In this undated picture, Mount Everest, the world's tallest mountain at 29,029 feet, stands behind the Khumbu Glacier, one of the longest glaciers in the world. Nepal has more than 2,300 glacial lakes, and experts say at least 20 are in danger of bursting.
The Himalayas are sometimes called the world's "third pole" because they are covered with thousands of glaciers. Water from those glaciers helps feed some of the world's most important rivers, including the Ganges and the Indus. And as those glaciers melt, they will contribute to rising sea levels.
So a lot is at stake in understanding these glaciers and how they will respond in a warming world. Researchers writing in the latest issue of Science magazine make it clear they are still struggling at that task.