Fifty-five million years ago atmospheric CO2 content increased, and the average global surface temperature rose 5 to 9°C (9° to 16°F). The Paleocene-Eocene Thermal Maximum (PETM) lasted upwards of 170,000 years, dramatically affecting life both on land and in the oceans. By documenting how this changed climate, plants, and animals, scientists can make predictions about how our current global warming event could impact life on Earth.