Wait till you read about anoxic events, like the one we got during the "global supergreenhouse" stage of the Cretaceous. The one that wiped out the ichtyosaurs, pliosaurs and a bunch of other marine life when rising temperatures first led to a giant algae bloom and then to most of the oceans eutrophying and becoming oxygen-free, like a pond tipping over and becoming a lifeless gooey shit puddle.

Did i mention that temperatures back then rose a whole lot slower than today and that organisms had much more time to adapt?