Well, this is not a surprise. Turns out there is no empirical evidence that increasing concentrations of CO2 in the atmosphere causes radiant warming. A critical assumption of IPCC consensus on CO2 concentrations is that it causes radiant heat to be retained in the upper atmosphere. This conjecture “lacks empirical confirmation.” Experiments continue to fail to show that CO2 is a factor in warming the atmosphere.
It turns out that any heat effect is due to the different density in gases. One experiment used pure (1,000,000 ppm) CO2 in one container and air (N2, O2) in another to demonstrate the CO2 container warms more than the air container. It ended up illustrating that CO2 molecules are heavier than nitrogen and oxygen molecules. Heavier CO2 molecules “reduce heat transfer by suppressing convective mixing with the ambient air.” In other words, the CO2 molecules aren’t warming the container via their radiative properties, but due to the density differential for CO2 relative to N2 and O2.
Another experiment, again using pure CO2 in a container, compared the radiative absorption properties of CO2 to that of argon, helium, and air (nitrogen and oxygen). The capacity to absorb radiation (sunlight) was found to be quite similar for CO2 and for argon, nitrogen, and oxygen. The latter 3 are non-greenhouse gases. Nitrogen and oxygen together constitute 99% of the atmosphere. Argon’s atmospheric representation is 0.93% (9,300 ppm) and CO2 is 0.041% (410 ppm).
In the experiment, the limiting absorption temperature for pure CO2 molecules wasn’t significantly different than the far more atmospherically abundant non-radiative gases. Dr Allmedinger summarizes, this means that “a significant effect of carbon-dioxide on the direct sunlight absorption can already be excluded.”