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…
@Chemman Feb 13, 2011 at 12:57 pm:
I’ve always assumed they all deal with it as 3D re-radiation – including only the downward re-radiation in the heat flow system. Otherwise some of the skeptics would have certainly ripped into them about it.
This is a very useful discussion, particularly for those not of a physics bent. As someone who has worked for many years in the field of fluid flow and heat and mass transfer, it is evident to me that the radiative efects of CO2 in the atmosphere are of 2nd or 3rd order compared to the radiative, convective and latent heat effects of H2O. Our climate is dominated by the water cycle in all its forms.
I have some hands on industrial R&D experience with heat flow vs temperature, and also with the reality of emissivity.
I ran experiments using what are called “engineering plastics” in order to find the best plastic for a 420°F application. In one, we heated the plastic to temperature and then subjected it to weight loading to see what kind of strain we got. In the process, I handled up to 500°F pieces of plastic (a bit higher than the real application, for “cushion”). I did this barehanded. Even with a thermocouple telling me the plastic was 500°F, the plastic was almost not even warm in my hand. It is not the temperature that burns; it is the heat flow. See the next paragraph…
As to emissivity, we also had highly polished and chrome plated tool steel (H13) that was oil-heated to the 420°F temperature. The polishing and chrome plating made the emissivity extremely low (how I still don’t “get”). I could put my skin well within 1/16″ of the surface of the hot metal and not even feel warmth. (It is not easy to do without jittering, but I did manage to do it, bracing my hand on something cooler, just to see.) However, once the heat transfer method went from radiation to conduction – when I actually touched the metal – it was instant BURN!
Low emissivity is amazing.
Low heat flow is also amazing.
(Note: By far the best fix for the occasional burns was using freon from a spray can. I was SERIOUSLY [snip . . irritated?] when they banned CFCs to protect the ozone hole. And I completely believe that in time that theory will be completely refuted.)
Ouch! That is seriously nasty.
ATTENTION: Thomas Fuller or CTM … would one of you please give Steve Mosher a call and let him know that one his laptops was stolen and that somewhere nearby in some dirty sleazy bar or seedy hotel with free Wi-Fi there is a nasty old miserable drunk posting on WUWT in his stead.
😉
“Domenic- the CO2 measurements by Scripps Institute are taken in several locations around the world including the locations near the North and South pole. See http://scrippsco2.ucsd.edu/research/atmospheric_co2.html These measurements support the findings of the measurements at Mauna Loa. They also show there is a lag of CO2 from the Northern to Southern Hemisphere (the levels in Antarctica lag those in the Northern hemisphere), as expected given the gains in CO2 are primarily from anthropogenic sources” … W. Falicoff
“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.” … Mikael Cronholm
So all you have to do now W.F. is show your repeatable science and you will have done something that would change the entire scientology of AGW
Mikael Cronholm says:
February 14, 2011 at 1:47 am
Re convection:
It is known as convective inhibition when cloud cover at night = warmer than cloudless night.
Clouds form a barrier. From IR it block some solar radiation, and from earth it prevents convection currents of rising air from leaving. Most energy leaving is via convection. It is known as atmospheric convection
Very interesting post & posts! Great source of knowledge down to little known details (such as spraying water on fruit). Lot of food for thought!
I only have one question to add to this conversation: Is it at all possible to measure the energy balance (or radiation balance) of the earth. By energy (radiation) balance I mean the difference between energy input and output. Please excuse if this question is put forward in terms which fall short of physicists standarts – that´s because I am just a curious layman.
to clear the matter: Since IR radiation from earth is weak, it can’t move through the atmosphere and is absorbed by water vapour mainly, and c02.
Since warmer air is less dense than cold air convection occurs to take energy upwards, via what they call advection
We have a little blue planet that is stirred internally by a big yellow monster, this same monster bombards us with the full spectrum of radiation. Mitigating factors protect us from this monster or we would perish. Like wise if it failed to arise tomorrow we would perish very quickly. Our little blue planet works its fanny off trying to balance an out of balance heat input caused by all sorts of wobbles and perturbations. The occasional large volcanic eruption is compensated for and the world returns to normal. A flea on elephant comes to mind as to effect of CO2 on the planetary climate. The cyclic changes we see if we live long enough are the result of the rules of thermodynamics in an open heat pump trying its utmost to balance itself.
It would be pure folly and ego on our part to contemplate that we could change the climate. Looking backward to Newton and celestial mechanics using real geometry is the key to finding the reasons behind ice ages and interglacials. When these are understood then we can look at the minor perturbations with some understanding and a modicum of confidence. Some scientists are looking at this aspect and finding a surprising correlation to the suns recalcitrant attitude.
I agree with everything MC said except (as Jim D noted) that IR is not reflected by CO2, it is absorbed and then re-emitted in all directions.
If the CO² molecules has radiatively absorped and is therefore above ground state state it will likely ‘reflect’ further incoming IR.
ThomasU says:
February 14, 2011 at 3:50 am
This is indeed a big problem. Temperature measurements are used, which are inadequate, sparse and unreliable.
Atmospheric energy should be measured in joules per cubic metre. Not in temperature
Cal says Feb 14, 12:49 am, Slacko says, Jim says
Sort it out, will you.
http://www.wisegeek.com/how-does-infrared-heat-work.htm
“To observe how infrared heat works, the heating and cooling of the earth is probably the most helpful example. Apart from driving all weather events and patterns, as well as ocean currents, infrared heat from the sun is what the Earth during the day, and it is what the ground gives off at night after the sun sets. It is interesting to note that while the sun does emit a huge amount of infrared heat, only about half of the heat we feel on the ground is from direct infrared radiation from the sun. The other half comes from energy from visible light that is absorbed by objects on earth, and then emitted later as infrared heat.”
So which is it?
“infrared radiation is what warms the earth during the day”
Infrared is the heat you feel, but cannot see.
I’m not understanding this idea that a 1deg rise in temps caused by CO2 will cause a further 2deg rise through the extra water vapour that is created.
Surely if that were true it would be possible to surround a small lake with something like the Eden Project biodomes, pump it full of CO2, and then extract the heat that all the extra water vapour created. It would be the ultimate passive energy creator, no windmills, solar or thorium required. At the very least we could do it on a small scale to test the thesis that that is what would actually happen.
Steve Reynolds says:, “I agree with everything MC said except… that IR is not reflected by CO2, it is absorbed and then re-emitted in all directions”
To which Latitude asks,
“Steve, Since it’s constantly being exposed to IR, when it’s saturated, does it just reflect because it can’t absorb any more?
Or is it in a constant state of absorbing and re-emitting? neutralizing itself?”.
The gases in our atmosphere (N2,O2 and CO2) do not ‘reflect ‘ light. If they did it would be impossible for us to see coherent images because the light would be bouncing all over the place. We can only form clear images where light travels in straight lines.
The same is true in the infra-red.You no doubt have seen pictures from infra-red imaging cameras, e.g. police helicopters. These are only viable because atmospheric gases do not ‘reflect’ infra-red radiation but allow it to travel in straight lines.
However, CO2 does absorb infra-red within a narrow wavelength band. The important absorption occurs at wavelengths between 14 and 16 microns (other CO2 absorption bands are not significant In the context of greenhouse warming because they do not obstruct the radiation emitted from the Earth’s surface). Photons of infra-red radiation around 15 micron have just exactly the right amount of energy to raise a CO2 molecule from one vibrational state to another one. Being thus ‘tuned’, they may be captured by a CO2 molecule which then changes state. Almost instantaneously, within nanoseconds, the CO2 molecule re-emits the photon and reverts to its original state. Because the photon can be re-emitted in any direction (spherically random) about half of them will be re-directed back to Earth and will represent an additional heat flux if they ever get there.
If the ‘excited’ CO2 molecule collides with another molecule, say of Nitrogen. before it can re-emit its captured photon, then it becomes ‘thermalised’ (or as Mark Wagner says, ‘quenched’). Its extra energy is transformed into heat and it can no longer emit a photon. If this happens the atmosphere is warmed.
Its physically impossible for a 1C rise in temperature by c02.
What causes temperature changes are weather systems (via convection).
Storms, snow, cyclones, clouds – the whole gamut are caused by convection. When air convects, it cools sufficiently for it to fall below its dew point. Thats when clouds form.
I don’t know why c02 was brought into meteorology and climatology.
Maybe it was to paint a human face on climate.
Bomber_the_Cat says:
February 14, 2011 at 4:18 am
what you haven’t mentioned is the temperatures at which this 14.77 peak of c02 absorbs radiation. It corresponds to -28C which is up in the lower troposphere. When it leaves that temperature range it thermalises. Now: There is no physical mechanism that can cause subzero temperature ranges to penetrate back to earth and warm it up beyond the nominal 14-15C. That is tantamount to saying that putting cold water in the freezer will cause it to be lukewarm
Best post I’ve seen here for some time. It’s a clear, concise essay which encourages the reader to do their own research elsewhere. Great stuff.
Jim Masterson The cloud cover is supposedly 62%. KT 1997 combines three cloud layers (49%, 6%, & 20%) to get that figure. They call it “random overlap,” whatever that means. It looks like an application of the Inclusion-Exclusion principle. I get 61.6% which rounds to 62%. Their famous energy diagram (fig. 7 in KT 1997 and fig. 1 in TFK 2009) should state: “62% cloud cover assumed.”
The Inclusion-Exclusion Principle requires that we know the overlap(s) to begin with, so it can’t give us the answer. The average of the minimum and maximum overlaps gives exactly 62%:
((49 + 6 + 20) + 49) / 2 = 62
but I’m not sure that this is what we’d get with random overlap, even if, as my calculation assumes, there are no real-world constraints.
Don V says February 14, 2011 at 1:47 am
An excellent post, Sir. IMHO non radiative transfer of energy to the tropopause by water completely swamps any radiative effects of increasing CO2. What happens at and above this point is more interesting, however.
P. Wilson says, “What you haven’t mentioned is the temperatures at which this 14.77 peak of C02 absorbs radiation”.
The CO2 absorption of photons at 15 micron is not dependent on temperature. A molecule of CO2 will absorb any photon with the ‘correct’ quanta of energy which impacts it, irrespective of temperature.
More interestingly, “There is no physical mechanism that can cause subzero temperature ranges to penetrate back to earth and warm it up beyond the nominal 14-15C”.
I assume that subzero here means below zero on the Celsius or Fahrenheit scales. Now ALL objects above absolute zero emit radiation; that includes you, me and an ice cube. The amount an object emits (Stephan’s Law) and the wavelengths of the radiation emitted (Plank’s Law) is determined by their temperature. So even cold objects, such as an ice cube, emit radiation. If that radiation impacts a warmer object then it is absorbed by the warmer object. The warmer object therefore receives energy that it wouldn’t receive if the cold object was not there – and so the warm object is kept warmer than it otherwise would be. Radiation is not somehow preferentially attracted only to colder objects. Thus the presence of cold objects can keep warm objects warmer!!! This does not infringe the 2nd law of thermodynamics, only a schoolboy misunderstanding of it.
As for making the Earth warmer, remember that the Earth is warmed by the Sun. The CO2 ‘blanket’ , by sending radiation back to the surface, simply acts as insulation. The incoming solar energy is what causes the Earth’s surface to rise.
At the top of the atmosphere of course, the amount of radiation leaving the Earth will always balance the radiation coming in – no matter how much CO2 there is in the atmosphere. But we don’t live at the top of the atmosphere, we live on the surface – and it is the surface temperature which is effected by the greenhouse gases.
P. Wilson says, “What you haven’t mentioned is the temperatures at which this 14.77 peak of C02 absorbs radiation”.
The CO2 absorption of photons at 15 micron is not dependent on temperature. It will absorb any photon with the ‘correct’ quanta of energy which impacts it, irrespective of temperature.
More interestingly, “There is no physical mechanism that can cause subzero temperature ranges to penetrate back to earth and warm it up beyond the nominal 14-15C”.
I assume that subzero here means below zero on the Celsius or Fahrenheit scales. Now ALL objects above absolute zero emit radiation; that includes you, me and an ice cube. The amount an object emits (Stephan’s Law) and the wavelengths of the radiation emitted (Plank’s Law) is determined by their temperature. So even cold objects, such as an ice cube, emit radiation. If that radiation impacts a warmer object then it is absorbed by the warmer object. The warmer object therefore receives energy that it wouldn’t receive if the cold object was not there – and so the warm object is kept warmer than it otherwise would be. Radiation is not somehow preferentially attracted only to colder objects. Thus the presence of cold objects can keep warm objects warmer!!! This does not infringe the 2nd law of thermodynamics, only a schoolboy misunderstanding of it.
As for making the Earth warmer, remember that the Earth is warmed by the Sun. The CO2 ‘blanket’ , by sending radiation back to the surface, simply acts as insulation. The incoming solar energy is what causes the Earth’s surface to rise.
At the top of the atmosphere of course, the amount of radiation leaving the Earth will always balance the radiation coming in – no matter how much CO2 there is in the atmosphere. But we don’t live at the top of the atmosphere, we live on the surface – and it is the surface temperature which is effected by the greenhouse gases.
P. Wilson says, “What you haven’t mentioned is the temperatures at which this 14.77 peak of C02 absorbs radiation”.
The CO2 absorption of photons at 15 micron is not dependent on temperature. It will absorb any photon with the ‘correct’ quanta of energy which impacts it, irrespective of temperature.
More interestingly, “There is no physical mechanism that can cause subzero temperature ranges to penetrate back to earth and warm it up beyond the nominal 14-15C”.
I assume that subzero here means below zero on the Celsius or Fahrenheit scales. Now ALL objects above absolute zero emit radiation; that includes you, me and an ice cube. The amount an object emits (Stephan’s Law) and the wavelengths of the radiation emitted (Plank’s Law) is determined by their temperature. So even cold objects, such as an ice cube, emit radiation. If that radiation impacts a warmer object then it is absorbed by the warmer object. The warmer object therefore receives energy that it wouldn’t receive if the cold object was not there – and so the warm object is kept warmer than it otherwise would be. Radiation is not somehow preferentially attracted only to colder objects. Thus the presence of cold objects can keep warm objects warmer!!! This does not infringe the 2nd law of thermodynamics, only a schoolboy misunderstanding of it.
As for making the Earth warmer, remember that the Earth is warmed by the Sun. The CO2 ‘blanket’ , by sending radiation back to the surface, simply acts as insulation. The incoming solar energy is what causes the Earth’s surface to rise.
At the top of the atmosphere of course, the amount of radiation leaving the Earth will always balance the radiation coming in – no matter how much CO2 there is in the atmosphere. But we don’t live at the top of the atmosphere, we live on the surface – and it is the surface temperature which is effected by the greenhouse gases.
P. Wilson says, “What you haven’t mentioned is the temperatures at which this 14.77 peak of C02 absorbs radiation”.
The CO2 absorption of photons at 15 micron is not dependent on temperature. It will absorb any photon with the ‘correct’ quanta of energy which impacts it, irrespective of temperature.
More interestingly, “There is no physical mechanism that can cause subzero temperature ranges to penetrate back to earth and warm it up beyond the nominal 14-15C”.
I assume that subzero here means below zero on the Celsius or Fahrenheit scales. Now ALL objects above absolute zero emit radiation; that includes you, me and an ice cube. The amount an object emits (Stephan’s Law) and the wavelengths of the radiation emitted (Plank’s Law) is determined by their temperature. So even cold objects, such as an ice cube, emit radiation. If that radiation impacts a warmer object then it is absorbed by the warmer object. The warmer object therefore receives energy that it wouldn’t receive if the cold object was not there – and so the warm object is kept warmer than it otherwise would be. Radiation is not somehow preferentially attracted only to colder objects. Thus the presence of cold objects can keep warm objects warmer!!! This does not infringe the 2nd law of thermodynamics, only a schoolboy misunderstanding of it.
As for making the Earth warmer, remember that the Earth is warmed by the Sun. The CO2 ‘blanket’ , by sending radiation back to the surface, simply acts as insulation. The incoming solar energy is what causes the Earth’s surface to rise.
At the top of the atmosphere of course, the amount of radiation leaving the Earth will always balance the radiation coming in – no matter how much CO2 there is in the atmosphere. But we don’t live at the top of the atmosphere, we live on the surface – and it is the surface temperature which is effected by the greenhouse gases.
P. Wilson says, “What you haven’t mentioned is the temperatures at which this 14.77 peak of C02 absorbs radiation”.
The CO2 absorption of photons at 15 micron is not dependent on temperature. It will absorb any photon with the ‘correct’ quanta of energy which impacts it, irrespective of temperature.
More interestingly, “There is no physical mechanism that can cause subzero temperature ranges to penetrate back to earth and warm it up beyond the nominal 14-15C”.
I assume that subzero here means below zero on the Celsius or Fahrenheit scales. Now ALL objects above absolute zero emit radiation; that includes you, me and an ice cube. The amount an object emits (Stephan’s Law) and the wavelengths of the radiation emitted (Plank’s Law) is determined by their temperature. So even cold objects, such as an ice cube, emit radiation. If that radiation impacts a warmer object then it is absorbed by the warmer object. The warmer object therefore receives energy that it wouldn’t receive if the cold object was not there – and so the warm object is kept warmer than it otherwise would be. Radiation is not somehow preferentially attracted only to colder objects. Thus the presence of cold objects can keep warm objects warmer!!! This does not infringe the 2nd law of thermodynamics, only a schoolboy misunderstanding of it.
As for making the Earth warmer, remember that the Earth is warmed by the Sun. The CO2 ‘blanket’ , by sending radiation back to the surface, simply acts as insulation. The incoming solar energy is what causes the Earth’s surface to rise.
At the top of the atmosphere of course, the amount of radiation leaving the Earth will always balance the radiation coming in – no matter how much CO2 there is in the atmosphere. But we don’t live at the top of the atmosphere, we live on the surface – and it is the surface temperature which is effected by the greenhouse gases.
Bomber_the_Cat says:
February 14, 2011 at 5:59 am
Well if I wasnt confused before, I am cerainly now, after reading your post. Was it an attempt on demonstrating backradiation with words? The same stuff coming again, and again, and again? Looked like a very unstable post to me.
W. Falicoff says:
February 13, 2011 at 3:40 pm
“… 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. This holds true in several fields. …”
Actually, repeated measurements cannot improve accuracy, it can only improve precision. If there is bias in the gauge then repeated measures will keep giving you the biased answer. Precision (e.g. the standard deviation) of the average value of the measurement can improve by the inverse square root of the sample size.
But there’s far more to it than increasing sample size. Check out MSA (Method System Analysis) or Gauge R&R (Repeatability and Reproducibility). In a manufacturing environment a Gauge (or measurement system) is not considered capable until the precision is at least 1/10th the specification range. So in terms of AGW, if the world is going to melt down at an additional 2C then the gauge should be able to repeatably and reproducibly measure to +/- 0.2C on the individuals….not multiple measurements to construct an average.
@- davidmhoffer says:
February 13, 2011 at 11:55 pm
“LW radiatiance cannot penetrate more than a micron or so of water before being absorbed. The result being that any longwave that does strike water is absorbed in a layer so thin that it immediately evaporates taking the extra energy from the LW, plus any energy that was already in that water with it into the atmosphere. ”
The LW absorbed in the surface layer may not be enogh to liberate a water molecule from the bonds at the surface layer, it may just increase the random kinetic energy of the molecules in the surface layer that is transported to the deeper layers millimetres further down by surface turbulence. Water is rarely so still that this transport mechanism is insignificant.
Even if it does provide enough energy for a water molecule to break free of surface bonds and ‘evaporate’ that molecule has a ~50% chance of colliding with the other molecules and bouncing back into the water surface adding to the thermal kinetic energy of the surface layer.
There is no way that the water surface acts like a one-way street for all incident radient energy. It is not Maxwell’s demon!
P Wilson says:
February 14, 2011 at 4:32 am
“what you haven’t mentioned is the temperatures at which this 14.77 peak of c02 absorbs radiation”
The temperature of the gas has little to do with IR absorption. The earth emits LWIR in a continuous blackbody spectrum with a peak emission at around 10um which corresponds to a blackbody at approximately 52F which is the average surface temperature of the ocean. CO2 absorbs narrow bands out of that continuous spectrum which excites the CO2 molecule and because the molecule is part of a cold dense mix of gases the excited molecule almost instantly bumps into a neighbor (most likely N2) which then thermalizes the N2. Re-emission up the upwelling narrow band energy is a continuous blackbody spectrum corresponding to the temperature of the gas at whatever altitude the re-emission occurs. The process starts from the ground up and proceeds to saturation. Looking down at the atmosphere from above with a spectrometer one sees a continuous blackbody spectrum with narrow absorption bands where the energy level falls off. The energy missing from those narrow bands is redistributed across the rest of the spectrum. The altitude/temperature to which you refer is the energy level at the top of the 15um band.
See figure 8.2 (spectrograph from 20km looking down on the north pole):
http://www.sundogpublishing.com/AtmosRadFigs.html
The blackbody emission curve is at about 265K which corresponds to the surface temperature at the pole at the time. You’ll notice a big hole in the spectrograph centered on 15um with the bottom of the hole following the 225K blackbody curve. The missing energy at 15um is what CO2 has absorbed beginning from the ground up and has been completely thermalized by an altitude where the air temperature is 225K which, applying the dry adiabatic lapse rate of 10K per 1000 meters is about 3000 meters or 10,000 feet (middle region of the troposphere).
The missing energy in the 15um, when thermalized, is re-emitted as continuous blackbody spectrum so the top of the curve at 265K (which is the surface temperature) is a bit higher than it would be otherwise. That bit higher surface temperature is the effect of CO2’s action as a greenhouse gas. It impedes the flow of 15um energy from surface to space which in effect acts like insulation making the surface temperature a little higher than it would be otherwise. The temperature of the cosmic void is about 3K and doesn’t change. The increased differential between surface and space raises the rate at which energy flows from surface to space re-establishing a new surface temperature equilibrium point between energy-in (short wave energy from the sun) and energy-out (long wave energy from the earth).
This is all undisputed except by cranks and and other assorted ignoramuses who refuse to accept the radiative absorption and emission characteristics of various gases according to physics theories that have been around for over 200 years and which were experimentally confirmed 150 years ago by John Tyndall and which have remained as well established as any theory in physics since then.
The controversy isn’t about the direct effect of increased CO2. That’s cut and dried number crunching of basic physics formulas. The bone of contention is in the feedbacks. The climate boffins on the “hockey team” insist there is a large positive feedback which will somehow cause a runaway greenhouse despite the fact that all paleo-climate evidence of every kind shows the earth has never in its history experienced a runaway greenhouse despite atmospheric CO2 levels far higher than could be obtained by burning every last drop, wisp, and crumb of recoverable fossil fuels. ALL the evidence says the feedback is negative which limits the maximum global surface temperature and where the temperature increase (we’re in a very COLD period of the earth’s history) is concentrated in the higher latitudes i.e. the tropics won’t get much warmer but the temperate and polar regions will. The usual state of affairs for the earth over the past billion years is warm and friendly for living things from pole to pole. The current terrestrial biosphere is a shrunken frozen shadow of itself much of the time over much of its extent compared to the warm (non-ice age) periods which is to say 90% of the time for uninterrupted periods lasting as long as hundreds of millions of years. The earth has been in a ice-age for the past 3 million years and ice ages are not the normal state of affairs – they are the exception to the rule of a planet lush, warm, and green from pole to pole with far higher atmospheric CO2 content and a far larger/faster carbon cycle driven by living things.