Plants are indicators of climate.
Fossil leaves and plants act as ancient thermometers, allowing scientists to study the ancient climate .
During the transition between the Paleocene and Eocene epochs, a sudden surge of carbon dioxide into the atmosphere prompted an extreme version of global warming, producing droughts and floods, widespread species extinctions and a redistribution of planetary life.
Whatever released C02 remains a mystery. Scientists wonder if it could happen again.
The leaves may reveal past temperature shifts, carbon cycling and pollen and soil changes that took place 56 million years ago. It could provide further evidence that C02 levels are a driver of climate change.