Hm! It is hard for me to believe that a gas (CO2) which is only a share of 0.04% of the air and of which 3% is human, should have such serious influences on the Earth's climate.
I invite you to consider 2 concepts: Firstly, that things in small concentrations can have very far-reaching effects. The fatal dose of Botulinum toxin for a healthy 80kg adult is 0.000168mg - or 0.000000000168 Kg. It's only a tiny proportion of the weight of the person being killed, but they will still die. It's the numbers of molecules that matter, not the proportion.
Secondly, the effect of altitude. The proportion of Oxygen in the atmosphere is the same at the top of Mount Everest as it is at sea level, at 21% So why can't a human being survive at those altitudes?
It's not the proportion of molecules that's significant, it's the absolute number. We are adding vast numbers of CO2 molecules to the atmosphere, and it's doing a great deal of damage even though it's not changing the proportion that much.
