In the early 2000s, as climate denialism was infecting political institutions around the world like a malevolent plague, an Australian epidemiologist named Anthony McMichael took on a peculiar and morbid scientific question: How many people were being killed by climate change? McMichael’s research team tallied up how many lives had been lost to diarrheal disease, malnutrition, malaria, cardiovascular disease (a proxy for heat-related illness), and flooding, worldwide, in the year 2000. The