Take two parallel mirrors, and launch a geometrical ray normal to one of the mirrors, to wards the other. It will in the geometrical limit, bounce back and forth along the same line indefinitely. If the angle is even slightly off normal, the ray will walk over to the edge of one mirror, and get reflected into the side walls. Parallel flat mirrors are a completely unstable resonator configuration.
Only certain mirror configurations produce stable multiple reflections that retain the energy within the resonator, except for small transmission losses that let light leak out of the business end of the laser. The other mirror is usually made as high a reflectance as technology allows, including the use of TIR mirrors.
Joel Shore says:
May 9, 2011 at 7:56 am
Allan M says:
The basis for the second law (and the first) is careful and accurate measurement, mostly paid for by wicked 19th century capitalists, who wanted to know how to get more from their steam engines, and also how to avoid being sold snake oil.
There is no need for a statistical ‘fudge’ unless you wish to introduce special pleading for “IPCC Approved” photons.
Experiment did provide the evidence for the Second Law. However, our modern (20th century) understanding of where the law comes from is based on statistical physics.
If you you use statistics properly, the tail doesn’t wag the dog.
Martin:
“The air above is not warming the orange grove but slowing the heat loss by radiating some of the LW radiation back. If no more energy enters the grove from the outside it will continue cool over time. It is only the law of conservation of energy at work, so the back radiation is not extra energy but only energy that has had it’s ability to leave the system delayed.”
Well, maybe so. But then aren’t you saying that the backradiation is affecting the lapse rate? That cannot be, since the lapse rate depends upon only Cp and g. ??
wayne said:
Clouds make warmer nights because the clouds are usually warmer than the normal air temperature at that altitude and therefore the surface’s rate of loss by radiation upward will be less leaving you with a warmer than normal night.
This is nonsense. Typically, clouds are much colder than the ground. (When they are the same temperature, we call it fog.) Instead, they are more like styrofoam cups, they scatter IR radiation back toward the ground without affecting their own temperature. This is because the bottom of a cloud is a phase change boundary and, therefore, the temperature has almost no effect on the amount of energy released. Stefan’s equation does not apply.
Bottom line, cold clouds make for warm nights. This is a part of the greenhouse effect.
Robert Clemenzi, THANKS for answering my question and for the link to your full explanation which I read and appreciate.
But, not surprisingly, I still have a problem understanding why multiplying the result of the Planck calculation by wavelength squared, thus moving the peak quite a bit to the longer wavelengths, makes physical sense.
I mentioned human visual sensitivity as a “sanity check” on which method make physical sense, because biological evolution and natural selection has no “agenda” pro- or con-AGW. According to Wikipedia, human visual sensitivity peaks at about 553 nm (“green”).
The Carleton spreadsheet comes with the Sun temperature set to 5880 K, and that value seems to best map to the actual measurements of the Solar spectrum as shown in Carleton and reproduced above as the leftmost panel of my second graphic. Carleton indicates maximum “Intensity” as 495 nm, which is 58 nm less than the value indicated by Wikipedia for human maximum color sensitivity. So far so good for Carleton.
When I modify the Carleton spreadsheet calculation by multiplying the formula by wavelength squared, the Solar peak jumps to 889 nm, which is 336 nm more than human maximum sensitivity. Indeed, 889 is all the way into the near-IR range and totally outside the range of human vision, which ends around 700 nm.
I have trouble believing that evolution and natural selection, which has had tens of millions (the Great Apes) if not billions of years to work on this problem, and an unlimited budget and “manpower”, could miss the actual peak power portion of Solar radiation by so much that it is out of the visual range. Therefore, I have to conclude that peak Solar radiation is closer to 553 nm than to 889 nm.
You claim that “.. people who believe in Global Warming always plot spectra versus wavelength.” That is certainly true, but that fact alone does not make it scientifically incorrect to do so.
You also claim that “… When you want to analyze the energy in the system, all plots should be versus frequency (normally expressed as a wavenumber) to show an honest plot. In that case, most of the energy from the Sun is in the IR. When plotted versus wavelength, the plots incorrectly imply that most of the energy is in the visible and UV spectra. …”
How do you square that conclusion with the undeniable facts of evolution and natural selection which have no “agenda” other than the survival and reproduction of animals, and, in our case, of the Great Apes and humans?
Again, I GREATLY APPRECIATE your work in this area, and your excellent write-up that I made clickable above, but I need some physical reason to accept that what you (and Perry) have done is a better representation of the energy in the Solar (and Earth) spectrum than what Carleton and Wikipedia and others have done.
advTHANKSance for your reply!
THANKS Bomber_the_Cat. The last part of your comment hit home. It reminded me of the guy who said his Black horses ate more than his Brown horses. It turned out that the guy simply had more Black horses than Brown ones!
OK, so, the 10-11μm range has 91 “horses” (Wavenumbers) and the 18-19μm range has only 29 “horses”. If we give each range an equal amount of “hay” (energy) each 10-11μm “horse” will have less than each 18-19μm “horse”, so the peak “eating” of “energy” will occur with the latter group of horses, because there are fewer of them.
In the “horses” example, if we give each “horse” and equal amount of “hay” the 91 “horses” in the 10-11μm range will, in total, consume about three times as much as the 19 “horses” in the 18-19μm range. Got it!
Now, go one step further and please explain why you like to plot against wavelength.
“Well, maybe so. But then aren’t you saying that the backradiation is affecting the lapse rate? That cannot be, since the lapse rate depends upon only Cp and g. ??”
My question is why we assume that N2 in the atmosphere doesn’t back radiate. All objects radiate depending on their temperature. As the atmosphere is mostly N2, that must be the source of most of the back radiation.
If we increased the atmospherice pressure 90 fold, such as on venus, then there would be 90 times as much N2 per cubic meter, and the back radiation would go up proportionally, as would the surface temperature. Thus, the surface temperature must be a function of atmospheric pressure, which is a function of gravity.
The standard radiative model ignores gravity, which is why it cannot be applied to other planets to see if it is correct. Thus the reliance on computer models, which have the added bonus that there is no way they can be proven wrong in the short term.
I’ve appreciated and agreed with all you have said so far on my threads here at WUWT, until your comment on Hansen.
The word on the street is that you are a Warmist. IMHO, there is nothing wrong with that. You appear to be totally honest, scientifically-oriented, intelligent, and well-informed. Your analysis of the available evidence leads to the belief that AGW is responsible for the majority of warming since 1880 and is likely to be dangerous for human civilization in the forseeable future. You conclude, therefore, that we (society) need to take action sooner than later. I’m a Lukewarmer-Skeptic whose analysis leads me to believe AGW has a real but minor effect compared to natural cycles and processes and data bias by the official climate Team, and that a bit of warming and higher CO2 levels may turn out to be of net benefit to humanity. Therefore we should do little about it. Our positions, while counter to each other, are both valid in the scientific sense, and deserving of mutual respect.
However, I cannot agree to “leave him [Hansen] out of it.” I believe Hansen was one of the primary science advisors to Al Gore on his lecture and movie An Inconvenient Truth. He is therefore responsible for the consequences of the Catastrophic CAGW the sky is falling fiction bought into by the major media and opinion leaders. That led to Ethanol, Wind, and other unwise subsidies, the Cap & Trade scam, and other economy-wrecking policies.
Gore is not and never has been a scientist, but Hansen, as a scientist and head of NASA GISS has misused his credentials and appears to have pressured his employees to cook the books, bending the temperature record by introducing “corrections” way after some of those measurements were old enough to qualify for Social Security, see Makiko Sato FOIA email and The PAST is not what it used to be.
Should we interpret your “leave him [Hansen] out of it” as a repudiation of Hansen and his leadership of NASA GISS or as simple embarassment at the antics of a nice old uncle who means well but sometimes leaves his fly down by mistake?
ferd:
“My question is why we assume that N2 in the atmosphere doesn’t back radiate. All objects radiate depending on their temperature. As the atmosphere is mostly N2, that must be the source of most of the back radiation”
N2 doesn’t radiate significally in the IR portions of the spectrum.
Can you provide a reference to a recognized standard text which supports this contention that it is only the net difference which must respect the Second Law of Thermodynamics?
The only instance I know of where a colder object can impart energy to a warmer object is in the entirely theoretical case of two objects being at negative Kelvin temperatures where the colder object must perforce be at a higher energy state the the warmer one. Yet in this case energy still flows from a higher state to a lower state and thus respects the Second Law.
Heat is the manifestation of energy flowing from a higher state to a lower state. It is why heat pumps are efficient and air conditioners aren’t.
Joel Shore
You cannot weasel out of your gross error.
You challenged me to discus the science.
I am here to do so.
If you prefer to avoid the science and instead issue smears instead then I will not be surprised.
This item is directly addressed to Ira’s post and deserves an answer from you!
On page 9 of your co-written Halpern et al comment paper you state that the Stephan Boltzmann Law can be used to work out the thermal energy exchange between atmospheric shells.
There is a whole series of statements on pages 8,9,and 10 referring to the atmosphere, Stephan Boltzman Law and indeed including the SB formula.
Gerlich and Tscheuschner specifically said that the Stephan Boltzman Law cannot be used for atmospheric gases.
Do you now agree with them and withdraw your comments?
Or will you persist in this unphysical assumption.
Depending on your answer we can perhaps call on Ira’s spreadsheet to settle the matter.
Your paper is shown below but I dont have a direct link.
Comment on ‘Falsification Of the atmospheric CO2 greenhouse effects within the frame Of Physics’ by Joshua B. Halpern, Chistopher M. Colose, Chris Ho-Stuart, Joel D. Shore, Arthur P. Smith, Jorg Zimmermann.
Dave Springer says:
Actually, there is plenty of evidence of the water vapor feedback, both existence and rough magnitude, as discussed here: http://www.sciencemag.org/content/323/5917/1020.summary
The only sense in which your argument for a negative water cycle feedback makes much sense is if you are grouping together cloud and water vapor effects in such a feedback (which I guess is not unreasonable when you refer to it as “water cycle” but becomes confusing when you refer to it as “water vapor feedback”).
The cloud feedback is indeed associated with quite a large degree of uncertainty and basically the only way in which we could be spared from having a fairly significant climate sensitivity is to have a significantly-negative cloud feedback. Alas, besides not being what all of the models show (which admittedly could be a problem with the models), such a negative feedback makes it rather difficult to explain paleo-climate without somehow coming up with much larger forcings than are estimated right now (for. e.g., the glacial – interglacial oscillations).
Limiting the controversy to specifically the feedback due to clouds, I essentially agree with this statement….which is why we both apparently find it so ridiculous to see people here wasting tons of time arguing about well-settled science that they have no hope of possibly overturning. (The most extreme cases being people like Allan M who apparently want to overturn all of modern statistical physics in order to come up with a version of the 2nd Law that is more toward their liking.)
People should realize that, even from a purely tactical point-of-view, it would be wise to pick your battles. When you argue that the greenhouse effect doesn’t exist, the only cause your further, at least within the scientific community, is the cause of those who would like to show how ridiculously ignorant of science the AGW skeptics really are. I would invite those who want to help demonstrate that to continue to make their arguments here; the rest of you should consider carefully reading what Dave, David Hoffer, Ira, myself and others are writing here and actually trying to understand the correct science.
“Bottom line, cold clouds make for warm nights. This is a part of the greenhouse effect.”
Hmmm. Maybe not. Clouds affect convection and the lapse rate (decrease rates), too. Water (clouds) also store 4 times as much heat as air. Water vapor stores twice as much. How do you separate these effects from the “radiative greenhouse effect?”
Ira Glickstein says:
Ira,
I think you may be over-interpreting the statement that I made. As far as I can tell, Hansen’s notion that if we really go to town using fossil fuels, we might trigger a true runaway greenhouse effect just seems rather vaguely-supported by any detailed argument or evidence at this point and does not seem to be the general belief within the climate science community. So, although I have a lot of respect for Hansen, who has the track-record of saying things that seem a bit far-out at the time but later become quite well-accepted by the scientific community (such as when he pronounced back in the late 1980s that the warming occurring was almost definitely due to greenhouse gases), I think it is at best premature to give much credence to this particular prediction of Hansen’s.
So, I was simply saying that the generally-accepted projections for AGW are that positive feedbacks amplify the radiative effects due to greenhouse gases alone but do not lead to an actual “runaway” instability. For some reason that I don’t totally fathom, some people on the skeptic side (like martin mason above or Smokey in other threads) seem to like to group together this prediction of feedbacks amplifying things and producing an actual “runaway” instability, perhaps because it makes a better “strawman” argument to attack.
Alleyne says:
Any text on thermodynamics that treats it from a statistical physics perspective ought to do fine. In the context of radiative heat transfer specifically, any text that talks about the exchange of radiation between two objects or any object and its surroundings ought to give you the basic radiative transfer equations that are used in computing the greenhouse effect.
Yes…So, heat (which is a macroscopic concept by its definition) always flows from hotter to colder (in the absence of work). However, note that the interpretation that the radiative energy flows in both directions, while having an abundance of empirical support, is not necessary to show there is a greenhouse effect. All that is really necessary to say is that the heat flow between two objects depends on the temperature of both objects and not just on the temperature of the hotter object.
I have no clue what you are trying to say in this last sentence. The term “heat pump” is sometimes used as a category that includes air conditioners and refrigerators. Other times, it is used to represent the subcategory of the “heat pump” in the above context that are actually used to heat a house rather than cool it. However, regardless of how the term is used, heat pumps used for heating and air conditioners operate by the same basic principle. Both use work to “pump” heat energy from cold to hot, i.e., in the opposite direction from which heat spontaneously “flows”.
JAE says:
May 9, 2011 at 11:28 am
Well, maybe so. But then aren’t you saying that the backradiation is affecting the lapse rate? That cannot be, since the lapse rate depends upon only Cp and g. ??
It’s not a question of back radiation effecting the lapse rate but rather the laps rate reduces the effectiveness of back radiation.
As the air thins then there is an increased possibility that some of the electromagnetic wave may find windows that are not closed by a receptive molecule. This being the case then the wave propagates out into open space and so is not absorbed and not re-radiated.
This is important with regard to H20, as humidity drops rapidly and the wave lengths that are absorbed by this molecule now escape at a greatly increased rate and so back radiation diminishes accordingly.
Ira, Why are leaves green?
It is because chlorophyll reflects green light. Leaves absorb and use the energy that is most abundant .. the near IR.
People also usually ignore the fact that our retinas are highly sensitive to UV light. So sensitive, in fact, that there is a special UV filter associated with the lens to absorb it. This was discovered when people with new artificial lenses were able to see in the UV. Because our eyes use simple lenses, this caused significant chromatic aberration such that they were not able to focus when out doors. I mention this because it argues against the common idea that our eyes are most sensitive to green light because “that is the brightest part of the spectrum”.
You should also consider that many people wear sun glasses because it is too bright near the equator. This implies that it is possible that our eyes developed to block the bright near IR and to use the significantly dimmer visible part of the spectrum.
Therefore, I reject the argument that “using human eyes for a sanity check” makes sense. Using leaves (chlorophyll) makes a lot more sense since they have (it has) been around a lot longer.
Remember, energy is expressed as frequency times Planck’s constant – E=hf. Therefore, when studying energy, frequency is the more appropriate x-axis.
As for physical sense, the distance between 1 and 2 is the same as the distance between 9 and 10. However, the distance between 1/1 and 1/2 (0.5) is NOT the same as the distance between 1/9 and 1/10 (0.011). Since the energy is measured as the area under a curve (an integral), an adjustment has to be made to keep the areas the same when using the wavelength. Remember, energy is linear only in the frequency domain.
Bryan says:
What you (and G&T) are engaging in has ABSOLUTELY nothing to do with science, unless you include undermining and obfuscating science. I have explained the philosophy behind using a hierarchy of models here: http://wattsupwiththat.com/2011/05/07/visualizing-the-greenhouse-effect-light-and-heat/#comment-655880 and here: http://wattsupwiththat.com/2011/05/07/visualizing-the-greenhouse-effect-light-and-heat/#comment-656374 . If you refuse to understand it, I don’t have any more to say to you.
You are adding only useless noise to this thread.
JAE says:
Hmmm. Maybe not. Clouds affect convection and the lapse rate (decrease rates), too. Water (clouds) also store 4 times as much heat as air. Water vapor stores twice as much. How do you separate these effects from the “radiative greenhouse effect?”
Your points are valid but clouds should not be appropriated by greenhouse enthusiasts
Clouds, raindrops and hailstones are much better radiators than gases.
Not because they are composed of so called “greenhouse gases”.
ANY solid or liquid can provide a much larger range of radiation than the line spectra of gases.
They don’t need to be composed of greenhouse gases to show this effect.
Ira Glickstein,
You have exactly conveyed my own world view regarding the effect and importance of CO2:
# # #
Alleyne,
Heat can flow from a colder to a warmer object; from higher to lower entropy. What is required is work. For example, a refrigerator does reverse entropy work. Work requires energy. Of course, total entropy in the universe only goes in one direction. It’s the exceptions that make it interesting.
Robert Clemenzi says:
May 9, 2011 at 11:34 am
wayne said:
Clouds make warmer nights because the clouds are usually warmer than the normal air temperature at that altitude and therefore the surface’s rate of loss by radiation upward will be less leaving you with a warmer than normal night.
This is nonsense. Typically, clouds are much colder than the ground. (When they are the same temperature, we call it fog.)
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Respectable Robert, what you say I said is not what I said at all. Read what I said again. I never said clouds were warmer than the surface (well, except rarely and even that was pointed out later). I think you jumped the gun a bit. ☺
Whew, I’ve read most of the comments over the last couple of days and yet I see nothing discussed about the cooling effect of GHGs.
How can we discuss the temperature of the atmosphere without understanding the transfer of heat by collisions? When I see Trenberth’s energy chart it ignores heat transfer by collisions of gas particles. While I accept radiation flows both ways I understand collisions create a heat flow between the Earth’s surface and the atmosphere that also goes both ways.
Therefore, the Earth loses energy at times to the atmosphere and gains energy at other times. However, just like in the case of radiation, the net flow is most likely to the atmosphere. Has anyone measured this heat flow? I’ve never seen it documented and yet it seems important if we are to understand the big picture.
Now, why is this important? Well, consider the situation without GHGs and ignore the Earth radiating energy for the moment. The Sun would heat the surface and the atmosphere. Energy would move between them but would have no way to escaping. It would get pretty darn hot.
Now, add GHGs to the system. The GHG-less atmospheric gases would start colliding with the newly added GHGs and heating them up. They would start radiating energy. Half would go down which would not change the heat in the system since none was escaping before adding the GHGs. However, half would go up and out of the system … thus cooling the atmosphere.
Of course, we know the GHGs would actually intercept radiation from the surface as well. The so-called GHE. So, we have two conflicting processes. One delays the heat leaving the system and the other increases the heat loss that occurred as a result of heating due by other means (collisions with surface and solar).
Without understanding both of these systems in detail how can we know the overall effect of GHGs? It seems to me only half the problem has been addressed by scientists, what am I missing?
“In the past 100 years since the formation of the ‘greenhouse’ theory of atmosphere, we have discovered that the atmosphere is a MILES DEEP, FRIGID, compressible fluid, HEAT CONDUCTIVE, IMMERSION BATH, held in place around the earth, by gravity.
The atmosphere possesses physical attributes like:
A: a big, warm blankie
B: a big, warm, greenhouse
C: a MILES DEEP, FRIGID, HEAT CONDUCTIVE, IMMERSION BATH
Someone who believes in a greenhouse effect will tell you the answer is A, but since it’s too complicated to talk about it as A, you can talk about it like it’s B, but not E.V.E.R. under A.N.Y. circumstances, is the answer C.
T.h.a.t. is who you’re dealing with.
N2 doesn’t radiate significally in the IR portions of the spectrum.
How is that possible? Every object radiates depending on its temperature. It may not absorb at certain frequencies, but how can it avoid radiating in IR if that is its temperature?