Those experiments have been done in the lab, they show far lower 'climate' sensitivity to CO2 than the IPPC's most benign estimate.Again your ridiculous standard. How about experiments showing that CO2 levels affect the temperature in a system with incoming light in the visible wavelengths and outgoing light in the infrared? That is a well tested fact.
OK, how about citing any experiment that shows a man made change in atmospheric CO2, release or capture some CO2 and show a corresponding change in the atmosphere from the Mauna Loa CO2 measurements. That experiment hasn't been done either.Ergo, if you change CO2 concentration, you will change temperature in the atmosphere, subject to potential positive and negative feedbacks.
It's easy to write "if you change CO2 concentration" but so far that's been impossible to do experimentally in the atmosphere.
The effect is real but the lack of experimental evidence indicates the effect of man made CO2 emissions are insignificant.You have already admitted to accepting this, on the basic that you know that additional CO2 has progressively less effect as concentration increases. Therefore you acknowledge that the effect is real.