The world wants an American climate leader, and Gavin Newsom is happy to play the part — even if the country he represents isn’t quite ready to follow.BELÉM, Brazil — Gavin Newsom can’t get out of a meeting or a talk at the international climate talks here without being swarmed by reporters and diplomats eager for a quote, a handshake, a photo.On a tour Tuesday of a cultural center with Gov. Helder Barbalho, the leader of the Brazilian state hosting the talks, a passerby recognized them both. “There’s the governor,” he exclaimed. “And there’s the California governor.” Later in the...