John All unzipped his tent, poked his shaggy blond head out into the thin alpine air, and took in the view. The sun sparkled off the freshly fallen snow on the jagged peaks and crags of Mount Himlung. It was just before 10 a.m. on May 19, 2014—a perfect morning in the Himalayas.
All, a 44-year-old scientist, had come to Nepal on a research expedition to collect snow samples for his study of pollution. His two climbing partners had retreated down to base camp until one of them could recover from a stomach ailment.