LOL, eventually human kind or creature will out of O2 and we have massive extinction from animal to plants.

CO2 is a nature cyclical process that exist, just with industrialised age, people converted and produced more CO2 compared to last time by burning fossil fuels or converted natural sources to energy form.

Naturally there are mechanism to absorb back the CO2 from ocean, to plants etc. Just human kind might offset the balance of it with industrialised age.