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[Links nur für registrierte Nutzer]For most people, the infrared absorption by CO2 in the atmosphere seems too complicated to be bothered to know more. Perhaps that is one reason some researchers could treat their hypotheses as a kind of truism. It would appear the case from either sides of the debate.
That’s why I have been trying to simply some related physics issues in the first place to invite more people to participate in such an unprecedented exploration of our earth, the only planet with an inhabitable biosphere in the universe we have known so far. Let’s go and have fun!
(Title: A Simple Graphical Explanation for IR Absorption in the Atmosphere)
4.Infrared radiation refers to the electromagnetic wave in the micro-meter wavelength range emitted by an object, whose surface temperature is a few hundred K, to a cold object.
5.In this context, IR radiation is also called as the terrestrial radiation because it has been assumed that the condensed-mater surface of the earth at its mean temperature 288K emits, or radiates, in almost the same way as a black-body does.
6.So far, the earth surface has been considered as the sole source for some gases in the atmosphere to absorb IR radiation, such as water vapor, CO2, O3 and so on. Therefore, it is not surprising so many research papers have been published on how exactly such an energy-exchange process occurs.
7.First, let’s consider a pipe whose length is just a few meters, or even shorter, as in the measurement in lab. An IR source and an IR detector are placed at the two ends. Then the pipe is filled with CO2 gas, as John Tyndall did in 1860.
8.Perhaps many people have known that CO2 can absorb part of the terrestrial IR radiation, predominately near 15 micron. It means that the amount of the IR absorption should be proportional to the product of the CO2 concentration and the length of the pipe. Do you agree?
9.If you still have difficult to understand this, then you could image each CO2 molecule is a circular target for the IR photons to hit. Those photons whose wavelength is around 15 micron would be swallowed by the circular targets in the pipe.
10.As a result, the transmitted IR radiation will decrease exponentially. The ratio of the incident IR intensity to that of the detected IR intensity is called transmittance, which is always less than 1.
11.Here it is the simple formula for transmittance, which is represented by the green curve. If we assume the emission is too weak, the the IR absorption, to be exact, the IR absorptivity, would be A=1-T.
12.Notice that the IR absorption A is the cumulative IR absorption from 0 to x while the transmittance T is the value at x. In fact, if we find the first derivative of A, called the absorption intensity, then the A is the area under this absorption intensity curve.
13.As you can see, the absorption intensity also decreases exponentially as the pipe length increases with the decay constant alpha.
14.In many a textbook, alpha is defined as absorption coefficient with unit 1/m in SI. Further, this absorption coefficient can be written as a product of two variables, called mass absorption coefficient, denoted by a Greek letter kepa, k, and the mass density of the gas, where mass density is proportional to gas concentration C.
15.In passing, that is where the Beer-Lambert law is valid, which was introduced in 1853 by August Beer. Bearing in mind, the Beer’s law is written as absorbance which actually represents attenuation because it is the proportional to log absorption.
16.Here, I simply write alpha=kC to keep our discussion going. This simple equation implies that both the IR absorption and the IR transmission are non-linearly determined by the gas concentration if kapa is is constant.
17.But, does this implies the dependence of the IR absorption intensity on the CO2 concentration shown in this calculated CO2 peak by Van Wijngaaden and Happer have to be logarithmic? Take it easy, we will see.
18.To illustrate this tricky point, I use my favorite 3D plotter provided by Academo. The vertical z-axis represents the transmittance, the x- and y-axis denote the pipe length and the gas concentration C, respectively.
19.As you can see, for a fixed x value, the transmittance decreases, which also shows the cumulative IR absorption A increases in the same manner.
20.If you watch more carefully, you would find that the asymptotic value is always a constant as long as the pipe length is long enough. For transmittance, this constant is zero.
21.For absorptivity, this asymptotic constant is 1, or unity, as you can see the red area in this 3D absorption diagram. This 3D profile looks like the top of those public buses I took in the 1970s.
22.What does this imply? Well, you can argue with others who use this logarithmic formula, simply because the asymptotic value for the logarithmic function is infinity, rather than a constant.
„Noch sitzt Ihr da oben, Ihr feigen Gestalten. Vom Feinde bezahlt, doch dem Volke zum Spott! Doch einst wird wieder Gerechtigkeit walten, dann richtet das Volk, dann gnade Euch Gott!“
(Theodor Körner 1791-1813)
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„Noch sitzt Ihr da oben, Ihr feigen Gestalten. Vom Feinde bezahlt, doch dem Volke zum Spott! Doch einst wird wieder Gerechtigkeit walten, dann richtet das Volk, dann gnade Euch Gott!“
(Theodor Körner 1791-1813)
Für die Lieschen Müllers unter uns wäre vielleicht auch folgender einfacher Ansatz, auch zur Vermeidung einer doch mittlerweile recht kompliziert anmutenden Co2-Physik, denkbar : Der Klimawandel an sich ist dabei unübersehbar. und somit auch unbezweifelbar. Die LM-Frage lautete somit : Was verursacht ihn dann wirklich, wenn es der Treibhauseffekt nicht tut ?
Das ist eine ziemlich umständliche und unübersichtliche Beschreibung des Lambert-Beerschen Gesetzes:
Output = Input * exp(-E * k * d)
E = Extinktionskoeffizient (stoffspezifisch und Wellenlängenabhängig)
k = Konzentration
d = Dicke oder Länge des optischen Weges durch das Medium
Dies ist seit über 100 Jahren bekannt und auch heute noch die Basis für Konzentrationsbestimmungen in jedem Chemielabor.
Gegen Ende des Videos kommt der Autor dann noch zum „Strahlungsantrieb“.
Dafür gibt aber weder er noch das IPCC eine physikalische Begründung an.
Das ist halt die übliche Masche der CO2-Scharlatane die Leute durch vermeintlich „echte“ Mathematik zu verwirren.
Um den kühlenden Effekt der einzig relevanten Treibhausgase H2O und CO2 zu verstehen,
braucht man lediglich elektromagnetische Spektren lesen können.
Dann sind die 100-fach auch in anderen Publikationen erschienen Spektren in Abb. 1 und 4
in meinem Beitrag #1 der unwiderlegbare Beweis für die kühlende Wirkung von H2O und CO2.
Geändert von hmpf (24.11.2024 um 07:49 Uhr)
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