A guest post by Ken Coffman and Mikael Cronholm
In clicking around on the Internet, I found an outstanding paper called Thermodynamics of Furnace Tubes – Killing Popular Myths about Furnace Tube Temperature Measurement written by Mikael Cronholm. The paper was clever and wise…and made a lot of sense. Clearly Mikael knows a lot about infrared radiation and I’m a guy with questions. A match made in heaven?
We exchanged e-mails. I want to be clear about this…Mikael corrected some of my wrong ideas about IR. I’ll repeat that for the slow-witted. Some of my ideas about infrared radiation were wrong. I am considered a hard-headed, stubborn old guy and that’s completely true. However, I want to learn and I can be taught, but not by knuckleheads spewing nonsense and not by authoritarians who sit on thrones and toss out insults and edicts.
Ken Coffman (KLC) is the publisher of Stairway Press (www.stairwaypress.com) and the author of novels that include Hartz String Theory and Endangered Species.
Mikael Cronholm (MC) is an industry expert on infrared radiation, a licensed, level III Infrared Training Center Instructor and holds two Bachelor of Science degrees (Economics and Business Administration).
The following is a summary of our conversation.
KLC: Hello Mikael. I found your paper called Thermodynamics of Furnace Tubes and I found it very informative, practical and interesting. I hope you’ll bear with me while I ask a couple of dumb questions. I am an electrical engineer, so I have some knowledge about thermodynamics of conduction and convection, but not so much about IR radiation. In return for your time, I would be happy to make a donation to the charity of your choice.
If I take an inexpensive IR thermometer outside, point it at the sky and get a temperature reading of minus 25°C, what am I actually measuring? Is there anything valid about doing this?
MC: Just as a matter of curiosity, how did you find my paper? I checked your website and I guess this has to do with the Dragon, no? If you want to make a donation I would be happy to receive that book. If you can, my postal address is at the bottom. I don’t follow the debate more than casually, but I am a bit skeptical to all the research that is done on climate change…it seems that the models are continuously adjusted to fit the inputs, so that you get the wanted output…and they argue “so many scientists agree with this and that”…well, science is not a democracy…anyway…
About radiation, then. There is more to this than meets the eye. Literally!
Looking at the sky with an infrared radiometer you would read what is termed “apparent temperature” (if the instrument is set to emissivity 1 and the distance setting is zero, provided the instrument has any compensation). Your instrument is then receiving the same radiation as a blackbody would do if it had a temperature of -25°C, if that is what you measure. It is a quasi-temperature of sorts, because you don’t really measure on a particular object in any particular place, but a combination of radiation, where that from outer space is the lowest, close to absolute zero, and the immediate atmosphere closest to you is the warmest. (I have once measured -96°C on the sky at 0°C ground temperature.) What we have to realize though, is that temperature can never be directly measured. We measure the height of a liquid in a common thermometer, a voltage in a thermocouple, etc, and then it is calibrated using the zeroth law of thermodynamics and assuming equilibrium with the device and the reference.
KLC: Global warming (greenhouse gas) theory depends on atmospheric CO2 molecules absorbing IR radiation and “back radiating” this energy back toward the earth. If you look at the notorious Ternberth/Keihl energy balance schematic (as shown in Figure 1 of this paper: http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/TFK_bams09.pdf ), you see the back radiation is determined to be very significant…more than 300W/m2. From your point of view as an IR expert, does this aspect of the global warming theory make any sense?
MC: The paper you sent me mentions Stefan-Boltzman’s law, but it does not talk about Planck’s law, which is necessary to understand what is happening spectrally. I suggest you read up on Planck and Stefan-Boltzman at Wikipedia or something. Wien’s law would be beneficial as well—they are all connected.
Planck’s law describes the distribution of radiated power from a blackbody over wavelength. You end up with a curve for each blackbody temperature. The sun is almost a blackbody, so it follows Planck quite well, and it has a peak at about 480nm, right in the middle of visual (Wien’s law determines that). The solar spectrum is slightly modified as it passes through the atmosphere, but still pretty close to Planckian. When the radiation hits the ground, the absorbed part heats it. The re-radiated power is going to have a different spectral distribution, with a peak around 10um (micrometer). Assuming blackbody radiation it would also follow Planck’s law.
S-B’s law is in principle the integral of Planck from zero to infinity wavelength. Instruments do not have equal response from zero to infinity, but they are calibrated against blackbodies, and whatever signal they output is considered to mean the temperature of the blackbody. And so on for a number of blackbodies until you have a calibration curve that can be fitted for conversion in the instrument.
That means that the instrument can only measure correctly on targets that are either blackbodies, or greybodies with a spectral distribution looking like a Planck curve, but at a known offset. That offset is emissivity, the epsilon in your S-B equation in that paper. It is defined as the ratio of the radiation from the greybody to that of the blackbody, both at the same temperature (and wave length, and angle…). Some targets will not be Planckian, but have a spectral distribution that is different. If you want to measure temperature of those, you need to measure the emissivity with the same instrument and at a temperature reasonably close to the one you will measure on the target later.
So, of course, the whole principle behind the greenhouse effect is that shorter wavelengths from the sun penetrates the atmosphere easily, whereas the re-radiated power—being at a longer wavelength—is reflected back at a higher degree. I have no dispute about that fact. It is reasonable. So I think the Figure 1 you refer to is correct in principle. My immediate question is raised regarding the numbers in there though. The remaining 0.9 W/m2 seems awfully close to what I would assume to be the inaccuracies in the numbers input to calculate it. You are balancing on a very thin knifes edge with such big numbers as inputs for reaching such a small one. An error of +/- 0.5% on each measurement would potentially throw it off quite a bit, in the worst case. But I don’t know what they use to measure this, only that all the instruments I use have much less accuracy than that. But with long integration times…well, maybe…but there may be an issue there.
KLC: I am interested in some rather expensive thermopile-based radiation detectors called pyrgeometers (an example is the KippZonen CGR 3 instrument http://www.kippzonen.com/?product/16132/CGR+3.aspx).
If a piece of equipment like this is pointed into the nighttime sky and reads something like 300W/m2 of downwelling IR radiation, what is it actually measuring? If I built a test rig from IR-emitting lightbulbs calibrated to emit 300W/m2 and placed this over the pyrgeometers, would I get the same reading?
MC: “What is it actually measuring?” Well, probably a voltage from those thermopiles…and that signal has to be calibrated to a bunch of blackbody reference sources to covert it either to temperature or blackbody equivalent radiation.
Your experiment will fail, though! If you want to do something like that, you have to look at a target emitting a blackbody equivalent spectrum, which is what the instrument should be calibrated to. IR light bulbs emitting 300W/m2 is simply impossible, because 300W/m2 corresponds to a very low temperature! Use S-B’s law and try it yourself. Like this: room temp, 20°C = 293K. The radiated power from that is 293K raised to the power of 4. Then multiply with sigma, the constant in S-B’s law, which is 5.67*10-8, and you get 419 W/m2 or something like that, it varies with how many decimals you use for absolute zero when you convert to Kelvin. For 300 W/m2 radiation I get -23.4°C at 300 W/m2 when I calculate it (yes, minus!). Pretty cool light bulb.
I don’t know what your point is with that experiment, but if it is to check their calibration you need a lot more sophisticated blackbody reference sources if you want to do it at that temperature. But you could do a test at room temperature though. Just build a spherical object with the inside painted with flat black paint, make a small hole in it, just big enough for your sensor, and measure the temperature inside that sphere with a thermocouple, on the surface. Keep it in a stable room temperature at a steady state as well as you can and convert the temperature to radiation using S-B’s law. You should get the same as the instrument. Any difference will be attributable to inaccuracy in the thermocouple you use and/or the tested instrument. Remember that raising to the power of 4 exaggerates errors in the input a lot!
I hope I have been able to clarify things a little bit, or at least caused some creative confusion. When I teach thermography I find that the more you learn the more confused you get, but on a higher level. Every question answered raises a few more, which grows the confusion exponentially. It makes the subject interesting, though.
Let me know if you need any more help with your project!
KLC: I found your paper because one of the FLIR divisions is local and I was searching their site for reference information about IR radiation. I know what a 100W IR lamp feels like because I have one in my bathroom. If someone tells me there is 300W/m2 of IR power coming from space, and I hold out my hand…I expect to feel it. What am I missing?
MC: Yeah, you put your hand in front of a 100W bulb, but how big is your hand…not a square meter, I’m sure. It is per area unit, that is one thing you are missing. The 100W of the bulb is the electrical power consumption, not the emitted power of the visual light from it. That’s why florescent energy-saving lamps as opposed to incandescent bulbs give much more visual light per electrical Watt, because they limit the radiation to the visual part of the spectrum and lose less in the IR, which we cannot see anyway. The body absorbs both IR and visual, but a little less visual.
And, here is the other clue. Your light bulb radiation in your bathroom is added to that of the room itself, which is 419 W/m2, if the room is 20°C. Your 300 W/m2 from space is only that. You will feel those 300 W/m2, sure. It will feel like -25°C radiating towards your hand. But you don’t feel that cold because your hand is in warmer air, receiving heat (or losing less) from there too.
Actually, we cannot really feel temperature—that is a misconception. Our bodies feel heat flow rate and adjust the temperature accordingly. It is only the hypothalamus inside the brain that really has constant temperature. If you are standing nude in your bathroom, your body will radiate approximately 648 W/m2 and the room 419 W/m2, so you lose 229 W/m2. That is what you feel as being cooled by the room, from radiation only. Conduction and convection should be added of course. The earth works the same way—lose some, gain some. It is that balance that is being argued in the whole global warming debate.
KLC: I still feel like I’m missing something. IR heat lamps are pretty efficient, maybe 90%? Let’s pick a distance of 1 meter and I want to create a one-square meter flooded with an additional 300W/m2. It must be additional irradiation, doesn’t it? That’s going to take a good bunch of lamps and I would feel this heat. However, I go outside and hold out my hand. It’s cold. There’s no equivalent of 300W/m2 heater in addition to whatever has heated the ambient air.
Perhaps I’m puzzled by something that is more like a flux…something that just is as a side-effect of a temperature difference and not really something that is capable of doing any work or as a vehicle for transporting heat energy.
It’s a canard of climate science that increasing atmospheric CO2 from 390PPM to 780PPM will raise the earth’s surface temperature by about 1°C (expanded to 3°C by positive feedbacks). From my way of thinking, the only thing CO2 can do is increase coupling to space…it certainly can’t store or trap energy or increase the earth’s peak or 24-hour average temperature.
Any comments are welcome.
MC: Efficiency of a lamp depends on what you want, if heat is what want then they are 100% efficient, because all electrical energy will be converted to heat, the visible light as well, when it is absorbed by the surrounding room. If visible light is required, a light bulb loses a lot of heat compared to an energy saving lamp. Energy cannot be created or destroyed—first law of thermodynamics.
When you say W/m2 you ARE in fact talking about a flux (heat flow is what will be in W). If you have two objects radiating towards each other, the heat flow direction will be from the hotter one, radiating (emitting) more and absorbing less, to the cooler one, which radiates less and absorbs more (second law of thermodynamics). The amount of radiation emitted from each of them depends on two things ONLY, the temperature of the object and its emissivity. So radiation is not a side effect to temperature, it is THE EFFECT. Anything with a temperature will radiate according to it, and emissivity. (If something is hotter than 500°C we get incandescence, emission of visible light.) Assuming an emissivity of unity, which is what everyone seems to do in this debate, the radiation (flux. integrated from zero to infinity) will be equal to what can be calculated by Stefan-Boltzmann’s law, which is temperature in Kelvin, raised to the fourth power, multiplied by that constant sigma. It’s that simple!
With regard to your thought experiment, it is always easier to calculate what an object emits than what it absorbs, because emission will be spreading diffusely from an object, so exactly where it ends up is difficult to predict. I am not sure where you are aiming with that idea, but it does not seem to be an easy experiment to do in real life, at least not with limited resources.
CO2 is a pretty powerful absorber of radiated energy, that fact is well known. Water vapor is an even stronger absorber. In the climate debate it is also considered a reflector, which probably also true, because that is universal. Everything absorbs and reflects to a degree. So I guess that the feedback you mention has to do with the fact that increasing temperature increases the amount of water vapor, which increases absorption, and so on. But my knowledge is pretty much limited to what happens down here on earth, because that is what matters when we measure temperature using infrared radiation. However, it is important to remember, again, that we talk about different spectral bands, the influx is concentrated around a peak in the visual band and the outgoing flux is around 10 micrometer in the infrared band, and the absorption may not be the same.
With so many scientists arguing about the effects of CO2 I am not the one to think I have the answers. I really don’t know what the truth is. And the problem that all these scientists have is that they will never be able to test if their theories are correct, because the time spans are too long. For a theory to be scientifically proven, it has to be stipulated and tested, and the test must be repeatable and give the same results in successive tests for the theory to be proven.
If not, it is not science, it is guessing.
More like a horoscope…
Guys/mods – Is my comment above stuck in the spam filter?
WOW! When Ken asked me if he could have our conversation offered for publication somewhere I had no idea it would create such an interest ans so many extremely initiated comments. I am glad I could contribute even if it is on a fairly basic level, and I apprecite everyones inputs.
I want to repeat again that I am not on any “side” in the global warming debate. And my opinion is that anyone who claims to be absolutely sure about it may be politically correct but never scientifically correct. There are no scientific proof, one way or the other. Science is not democratic, so counting the forces in your camp is merely silly.
I do stand corrected on the 300W/m2 calculation, it turns out to be about -3.3C. It does not change the point I was making though.
I also understand the objection when I say “reflected” regarding the radiation from that is returned to the earth from the atmosphere. Anything WILL reflect, unless it is a blackbody, but true, in IR where I am familiar only about 5% is reflected from water or ice. The rest is absorbed and re-radiated. But my expertise, as I pointed out mainly down on earth.
Water is an amazing substance and the more I study it the more it amazes me. It has several unique features, among them its incredible ability to store heat, especially latent heat. Just the simple fact that it is a dipole and therefore orders the molecules when it freezes in such a way that the density goes down (unique!) is an important fact that is overlooked. If not for that, we could forget about fish in most freshwater lakes up north, for example.
But the most important thing with water is its ability to moderate temperature here on earth. The greenhouse effect as such is not a threat – it is an absolutely necessary condition for life on earth. It creates the moderated thermal equilibrium that allows us to live on a planet that does not change its temperatures too much over the day and year. Whether or not we are tinkering too much with that equilibrium is what this whole debate is about, and no proof is yet presented, one way or the other.
I will look through the comments again one by one when I have a little more time to spend and see if I can make any additional contributions.
Thanks Ken for pulling these things out of me, and thanks everyone for scrutinizing and commenting on our conversation!
Key point by Mikael Cronholm about the uncertainties……
Mix in variable convection and possible gas density ‘layering’ and the difficulty in measurement is compounded.
_Jim,
Your comment claims elementary physics around the CO2 molecular bond and transitions. Would you mind explaining whether the transition energy or the bond energy is more important at atmospheric temperatures and why?
richard verney says:
February 13, 2011 at 4:11 pm
“CO2 delays IR finding its way out to space. However, what I do not understand is how this effectively heats up the Earth.”
It doesn’t heat the earth any more than insulation in your attic heats your house in the winter. It slows down how fast heat can escape. Since the heat is arriving at the same but leaving at a slower rate this causes the surface to become warmer which then increases the rate at which heat moves across the boundary. A new higher surface equlibrium temperature is thus established. In reality too many other things change too rapidly for equilibrium to ever be attained but the theoretical equilibrium point will rise and thus the target which the system seeks is that much higher.
Slacko says:
February 13, 2011 at 7:47 pm
=======
So, other than your rant, have you anything to add?
I can’t wait.
Mikael Cronholm,
In your paper you say “Radiation is the strongest heat transfer mode”. Please elaborate. From my anecdotal experience conduction and evaporation are stronger modes of heat transfer: sweating is better for cooling down than not, blowing on a cup of hot chocolate is better than letting it cool by radiation.
What do you think of the concept of “back radiation” whereby “downwelling radiation” from colder air warms the warmer surface of the earth.
Domenic says:
February 13, 2011 at 7:41 pm
“The polished tube method is not exact. It’s an approximation.”
It might not be exact but when you have a vacuum in the tube and nitrogen in the tube the thermopile output is uneffected but when you have a greenhouse gas in the tube the thermopile output is reduced.
That proves beyond a shadow of a doubt that there’s something very different about greenhouse gases illuminated by infrared.
Feel free to explain the difference via some mechanism other than some gases being transparent to IR and some being opaque. Alternative explanations have two defining characteristics: they are always entertaining and never true.
Mikael Cronholm says February 13, 2011 at 8:02 pm
All your Joule are belong to us.
Awesome article.
“From my way of thinking, the only thing CO2 can do is increase coupling to space…it certainly can’t STORE or TRAP energy or increase the earth’s peak or 24-hour average temperature.”
Every AGW supporter I have spoken to cannot get their heads around this concept.
Mikael Cronholm says:
February 13, 2011 at 8:02 pm
“There are no scientific proof, one way or the other.”
Insofar as some gases absorb infrared radiation and some do not was scientifically proven in the mid-19th century. Your continued denial only means you know less about the physical properties of gases than mid-19th century physicists.
J. Bob says:
February 13, 2011 at 7:28 pm
W. Falicoff says: “Further, your statement that is not possible to achieve a measurement less than the accuracy of an instrument is also not correct, as the accuracy can be increased by taking many measurements (up to a threshold). The resultant accuracy is approximately proportional to the square of the number of readings.”
HHmmmm. If a basic sensor has a mean error of 0.75 deg., and 3 sigma of say +/- 0.25 deg., your true error will be between 0.5 & 1.0 deg no matter how many readings you take. You might want to add a few qualifiers.
If the mean error is know, the readings can be adjusted. If the mean error remains constant, than the temperature anomaly, which is what is being sought will not suffer in accuracy. This is the important point, that many who argue about the problems with temperature data seem to ingore, or not understand.
Bill Illis says:
February 13, 2011 at 4:55 pm
In essence, the Earth has accumulated 1.9 days worth of solar energy. If the Sun did not come up tomorrow, it would take around 86 hours for at least the land temperature to fall below -200C.
What!?? Where I live it can sometimes fall from +40C to +36C between sunset and sunrise. I think maybe you left the atmosphere out of that equation.
Dave Springer says:
February 13, 2011 at 7:54 pm
“Actually that’s not quite right. At low CO2 concentrations it’s nearly linear and as concentration rises it becomes logarithmic. John Tyndall experimentally discovered that too by experiment over 150 years ago. It’s pretty much a case of the proverbial low-hanging fruit. The first few molecules get all the fruit they can handle but as the number of molecules increase there’s less and less fruit available per molecule. IIRC correctly the curve is logarithmic by the time concentration reaches 100ppm.”
Not sure I like that. The form of the equation shouldn’t change for different numbers unless there’s a discontinuity. It has to be logarithmic over the entire range of positive real numbers and obviously isn’t physical for negative numbers. I think you mean that for low concentrations of Co2 the dependence diverges only slightly from a simple linear dependence and the divergence grows as the concentration grows.
MC – excellent discussion, simple straight forward answers referencing the actual physics. We need more of this in the discussion, not more slogans, so thanks for stepping up!
Now – H2O vs CO2
For all the skeptics who have been trying to present the argument that water vapour is so much stronger an absorber than CO2 that CO2 doesn’t matter, sorry, but you are wrong. And I am a hard core skeptic!
Water vapour is in fact a much stronger absorber than CO2 and in the same approximate spectrum. If water vapour and CO2 were mixed evenly in the atmosphere, that would make CO2 insignificant. But they are NOT. CO2 is reasonably well mixed throughout the troposphere, but water vapour concentration falls rapidly with temperature. As a consequence water vapour declines with both altitude and latitude. What ever CO2 does or does not do, well over 90% of it exists in the atmosphere at temperatures low enough that water vapour is also low enough that CO2 becomes significant by comparison.
That said, I repeatedly ask the logical next question that I have yet to see a reasonable answer for from the warmists. If CO2 reflects/re-radiates/back-scatters what ever you want to call it, upwardly bound long wave, it makes sense that this would result in a temperature increase which in turn would increase water vapour. BUT, and I repeat BUT, does it not also follow that any increase in water vapour works both ways? That is, certainly the water vapour would re-radiate upward bound LW from earth surface, but it would ALSO re-radiate DOWNWARD bound LW too. The downward bound LW that would normaly have been absorbed at earth surface now has an increased % chance of being re-radiate back up. And we’re not talking about just the downward LW from increased CO2, we’re talking ALL the downward LW from ALL sources. In other words, increased water vapour may in fact have a net positive feedback, but it has a huge, built in, negative feedback too that likely renders the whole calculation near meaningless.
THERMAL QUENCHING – I saw some comments on this too. This was a big issue for Ernst Beck (may he rest in peace) who felt that this was an under estimated effect of CO2 LW absorption. His explanation was way, Way, WAY over my head. It was a seriously complex issue as there are so many factors that govern how an individual molecule can or cannot aborb or lose a photon when in collision with another dismilar molecule, at what temperature, and at what time period before re-emission would happen anyway. I don’t have any certainty that he was correct, but the explanations and rebuttals showed one thing pretty clearly – no one has a real good grip on the complexities, in the atmosphere in particular, and measuring thermal quenching is darn near impossible.
For completeness and accuracy of the article it should be noted that the “inexpensive” household IR (non-contact single point) thermometers are designed to measure emission from distant solid objects. Therefore they use the “atmospheric window” where air has the least interference with IR and CO2 does not absorb nor emit, so they can get better distant readings of objects they are designed to measure. Hence the device uses an IR detector working in a narrow 8-12um range, right in the center of the window. When pointing to sky, only clouds/haze/smog can affect readings.
Regarding the Antony’s picture, he should be able to recalibrate the scale of his FLIR camera to colder side, and it is likely that he would see IR images of clouds behind his house in minus-40-50 range, where they fly.
Richard Sharpe says:
February 13, 2011 at 7:33 pm
What you have said, Wayne, does not seem correct to me.
It seems to me that approximately half the energy absorbed by CO2 would be re-radiated upwards and half downwards.
——-
Two units of energy goes up, cooling the suface, surface -2, and is absorbed warming the atmosphere, atmosphere +2, your radiators means one unit always goes upward to space, atmosphere now +1, space +1, and one back down to the surface, surface -1, atmosphere is now zero. Plaease tell me what has just happened, for the surface is -1 unit of energy and space is now +1. Why is this so confusing to you?
And I do know this is ignoring energy that goes via the radiative window directly to space but that effect is exactly the same.
The following is pretty elementary compared with what has been presented in the text and in the comments, but…..this example may help visualization of “back radiation”. I shower in the same stall daily. In the summer, I have to run the water a little cool to keep from overheating myself when the temperature is, say, 20°C. In the winter I have to run the water considerably warmer and keep the air temperature around 22° to keep comfortable. I figure that the difference is due to the difference in temperature of the walls and ceiling in the two seasons.
Related to this, friends heat their house by means of electrical heating panels that warm the drywall panels in the ceiling. Even though they are barely warm to the touch, they are adequate to keep people in the room comfortable. Radiant energy.
IanM
u.k.(us) says:
February 13, 2011 at 8:17 pm
Slacko, — other than your rant, have you anything to add?
I can’t wait.
What rant? I repelled a rant and posed a question.
So while you’re waiting, maybe you can figure out “What physics do skeptics deny?” If you lot think you can get away with accusing me of your own folly, you’re wasting your time.
chico sajovic says:
February 13, 2011 at 8:20 pm
“Mikael Cronholm,
In your paper you say “Radiation is the strongest heat transfer mode”.”
Ultimately it’s the ONLY mode as convection, conduction, and mechanical transport (evaporation/condensation) ends where the atmosphere ends.
But that is certainly a valid point as we live and breathe and raise our crops on or very near the surface and these mechanisms can accelerate the transfer of heat from surface to above the cloud layer resulting in practically no change at the surface. The increase in temperature caused by increased CO2 doesn’t have to be at ground level. It could be at 10,000 ASL and not effect our surface activities one tiny bit. In fact the climate boffins expected to find the CO2 “signature” as a hotspot in the upper troposphere where the air is very dry and they were confounded when the temperature rise was found to be greatest at the surface where the air is very wet. This should have been their first clue that their climate models were fundamentally wrong. But they’d already decided by then that fossil fuel consumption was going to cause great harm to the planet so they had to continue blaming it. The mantra morphed from “global warming” first to “climate change” then when that didn’t resonate with the unwashed masses they changed it again to “global climate disruption”. That’s not science it’s a marketing campaign for an ecoloon religion. A floundering campaign, by the way, which is losing ground at an accelerating rate with every passing day.
From the article:
“KLC: I still feel like I’m missing something. IR heat lamps are pretty efficient, maybe 90%? Let’s pick a distance of 1 meter and I want to create a one-square meter flooded with an additional 300W/m2. It must be additional irradiation, doesn’t it? That’s going to take a good bunch of lamps and I would feel this heat. However, I go outside and hold out my hand. It’s cold. There’s no equivalent of 300W/m2 heater in addition to whatever has heated the ambient air.”
What’s missing is that the lamps are already radiating based on their room temperature. The 300W/m2 from the lamps when they are turned on is, of course, additional, whereas the 300W/m2 from the sky is the total heat flux from the sky. The two are not comparing the same thing at all.
It was also nice to see all the talk about the importance of emissivity. It’s a subtle point that many get wrong.
So far the only things that have been discussed are the thermodynamics of CO2 vs H2O vapor. What about ICE clouds (slide 23)?
@chico sajovic, 8.20. I think you talk about the furnace paper then, and in a furnace radiation is much stronger than any other mode. In the radiation section at the bottom, where the flames are, radiation is completely dominant. Up in the convection section, the tubes draw out the remaining energy they can from the exhaust gases, but that is much less than what is added to the feedstock in the radiation section. The clue is that radiation increases with the temperature to the power of 4, according to Stefan-Boltzman’s law, while conduction and convection don’t. Conduction is linear, convection probably less strong than linear, with temperature (logic: just because a surface is 1000C it does not create a storm around it by convection).
my comment above has a mistake. I meant to say “square root” not “square”. Let me provide an example. If we take a photo of an astronomical object such as a star or nebula using a CCD camera that has a Signal to Noise Ratio (SNR) for one image of say x, then if we take N images of that same object, the SNR will increase by the square of N. That is the new SNR will be (square root of N) times x.
@ur momisugly Dave Springer. I was not discussing properties of gases. I just say there are no scientific proof that increased CO2 emission causes climate change, or that it does not. And I am not on any side in the debate, for that very reason.