> 50 million years to breathe up all the oxygen our atmosphere has stored Surely CO2 level would reach unsustainable levels long before that? IIRC it would onl

> 50 million years to breathe up all the oxygen our atmosphere has stored Surely CO2 level would reach unsustainable levels long before that? IIRC it would only need to increase to ~0.5% before air would become unbreathable for more than a few hours..