Providing sound evidence to inform decision-making that considers the needs of the most vulnerable to climate change will help both adaptation and development efforts. Such evidence is particularly important in climate change “hot spots”, where strong climate signal and high concentrations of vulnerable people are present. These hot spots include semiarid regions and deltas of Africa and Asia, and glacier- and snowpack-dependent river basins of South Asia. In advance of a major research effort focusing on these three hot spots, studies were commissioned to identify and characterize the current status of knowledge in each on biophysical impacts, social vulnerability, and adaptation policy and practice. The resulting seven papers are brought together in this special edition, with this editorial introduction providing background on these hot spots, the program through which the studies were commissioned, and an overview of the papers that follow.