I did the calculations on this once it's simple, you can do it too, if I wasn't lazy I'd post it but it's something like this:

1. Earth is sphere, get volume.

2. Get volume of atmosphere 50 miles out or X miles out to whatever tier of atmosphere you want to examine. Subtract them, this gives u volume of whatever atmosphere tier u want to look at.

3. Get numbers of CO2 released by humans every year, and subtract the amount that goes back into the trees and oceans (which btw is a lot, if not all is just absorbed back into the oceans).

4. After calculations, it's something like 100-1000+ years before the CO2 in our atmosphere doubles. (which doesn't fucking matter anyway). (depending on what numbers you use this can also be infinite time before doubling if using reasonable ocean replenishment rate ).

5. Also realize water vapor fluctuations are from like 0.2%-4% of atmospheric makeup, which is waaaaaaaaay more potent for warming/cooling effects.

6. Also realize the distance the earth is from the sun, and the shit that the sun is doing, is far more potent than literal "nano"-amounts of gases in comparison to the distance fluctations in the sun-earth distance.

7. This is the simplest shit ever how are people still falling for global warming. It took me like 2 hours to do this back in highschool.