It is all a question of balance.
Is there higher probability for a thriving ecosystem when CO2 level is higher than today or is there higher probability with a lower level of CO2?
You take out one parameter of several and think to evaluate the impact only based on this. This is an obvious oversimplification fallacy.
Absolutely yes.
Refer to Cambrian explosion where explosion of life occurred with 10x co2 levels today.
You are actually comparing a time, when there was very little to no complex forms of live to today? It is like thinking, since an embryo does not have to breath, an adult does not have to breath neighter.
Circumstances matter.
