Under the worst climate change scenarios, American cities, beginning with Miami, are already experiencing rising seawater levels that mirror Ernest Hemingway’s warning about bankruptcy: “At first you go bankrupt slowly, then all at once.” The Paris Agreement, adopted in 2016 and now with 195 signatories, had aimed to avert climate catastrophe by keeping long-term global temperature increases below 2 degrees Celsius compared to preindustrial levels. And on Jan. 20, 2021, as one of his first acts...