War makes climate change worse in many ways, and vice versa. The human costs of the U.S.-Israel attack on Iran—the hundreds of people who have died, including more than 100 girls and teachers killed at an elementary school—are surely a tragedy. The mounting economic risks—disrupted supply chains, spiking energy prices, shaken stock markets—are ominous. The danger that this war of choice launched by two nuclear-armed states will escalate further, drawing in powers across the region and beyond, is...