Classic SSDD. There really is no evidence at all - not even an experiment you could perform yourselfin your owm backgarden - that could get those blinkers off your eyes, is there?
It has been proven beyond any reasonable doubt that backradiation does exist.
What do you get out of ignoring obvious facts?
There is an experiment that I can, and have performed in my back yard that would prove backradiation if it existed. You can do it as well for less than 25 dollars. Build yourself a small solar oven (I can provide plans). Aim it at clear sky on a sunny day. Place a thermometer at the focal point of the oven and watch the temperature decrease. If backradiation existed, the temperature would increase as it would be collecting backradiation.
Wait till nightfall when the temperature is above freezing but not more than 45 degrees F. Point your oven at clear sky and place a bowl of water at the focal point of the oven. Ice will form even though the ambient temperature is above freezing. If backradiation were happening, that could not happen. Observable, repeatable, positive proof that backradiation is not happening.
Aside from that, the second law of thermodynamics says that backradiation is not possible. How much more proof do you need? An experiment that produces the very result predicted by the second law of themrodynamics proving that backradiation is not happening...and I wager that you will continue to believe in backradiation.