|Oh... Wait,,, it wasn't dinosaur farting that caused the extinction. Perhaps it was a global flood, the "mother of all mass extinctions".
Couldn't it simply have been a meteorite strike or erupting volcanoes? That would have made the climate much colder. In the 1970s some scientists suspected that fossil fuel burning could cause a similar phenomenon but there was never any consensus about it. Even in the 1970s most climate scientists believed that the climate would become warmer because of carbon dioxide emissions.