Around 252 million years ago, the world suddenly heated up. Over a geologically brief period of tens of thousands of years, 90% of species were wiped out. Even insects, which are rarely touched by such events, suffered catastrophic losses. The Permian-Triassic mass extinction, as it’s known, was the greatest of the “big five” mass extinctions in Earth’s history.

Scientists have generally blamed the mass extinction on greenhouse gases released from a vast network of volcanoes which covered much of modern day Siberia in lava. But the volcanic explanation was incomplete. In our new study, we show that an enormous El Niño weather pattern in the world’s major ocean added to climate chaos and led to extinctions spreading across the globe.