http://wattsupwiththat.com/2012/07/21/some-thoughts-on-radiative-transfer-and-ghgs/
Some thoughts on radiative transfer and GHG’s
Absorptions bands in the Earth’s atmosphere created by
greenhouse gases and the resulting effects on transmitted radiation. (Photo
credit: Wikipedia)
The following example illustrates the issues I have with reasoning often used to argue that increasing the amount of CO2 in the Earth’s atmosphere will increase both the Earth’s surface temperature and the Earth’s atmosphere temperature. Immediately following is a direct quote from URL
“The present situation is that there has been an increase in infrared-absorbing gases in the atmosphere, such as carbon dioxide (CO2) and methane (CH4). Energy that would normally escape into space is absorbed by these molecules, thus heating the atmosphere and spreading through convection currents. The average temperature of the atmosphere has increased 0.25 °C since 1980, mainly attributed to an increase in infrared-absorbing gases in the atmosphere.”
Although the above statement makes no direct reference to Earth surface temperature, I believe it carries the implication that greenhouse gases in the Earth’s atmosphere increase the Earth’s surface temperature.
I make two comments: the first is relevant only if the above implication is valid, the second is relevant independent of the validity of the implication. First, placing matter adjacent to a warm surface such that the matter is capable of absorbing/blocking radiation to space from the warm surface can lead to a decrease in the warm surface’s temperature. Second, increasing the amount of the absorbing/blocking matter can lower the temperature of the absorbing/blocking material.
Take for example an internal
combustion engine whose metal surface is exposed to a vacuum. In addition to
doing useful work, the engine produces thermal energy (heat). That thermal
energy will produce a rise in the temperature of the engine’s surface such that
in energy-rate equilibrium the rate energy is radiated to space from the
engine’s surface is equal to the rate thermal energy is generated within the
engine. By attaching radiating plates to the engine’s surface, some of the
energy radiated to space from the engine’s original surface will be
absorbed/blocked by the plates;
not true only radiation leaving the surface at some acute angle will be re-absorbed
but because thermal energy can be transferred
from the engine to the plates via both radiation and conduction, the temperature
of the engine’s original surface will be lowered.
Wrong - if less radiation is leaving the engine gets hotter
This is the principle of an
air-cooled engine[1]: provide a means other than radiation of transferring
heat from an engine to a large surface area from which heat can be removed via a
combination of conduction, convection and radiation, and the engine’s surface
temperature will be lowered.
If plates at a temperature lower than the original engine surface temperature
are attached to the engine, it’s true that the temperature of the plates will
increase to establish energy-rate equilibrium. Once energy-rate equilibrium is
established, however, increasing the plate radiating area (adding additional
matter that blocks more of the energy radiated from the original engine surface)
will likely lower the plate temperature.Depends on conduction of fin and relative temperature of cooling air and fin
Thus, blocking the amount of surface radiation escaping to space does not necessarily increase the surface temperature; and increasing the amount of radiation blocking material does not necessarily increase the temperature of that material. In both cases (the Earth/Earth-atmosphere and the internal combustion engine in a vacuum), the heat eventually escapes to space–otherwise the temperature of the Earth’s surface and the engine would continue to rise indefinitely.
All that is just garbage. All solids radiate (accoding to its temperature and emissivity - not necessarily fitting a black body curve). Take away any GHGs and the surface of the earth radiates directly to space with no back radiation and no impeding of radiation to the background temp of space. O2 an N2 and H2 etc. do not stop significant radiated energy but they will be warmed by the earth - none of the O2 N2 will be able to radiate this heat to space. The temperature of the O2 and N2 will get NO HOTTER than the surface of the Earth, but they WILL NOT enable the earth to heat up further. Add GHGs and each molecule will "absorb" and "retransmit" radiation. The radiation retransmitted can be in any direction but nearly 50%- hits the earth and 50%+ goes to space. The 50% hitting the earth is 50% that would have escaped had there been no GHG. -The earth warmed by the sun cools slower because of GHG presence. The earth conducts to the rest of the atmosphere warming it.
The difference isn’t that the energy doesn’t eventually escape to space (it does in both cases), the difference is in the path the energy takes to reach space. The amount of generated thermal energy in conjunction with the path the thermal energy takes to get to space determines temperatures along the path; and adding more material may increase or decrease those temperatures. To say that “Energy that would normally escape into space is absorbed by these molecules, thus heating the atmosphere…” by itself is unwarranted; because an equivalent statement for the case of adding extra plate material to the engine would be “Energy that would normally escape to space from an engine with small attached plates is absorbed by additional plate material, thus heating the plates…” For air-cooled engines, this statement is not true—otherwise the plate surface area of air-cooled engines would be as small as possible.
WHAT!!!!
It’s fairly easy to visualize why (a) adding thermally radiating plates to an air-cooled engine might decrease the engine’s surface temperature, and (b) increasing the area of the radiating plates might decrease the plate temperature. It’s not so easy to visualize, and may not be true, why (a) adding greenhouse gases to the Earth’s atmosphere decreases the Earth’s surface temperature; and (b) increasing the amount of atmospheric greenhouse gases lowers the temperature of the Earth’s atmosphere. I now present one possible argument. I do not claim that the argument is valid for greenhouse gases in the Earth’s atmosphere, but I do claim that the argument might be valid, and can only be refuted by an analysis more detailed than simply claiming “Energy that would normally escape into space is absorbed by these molecules, thus heating the atmosphere.”
I do not believe photons absorbed by GHGs heat the atmosphere The photons emitted from GHGs eventually(perhaps after many absorbtion/retransmittions eithe leave the system or hit the earth warming it. The warm earth heats the atmosphere
If we assume that (a) matter cannot leave the Earth/Earth-atmosphere system, and (b) non-greenhouse gases radiate negligible energy to space, then for a non-greenhouse gas atmosphere the only way thermal energy can leave the Earth/Earth-atmosphere system to space is via radiation from the surface of the Earth. The rate radiation leaves the surface is in part a function of both the area and temperature of the surface. For a greenhouse gas atmosphere, energy can leave the Earth/Earth-atmosphere system to space both via radiation from the Earth’s surface and radiation from greenhouse gases in the atmosphere. Suppose it is true that the density of greenhouse gases near the Earth’s surface is such that radiation emitted from low-altitude greenhouse gases does not directly escape to space, but is in part directed towards the Earth’s surface and in part absorbed by other atmospheric greenhouse gases. As the atmospheric greenhouse gas density decreases with increasing altitude, radiation emitted from high-altitude greenhouse gases can directly escape to space.
Now it’s not impossible that since (a) in addition to radiation, heat is transferred from the Earth’s surface to greenhouse gases via conduction, and (b) convection currents (i) circulate the heated greenhouse gases to higher altitudes where energy transfer to space can take place and (ii) return cooler greenhouse gases to the Earth’s surface, that the process of heat transfer away from the Earth’s surface via greenhouse gases is more efficient than simple radiation from the Earth’s surface.
Heated molecules share heat by conduction. In space there is nothing to conduct to. No heat is transfered. What is transfered to space is radiation, From photons absorbed by GHGs and from photons emitted from earth that are not touched by GHGs (wrong wavelength)
Many engines are cooled using this concept. Specifically, a coolant is brought into contact with a heated surface which raises the coolant’s temperature via conduction and radiation, and the coolant is moved to a location where thermal energy transfer away from the coolant to a heat sink is more efficient than direct thermal energy transfer from the heated surface to the heat sink.
One way to realize increased thermal transfer efficiency would be to use a coolant, such as greenhouse gases, that efficiently radiates energy in the IR band (i.e., radiates energy at temperatures around 500 K). Another way would be to spread the heated coolant over a large surface area. Since surface area increases with increasing altitude, thereby providing expanded “area” (in the case of a gas, expanded volume) from which radiation to space can occur, it’s not clear to me (one way or the other) that greenhouse gases won’t act as a “coolant” reducing both the temperatures of the Earth’s atmosphere and the Earth surface.
Ye Gods!, did Tony read this before publishing... or is this what he believes??!!!!!!
RGB loses his cool with a true sceptic (at last!)
LET US HEAR WHAT YOU HAVE GOT TO CONTRIBUTE!
I may admit I may not always be right but sure as hell you lot do not even know the people you are quoting.
You not only aren’t “always right” in regard to radiation theory, you are so infinitely wrong that you are, quite seriously, almost stunning in any conversation. Worse, you haven’t a clue that you are clueless, and make your vastly incorrect statements to correct somebody that actually has a clue.
Here’s what I have to contribute. Light is electromagnetic radiation. Go on, look it up. The entire electromagnetic spectrum is light. Radio waves are light. Microwaves are light. Infrared radiation is light. Visible light is a narrow band of light. Ultraviolet radiation is light. X-rays are light. Finally, gamma rays are light. The only thing that differentiates a gamma ray from a radio wave is its frequency and wavelength, and those aren’t even invariant properties — one can in principle doppler shift a radio wave into an x-ray by moving through it fast enough.
Second, the only thing the human eye can see is light. I mean good God, man, why do you think they call it turning on the lights when you enter a dark room?
Third, radiation from the sun does not, for the most part “turn into light” only when it reaches our atmosphere. Again, this is so wrong it is difficult even know how to begin. Children understand this better than that. Sunlight is emitted as light by our very hot sun. It travels as light — both visible and invisible, an entire spectrum of light — through the near-vacuum in between the Sun and the Earth. When it reaches the Earth, in very crude terms some of it is reflected at some point or another by the atmosphere without losing (much) energy, some of it is transmitted, and some of it is absorbed. How much of each depends on a host of things — clouds reflect more energy back to space than clear dry air, but clouds and water vapor also absorb more on the way to the ground than clear dry air. Of the radiation that reaches the ground, some is reflected and again passes more or less completely out of the atmosphere without significant loss, and the rest is absorbed. Of the radiation that reaches the ocean, some is reflected at or near the upper surface, and virtually all the rest is absorbed.
Fourth, if you want to understand the way electromagnetic radiation is created, transmitted, absorbed, scattered, you have to begin by learning Maxwell’s Equations. Maxwell’s equations are the classical partial differential equations that describe the electromagnetic field. They aren’t complete — they are classical and atoms and molecules are really quantum mechanical — but to even think of understanding quantum electrodynamics it helps to start with classical electrodynamics. To understand classical electrodynamics, it would really help you to take a class in introductory physics one day, assuming that your calculus background is up to the task. Even in a first year intro physics course in E&M, like the one I am teaching right now, you would learn all of the things I listed above and more besides — I generally try to teach my students that transmitted electromagnetic power is the flux of the Poynting vector through the specified surface, for example, which is entirely apropos of the current conversation.
If you cannot afford a physics textbook, feel free to use the ones I’ve written — they are available for free online here:
but be warned, it isn’t for the faint of heart and you’ll need a reasonable proficiency with partial differential equations and non-Abelian algebras and Lie groups to get through the book. A knowledge of tensors would also be very useful, but sadly few students (even physics graduate students) have much of one so the book tries to be self-contained in this regard. It is also intended to be the second semester of a two semester series, so it presumes you’ve already mastered the Poisson equation and spherical decompositions and magnetostatics and are ready to get on with Maxwell’s equations and true Electrodynamics.
Now “we lot” — by which I assume you means “warmists” used as a pejorative term — sometimes do know very, very well precisely of what we speak. I, for example, do. And I’m not a “warmist”, for that matter. That smacks of religion, and I can and do justify my opinions about almost anything all the way down to the microscopic level — or admit ignorance.
So it is from a state of very much non-ignorance that I repeat — your previous statement, criticizing the entirely correct statement of Mr. Hoffer who is also no warmist, merely a rational skeptic who doubts the alleged magnitude or importance of the GHE, not its very existence — was something that left anyone who read it very slightly dumber. I could feel my own brain cells reeling in shock from it. Radiation turning into light only when it hits the atmosphere? Eyes unable to see light? It made me feel that my entire professional career, spent teaching people far better than that, has been wasted. How is it even possible for a high school education to turn you out into the world that ignorant? I knew better in grade school.
So your statement was not only not a rebuttal of David Hoffer — it was an open insult to the entire US educational system. It was unamerican! Do you want the entire world to laugh at us?
Hence my unaccustomed vigor in striking down your contribution, which, you will note, I am continuing. I’m quite serious. You owe it to yourself, you owe it to simple honesty to crack a physics book and at least try to understand what electromagnetic radiation is before again entering a public debate on the subject and attempting to correct people that have actually studied it, or teach it.
But of course you won’t, will you? Neither will Greg House, or any of the others that make absurd statements about radiation being unable to be reflected back to a warm surface and thereby slow its cooling. It’s so startlingly ignorant a statement that it makes one want to simply throw one’s hands up in despair. Not even my suggestion to go buy a space blanket and wrap yourself in it to gain firsthand experience of “warming” by trapping your own body’s radiation — an “experiment” you can actually perform at home — will actually get you to do it. Or taking an ordinary light bulb and placing it in front of a sheet of plastic wrap, then in front of a sheet of aluminum foil, to see which one reflects more heat (and note well — reflects heat from something much cooler than the light bulb filament). I could probably think up a half dozen other table top experiments to demonstrate radiative heating and cooling — they are elementary school science fair stuff — but of course to you they can’t exist because you know radiation only turns into light when air molecules experience friction or some other long line of complete, utter, absurdities.
I do declare, with people like you “helping” the skeptical “cause”, it doesn’t need to be opposed — the real warmists of the world can just point at you and wait for people to stop laughing themselves to death. Which is a logical fallacy, of course — you can disbelieve in CAGW because a pink unicorn came to you in a dream and told you to and still be right, just as they can be supported by not entirely implausible arguments and still be wrong, and wise people look at the arguments themselves and not individuals — but it does make it all to easy for sensible skeptical arguments to be dismissed when there exist “skeptics” whose arguments are only a hair better than pink unicorns.
rgb
I may admit I may not always be right but sure as hell you lot do not even know the people you are quoting.
You not only aren’t “always right” in regard to radiation theory, you are so infinitely wrong that you are, quite seriously, almost stunning in any conversation. Worse, you haven’t a clue that you are clueless, and make your vastly incorrect statements to correct somebody that actually has a clue.
Here’s what I have to contribute. Light is electromagnetic radiation. Go on, look it up. The entire electromagnetic spectrum is light. Radio waves are light. Microwaves are light. Infrared radiation is light. Visible light is a narrow band of light. Ultraviolet radiation is light. X-rays are light. Finally, gamma rays are light. The only thing that differentiates a gamma ray from a radio wave is its frequency and wavelength, and those aren’t even invariant properties — one can in principle doppler shift a radio wave into an x-ray by moving through it fast enough.
Second, the only thing the human eye can see is light. I mean good God, man, why do you think they call it turning on the lights when you enter a dark room?
Third, radiation from the sun does not, for the most part “turn into light” only when it reaches our atmosphere. Again, this is so wrong it is difficult even know how to begin. Children understand this better than that. Sunlight is emitted as light by our very hot sun. It travels as light — both visible and invisible, an entire spectrum of light — through the near-vacuum in between the Sun and the Earth. When it reaches the Earth, in very crude terms some of it is reflected at some point or another by the atmosphere without losing (much) energy, some of it is transmitted, and some of it is absorbed. How much of each depends on a host of things — clouds reflect more energy back to space than clear dry air, but clouds and water vapor also absorb more on the way to the ground than clear dry air. Of the radiation that reaches the ground, some is reflected and again passes more or less completely out of the atmosphere without significant loss, and the rest is absorbed. Of the radiation that reaches the ocean, some is reflected at or near the upper surface, and virtually all the rest is absorbed.
Fourth, if you want to understand the way electromagnetic radiation is created, transmitted, absorbed, scattered, you have to begin by learning Maxwell’s Equations. Maxwell’s equations are the classical partial differential equations that describe the electromagnetic field. They aren’t complete — they are classical and atoms and molecules are really quantum mechanical — but to even think of understanding quantum electrodynamics it helps to start with classical electrodynamics. To understand classical electrodynamics, it would really help you to take a class in introductory physics one day, assuming that your calculus background is up to the task. Even in a first year intro physics course in E&M, like the one I am teaching right now, you would learn all of the things I listed above and more besides — I generally try to teach my students that transmitted electromagnetic power is the flux of the Poynting vector through the specified surface, for example, which is entirely apropos of the current conversation.
If you cannot afford a physics textbook, feel free to use the ones I’ve written — they are available for free online here:
http://www.phy.duke.edu/~rgb/Class/intro_physics_1.php
http://www.phy.duke.edu/~rgb/Class/intro_physics_2.php
and if you want to try to tackle real graduate level electrodynamics,
you can try:http://www.phy.duke.edu/~rgb/Class/intro_physics_2.php
but be warned, it isn’t for the faint of heart and you’ll need a reasonable proficiency with partial differential equations and non-Abelian algebras and Lie groups to get through the book. A knowledge of tensors would also be very useful, but sadly few students (even physics graduate students) have much of one so the book tries to be self-contained in this regard. It is also intended to be the second semester of a two semester series, so it presumes you’ve already mastered the Poisson equation and spherical decompositions and magnetostatics and are ready to get on with Maxwell’s equations and true Electrodynamics.
Now “we lot” — by which I assume you means “warmists” used as a pejorative term — sometimes do know very, very well precisely of what we speak. I, for example, do. And I’m not a “warmist”, for that matter. That smacks of religion, and I can and do justify my opinions about almost anything all the way down to the microscopic level — or admit ignorance.
So it is from a state of very much non-ignorance that I repeat — your previous statement, criticizing the entirely correct statement of Mr. Hoffer who is also no warmist, merely a rational skeptic who doubts the alleged magnitude or importance of the GHE, not its very existence — was something that left anyone who read it very slightly dumber. I could feel my own brain cells reeling in shock from it. Radiation turning into light only when it hits the atmosphere? Eyes unable to see light? It made me feel that my entire professional career, spent teaching people far better than that, has been wasted. How is it even possible for a high school education to turn you out into the world that ignorant? I knew better in grade school.
So your statement was not only not a rebuttal of David Hoffer — it was an open insult to the entire US educational system. It was unamerican! Do you want the entire world to laugh at us?
Hence my unaccustomed vigor in striking down your contribution, which, you will note, I am continuing. I’m quite serious. You owe it to yourself, you owe it to simple honesty to crack a physics book and at least try to understand what electromagnetic radiation is before again entering a public debate on the subject and attempting to correct people that have actually studied it, or teach it.
But of course you won’t, will you? Neither will Greg House, or any of the others that make absurd statements about radiation being unable to be reflected back to a warm surface and thereby slow its cooling. It’s so startlingly ignorant a statement that it makes one want to simply throw one’s hands up in despair. Not even my suggestion to go buy a space blanket and wrap yourself in it to gain firsthand experience of “warming” by trapping your own body’s radiation — an “experiment” you can actually perform at home — will actually get you to do it. Or taking an ordinary light bulb and placing it in front of a sheet of plastic wrap, then in front of a sheet of aluminum foil, to see which one reflects more heat (and note well — reflects heat from something much cooler than the light bulb filament). I could probably think up a half dozen other table top experiments to demonstrate radiative heating and cooling — they are elementary school science fair stuff — but of course to you they can’t exist because you know radiation only turns into light when air molecules experience friction or some other long line of complete, utter, absurdities.
I do declare, with people like you “helping” the skeptical “cause”, it doesn’t need to be opposed — the real warmists of the world can just point at you and wait for people to stop laughing themselves to death. Which is a logical fallacy, of course — you can disbelieve in CAGW because a pink unicorn came to you in a dream and told you to and still be right, just as they can be supported by not entirely implausible arguments and still be wrong, and wise people look at the arguments themselves and not individuals — but it does make it all to easy for sensible skeptical arguments to be dismissed when there exist “skeptics” whose arguments are only a hair better than pink unicorns.
rgb
