Dr. Irwin Redlener spends a lot of time thinking about what can go wrong. For decades, he has advised governments about how to handle the public health consequences of hurricanes, tornadoes, terrorist attacks, earthquakes, and the like. That’s because, as director of the National Center for Disaster Preparedness at the Earth Institute at Columbia University, analyzing all the various catastrophes that can befall human beings—as well as figuring out strategies for preparing to withstand disaster and recovering when the worst happens—is, quite simply, his job.