In what possible way can freeing fossilized carbon back (where it came from) into the carbon cycle "reduce long term habitability of the planet"?. It may make it awkward for some low lying cities in the short term, but long term it guarantees a warmer, moister, more bountiful planet if anything.
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.
