Around the world, municipalities assume a crucial role in addressing climate change. On 1-2 October 2015, participants gathered at the International Conference on Climate Action (ICCA2015) in Hanover, Germany, to learn from best practices and highlight further potentials of local climate action. Under the theme "Local Governments Driving Transformation" the conference gathered more than 400 representatives from municipalities, politics, networks, foundations and research institutions from Germany and abroad. Participants took the opportunity to discuss and learn from different concepts and approaches to local climate action. The conference was hosted by Germany’s Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB), the Ministry for Environment, Energy and Climate Protection of Lower Saxony, Germany, and the German Institute of Urban Affairs (Difu). adelphi supported the implementation through conceptual design, organisational work, and moderation in a number of workshops. The proceedings document important speeches, discussions and outcomes of the conference, including the Hanover Declaration.