Humans are engineering the planetary environment with emerging technologies such as synthetic nitrogen fertilizers, geoengineering, and gene-drives—all of which offer new opportunities while posing new risks. What policies should guide the development of such technologies? Earth’s environment is unified by flows of nitrogen, carbon, and genetic information; it is also being engineered—and often plundered—by a species whose world is politically fragmented, yet increasingly interconnected by flows of bytes and genes. How can sound policies be developed in such a world? What institutions can enforce such policies? Climate will serve as a case study through which we will explore policy for an engineered planet. Lectures will cover disruptive climate technologies from biofuels to geoengineering to carbon removal. We will first look backward, exploring the sharp contrast between the meager progress in restraining carbon emissions and the rapid—albeit uneven—advancements in managing complex environmental challenges such as air and water pollution, DDT, and stratospheric ozone loss. Then, we look forward, with students working in small teams to propose and critique new ideas for governing the planetary environment.