I always used to worry more about 'running out of oxygen' than CO2 emissions as I became aware of environmental science and the growing discussion about climate

I always used to worry more about 'running out of oxygen' than CO2 emissions as I became aware of environmental science and the growing discussion about climate change. I think there are two main reasons scientists do not worry about it as much as originally seemed intuitive (to me): First, the raw amount of oxygen in the atmosphere is large enough that fluctuations can go unnoticed. To decrease the percentage of oxygen by 5% would result in many orders of magnitude more CO2 (proportionally) being released, such that the oxygen would be negligible. There's also the geology of it: rocks absorb and release oxygen over millions of years and add hysteresis to atmospheric composition. The amount of atmospheric gases trapped in the Earth's crust is significant and resists long-term changes.