Carbon dioxide absorbs infrared radiation (IR) in three narrow bands of wavelengths, which are 2.7, 4.3 and 15 micrometers (µM). This means that most of the heat producing radiation escapes it. About 8% of the available black body radiation is picked up by these "fingerprint" frequencies of CO2.
Several decades ago, before global warming was an issue, scientists concluded that carbon dioxide blocked 8% of the infrared radiation from going through the atmosphere. This is consistent with bandwidth. The width of the 15 micron peak is two microns wide from outer edges of shoulders.
The total range of infrared radiation, called black body radiation, is about 100 microns, tapering off after 50 microns. Black body radiation is all infrared radiation given off by matter. It increases with temperature.
A measured absorption spectrum is shown here. See an exactly measured 15 micron peak in Heinz Hug's paper.
Heinz Hug showed that carbon dioxide in the air absorbs to extinction at its 15µM peak in about ten meters. This means that CO2 does whatever it's going to do in that amount of space. Twice as much CO2 would do the same thing in about 5m. There's no significant difference between 5m and 10m for global warming, because convectional currents mix the air in such short distances.
This is nothing new. Climate scientists know that more CO2 does not result in more heat under usual conditions. So the mythologists among them try to salvage the global warming propaganda by pretending that something esoteric occurs higher in the atmosphere. The difference is that the absorption peaks for CO2 separate from the peaks for water vapor. Then supposedly, radiation which misses CO2 does not get picked up by water vapor and travels into outer space; and more CO2 causes less radiation to get missed on the shoulders of the peaks.
Everything about that rationalization stretches reality to a point of misrepresentation. The increase in CO2 levels could only be relevant for the last cycle of absorption near the outer edges of the atmosphere, where there is not enough influence of the lower atmosphere to be significant. But the rationalizers claim it is significant in the mid levels of atmosphere. Not so. Doubling the CO2 would only shorten the distance of radiation travel before total absorption occurs.
What Miniscule Shoulders Mean
This image is the distance infrared radiation travels at the present concentration of CO2 in the air.
The outer edges of the shoulders of the absorption peaks are said to be unsaturated, because they don't absorb all radiation available to them. The unsaturated area is virtually nonexistent. The image at right shows how the distance of absorption increases as shoulder molecules get thinner. Where the molecules are one tenth the density, the distance is ten times as much, which is 100 meters. Where the density is one hundredth, the distance is 1,000 meters. Where is the unsaturation supposed to be? Fake equations are contrived to show a result in contradiction to the obvious logic.
The green part of the image is the absorption spectrum superimposed onto the atmospheric effects. The yellow areas on the edges of the shoulders are supposedly where the heat is added to the atmosphere.
The question is phrased in terms of what happens when CO2 in the atmosphere is doubled. Doubling only shortens the distance the radiation travels before being completely absorbed, as shown in the small image.
Spreading miniscule radiation over long distance means the supposed heat is spread extremely thin. It means the effect is ridiculous.
At mid levels of the atmosphere, the center of the peaks would absorb at about 30m instead of 10m, while the shoulders would absorb at about 300m instead of 100m. Reducing those distance by half is not relevant. But just like relativity, if it takes more than a mouthful of arguing to prove them wrong, frauds decree the obfuscation to be fact.
As shown on the page titled "Crunching the Numbers," the quantities involved are so miniscule as to be totally incapable of causing global warming.
Frauds are creating the impression, and uninformed persons such as Al Gore are assuming, that all of the heat on the planet is bouncing right back on top of everyone due to carbon dioxide. The image above shows what all scientists knowthat only the most infinitesimal amount of heat is even in question.
There's another major reason why the fix is unreal. Supposedly, it is the outer shoulders on the CO2 peaks which are responsible for global warming. Not only is a small percent of the CO2 influenced by the shoulder radiation, but the distance increases for absorption. There is more nitrogen and oxygen per CO2 molecule in this area. Dilution reduces the temperature increase per unit of energy. If there is 5% as much CO2 on the shoulders, it is spread over 20 times as much space in the atmosphere. This means the temperature effect on the shoulders should be multiplied times 5% twiceonce for the decrease in amount of CO2 and once for the dilution of the energy in the atmosphere. So much dilution of so few molecules could not be responsible for a significant amount of temperature increase.
The miniscule area of concern on the shoulders of the absorption peak for CO2 is shown on one of Heinz Hug's graphs.
Most of the infrared radiation in the atmosphere is emitted from the atmosphere, not the ground. Heat causes all matter to emit black body radiation, and this includes the atmosphere. Most climatologists have been adhering to the concept that the radiation emitted high in the atmosphere is most relevant.
The image at right shows what happens to radiation emitted in the atmosphere. It travels a short distance and gets absorbed, when it is of a suitable wavelength. At ground level, the wavelength which is centered on 15 microns travels about 10 meters before getting absorbed by CO2, while nearby wavelengths, between 14 and 16 microns, travel about 100 meters. At the top of the troposphere, the distance is about ten times as much.
When the amount of carbon dioxide in the atmosphere is doubled, the distances are reduced to one half, as shown in the right hand portion of the image.
It's important to realize that climate alarmists are contradicting this concept in pretending that radiation goes through the atmosphere without saturating. If that were true, each dot would be larger than the troposphere, and the edges would extend beyond the troposphere and into the stratosphere.
Pretending that radiation goes through the atmosphere at wavelengths absorbed by CO2 is the most basic fraud of climate alarmists. They apply the Beers-Lambert analysis to the atmosphere pretending to calculate how much energy is held up in the atmosphere as carbon dioxide increases. That type of analysis only applies to purified conditions in a laboratory, where some of the radiation continues to go through the gas. It does not apply to saturation, were all of the radiation gets absorbed in a short distance. So climatologists modified the Beers-Lambert analysis and replaced it with a fudge factor which gives them a similar logarithmic curve and then tacked on a constant which produces the result they want, as described on the page titled Fake Equations.
The assumption of some persons is that shorter distances mean the heat stays in the atmosphere longer before escaping into space. Supposedly, the radiation will be re-emitted and re-absorbed more often, when distances are shorter. But they err in two ways. One is in not taking into account the convection which removes the relevance of short distances. The other is in assuming the direction is toward space.
When radiation is re-emitted in the atmosphere, it moves in all directions. The energy does not move closer to space, because it is not directional. The way heat moves toward the outer atmosphere is either through convectional currents or long wave infrared radiation which is not affected by greenhouse gasses.
Here's how the dynamic works. The IR is emitted from the surface of the earth as black body radiation, which has a wide bandwidth. Then CO2 absorbs a fingerprint set of frequencies, which is 8% of the available black body radiation. As it is absorbed, it is instantly converted into heat (in less than a pico second). The heat is distributed over all molecules in the atmosphere, which means 78% nitrogen and 21% oxygen. After some time, an equivalent amount of black body radiation is emitted from everything in the atmosphere, and 8% of it is absorbed by CO2 as fingerprint radiation.
The amount of delay before re-emission determines how much heat is held within the atmosphere. No one knows how much time delay there is, so no one knows how much heat the atmosphere should hold in the processes of releasing it into space. The temperature can be measured, but theory cannot be applied through the fake science and computer models being applied to the subject.
Another ill-informed assumption is that radiation absorbed by CO2 must be re-emitted by CO2 in exactly the same way it was absorbed, because electrons jump to a higher orbit when absorbing and must fall back to a lower orbit when emitting.
Electrons changing orbit does not apply to global warming. Electron orbit shift only applies to things like fluorescence or lasing. Global warming is about so-called finger print radiation being absorbed. This is due to covalent bonds stretching and bending during vibrations, where no electrons shift orbits.
This means that when finger print radiation is absorbed the energy is instantly converted to heat as increased vibration of the molecule. If the energy as heat is re-emitted by transforming into radiation, it is emitted as black body radiation, which all matter emits based on its temperature.
Some supposed experts insist that CO2 will absorb and instantly re-emit at the same wavelength in the atmosphere. They are wrong, but if they were right, it would be irrelevant, because instantly re-emitting at the same wavelength is no different from not absorbing at all. No heat is produced.
Fakes like to make claims of that sort, because there is no detectable difference between it happening and it not happening, so no one can prove them wrong. But then what relevance would it be? Spewing fraud has the purpose of stripping rationality from the subject.
Basic principles create knowledge in science allowing claims and predictions to be accurate without tests. Incompetent persons try to strip knowledge and rationality from science, because it leaves them behind and exposes their corruptness.
Proponents do not have clear explanations for their assumptions. They use computer models and juggle the numbers until they get the results they want.
I notice that fakes keep referring to radiation which is directed back to the surface of the earth. Often, the whole concept of how greenhouse gasses create global warming is described in terms of such radiation being redirected to the surface of the earth.
The concept of redirected radiation is absurd. The wavelengths in question saturate, meaning they get totally absorbed. They can't travel far enough to get to the surface of the earth, unless they are emitted from air which is very close to the earth's surface. Such radiation certainly can't get from the top of the troposphere to the surface of the earth. If greenhouse gasses are absorbing radiation on its way up, they are going to absorb it on its way down.
The above explanations apply to this. There is no reflection involved. Greenhouse gasses absorb at one set of wavelengths (fingerprint radiation) and emit at a different set (black body radiation) after some delay.
All matter absorbs and emits black body radiation. This includes the atmosphere and CO2 in the atmosphere. If the earth were giving off significant black body radiation, it would be absorbed by the whole atmosphere, not just the greenhouse gasses, which absorb a small percent of the wavelengths as fingerprint radiation. But the earth only gives up its energy as 1% black body radiation, in my estimate, while fakes say it is 40%. Whatever it is, the matter in the atmosphere will absorb it without greenhouse gasses, but in longer distances. Greenhouse gasses only shorten the distance that some wavelengths get absorbed.
Saturation makes the entire subject of what greenhouse gasses do irrelevant. The planet is cooled by radiation which goes around the greenhouse gasses, not through them. Increasing the amount of greenhouse gasses does nothing. See It's Like a River, Not a Window
All biology is on the verge of becoming extinct due to a shortage of carbon dioxide in the air, which is needed for photosynthesis. There was five times as much CO2 in the air during dinosaur years, and twenty times as much when modern photosynthesis began.
The fingerprint type of IR absorption is due to stretching and bending of internal bonds. Nitrogen does not do that. But all matter absorbs and emits IR in proportion to its temperature. This is called "black body" radiation. Physicists say all matter has the same characteristics in absorbing and emitting black body radiation, except that the quantitative proportions vary, mostly due to reflection. For nonreflective substances, such as wood and concrete, the percent IR absorbed or emitted (called emissivity or absorptivity) is around 90% of a perfect black body. Metals are good reflectors of IR, so they have an emissivity of around 50%. This means they emit or absorb about 50% of the infrared radiation which contacts them. Kirchhoff's law says emissivity equals absorptivity, which means everything absorbs and emits black body radiation in the same way.
There is a curve for black body radiation, and it applies to all matter. The curve slides toward higher frequencies for higher temperatures. At earth temperatures (around 300 degrees Kelvin) the black body curve (or Planks curve) peaks at a wavelength of about 10然. The sides of the curve taper off at about 1然 and 30然. Visible light is 0.4 to 0.8然, which is just above the curve for cold black body radiation, but hot objects will radiate into the visible range, which is of course how an incandescent light bulb works. Carbon dioxide has fingerprint peaks at 2.7, 4.3 and 15然, which are all within the black body radiation curve.
In some quantity, everything in the air including nitrogen and oxygen absorbs and emits black body radiation at frequencies which overlap the frequencies absorbed by CO2. In fact, the only reason why there is IR in the air is because the surface of the earth emits black body radiation in proportion to its temperature. The air then does the same thing at some level.
The question then is, in what quantity is the atmosphere absorbing and emitting black body radiation. The emissivity of nitrogen and oxygen gasses should be closed to 100%, since they do not reflect IR significantly. But the larger question is how does the quantity of black body absorption compare to the fingerprint absorption of CO2. Actual measurements and numbers do not seem to exist. So promoters use computer models and pull numbers out of the hat which say increases in CO2 levels will create a global temperature increase of about 6蚓. This is about 20% of the 33蚓 which the atmosphere is said to contribute to the temperature of the globe.
The reason why CO2 absorbs fingerprint radiation but emits almost none, is because all molecules absorb a lot of radiation and emit very little. This is why black asphalt heats in the sun. It absorbs most of the radiation and emits almost none. Radiation leaves almost entirely as black body radiation, because vibration of whole molecules, which creates black body radiation, is vastly greater than vibration within molecules, which creates fingerprint radiation.
There are about 30 times as many water vapor molecules in the air as CO2 molecules, and water vapor has a more effective fingerprint spectrum which is about three times wider than that of CO2. It is also much more variable. This means water vapor will swamp whatever CO2 does. It is obviously not being honest to say CO2 does twenty percent of the heating, when there is a hundred times as much effect by water vapor doing the same thing.
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4. Myhre, G., E.J. Highwood, K.P. Shine, and F. Stordal, 1998. New estimates of radiative forcing due to well mixed greenhouse gases. Geophys. Res. Lett. 25:2715-2718.