Mass extinctions happened multiple times throughout Earth’s history. These events dramatically changed the biosphere and altered the course of evolution. Many of these seem to be linked to CO2 degassing, global warming, and other major environmental perturbations. I have ongoing collaborations related to geochemical change across the End-Cretaceous extinction. I am also working with a team to use physiological modeling of dinosaurs and other tetrapods to determine environmental change across the End Triassic Extinction.