[Spirochete]

Years ago, it passed the 350 ppm mark that many scientists say is the highest safe level for carbon dioxide. It now stands globally at 395.

Air bubbles in Cretaceous amber show that CO2 levels then were around 3,200 ppm.

[HiTech RedNeck]

Yup. “Gaia” has survived far greater atmospheric levels of carbon dioxide, and she has come back from it smelling like a rose. The hard question is how can you manage to kill the earth, not how can you keep from killing it.