Policy evaluation has great potential to enhance polycentric climate governance, but that potential has not yet been fully realized. This concluding chapter draws together the key contributions of the book, which not only emerge from significant theoretical development, but also from a novel empirical analysis that is the first to investigate policy evaluation in the polycentric setting of the EU, as well as in Germany and in the United Kingdom. Future research should further explore causal drivers of the emergence of policy evaluation in polycentric governance systems, and unpack the actual use of knowledge in policy-making, a difficult, but necessary area of inquiry going forward. Additional aspects of polycentric governance theory, such as the role of evaluation in building trust and generating linkages between different actors, should also be explored. The collective research and climate governance endeavor will continue—this book has offered some new directions in which the journey may advance.