Sharing lessons is critical for ensuring that finite funding for climate change adaptation is deployed in ways that provide the most value and impact. Successes are celebrated, but failures are habitually obscured, leaving a major knowledge base untapped. This commentary calls for the urgent sharing of failures as a source of critical learning. Authors: RossWestoby1 Mohammad FeisalRahman2 Karen E.McNamara3 SaleemulHuq4 …