Scientists are unraveling the environmental changes that took place around the Arctic during an exceptional episode of ancient global warming. Around 56 million years ago there was a period of global warming called the Paleocene-Eocene Thermal Maximum, during which global sea surface temperatures increased by approximately 5°C. The warming of the oceans led to profound ecological changes, including the widespread extinction of many types of foraminifera, tiny single-celled organisms with distinctive shells.