Adequate mitigation of the risks of climate change requires rapid displacement of fossil fuels with carbon-free energy sources. This imperative has prompted a growing chorus of energy analysts, policy makers, and industry advocates to press for a resurgence of nuclear energy. Even some environmentalists are urging reconsideration of the nuclear option, so long anathema to their own movement. Yet, with critical problems unsolved—safety and cost, waste storage, and nuclear weapons proliferation—nuclear power remains a deeply problematic response to the climate challenge, and to the wider challenge of global sustainability. Therefore, the transformative energy strategy of a Great Transition relies on three major prongs: renewable resources, deep efficiency, and a model of development based on environment-sparing consumption and production patterns.