In a major United Nations report released last Monday, the more than 230 scientists who make up the Intergovernmental Panel on Climate Change described "unprecedented" climate change over the past century and warned in similarly unambiguous language that the world will descend further into catastrophic warming absent rapid and aggressive action to cut emissions of carbon dioxide and other heat-trapping gases. We asked Peter Huybers, a professor of Earth and planetary sciences, about the research behind the report, the panel's first since 2013, and the harrowing details contained within it.