The fixation on the 0.04% is particularly confusing, as the other 99.96% of the atmosphere is mostly completely transparent to the relevant frequencies. Going b

The fixation on the 0.04% is particularly confusing, as the other 99.96% of the atmosphere is mostly completely transparent to the relevant frequencies. Going by volume or ppm is wrong when all we care about is the absorption factor. Greenhouse gases don't absorb less infrared radiation by adding transparent nitrogen, even though it would reduce the greenhouse gas concentration.