Guest post by Ira Glickstein
The Atmospheric “greenhouse effect” has been analogized to a blanket that insulates the Sun-warmed Earth and slows the rate of heat transmission, thus increasing mean temperatures above what they would be absent “greenhouse gases” (GHGs). Perhaps a better analogy would be an electric blanket that, in addition to its insulating properties, also emits thermal radiation both down and up. A real greenhouse primarily restricts heat escape by preventing convection while the “greenhouse effect” heats the Earth because GHGs absorb outgoing radiative energy and re-emit some of it back towards Earth.
Many thanks to Dave Springer and Jim Folkerts who, in comments to my previous posting Atmospheric Windows, provided links to emission graphs and a textbook “A First Course in Atmospheric Radiation” by Grant Petty, Sundog Publishing Company.
Description of graphic (from bottom to top):
Earth Surface: Warmed by shortwave (~1/2μ) radiation from the Sun, the surface emits upward radiation in the ~7μ, ~10μ, and ~15μ regions of the longwave band. This radiation approximates a smooth “blackbody” curve that peaks at the wavelength corresponding to the surface temperature.
Bottom of the Atmosphere: On its way out to Space, the radiation encounters the Atmosphere, in particular the GHGs, which absorb and re-emit radiation in the ~7μ and ~15μ regions in all directions. Most of the ~10μ radiation is allowed to pass through.
The lower violet/purple curve (adapted from figure 8.1 in Petty and based on measurements from the Tropical Pacific looking UP) indicates how the bottom of the Atmosphere re-emits selected portions back down towards the surface of the Earth. The dashed line represents a “blackbody” curve characteristic of 300ºK (equivalent to 27ºC or 80ºF). Note how the ~7μ and ~15μ regions approximate that curve, while much of the ~10μ region is not re-emitted downward.
“Greenhouse Gases”: The reason for the shape of the downwelling radiation curve is clear when we look at the absorption spectra for the most important GHGs: H2O, H2O, H2O, … H2O, and CO2. (I’ve included multiple H2O’s because water vapor, particularly in the tropical latitudes, is many times more prevalent than carbon dioxide.)
Note that H2O absorbs at up to 100% in the ~7μ region. H2O also absorbs strongly in the ~15μ region, particularly above 20μ, where it reaches 100%. CO2 absorbs at up to 100% in the ~15μ region.
Neither H2O nor CO2 absorb strongly in the ~10μ region.
Since gases tend to re-emit most strongly at the same wavelength region where they absorb, the ~7μ and ~15μ are well-represented, while the ~10μ region is weaker.
Top of the Atmosphere: The upper violet/purple curve (adapted from figure 6.6 in Petty and based on satellite measurements from the Tropical Pacific looking DOWN) indicates how the top of the Atmosphere passes certain portions of radiation from the surface of the Earth out to Space and re-emits selected portions up towards Space. The dashed line represents a “blackbody” curve characteristic of 300ºK. Note that much of the ~10μ region approximates a 295ºK curve while the ~7μ region approximates a cooler 260ºK curve. The ~15μ region is more complicated. Part of it, from about 17μ and up approximates a 260ºK or 270ºK curve, but the region from about 14μ to 17μ has had quite a big bite taken out of it. Note how this bite corresponds roughly with the CO2 absorption spectrum.
What Does This All Mean in Plain Language?
Well, if a piece of blueberry pie has gone missing, and little Johnny has blueberry juice dripping from his mouth and chin, and that is pretty good circumstantial evidence of who took it.
Clearly, the GHGs in the Atmosphere are responsible. H2O has taken its toll in the ~7μ and ~15μ regions, while CO2 has taken its bite in its special part of the ~15μ region. Radiation in the ~10μ region has taken a pretty-much free pass through the Atmosphere.
The top of the Atmosphere curve is mostly due to the lapse rate, where higher levels of the Atmosphere tend to be cooler. The ~10μ region is warmer because it is a view of the surface radiation of the Earth through an almost transparent window. The ~7μ and 15μ regions are cooler because they are radiated from closer to the top of the Atmosphere. The CO2 bite portion of the curve is still cooler because CO2 tends to be better represented at higher altitudes than H2O which is more prevalent towards the bottom.
That is a good explanation, as far as it goes. However, it seems there is something else going on. The ~7μ and ~15μ radiation emitted from the bottom of the Atmosphere is absorbed by the Earth, further warming it, and the Earth, approximating a “blackbody”, re-emits them at a variety of wavelengths, including ~10μ. This additional ~10μ radiation gets a nearly free pass through the Atmosphere and heads out towards Space, which explains why it is better represented in the top of the Atmosphere curve. In addition, some of the radiation due to collisions of energized H2O and CO2 molecules with each other and the N2 (nitrogen), O2 (oxygen) and trace gases, may produce radiation in the ~10μ region which similarly makes its way out to Space without being re-absorbed.
There is less ~15μ radiation emitted from the top of the Atmosphere than entered it from the bottom because some of the ~15μ radiation is transformed into ~10μ radiation during the process of absorption and re-emission by GHGs in the atmosphere and longwave radiation absorbed and re-emitted by the surface of the Earth.
Source Material
My graphic is adapted from two curves from Petty. For clearer presentation, I smoothed them and flipped them horizontally, so wavelength would increase from left to right, as in the diagrams in my previous topics in this series. (Physical Analogy and Atmospheric Windows.)
Here they are in their original form, where the inverse of wavelength (called “wavenumber”) increases from left to right.
Source for the upper section of my graphic.
Top of the Atmosphere from Satellite Over Tropical Pacific.
[Caption from Petty: Fig. 6.6: Example of an actual infrared emission spectrum observed by the Nimbus 4 satellite over a point in the tropical Pacific Ocean. Dashed curves represent blackbody radiances at the indicated temperatures in Kelvin. (IRIS data courtesy of the Goddard EOS Distributed Active Archive Center (DAAC) and instrument team leader Dr. Rudolf A. Hanel.)]
Source for the lower section of my graphic.
Bottom of the Atmosphere from Surface of Tropical Pacific (and, lower curve, from Alaska).
[Caption from Petty: Fig. 8.1 Two examples of measured atmospheric emission spectra as seen from ground level looking up. Planck function curves corresponding to the approximate surface temperature in each case are superimposed (dashed lines). (Data courtesy of Robert Knutson, Space Science and Engineering Center, University of Wisconsin-Madison.)]
The figures originally cited by Dave Springer and Tim Folkerts are based on measurements taken in the Arctic, where there is far less water vapor in the Atmosphere.
[Fig. 8.2 from Petty] (a) Top of the Atmosphere from 20km and (b) Bottom of the Atmosphere from surface in the Arctic. Note that this is similar to the Tropical Pacific, at temperatures that are about 30ºK to 40ºK cooler. The CO2 bite is more well-defined. Also, the bite in the 9.5μ to 10μ area is more apparent. That bite is due to O2 and O3 absorption spectra.
Concluding Comments
This and my previous two postings in this series Physical Analogy and Atmospheric Windows address ONLY the radiative exchange of energy. Other aspects that control the temperature range at the surface of the Earth are at least as important and they include convection (winds, storms, etc.) and precipitation (clouds, rain, snow, etc.) that transfer a great deal of energy from the surface to the higher levels of the Atmosphere.
For those who may have missed my previous posting, here is my Sunlight Energy In = Thermal Energy Out animated graphic that depicts the Atmospheric “greenhouse effect” process in a simlified form.
I plan to do a subsequent posting that looks into the violet and blue boxes in the above graphic and provides insight into the process the photons and molecules go through.
I am sure WUWT readers will find issues with my Emissions Spectra description and graphics. I encourage each of you to make comments, all of which I will read, and some to which I will respond, most likely learning a great deal from you in the process. However, please consider that the main point of this posting, like the previous ones in this series, is to give insight to those WUWT readers, who, like Einstein (and me :^) need a graphic visual before they understand and really accept any mathematical abstraction.
Fred Souder says:
March 10, 2011 at 5:53 am
Ira,
You should stop saying the greenhouse gases in the atmosphere warm the earth to this crowd. Too may engineers running around here. The atmosphere slows the rate at which the earth loses energy to deep space. Thus, the earth in the sun-earth-space system has a higher equilibrium temp. The “old” rules of thermodynamics still apply: a warm object cannot gain net thermal energy from a cold object.
But a warm object with a continuous heat source surrounded by a radiatively active atmosphere which is warmer than space will reach an equilibrium temperature which is warmer than it would otherwise be in the absence of such an atmosphere. Some of the BB emitted from the surface will be recycled to the surface (and be measured) ask some of the ChemEs what the effect of 50% recycle is on throughput, is that contrary to conservation of mass? Ask the MechEs why when they measure the exhaust from a gas turbine with a thermocouple they get a certain temperature but when they put a thin radiation shield around it the temperature goes up, is that contrary to the laws of thermodynamics?
“”Phil. says:
March 10, 2011 at 9:31 am
Domenic says:
March 10, 2011 at 8:30 am
to Harry Dale Huffman
Good post. Great analysis. Far more valid than the nonsense out there.
Except it’s wrong!””
________________
Phil, go back and actually read the analysis here:
http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html
The calculations are relatively simple, are applied at the 1000mb level, and are congruent with earth at 1000mb. It’s straight, simple, to the point and beyond refutation. Maybe Harry will come back and answer you directly, but I think when he writes, “The Venus/Earth comparison directly indicates this, because the ratio of temperatures, Venus/Earth, is essentially a constant (1.17) which is just that due to the distances of the two planets from the Sun, NOTHING ELSE. It does not depend upon CO2 concentration (Earth has 0.04% CO2, and Venus a whopping 96.5%); and it does not depend upon albedo, either at cloud tops or planetary surfaces (Earth’s surface is 70% deep ocean, while Venus is solid crust) — These great differences in the two atmospheres and surfaces mean nothing, introduce no complicating effects. The Venus/Earth comparison shows they have no overall effect, because the solar distance explains the entire difference, over a broad range of atmospheric pressures.”, his comments are substantiated by the math. Very simple.
Phil. says:
March 10, 2011 at 9:31 am
“Venus has a bond albedo of 0.75 due to the sulfuric acid clouds whereas the earth has a bond albedo of 0.29, you bet the temperature depends on the albedo. Venus absorbs 25% of the light incident on it and Earth 71% but the ratio of temperatures still only depends on the distance from the sun? Even a physicist should see the problem with that.”
I think Phil has either missed the point here or he hasn’t read Harry’s article. http://theendofthemystery.blogspot.com/2010/11/venus-no-greenhouse-effect.html
He clearly states that Earth and Venus are heated top down by incoming IR.
Quote: “This in fact indicates that the Venusian atmosphere is heated mainly by incident infrared radiation from the Sun, which is not reflected but absorbed by Venus’s clouds, rather than by warming first of the planetary surface. (It also indicates that the Earth atmosphere is substantially warmed the same way, during daylight hours, by direct solar infrared irradiation, and that the temperature profile, or lapse rate, for any planetary atmosphere is relatively oblivious to how the atmosphere is heated, whether from above or below.)”
Albedo applies to visible electromagnetic radiation not invisible IR.
You have gone to great lengths to explain the spectral absorption features of the greenhouse gases. These gases are in the atmosphere and that is what they do. But it is unhelpful to know what the gases that are sitting there do when the atmosphere is in a stationary state. What is important to know is how does the addition of more carbon dioxide to the atmosphere change this picture. We are told that if you do that the atmospheric absorption will simply increase at the wavelengths that the added gas absorbs and in proportion to the amount added. But is this really true? There are no direct instrumental measurements of this and we simply have to believe theory about it. But what if there was a way to actually observe how the total atmospheric absorption changes as we increase the amount of CO2 we add to the atmosphere? It turns out that there is as Ferenc Miskolczi has pointed out. NOAA has been keeping a database of weather balloon observations since 1948 and these can be used to determine the relevant atmospheric absorption parameters. Miskolczi used this database to calculate how the global annual infrared optical thickness of the atmosphere varied throughout these years. And he found that the optical thickness of the atmosphere in the infrared where carbon dioxide absorbs remained constant for 61 years, with a value of 1.87. This tells us that the transparency of the atmosphere in the infrared did not change for 61 years despite constant addition of CO2 to the atmosphere through all this long stretch of time. Hence, the greenhouse absorption signature of the added carbon dioxide which we are told about simply isn’t there. This is an empirical finding, not something derived from theory, and it overrides any calculations from theory that do not agree with it. Theories that disagree must either be modified or discarded. I want to point out also that his work came out in 2009 and no one so far has attempted to present any peer-reviewed arguments against it. Miskolczi concludes: “It will be inferred that CO2 does not affect the climate through the greenhouse effect.”
I am enjoying the various views expressed in the various comments.
As regards the various arguments as to whether heat can flow from a cooler body to a warmer body, net heat flow, the rate of net heat flow etc, given the importance of this issue, it amazes me that there appears to be no experimental data on this. Whilst this is not my field, surely, it cannot be that difficult to devise a suitable experiment. Possibly along the lines:
1. A very larger insulated air chamber with a well mixed air temperature at say 290K.
2. Suspend within the chamber a modest size blackbody sphere at say 340K and measure the time taken to cool to 320K.
3. Repeat 2 above but this time additionally suspend within the chamber a significantly smaller blackbody sphere (say perhaps 1/10th surface area) at 300K say 2 metres away from the larger 340K blackbody. Measure the time taken for the 340K blackbody to cool to 320K. Measure the heat radiated on both sides of that blackbody to see whether there is a difference in the amount of heat being radiated on the side which is adjacent to the smaller cooler blackbody. Measure the heat being radiated by the smaller blackbody to see whether there is a difference in the amount of heat being radiated on the side adjacent to the warmer blackbody.
4. Repeat 3 above but with the smaller blackbody at 280K.
5. Repeat the experiment with different sizes of blackbodies, and different temperatures for each blackbody and different distances between the blackbodies.
6. Repeat the experiement with the chamber of air having 500ppm, 600ppm, 700 ppm and 800ppm of Co2.
7. Repeat the experiment but with a slow running fan placed under and sime distance away from the blackbody spheres.
8. Carry out a number of experimental runs as appropriate.
9. Collect data and analyse.
I am not suggesting that the above experiment but some experiment along those lines ought to establish what really happens in the real world.
Phil,
In fact, I was one of those Chem E’s! Thank you for your compliment!
I agree with what you say. I am just telling Ira that his use of language is contrary to what we would teach in a thermodynamics classroom. An atmosphere won’t transfer net heat to a warmer body. It may slow the rate at which EMR is emitted from the body, or change the equilibrium temp of the body, but the “Heat Transfer” will always go from the Hot source to the Cold source. You can’t make statements like -“A real greenhouse primarily restricts heat escape by preventing convection while the “greenhouse effect” heats the Earth because GHGs absorb outgoing radiative energy and re-emit some of it back towards Earth” – to a group of engineers.
Phil. says:
March 10, 2011 at 9:44 am
a warm object with a continuous heat source surrounded by a radiatively active atmosphere which is warmer than space will reach an equilibrium temperature which is warmer than it would otherwise be in the absence of such an atmosphere.
And a warm object which has lower albedo for 25 years allowing more energy from the continuous heat source onto its surface will too.
Unfortunately we have low clouds in the middle of the optical path.
If the emission is a function of surface temperature.
Nobody knows the correct temperature.
The interface temperature (SSTint)
At the exact air-sea interface a hypothetical temperature called the interface temperature (SSTint) is defined although this is of no practical use because it cannot be measured using current technology.
The skin sea surface temperarature (SSTskin)
The skin temperature (SSTskin) is defined as the temperature measured by an infrared radiometer typically operating at wavelengths 3.7-12 µm (chosen for consistency with the majority of infrared satellite measurements) that represents the temperature within the conductive diffusion-dominated sub-layer at a depth of ~10-20 µm. SSTskin measurements are subject to a large potential diurnal cycle including cool skin layer effects (especially at night under clear skies and low wind speed conditions) and warm layer effects in the daytime.
http://www.ghrsst.org/SST-Definitions.html
On the other hand, consider a cloud that is made up of 10 µm-diameter water droplets: it behaves like a homogeneous medium with respect to the long wavelengths of microwave radiation even though it is quite inhomogeneous with respect to visible and infrared radiation.
in,
A First Course in Atmospheric Radiation page 72.
Unfortunately we have low clouds in the middle of the optical path.
In those circumstances it seems reasonable that the input is different from the output. Without necessarily indicate an energy imbalance (caused by CO2).
I keep seeing the argument that heat cannot flow from a cold body to a hot body. If I follow this argument then a emergency reflective blanket sold in camping stores will not keep you warmer. The second law says there cannot be any NET flow from cold to hot but says nothing about an absorbing gas reducing the rate of heat flow from the hot body.
Here is an actual experiment. I was using a hot filament in high vacuum to heat a sample to high temperature (~1000°C). I could not get one sample hot enough so I put a shiny metal cylinder around but not touching the filament or sample. The reflected heat increased my sample temperature over 100°C. The added radiation from the relatively cold cylinder increased the temperature of the white hot filament. The net flow of heat of course was from hot to cold. This is a pure radiation example and some heat did radiate from the cold reflector to the hot filament.
An electric blanket has an internal heat source and thus isn’t an appropriate comparison. An electric blanket can warm another object above the object’s starting temperature. A regular blanket can’t do that. A regular blanket can only slow down the rate of heat loss from an object it covers. Stick to a pair of black rocks that are exposed to the sun during the day and one of them gets a blanket over it at night. That’s about as close to reality as you’re going to get using ordinary objects in a way that almost everyone can understand from personal experience. Most people also understand that each additional blanket is less effective at retaining warmth than the previous blanket i.e. the first blanket makes a huge difference while a tenth blanket won’t help nearly as much as the first.
After that the argument is just over the exact amount of warming (not much for CO2 & CO2 equivalents alone which isn’t a matter of great dispute) and whether or not there is any positive feedback from water vapor. The water vapor feedback is the matter of great dispute and appears to be nothing more than a wholesale fabrication without a wisp of empirical evidence in support of it and posited for the sole purpose of turning a little bit of welcome, beneficial warming into something worth worrying about.
mkelly says:
March 10, 2011 at 9:21 am
Phil. says:
March 10, 2011 at 8:36 am
“As you’ve been told before you can’t use the gas laws this way, it’s utter nonsense to do so. I didn’t ask about Titan but Triton, where the atmosphere (N2) is far from the critical point.”
Sorry for the mistake between the two moons. But my comment stands as I went back to my themodynamics book and what I said is a virtual quote about critical temperature and being able to use it about air within a 1% error here on earth. If you disgree then you disagree with not only me but my old text book.
Your old text book correctly tells you the accuracy with which the gas laws apply to the Earth’s atmosphere, they don’t tell you that PV=nRT heats the Earth which is what you said!
At the surface P is effectively constant so the gas laws tell us that the density of the atmosphere is a function of T, i.e. n/V=P/RT. The surface temperature is determined by radiational exchange with the sun and the surface heats the atmosphere, the hotter it gets the lower the density, Temperature does not depend on PV=nRT!
Again with the preconceptions. There was a disagreement on the last thread about this and just because you post a link to somewhere does not make it definitive. But let’s say you are correct that N2 and O2 do not radiate according to thier temperature. Then why Phil: “Since 1979, NOAA satellites have been carrying instruments which measure the natural microwave thermal emissions from oxygen in the atmosphere.” Is NOAA wrong? The quote is from an earlier story here on WUWT.
N2 and O2 do not emit BB radiation according to their temperature, they can only emit where there are transitions between energy levels which are determined by molecular structure. At any given temperature they will not emit more that given by S-B at that wavelength. O2 has pure rotationa transitions in the microwave spectrum around 60μm, the fraction of BB emissions from the Earth at that wavelength is extremely small and has no significant contribution (line intensities ~10^-26, BB spectral radiance ~1%) compared with H2O and CO2 (many more lines, line intensities ~10^-19, right in the heart of the BB radiance spectrum). Those microwave emissions are useful diagnostically because they’re in a region which is sparsely populated by other spectra (a little H2O), they don’t contribute to the energy balance of the atmosphere.
Learn something about the physics of gases rather than pick up snippets that you don’t understand and think it shows that those who’ve researched the subject and taught it at the graduate level missed something.
@sjoerd: “”Please leave out the “degree” when talking about Kelvin. It’s “degree Fahrenheit” and “degree Celsius”, but it’s “Kelvin” (without the “degree”). Same when abbreviated: It’s 270K, not 270ºK.””
Only to kids. We old farts grew up with “degrees Kelvin”, before it was changed by a convention in the early 70’s. Just like many of us grew up with “degrees Fahrenheit”, before many countries started changing to “degrees Celsius”. We also used to know it by “Centigrade”, not “Celsius”. How about you wait till we’re all dead before waxing on about your superiority, huh?
Will says:
March 10, 2011 at 9:37 am
mkelly says:
March 10, 2011 at 9:21 am
You are correct, all substances radiate according to their respective temperatures, there are no exceptions to that fact.
There are many exceptions to that ‘fact’ because it’s simply not true, if it were there would be no need to go to the difficulty of constructing a BB cavity for calibration purposes. Gases in particular emit line spectra not BB continua.
Michael J says:
March 10, 2011 at 9:32 am
…..”Any matter that is not at zero Kelvin will emit energy.”….
Yes but some molecules radiate quite a lot at certain frequencies and some hardly any.
For O2 and N2 we can ignore any radiation in the IR for all practical purposes.
……”So when the second law forbids the transfer of heat from the cold body to the warm, I think it refers to net heat transfer.”……
Radiation goes from cold to hot but not heat.
Being an engineer you can think of lots of ways to get work done by a machine taking heat from a high temperature then e.g. operating a piston and rejecting unused heat to a lower temperature.
However you cannot think of one device that takes heat from a lower temperature does some work then rejects unused heat to a higher temperature.
John Marshall says:
March 10, 2011 at 2:04 am
May I respectfully suggest you go read a junior level physics text book.
Arno Arrak says:
March 10, 2011 at 10:11 am
You have gone to great lengths to explain the spectral absorption features of the greenhouse gases. These gases are in the atmosphere and that is what they do. But it is unhelpful to know what the gases that are sitting there do when the atmosphere is in a stationary state. What is important to know is how does the addition of more carbon dioxide to the atmosphere change this picture. We are told that if you do that the atmospheric absorption will simply increase at the wavelengths that the added gas absorbs and in proportion to the amount added.
Who’s telling you that? It depends on the gas, for CO2 it’s approximately logarithmic at present atmospheric conditions.
But is this really true? There are no direct instrumental measurements of this and we simply have to believe theory about it.
There are plenty of instrumental measurements of this, the broadening of spectral lines is well understood.
Bryan,
“Vince Causey perhaps is confusing radiation with heat.”
Yes, I was using the two terms interchangably. If we take heat flow to mean something getting warmer, then it is certainly impossible for a cooler body to make a warmer body still warmer. What I was trying to say was that energy will flow from the cooler body but heat will not – ie, the warmer body will not heat up, but will still cool down and equilibriate with the cooler body.
I was attempting to respond to a poster who asserts that the GHG effect violates the 2nd law of thermodynamics which forbids heat flowing from a cooler body to a warmer body. A better worded response would be to say that GHG does not depend on ‘heat’ flowing in that direction, merely the flow of energy, and that energy flow will have the effect of slowing down heat loss from the warmer body.
Fred Souder says:
March 10, 2011 at 10:16 am
2nd Law. Disorder to order. Low entropy to High Entropy. And everyone still appear to be mixing classical and quantum reactions. Kinetic and convective transfer are classical effects. Radiative is a quantum effect. What ‘see’ will be different for both models.
GaryP says:
March 10, 2011 at 10:47 am
Nail, head. Radiative not kinetic.
Will says:
March 10, 2011 at 9:58 am
Phil. says:
March 10, 2011 at 9:31 am
“Venus has a bond albedo of 0.75 due to the sulfuric acid clouds whereas the earth has a bond albedo of 0.29, you bet the temperature depends on the albedo. Venus absorbs 25% of the light incident on it and Earth 71% but the ratio of temperatures still only depends on the distance from the sun? Even a physicist should see the problem with that.”
………..
Albedo applies to visible electromagnetic radiation not invisible IR.
No: “The Bond albedo is the fraction of power in the total electromagnetic radiation incident on an astronomical body that is scattered back out into space. It takes into account all wavelengths at all phase angles.
It is an important quantity for characterizing a planetary body’s energy balance.
For objects in the solar system, the relevant weighting of each wavelength is proportional to the solar power spectrum. Visible light is a major contribution because over 40% of solar output is in this range.
Like most albedos, the Bond albedo is a value between 0 and 1.”
Morris Minor,
“If this is true why isn’t this energy collected and used as an energy source (better than solar energy as no need for storage – this can be collected 24 hours /day).”
Actually heat is collected from the ground. Thermal heat collectors based on heat pumps are able to extract that heat from the 2 metres below the surface and can be used to warm houses.
tallbloke says:
March 10, 2011 at 8:24 am
Be careful about wavelength v penetration in water. Submarines use very longwave radiation for communication and detection because higher frequencies and therefore higher energy waves are rapidly attenuated in water. I have not data at all beyond these details because I designed adaptive filters for one of the first sideways viewing ‘radars’ back in the late ’70s’.
GaryP says:
……”Here is an actual experiment. I was using a hot filament in high vacuum to heat a sample to high temperature (~1000°C). I could not get one sample hot enough so I put a shiny metal cylinder around but not touching the filament or sample. The reflected heat increased my sample temperature over 100°C. The added radiation from the relatively cold cylinder increased the temperature of the white hot filament. The net flow of heat of course was from hot to cold. This is a pure radiation example and some heat did radiate from the cold reflector to the hot filament.”…..
All your reflector did was to insulate the hot filament.
When you put on clothes you reduce heat loss from your body.
The clothes also radiate IR as well as reducing heat loss by conduction and convection.
You would not saythat you wear your own greenhouse effect clothing would you?
Net heat will go from the warmer object toward the cooler. You are absolutely right about that. You are, however, wrong about radiation.
A weaker source will radiate toward a stronger source. The radiation from the stronger source does not magically drive back that of the weaker source.
I give a couple of examples in a longer post above which I will repeat here.
Infra-red is electromagnetic radiation. It behaves like any other kind of EM radiation.
Ira’s statement is just fine.
peter_ga says:
March 10, 2011 at 3:21 am
“Earth is warmer because of its oceans, through an indirect greenhouse mechanism, that has nothing to do with co2.”
Bingo!
see here:
http://climaterealists.com/index.php?id=1487&linkbox=true&position=4
“The Hot Water Bottle Effect.”
and while I’m about it the one most important thing I have realised from the advice of solar expert Leif Svalgaard is that it is not all about radiative physics (sorry Ira).
If we are going to explain movements of the Earth’s air circulation systems to fit observations then radiative physics just does not work.
We see a cooling stratosphere/mesosphere when the sun is active and a warming stratosphere/mesosphere when the sun is inactive. That is the opposite of conventional climatology.
Thus the air circulation systems move poleward when the sun is active and equatorward when it is inactive. That affects global albedo and energy input to the oceans.
What we are left with is atmospheric chemistry involving ozone overriding radiative processes to shift the air circulations, affect global cloudiness and albedo and thereby switch the oceans from net energy gain to net energy loss. The tropospheric air temperatures then follow in due course.
This is my latest effort on that issue:
http://www.irishweatheronline.com/irishweather/how-the-sun-could-control-earths-temperature.html
“How The Sun Could Control Earth’s Temperature”
Alternative suggestions are welcome but they need to fit real world observations at least as well as do my proposals.