What is a Watt???

[Richard111]

Yes! Very good point. Me, being a simple trusting soul, assume they always meant the "blackbody" equivalent of 1 square metre for each level of radiation defined in watts per square metre.

I have several times asked the question how to you define the radiation from a VOLUME of the atmosphere? I am currently trying to learn about infrared detectors as used in the satelites. So far it is not encouraging. The best I've read about so far only record IR from 4 microns to 20 microns. Big deal! There is still IR radiation down to 1,000 microns! It also appears they "average" all the readings. For example they will see high intensity narrow band (8 to 12 microns) through the 10 micron atmospheric window. They will also see low intensity wide band radiation from the cloud tops (most of which will be missed due to cutoff at 20 microns in the measuring instrument) and then there will be the very low intensity 15 micron radiation from CO2 in the cold upper troposphere where water vapour does not exist in any great quantity.

All of that is somehow added together to show -18C (255K) radiation from the whole earth from a source claimed to be radiating at 240 watts per square metre.

I know all the sums add up but verifying the input parameters seems fraught.