As glaciers melt and pour massive amounts of water into nearby lakes, 15 million people across the globe live under the threat of a sudden and deadly outburst flood, a new study finds. More than half of those living in the shadow of the disaster called glacial lake outburst floods are in just four countries: India, Pakistan, Peru and China, according to a study in Tuesday’s Nature Communications. A second study, awaiting publication in a peer-reviewed journal, catalogs more than 150 glacial flood outbursts in history and recent times.