Stephen Hammer

Senior Fellow

Stephen Hammer is a senior fellow in climate finance with a joint appointment at the Kleinman Center for Energy Policy, the Penn Institute for Urban Research, and Perry World House. He currently advises governments and international institutions on climate finance and policy issues and has more than 30 years of experience working on climate issues at the global, national, and local levels.

Between 2023 and 2025, he served as the founding CEO of the New York Climate Exchange, leading a coalition of academic, corporate, and community partners to build a center for climate solutions and accelerate climate action at speed and scale.

He previously held senior positions at the World Bank, shaping the Bank’s international climate strategy and its engagement with the UNFCCC, the UN Secretary-General’s team, and G7/G20 climate discussions. He also helped design and launch key international partnerships, including the Coalition of Finance Ministers for Climate Action and the City Climate Finance Leadership Alliance. In 2023 he was seconded to support the UNFCCC Transitional Committee that established the Fund for Responding to Loss and Damage (FRLD).

Before joining the World Bank, Hammer was a professor at MIT’s Department of Urban Studies and Planning (DUSP), where his work focused on urban energy and climate policy. Prior to that, he taught at Columbia University’s School of International and Public Affairs, where he founded and directed the Urban Energy Program.

Hammer holds a PhD from the London School of Economics, an MPP from Harvard’s Kennedy School of Government, and a BS from the University of California, Davis.