The greater Himalayan region contains the largest areas covered by glaciers and permafrost outside the polar regions. The region and its water resources play an important role in global atmospheric circulation, biodiversity, agriculture, and hydropower, while serving more than 1.3 billion people in the basin areas of ten large Asian rivers. Climate change is affecting the amount of snow and ice and rainfall patterns, but there is a severe lack of the data needed to understand these processes. This paper discusses these issues, the need to close the knowledge gap, the need for adaptation strategies, and the importance of strengthening local knowledge and the institutions relevant for adaptation.