The Earth’s archives can provide valuable clues to the possible scale of future climate change through greenhouse gas emissions. 55 million years ago the sudden release of > 1500 gigatonnes of carbon in the form of carbon dioxide and/or methane resulted in dramatic global warming, with tropical temperatures in the Arctic, acidification of the oceans and species mass extinction. Where did the gas originate from, what was the trigger for the release, and how long did it take for the Earth’s climate to recover to previous levels? These are familiar questions, but new high precision age dating results may provide some clues.