In the early twenty-first century, New York and other cities established targets to reduce their greenhouse gas emissions to help limit global climate change. Limiting these emissions is not an obvious task for local governments: no city’s efforts will materially affect planetary temperatures, and curtailing these emissions imposes costs on local actors mainly for the benefit of the world as a whole. Between 2007, when the city set its first GHG reduction target, and 2019, the city’s emission reduction efforts were consistent with the preoccupation of local elites with economic growth. The city did not impose costly requirements on local actors to reduce their emissions, and the city did not achieve significant emission reductions. However, in 2019, the city government passed a local law that establishes declining caps on greenhouse gas emissions from buildings, and portends real costs on private actors – including the owners of residential real estate – if the city enforces the law. This 2019 law emerged from the efforts of city insiders, and local progressive interest groups motivated by environmental, social justice and labor concerns in the first Trump presidency. The history of the city’s efforts to reduce greenhouse gas emissions illustrates the precarious politics of local decarbonization efforts.