Climate change is emerging as a potent driver of internal migration. The report Groundswell: Preparing for Internal Climate Migration (2018) projects that, by 2050, without concrete climate and development action, just over 143 million people—or around 3 percent of the population across Sub-Saharan Africa, Latin America and South Asia —could be forced to move within their own countries to escape the slow-onset impacts of climate change. In South Asia, “internal climate migrants” could number over 40 million, representing up to 1.8 percent of the region’s total population. Climate migrants are projected to increase by a factor of six between 2020 and 2050, and the share of climate migrants in all internal migrants could reach as high as 25 percent in the subregion. Climate migrants will move from less viable areas with lower water availability and crop productivity and from areas affected by rising sea level and storm surges. The poorest and most climate-vulnerable areas will be hardest hit. These trends, alongside the emergence of “hotspots” of climate in- and out-migration, will have major implications for climate-sensitive sectors and for the adequacy of infrastructure and social support systems in both rural and urban areas. While some climate migration cannot be avoided due to the lock-in of climate effects of past emissions, the results also indicate that future trajectories of climate migration are not set in stone. Climate migration in South Asia can have substantial development implications, and the stakes are high. Achieving a resilient society—where people can either adapt in place and thrive or migrate with dignity toward areas of higher opportunity—is an important part of meeting national development goals. Internal climate migration may be a reality but it doesn’t have to be a crisis. Concerted action on climate change mitigation and adaptation, together with inclusive development policies and embedding climate migration into policy and planning, could help to substantially reduce the number of internal climate migrants by 2050. Policy decisions made today will shape the extent to which the effects of climate change will be positive for migrants and their families. Inaction would mean missing a window of opportunity to reconfigure where, when, and how climate-resilient investments are made in support of robust economies.