[rstuart4133]

It's not the only mechanism for CO2 removal. There is also a geo cycle. I've forgotten the exact details, but it involves the acidity created by CO2 increasing the speed of rock weathering, and the result sediments being incorporated into the plates, plate tectonics removing the carbon from the upper crust and volcanoes re-introducing it. It's self regulating but very slow, taking millions of years.

Granted, biological removal is much faster, now. But during snowball earth in particular there was so little biological activity the geo cycles dominated CO2 regulation.

Neither of those two mechanisms are relevant right now, as mankind's production of CO2 has swamped both mechanisms. That will stop one way or another of course.