gslack
Senior Member
- Mar 26, 2010
- 4,527
- 356
LOL, reflection IS absorption and re-radiation. As is scattering.
Laser emmision is even more awesome. The atoms absorb at one wavelength then as an electromagnetic energy passes by, it stimulates the atom to emit radiation it the same direction as the passing energy.
Reflection is the opposite of absorption..
The reflectivity of something is proportional to it's absorbivity. Meaning the more something absorbs EM the less it reflects. And equally, the more it reflects, the less it absorbs..
https://en.wikipedia.org/wiki/Reflection_(physics)
A claim can be made for how much IR is absorbed vs how much is absorbed, and a fair statement would be that some is reflected back towards earth. But that would be minuscule to the reflective abilities of a cloud. GH gases can't be a good absorber and good reflector simultaneously. Just as nothing can be both a good emitter and absorber simultaneously.
IGCSE - Thermal Physics Revision - Radiation
Again, it can reflect some and absorb some, but it cannot be completely efficient at either one at the same time.
The MET office likes to misuse the terms so they don't have to actually prove anything.
Anthropogenic Global Warming theory
It's a fine example of just how un-scientific the methods used to further this ridiculous theory.
Frankly You can buy their story or buy Kirchoff's law... I take the law...
Kirchhoff's law of thermal radiation - Wikipedia, the free encyclopedia
n thermodynamics, Kirchhoff's law of thermal radiation refers to wavelength-specific radiative emission and absorption by a material body in thermodynamic equilibrium, including radiative exchange equilibrium.
A body at temperature T radiates electromagnetic energy. A perfect black body in thermodynamic equilibrium absorbs all light that strikes it, and radiates energy according to a unique law of radiative emissive power for temperature T, universal for all perfect black bodies. Kirchhoff's law states that:
For a body of any arbitrary material, emitting and absorbing thermal electromagnetic radiation at every wavelength in thermodynamic equilibrium, the ratio of its emissive power to its dimensionless coefficient of absorption is equal to a universal function only of radiative wavelength and temperature, the perfect black-body emissive power.[1][2][3][4][5][6]
Here, the dimensionless coefficient of absorption (or the absorptivity) is the fraction of incident light (power) that is absorbed by the body when it is radiating and absorbing in thermodynamic equilibrium. In slightly different terms, the emissive power of an arbitrary opaque body of fixed size and shape at a definite temperature can be described by a dimensionless ratio, sometimes called the emissivity, the ratio of the emissive power of the body to the emissive power of a black body of the same size and shape at the same fixed temperature. With this definition, a corollary of Kirchhoff's law is that for an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity is equal to the absorptivity. In some cases, emissive power and absorptivity may be defined to depend on angle, as described below.
Kirchhoff's Law has another corollary: the emissivity cannot exceed one (because the absorptivity cannot, by conservation of energy), so it is not possible to thermally radiate more energy than a black body, at equilibrium. In negative luminescence the angle and wavelength integrated absorption exceeds the material's emission, however, such systems are powered by an external source and are therefore not in thermodynamic equilibrium.
Before Kirchhoff's law was recognized, it had been experimentally established that a good absorber is a good emitter, and a poor absorber is a poor emitter. Naturally, a good reflector must be a poor absorber. This is why, for example, lightweight emergency thermal blankets are based on reflective metallic coatings: they lose little heat by radiation.
You worked pretty hard there.. Hope it stimulates some neurons somewhere..
But I think the hard-core denialists are focused on the "other" excitation source. Not the sun. GHouse theory works 24 hrs a day and has little to do with DIRECT solar irradiation.. CO2 is a poor absorber of sunlight because it's so narrow band. Water vapor (clouds) are much better absorbers on INCOMING sunlight.
It's the heat coming from the earth as a thermal tank -- going UP --- that the denialists have problems with. Because they quote thermodynamics in error -- not realizing that the EARTH emits a spectrum of IR where MORE of the energy is shifted into the absorption bands of CO2 and the other GHGases.. That's why clouds keep the surface warm at night (except in the desert where there is little water vapor to act as the PRINCIPLE GHGas).
No thermal conduction or convection required.. Mostly done by EM radiation....
Bottom line --- Go find the few studies that studied the GreenHouse at NIGHT, in the DESERT, controlled for water vapor that tried to find the warming due to the rest of the GHGases.. Not many exist --- because LARGELY they don't confirm that CO2 is a huge factor... And the hysteria industry is NOT gonna publish findings that contradict the Warmer Bible..
And none of what I wrote or quoted was specific to short wave radiation from the sun, but rather long wave radiation from the planets surface.
Also, I do not have a problem with IR emitted from the surface interacting with GH gases, that's been studied over and again, I am pretty sure it's recognized fact. What I, and most other people with any sense take issue with is the Down Welling Long Wave IR warms the warmer surface of the planet, it's heat source.
There is no misunderstanding of of the spectrum or wavelength differences between EM from the sun directly, and that of IR from the warmed surface. That is understood and acknowledged, and I don't see where you got that from anything I have said on here..
The issue with AGW theory with me is, the energy coming in from the sun, some gets reflected, some refracted, some absorbed, some used to warm the surface, and that which the surface emits as IR, warms the Atmosphere and then has enough left to warm it's own heat source further... It's a silly claim made by men that although were brilliant, were still wrong in their assumptions. The theory defies the 2nd law and does some nifty work around the 1st one as well.