Basic biology? Are you seriously asking or just being obtuse? Do you know what the world looked like the last time we had 1000+ ppm CO2? Teeming with plant life. C3 plants were facing extinction if CO2 levels dropped any further than they had, we've done the biosphere a huge favour by digging it up and putting it back in the air where it came from. Maybe we haven't done humans a favour, but that's a different conversation.