Well we finally thawed out here in Manitoba.
So I went outside to see if it was the sun that did it or all that "back radiation".
I used a laser thermometer which converts IR watts radiated to degrees C.
The sun had warmed the ground I stood on to +37 C which is a lot more than the +16C average used in Trenberth`s "energy budget" which zaps us with 333 watts/m^2 "back radiation"
Pointing the gun straight up at the clear sky it should have registered +3.8 C if there were 333 watts coming back down, but all I got was a bone chilling -18 C which corresponds to 237 watts.
So even with all that CO2 up there it`s still 100 watts/m^2 short of a climax scientist`s orgasm.
Conduction at ground level where air meets the warmer ground...(your registering ground temp) convection from water vapor in the air once warmed (your IR beam is bouncing off water vapor in the air)... and no measurement of what LWIR is doing (down welling) because your hand held device cant measure it.
Fooling yourself with equipment is easy to do.. However you have identified two elements in the atmospheres temperature. The question is, do you think that BBR (Black Body Radiation- LWIR) returning to the earths surface after being emitted from the surface (caused by CO2 or other gases) is capable of making up 170Wm^2 in the energy budget of the earth?