There is medium evidence and high agreement that optimal adaptation depends critically on inter-state cooperation , which in turn requires trust and norms of reciprocity among all those involved . Reciprocity is central to international cooperation on climate change, where actors are more inclined to cooperate when they perceive that the expected outcome will be fair in terms of costs and benefits of implementation . Indeed, cooperation at the international level is less probable to occur if participants do not trust each other . In climate-related water adaptation, transboundary cooperation is essential, as 60% of global freshwater resources contained in 276
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report