Ancient hot spell is linked to copious carbon dioxide

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.

HOT TIMES. The nahcolite layers (brown) in this rock indicate that when the mineral formed about 50 million years ago, concentrations of carbon dioxide in the atmosphere were three times those found today.