As the primary locus of greenhouse gas emissions and the hub of economic and social activities, municipalities represent both challenges and opportunities to reach a low carbon and resilient future. While there are many studies on the leadership of frontrunner cities and the importance of leaders (often mayors) within those cities, this research highlights the role of emerging networks of key individuals and organisations in urban settings. The paper presents a qualitative comparison of two metropolitan agglomerations in the U.S. (Boston and Cambridge (MA)) and in Germany (Berlin and Potsdam) in view to urban climate governance. The study is based on a range of 50 interviews with key stakeholders and a document analysis focusing both on mitigation and adaptation measures. By focusing on a small number of cities, which are quite similar regarding climatic conditions, yet quite different in terms of their size, economic power and civil society, we analyze differences (and commonalities) in the way climate mitigation and adaptation policies are formulated and eventually implemented. Through the lens of a multi-level governance perspective special attention is paid to the influence of vertical governance settings which reflect differences in the US and German politics. As climate policies have been nearly stalled at the federal level in the US, it is of particular interest to study the actions on more progressive states and cities. The state of Massachusetts (including its capital) has presented itself has a frontrunner in terms of energy-efficiency and renewable energy schemes, but raising adaptive capacity to climate impacts seems more complex. While adaptation is arguably a less salient issue in the case of Berlin, urban policies are much more embedded in European and German stringent environmental policy frameworks. The paper concludes with a comparison how different policy arenas influence the importance of local leaders and vice versa.
