For what its worth most of the carbon from back then has been sinked into the ground, and while we extracted and burned enough of it to fuck the climate, it is nowhere near enough to have caused a relevant change in the atmospheric oxygen concentration.
But where is the oxygen now then?
For what its worth most of the carbon from back then has been sinked into the ground, and while we extracted and burned enough of it to fuck the climate, it is nowhere near enough to have caused a relevant change in the atmospheric oxygen concentration.
Google geological oxygen sinks.
Animals breathed it in and exhaled CO2 over millions of years