Earth’s temperature has been much cooler in the past than previously thought, meaning it could be moving toward the warmest it’s ever been.

Research at the University of Leeds used a new method to understand how warm Earth’s temperature has been over the Phanerozoic period—from around 540 million years ago to the present day.

Studies previously estimated that the planet’s temperature could have reached up to 20 degrees Celsius above preindustrial levels during some geological periods, and maybe even up to 30 degrees above preindustrial in earlier times when the first animals evolved.