red31 wrote:
anyone know what it was like during earth's accretion or the billions of years after
You mean the CO2 concentration? It varies by time, not too long ago (geologically speaking) it was up to 3000 ppm and the earth didn't melt, it was cooler than it is now. But free Oxygen in the atmosphere didn't exist in the earliest periods. The last theory that I heard about the release of O2 was that blue green algae evolved into existence and emitted O2 as a by product of photosynthesis. This was an absolute disaster for most life on the planet and you have to search in very out of the way places to find remnants of that life--the Archaea. Found in places like the deep ocean 'hot smokers'. So the atmosphere has never been static and there is no golden period that we should spend untold trillions of wealth to maintain.
