Ignorance is a growth industry. One of the fastest moving products is that the temperature of the warmer surface cannot be maintained by back radiation from the colder atmosphere because this violates the second law of thermodynamics. Eli has an argument demonstrating that this is a bucket load of cods wallop, so simple that . . . . (fill in the blank
It goes like this:
- The surface is at ~290 K. It radiates ~400 W/m2. In addition there are losses from latent heats (maybe another 100 on average).
- The average solar power absorbed by the surface is ~190 W/m2, call it 200 W/m2.
- That means, neglecting latent heats, if there is no radiation from the atmosphere absorbed by the earth, the surface will cool until the net outflow of radiation in the IR matches the radiation absorbed from (corrected-ER) the sun.
- Do the math E = 200 W/m2 = σ T4, so without back radiation from the atmosphere, the temperature of the surface will reach an equilibrium at 244 K. If you include convection, which is strictly a loss from the surface, the temperature would go even lower.
- OTOH, if 200 of the 400 W/m2 radiated into the atmosphere in the IR are returned to the earth from the colder atmosphere, there is a balance between energy absorbed at the surface, Sun + Atm Return =200 +200 and surface radiation = 400 W/m2.
- There is still a NET heat flow from the warmer surface to the colder atmosphere (400 - 200 = 200 W/m2) so the second law is obeyed
Read the comments. . .