By early November, it was virtually certain that 2024 would be the hottest year on record. The evidence was being felt around the world—from flooding that killed hundreds in Spain to drought in 48 of America’s 50 states. Insurance-giants dropped coverage in danger zones and warned about the growing challenge posed by climate change. Amid all that, a casual observer might have expected negotiators gathered at U.N. climate talks in Baku, Azerbaijan, to double down on the most critical efforts to...