A public symposium honoring Robert H. Williams, senior research scientist, on the occasion of his retirement from Princeton University. Held on April 3, 2017 at Princeton's Andlinger Center for Energy and the Environment. Talks include: Welcome and introduction (Yueh-Lin Loo and Eric D. Larson); "Carbon Mitigation in the Context of Sustainable Development" (Thomas B. Johansson); "The Past, Present, and Future of Energy Efficiency" (Howard Geller); "The Future of Renewable Energy: Challenges and Opportunities" (Sam Baldwin); "Carbon Capture and Storage for a Tolerable Climate Change" (Stefano Consonni); "Enabling Fossil Fuels to Survive in a Carbon-Constrained World" (Vello Kuuskraa); "Estimation of CO2 Leakage along Old Wells using Numerical Models and Field Measurements" (Michael Celia); "Nuclear Power: Trapped in a Safety Quagmire" (Frank von Hippel); "Charting a Transition to Sustainable Transportation" (Joan Ogden); "Overcoming Commercial Challeneges for Deployment of Large-scale Low-carbon Energy Systems" (Chris Greig); "Climate Change and Our Future Electricity System - Europe in 2050" (Wim Turkenburg); "Toward Reduced Costs for CO2 Capture and Storage for Power Grids with High Levels of Intermittent Renewable Electricity" (Robert H. Williams); and panel discussion on "Are U.S. Policy Advances to Mitigate Climate Change Possible in the Trump Era?" (Robert H. Socolow, Brad Crabtree, Richard Duke, Ottmar Edenhofer, Jos ̌Goldemberg, David Hawkins, John Holdren, and Henry Kelly).