Matt Damon investigates the impact of extreme heat on human health and mortality, with a focus on research that has uncovered how rising temperatures are creating a worldwide public health emergency. Michael C. Hall visits Bangladesh to explore the prediction that by 2050, a global migration of upwards of 150 million people will produce the single most daunting burden to our future. And Thomas L. Friedman travels to Yemen to conclude his look into how climate stress can push volatile political situations over the edge.