Around 6,000 years ago, the Sahara was a lush grassland. Then, as if a switch flipped, it began to dry out, becoming the desert that we know today. Tipping points are moments in Earth’s history where gradual change suddenly becomes rapid and forms a new equilibrium. They’re one of the most alarming threats of our planet’s near future — and one of the most uncertain. When will a tipping point occur? Mathematicians are attempting to turn vague, apocalyptic visions into something that we can actually prepare for and deal with. On this week’s episode, host Samir Patel speaks with contributing writer Gregory Barber about what tipping points can — and cannot — tell us about the future of our planet. This topic was covered in a recent story for Quanta Magazine. Each week on The Quanta Podcast, Quanta Magazine editor in chief Samir Patel speaks with the people behind the award-winning publication to navigate through some of the most important and mind-expanding questions in science and math. Audio coda courtesy of Gresham College.