It's also possible that an increase in CO2 could actually lead to a decrease in CO2. Increased temperature could lead to increased evaporation and therefore precipitation, which would start to remove CO2 from the atmosphere, as would the increased wave action likely on the surface of oceans. This would not cool the planet to Snowball levels though, only stabilize the CO2 levels. This is what is thought could have happened after the end of a Snowball Earth period.
Or in the case of the Carboniferous period to a lesser extent, the carbon gets locked up into the plants which die, get buried and over time turn into the fossil fuels we are burning today.
And yes off topic post is off topic, but we're still talking about oxygen atmospheres.
Let's end the offtopicness here
On a thread related note, has anybody managed to get the Alpha Centauri system to generate with all procedural planets? (tbh though, it would be cool to see what it would have if the custom planets weren't there). There was a mention that someone tried to do that in another thread in this section, but there doesn't seem to be any other mentions about it.