BEIJING—Glaciers in China that are a critical source of water for drinking and irrigation in India are receding fast, according to a new comprehensive inventory. In the short term, retreating glaciers may release greater meltwater, “but it will be exhausted when glaciers disappear under a continuous warming,” says Liu Shiyin, who led the survey for the Cold and Arid Regions Environmental and Engineering Research Institute in Lanzhou.

In 2002, Chinese scientists released the first full inventory of the country’s glaciers, the largest glacial area outside of Antarctica and Greenland. The data came from topographical maps and aerial photographs of western China’s Tibet and Xinjiang regions taken from the 1950s through the 1980s. That record showed a total glacial area of 59,425 square kilometers. The Second Glacier Inventory of China, unveiled here last week, is derived from high-resolution satellite images taken between 2006 and 2010. The data set is freely available online.

Liu and his colleagues calculated China’s total glacial area to be 51,840 square kilometers—13% less than in 2002. That figure is somewhat uncertain because the previous inventory used coarser resolution images that may have mistaken extensive snow cover for permanent ice, says Raymond Bradley, director of the Climate System Research Center at the University of Massachusetts, Amherst, who was not involved in the project.

Methodological quibbles aside, the latest inventory flags a marked retreat of glaciers in the southern and eastern fringes of the Tibetan Plateau. “We found the fastest shrinking glaciers are those in the central upper reach of the Brahmaputra River, between the central north Himalaya [and] the source region of the tributary of the Indus River,” Liu says.

Matthias Huss, a glaciologist at the University of Fribourg in Switzerland, applauds the openness in sharing data, which hasn’t always been the norm in China. “It is highly useful that the colleagues from China have made their data set available to the community. It will feed directly into global efforts to compile a worldwide glacier inventory and is a major improvement,” he says. “It will, for example, greatly support the effort of global glacier modeling to improve our understanding of glaciers’ response to climate change.”