Not only is this a weak attempt at global warming denial, it is absolutely NOT BREAKING HEALTH NEWS, grizz. Sorry, but this has to be said [unfortunately, it has to be said repeatedly...].
some terms to look up related to past extinctions:
Canfield Oceans [anoxic]; Clathrates of methane;
Also, possibly the most urgent reason to reduce CO2 Emissions: Oceanic carbonisation.