- Do you dispute that if you put an infrared radiometer on the surface of the earth and point it upwards, that it will measure an IR radiance or irradiance (depending on how the instrument is configured)? Go to http://www.arm.gov for decades worth of such measurements. And that this infrared radiation comes from IR emission by gases such as CO2 and H2O and also clouds? If you say yes, well this is what people are calling back radiation (a term that I don’t use myself). If you say no, then I will call you a crank – all your manipulations of Maxwell’s equation will not make this downwelling IR flux from the atmosphere go away.
onsdag 2 februari 2011
Judy Curry and "BackRadiation"
In the comment Febr 1 12:28 to the thread on Slaying the Sky Dragon on Judy Curry's blog, Judy asks me:
I address this question in Section 7.4 of my Sky Dragon article Computational Blackbody Radiation, and Judy's question indicates that she has not read my article. I explain there that an IR camera (infrared radiometer) directed to the sky measures the frequency of incoming light and computes by Wien's displacement law the temperature T of the emitter, and then by Stefan-Boltzmann's law Q = sigma T^4 associates a "downwelling IR-flux from the atmosphere" of size Q.
The IR camera thus measures frequency/temperature which by SB is translated to "downwelling IR-flux" or "backradiation". So everything hinges on this translation. Is it
Is it correct to use SB in the form Q = sigma T^4? No, because this law gives the radiated
energy from a blackbody into an environment of 0 K. But the Earth surface is not at 0 K,
but even warmer than the atmospheric emitter. The translation Q = sigma T^4 is thus incorrect in the sense that it indicates a fictitious "downwelling IR flux from the atmosphere" obtained by an erronous translation.
Judy calls me a "crank" because I say "no to downwelling IR flux from the atmosphere".
Let me then remind Judy that just saying "crank" does not mean that I am a crank in reality, and just saying "downwelling IR flux from the atmosphere" does not mean that in reality there is anything like that. Right Judy?