Melting glaciers, loss of seasonal snow, and precipitation changes pose significant risks to the stability of water resources in the South Asia region. Glaciers help to moderate river flows in the region's major rivers by providing a source of meltwater in hot, dry years and storing water during colder, wetter years. The dependence on glaciers and snow makes these rivers particularly vulnerable to climate change. In addition to threats from global climate change, black carbon produced and circulated within the region is both increasing the absorption of solar radiation by the glaciers through decreasing the glacier surfaces’ reflectance and raising air temperatures, which also increases melt. In these ways, black carbon is becoming a significant factor in the retreat of some Himalayan glaciers.The purpose of this study is to identify the causes of potential changes to the glacier and snow dynamics in the Himalaya, Karakoram, and Hindu Kush mountain ranges, present scenarios of possible glacier and snow changes under different climate change and black carbon scenarios, and determine implications for water resources within the Indus, Ganges, and Brahmaputra basins. Since changes in regional climates are largely linked to global-scale actions and processes, the response of glaciers and snow changes must be approached in the context of the need to reduce global greenhouse gas emissions; however, there are local actions that may reduce or offset the impacts in the short term. The overall objective is to provide sound analytical underpinnings for policy making, investments, and other initiatives that could be further supported by Bank-financed operations.
