If Atmospheric CO2 caused life forms to evolve and proliferate, why do you think the same amount of CO2, back in atmosphere can cause global climate catastrophe.
Well, given that it will be far beyond a climate ever seen during all of civilization, I think it’s worth worrying about.
Something doesn’t seem to compute stoichiometrically. It may become warmer and unpleasant for certain species, including humans but hard to conclude this may cause extinction.
Indeed, once it was so warm that crocodiles were swimming in the Arctic.
The fossil record also shows mass extinctions corresponding to large shifts in climate. And yes that could have been catastrophic to the animals living at the time if they realized it.
But today, the human population is many orders of magnitude larger than it would be without agricultural development. As an example, compare population density of natural-living non-human hominids in Africa to homo sapiens in Rwanda. And that development—patterns of water, soil nutrients, and which crops grow where has been developed entirely with respect to the climate of the last 10000 years during which civilization arose. That climate has been stable to about 0.5 degrees C.
So the demands on the specific nature of the biosphere and sensitivity of humans to climate is very substantial, more than people realize, because of this.
Going to a circumstance not seen since literally before the evolution of homo sapiens—much less civilization—is not comforting in the slightest.
Sure, there will continue to be multi-cellular life somewhere on the planet. So what?
