The GreenHouse Effect GHE is supposedly captured in the above radiance spectra showing the radiance in W/ m2 per wavenumber as function of wavenumber/frequence looking down from a satellite (top) and looking up from the Earth surface (bottom), with the radiance supposedly being measured by an instrument sensitive to infrared radiation, like a pyrometer, bolometer or infrared camera.
The ditch in the outgoing long wave radiation OLR (top) around 15 mikrons is supposed to show the major impact of atmospheric CO2 by "blocking radiation" with a warming effect. The big hump to the right in the downwelling long wave radiation DLR (bottom) is supposed to show massive "back radiation" to the Earth surface from the atmosphere, with an even more impressive warming effect.
Having seen the big ditch and massive hump, how could you ever doubt that that the atmosphere has a warming effect by blocking outgoing radiation and by backradiation? This argument has convinced many scientists into believing in CO2 global warming, with the evidence being the reading of an instrument supposedly recording a radiance spectrum.
But to properly understand the relevance of the reading of the instrument, it is necessary to understand the functioning of the instrument used. In the last sequence of posts I have shown that an instrument like pyrometer or bolometer does not measure radiance, but instead temperature, and then computes radiance from Planck's law assuming emissivity = 1. The correct scale of the instrument is thus in Kelvin and not W/m2, which makes a difference if the emissivity is not known, which is the case in general.
The instrument should be viewed as an infrared thermometer capable of measuring the temperature of a distant radiating object by radiative equilibrium between object and detector, for different wave numbers.
The measured (total) emissivities of the Earth atmosphere recorded in
- Effective Atmospheric Emissivity under Clear Skies
- Parametrization of Atmospheric Longwave Emissivity...