At the stroke of midnight Wednesday, when the United States became the only country to formally quit the Paris Agreement, the global accord designed to avert catastrophic climate change, it fulfilled a campaign promise that Donald J. Trump made four years ago. But a lot has happened in those four years. The costs of climate disasters have grown. Banks and investors have begun to turn away from fossil fuels as the price of renewable energy drops precipitously. Not least, key United States allies have rushed to stake out their own climate action targets. Britain, the European Union, Japan and South Korea have all said they would aim to neutralize their own emissions of planet-warming gases by 2050. And, in a shrewd move to outshine whoever is the next occupant of the White House, China, too, announced its own net-zero ambitions . “The […]