For billions of years, Earth has experienced periodic glacial cycles governed by its orbit around the Sun. No force on the planet could disrupt this eons-long cycle—until we came along.

A new study published in the journal Science suggests that a new glacial period was beginning some 2,000 years ago, but by the 1960s, greenhouse gas emissions had raised global temperatures enough to reverse it. Future emissions could forestall the next ice age for hundreds of thousands of years, altering one of Earth’s most fundamental natural cycles.

“It was just getting started, everything was normal, the next glaciation was about to happen—and yet it stopped,” first author Nicolás Young, a geochemist at Columbia University, said in a statement.…