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…
Bill Illis says:
February 13, 2011 at 4:55 pm
“The IR emitted by the surface is not skipping Nitrogen and Oxygen molecules and preferentially seeking out CO2 and H20 only.”
I would say the IR photons *do* skip the N2 and O2 molecules as these molecules can’t absorb IR. The IR photon does not “see” these molecules but passes through them as if they weren’t there.
Of course, after the IR photon is absorbed by, say CO2, the energy is thermalized and can be transferred from, say CO2 to N2 – but also back from N2 to CO2, and the CO2 can re-emit an IR photon.
steven mosher says:
yup, but there is more to it than that. If you want to do IR design today ( of sensors, or counter measures or stealth technology) the physics you use is the same physics that many skeptics deny. good thing we don’t let them design the machines that our
safety as a nation depends upon.
Wow, mosher. You must be bored to start taking cheap shots at strawmen. As far as I know, there aren’t many skeptics that deny the physics, just the conclusions that Earth is going to see a large temperature increase because of it.
Charles Nelson says:
February 13, 2011 at 1:06 pm
Absolutely brilliant…thank you. I like the term ‘increase earth’s coupling with space’ I have been trying to explain this to the numpties for ever.
One question I ask CO2 Warmists is, ‘have you ever noticed the outside temperature when flying on a plane at cruising altitude…-30 to -60 degrees C. right? Have you ever looked down and wondered what is happening at the top of the cloud layer…heat loss right? So if the atmosphere was to get warmer wouldn’t these clouds simply rise a little higher because of convection and lose their energy through radiation into the vast reservoir of coldness above?
Interestingly I find that when I use words like radiation and convection they tend to glaze over and lose interest. In fact I don’t think that ‘science’ matters that much to believers…
Keep up the good work guys.
Brilliant. Focus on one particular phenomenon, radiation from the tops of clouds, as if that is all that is going on. No need to look at any other effect to determine the plausibility of the idea that GHG’s emission are going to warm the planet. No need to do any mathematical modeling. All you need to do is believe what you want to believe, and select those phenomena which confirm your beliefs and focus on it.
It is great propaganda and apologetics, but hardly science.
REPLY:
“Brilliant. Focus on one particular phenomenon, radiation from the tops of clouds, as if that is all that is going on.”
Well said, we should stop focusing on CO2, as if that is all that is going on. – Anthony
There’s no need to be confused. The “canard” the author refers is no canard but a manifestation of his ignorance. The infrared absorption characteristics of various gases was measured experimentally 150 years by John Tyndall. If you shine far infrared light through a column of IR-transparent gas the amount of radiation you get on the far side of the column is the same as you get going through a column of vacuum. If you replace the transparent gas (like nitrogen) with an IR-absorptive gas (like water vapor) there is less radiation emitted at the far end of the column. The gas absorbs the radiation from a directional source and re-emits it in all directions. In Tyndal’s apparatus there were only two exits for the radiation since the column was a brass tube polished to a mirror finish on the inside – the two exits were plates of rock salt at either end of the tube. The radiation entering the column remains the same no matter what gas (or vacuum) is in the column but the radiation exiting the column at the far end varies according the kind of gas in the column. Energy must be conserved so what’s missing at the far end of the tube has to be going somewhere – in fact it heats the gas which increases the amount of energy the gas is emitting and since the gas emits in all directions some of the energy goes through the rock salt entrance plate instead of the exit plate while some smaller portion will heat the brass tube through conduction and some even smaller amount will heat the tube through absorption because even brass polished to a mirror finish isn’t quite 100% reflective.
For 300 W/m2 radiation I get -23.4°C at 300 W/m2 when I calculate it (yes, minus!). Pretty cool
———-
I get the impression that there is some miscomprehension here.
I would say that the flux of 300W/m2 being calculated here, is not the same as the 300W/m2 of down-radiated atmospheric IR.
Maybe the definition of terms and conditions in the SB formula needs to be verified.
Well said, we should stop focusing on CO2, as if that is all that is going on. – Anthony
===============================================
Now that really was brilliant! good one………
Hans Erren says:
February 13, 2011 at 4:57 pm
Adding water vapour in the tropics gives the tropics a greenhouse effect, I remember very well when I left the airconditioned hotel in Dhaka Bangladesh, a wall of humid heat hit me and I had to wipe my glasses.
Every added particle to the atmosphere is a small downward radiator, adding more particles therefore adds more radiators. That’s in a nutshell the greenhouse effect.
———-
That’s right. Every added particle to the atmosphere is a small upward radiator also, adding more particles therefore adds more radiators. That’s in a nutshell is why there is no real “greenhouse effect”. The two effects always cancel. You say ‘more warming downward’ and I say ‘also equal cooling upward’.
You see, it’s a two way street in real physics, you just ignore the part that doesn’t fit your (incorrect) view.
That to me that is why Miskolczi came up with the results he did. Now why, No one has answered that. Is it that with the small increase of temperature we have seen and the small expansion of the atmosphere does cause a higher fraction to escape to space because we do live on a sphere and not an infinite plane and that is merely a geometric effect (ex-secant correction)? Could it be that there is one or more negative feedbacks? Is it a combination of both? I’m still searching.
To Steve Reynolds
1. There is not a great deal of difference, if any, between liquid phase H2O spectral transmission and water vapor spectral transmission. I used those two graphs because data from NIST tends to be more reliable than most that I have seen.
But here’s another graph for you http://en.wikipedia.org/wiki/File:Atmosfaerisk_spredning.gif
See the wide absorption band at 5.5 to 7.7 microns…that is entirely by water vapor, H2O. Compare it to the narrow bands absorbed by CO2 in the same graph. In the vapor state, it is still at least 10X greater for this wavelength spread.
There is a problem though, and that is that we have to speculate over the entire spectral output of the dominating forces especially the sun, which outputs much energy in shorter wavelengths to the earth. To my knowledge, that data (spectral absorption and transmission and reflection of CO2 and H2O) has never really been assembled as there had never seemed to be a need for it.
2. CO2 does indeed have a reflective component as does H2O. Only a black body has no reflective component. The reflective component of H2O is better known than that of CO2 because water is more common, and has been tested for IR more thoroughly. All real world materials are reflective, absorptive and emissive. In general, metals are highly reflective (think Al foil, etc) on one end of the scale, organics and others less so, water being one of the most absorptive, least reflective. And the reflective component is highly wavelength measured dependent, as well as angularly dependent (the angle with which the wavelength strikes the molecule).
But for magnitudes of the effect on the atmosphere in terms of greenhouse effect, the known data is sufficient to see the HUGE differentials between water vapor effects vs. CO2 effects.
Dennis Wingo says:
February 13, 2011 at 12:36 pm
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.
There is no such thing as absolute proof of a theory in science. We don’t need that in order to take action on the basis of the knowledge that we have.
More detailed observations can tell us more precisely what is happening in the present, so that we don’t have to wait 100 years to find out the outcome of increasing CO2 concentrations. That is the purpose of the scientific research that is going on. Observations of radiation, behavior of clouds, and other phenomena that are involved, plus innovation in computers and models, provide the information needed to produce better predictions of climate change.
Now that is a wise statement. As someone who designs temperature measurement systems (principally for spacecraft) I have always been amused that the AGW community can make the statement that they can use an instrument with 0.5 degree accuracy and get 0.001 degree temperature variation out of it.
No one is claiming that as far as I have seen.
In designing thermal control systems for spacecraft you have to be incredibly sensitive to the absorptivity/emissivity (a/e ratio). If you get this even slightly wrong in spacecraft design, you either run the equilibrium temperature too high and it will fail, or too low and it will fail.
MC makes the observation that the radiated temperature is 100% dependent upon emissivity, which is correct, but I have never seen this really integrated into AGW models, they simply use a blackbody approximation, which is a terrible reference in that this varies wildly around the world.
I think you are wrong about this. Models provide for different emissivities for snow, forests, grassland, rocks ocean etc.
Also, the models do not take into account the dramatic differences in resulting temperature based upon altitude, especially in desert regions of the globe.
This is clearly wrong. Models do take altitude into account in the prediction of climate change.
http://journals.ametsoc.org/doi/abs/10.1175/1520-0442%281997%29010%3C0288%3AEDOTSC%3E2.0.CO%3B2
Elevation Dependency of the Surface Climate Change Signal: A Model Study
A lot of physics modeling operates by making simplifying assumptions, but how many of these assumptions are testable and repeatable?
These assumptions are constantly being tested. One of the first assumptions made, by Arrhenius in 1896, in his modeling of CO2’s impact on global temperature was that average Relative Humidity would be constant and water vapor concentration in the atmosphere would increase, resulting in positive feedback for temperature increase. Satellite observations are being made which seem to confirm this assumption.
http://news.cisc.gmu.edu/doc/publications/Chung%20et%20al%202010.pdf
In spite of significant biases in tropospheric temperature
and humidity in climate models [John and Soden,
2007] and resultant compensating effects in simulating the
clear-sky OLR, our analysis finds broad consistency between
the observed and modeled rates of clear-sky OLR radiative
damping. This consistency is noted over a broad range of
observable sources of climate variations, suggesting that the
strong correlations between water vapor and temperature
necessary to generate such sensitivities are a robust feature
of both models and observations. This analysis offers
further evidence to support the ability of climate models
to depict the physical processes related to the combined
water vapor and temperature climate feedback.
This is the basis of a lot of my skepticism on the models involved.
It seems then that the basis of your skepticism is not real.
Domenic says:
February 13, 2011 at 1:30 pm
“In addition, water vapor is approx 3.5% of the atmosphere or 35000 ppm. (That’s a global average. At the poles the air is drier. In the tropics, the air is much wetter.)”
True enough. It varies between 1% (Sahara) and 5% (Amazon) except for Antarctic interior where it is close to 0%. But that’s at the surface. Adiabatic lapse rate squeezes out the water vapor with falling temperature while CO2 concentration remains constant with altitude.
Tyndall (circa 1850) however found that the concentration of the gas doesn’t matter but rather the total amount of the gas in the column is all that matters. He confirmed that by varying the pressure and length of the column. Tyndall performed literally thousands of experiments with varying, varying pressures, varying column lengths, and varying infrared frequencies.
To begin understanding the physics of greenhouse gases one must at least be familiar with what was experimentally demonstrated by physicists in the mid-19th century.
There’s plenty to complicate the situation in the real world beyond comprehension because the atmosphere is a dynamic system with varying gases, pressures, and many physical processes other than radiation going on that are moving heat from one place to another and radically different and rapidly variable rates.
the physics you use is the same physics that many skeptics deny.
This statement is an insult to the intelligence of people who actually work in the field. The parameters related to the absorption and re-emission of IR radiation by CO2 were worked out by the USAF (the early parts were classified), in what used to be called “upper atmospheric research”. Spectrometer technology was specifically improved to the point to where the individual quantum absorption and emission lines were discerned by the mid-late 1950’s.
These measurements were used as a validation of the gaussian to Lorentz transform that characterizes the increase in the absorption/emission lines of CO2 and other IR absorbers/emitters. This was used to design the IR sensors of ALL of our inventory of IR sensing missiles.
If you find the equations for this emission/absorption, you will find that the increase in the line widths is proportional to the increase in the minor gas against the ENTIRE atmosphere, not just the concentration of the gas relative to the arbitrary baseline of 280 ppm. The absorption/emission of CO2 has two dependent variables, temperature and pressure, neither of which are accurately characterized in the models used by the AGW community.
All of this is set forth in any Quantum Mechanics book on the theory of light, of which the relevant IR wavelengths absorbed/emitted by CO2 are a part. The relevant text I use is from Loudon, pages 82-89.
Why don’t you have the moral courage to look that up and derive the effect of the increase of CO2 yourself. You will be surprised at the result.
Anthony,
This exchange was a treat, it amazes me sometimes what can be learned on the web.
This quote
“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…”
—–
Is intriguing as well. Gore and company stopped long ago trying to prove anything. They were more interested in having enough of their theories “accepted” to stay at the grant trough. In a way it is reminiscent of the times when it was “accepted” that the Sun orbited the Earth. But then it was more for religious reasons than scientific. Today Gore strives to maintain his religious acceptance of CAGW to prop up the price of his offset credits.
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.
A safe statement is “increasing atmospheric CO2 will result in increasing surface temperature if nothing else changed“. What causes “confusion at a higher level” is that lots of other things DO change and the amount of warming directly attributable by CO2 infrared absorption and re-emission is small and can be utterly swamped (lost in the noise) by many other dynamic processes. Water in all its phases has the starring role in shaping our climate. CO2 plays a major role in surface temperature only during so-called “snowball earth” episodes when most of the water vapor has been frozen out of the atmosphere and there’s little to no liquid water presenting on the surface. In that case there are no working CO2 sinks so volcanoes, which keep on belching out CO2, gradually build up the amount of CO2 in the column until there’s enough greenhouse effect to begin melting the planet. If it weren’t for CO2 the earth would likely be covered in ice with no hope of ever melting. That’s the most commonly accepted hypothesis at any rate and I personally haven’t seen anything that seriously disputes it.
Maybe those who doubt the ‘frequency selective’ nature of CO2 IR spectra should investigate Molecular Spectroscopy as it relates to the vibrational modes of CO2 (and the other important GH gas WV) on account of it’s molecular properties:
Also: http://en.wikipedia.org/wiki/Infrared_spectroscopy
High-school level physics, boys …
.
wayne says on February 13, 2011 at 7:01 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.
They do not cancel.
The energy remains in the atmosphere for a little longer than it otherwise would, but I suspect that it does not matter as H2O transports much more energy out of the atmosphere and any that is “trapped” by CO2 quickly departs during the night.
There is no reason for the warmist to exhibit glee to the admission of CO2 narrow back-scatter effect. All substances absorb and emit IR (yes, even salt and quartz windows). It is all about spectrum or frequency and a molecule’s representative target cross sectional area .
The debate is entirely about CO2 back-scatter’s significance on the actual climate.
Since theoretically, CO2 IR spectrum is already saturated, any additional molecules, simply cannot affect much. The same is not true concerning the planets biomass. It will expand exponentially to increased temps, increased CO2, and increased available moisture. This too will have a feedback. As stated many times, this is about climate sensitivity as per much debated feedbacks and forcings. GK
Dennis Wingo says:
February 13, 2011 at 7:17 pm
… The absorption/emission of CO2 has two dependent variables, temperature and pressure, neither of which are accurately characterized in the models used by the AGW community. …
– – – – – – – –
Dennis, I see you great point but could you expand a bit on your statement above? I’m wondering if that could be temperature and density, for a slightly warmer atmosphere will expand but the mass remains constant, therefore, density drops but the pressure remains constant at sea level (average that is). Does it make sense?
Anthony,
doesn’t your camera “see” in the near infrared? The earth emits in the far infrared. The cut-off is at about 4um between the two I believe.
Some of that wonderful military hardware some people keep talking about is working in the near infra-red and has little applicability to the back radiation issue!!
The scatter, reflection, absorption bit I have been trying to clarify also. Reflection generally refers to the effect where a particle or wave encounters and leaves an object or field at the same angle. Scatter is where the direction is random. Absorption, of course, is where there is no exiting wave or particle. They are different.
Electromagnetic radiation in the atmosphere is rarely reflected by gasses, only particles like water droplets or aerosols. They are either scattered or absorbed.
Someone please correct me as I am obviously not the expert here.
To Dave Springer
Re the measurement of IR absorption.
The polished tube method is not exact. It’s an approximation. It does not account for angular effects of wavelengths and reflective effects of wavelengths striking the molecules accurately. In addition, it relies on imperfect ‘spectal window transmission coatings’ on the sensor window material, and other factors.
The science is nowhere as accurate as many believe it to be.
“Back Radiation” is such a horrible analogy, description or way to think about heat transfer in the atmosphere, that I wish it would just go away. What we are concerned with is the flow of heat from the surface of the earth to space. Its not that the surface warms the co2 in the air then the co2 “back radiates” re-warming the surface, its that when the co2 in the air is warmed the flow of heat from the surface to the warmed co2 is reduced, thus increasing the temperature of the surface until the flow of heat returns to equilibrium.
1) sun rays heats surface of earth
2) warmed surface radiates, heating greenhouse gasses
3) smaller temp delta between surface and greenhouse gasses reduces heat flow
4) reduced heat flow from surface increases surface temperature
5) equilibrium is restored with higher temp surface and greenhouse gas
My problem with the greenhouse effect is how do you separate radiation from the effects evaporation, condensation, conduction and convection. Anecdotally I feel that conduction is a far superior mode of heat transfer and evaporation is even better.
To cool my cup of hot chocolate faster is should:
a) hold it up to the sky on a low humidity night
or
b) blow on it
When I am hot I should:
a) stand outside naked on a low humidity night
or
b) get soaked in water and stand in front of a fan
Brilliant conversation, thanks for sharing.
Considering the energy smart rattle being waved by local authorities, one wonders how derelict Urban Authority, IR emission equipment callibration, will be.
And i’ve learnt the hard way that the moment one puts Red on a map, some policy wonk will smell promotion and run with even the most tenuous data, and as this site so often points out Policy = Misspent funding. Usually when one says IR, the colour red shows up somewhere, and RED = Hot right and away we go.
One may point out a scale can be quite tight, with the banding representing a single degree, case in point, IR work done in winter. All of a sudden ones city glows bright red, the Policy wonk will scream ‘Look at all that energy wasted!’, until Johnny lab coat points out, ‘That sir is a mere 14 degree’s centigrade’. And you’d be amazed when you point out that water holds a lot of heat, their eyes cross, they don’t like the notion the very landscape is bleeding heat.
I’d be keen to know what tolerances and ranges equate to a fair IR reading within an urban environment, and with emissivity being so key, one can imagine Urban Authorities taxing by the W/m radiated.
Good luck with your endeavors.
Oh no, the Ham and radio guys are gonna get me.
In my statement above I left out the effects of IONIZED gasses which DO reflect electromagnetic radiation.
steven mosher says:
February 13, 2011 at 3:39 pm
If you want to do IR design today ( of sensors, or counter measures or stealth technology) the physics you use is the same physics that many skeptics deny.
And if you had any idea what that was, you would have told us instead of delivering that empty and useless trollbuttal. What physics are being denied? Put up or shut up!
Steve Reynolds says:
February 13, 2011 at 2:43 pm
“Even when you correct that, you need to take into account that absorption reaches near 100% in narrow spectral lines, so adding more does not increase absorption linearly. That is why the effect of CO2 only increases approximately as the log of concentration.”
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.