The window of opportunity for climate adaptation action is closing fast because of warming and development trends (1). Yet efforts toward enhancing adaptation policy, implementation, and finance are not considered at adequate scale globally (2, 3). Scaling up such efforts requires substantial international investment, which we argue should include support for transdisciplinary adaptation research to enhance scientific foundations to feed into more effective policy engagement and funding for implementation. Here, we identify opportunities associated with three scientific frontiers: understand the potential for effective climate risk reduction (including understanding maladaptation, residual risk, and adaptation limits); assess systemic, cascading, and transboundary risks; and track adaptation progress.