By Sid Perkins
The presence of a particular mineral in ancient rock suggests that during an extended warm period in Earth’s past, the atmosphere held at least triple the concentration of carbon dioxide that it does today, a new analysis shows.
Between 52 million and 50 million years ago, Earth’s climate was the warmest it had been since the dinosaurs died out 65 million years ago. The temperature of the deepest water in the oceans, an indication of global climate, was at least 10°C higher than it is today.