Curt Stager 11.02.11 12:55 AM New research into just how hot it was on Earth 60 million years ago—and what that heat did to the planet—isn't a vision of doom for the future. But it should give us some warning about where we're headed: to a planetary sauna. Newsletter Get the latest Fast Company stories delivered to your inbox daily. Send I'd also like to receive special Fast Company offers ARE YOU REGISTERED TO VOTE? Register now to make sure you have a voice in the election.