Pope Francis’ June 2015 encyclical “Laudato Si: On care for our common home” has been praised for supporting the science on climate change. But as Johan Rockström, who’s been involved in high-level discussions between scientists and the Vatican, explains, the story of how the Pope has integrated science and religion represents a profound shift in world view.

Johan Rockström’s theory of climate boundaries has proven so influential it’s been adopted by the Vatican. Writer John Carey digs into the theory — and why Rockström says his isn’t, actually, a doomsday message.