This policy brief is an outcome of discussions based on an overview paper presented at regional workshops in Africa, Asia, Latin America (2013) and a workshop held in Paris (2014) in the context of "Climate Change Impacts in Major Mountainous Regions of the World : Multidisciplinary Network for Adaptation Strategies (Africa, Asia, Latin America and Europe)". This policy brief is a contribution to the VIIth Phase (2014-2021) of the IHP "Water security : responses to local, regional and global challenges."