Coal and potential global glaciation

Climate model simulations indicate that global glaciation could have occurred during the early Permian, which directly followed the formation of the bulk of Earth's coal deposits, if atmospheric carbon dioxide concentrations had decreased to approximately 37.5 ppm; the study suggests that the formation of Earth's coal deposits may have almost led to a global glaciation during the early Permian.

Article #17-12062: "Formation of most of our coal brought Earth close to global glaciation," by Georg Feulner.