The Permian/Triassic event, approximately 251 million years ago, was probably triggered by an outpouring of volcanic CO2, and caused extinction of 96% of all marine species and 70% of vertebrate species, see Permian–Triassic extinction event. There was wide-spread desertification on land, and anoxia in the oceans, coupled with acidification. The global temperature increased by 6 degrees, according to some models. [1]