An artist’s illustration shows Earth from orbit. (Credit: Dima Zel/Shutterstock)

Our planet is getting warmer today, that’s a fact. But, this isn’t the hottest time in our planet’s history — far from it, in fact. At various points, millions or billions of years ago, Earth was much more toasty than it is now.

One of the most notable hot flashes came 56 million years ago, during the Paleocene-Eocene Thermal Maximum, or PETM. It was a relatively brief period of rapid, abnormal warming. Duri