2.3 billion years ago, «the probably most significant extinction event in history» took place. (lindau-nobel.org)
And yet the IPCC itself warned last year that as global average temperature increase exceeds about 3.5 °C [relative to 1980 - 99], model projections suggest significant extinctions (40 - 70 % of species assessed) around the globe. (cato-unbound.org)
As he noted the absence of quail (Coturnix sp.), roadrunners (Geococcyx californianus), sage thrashers (Oreoscoptes montanus), and other chaparral - dependent species, he realized that there had been significant extinction in some of these old patches. (scientificamerican.com)