Agency at the time of the Anthropocene

1) We've pushed the Earth to it's breaking point.

2) We once had to worry about the effects we had on the Earth and how to protect it, but now we have to worry about the protection of us.

3) We are close to crossing maximum CO2 level

Question: What exactly will happen when the Earth reaches it's "breaking point"? And I understand that this is something that we don't want, but should we really be that worried as far as the CO2 level if it has already been crossed before, as well as other thresholds, and yet we are still here today?