In January 2020, Larry Fink, the CEO of BlackRock—the world’s largest asset-management firm—released his annual letter to corporate executives. The letters had become something of a tradition: part investor missive, part State of the Union, dispatched each year from the top of the financial world. This one struck a tone of alarm that would reverberate far beyond Wall Street. “Climate change has become a defining factor in companies’ long-term prospects,” Fink warned.