For effective climate change mitigation, the global use of fossil fuels for electricity generation, transportation and other industrial uses, will need to be substantially curtailed this century. In a recent Viewpoint in Energy Policy, Trainer (2010) argued that non-carbon energy sources will be insufficient to meet this goal, due to cost, variability, energy storage requirements and other technical limitations. However, his dismissal of nuclear fission energy was cursory and inadequate. Here I argue that fossil fuel replacement this century could, on technical grounds, be achieved via a mix of fission, renewables and fossil fuels with carbon sequestration, with a high degree of electrification, and nuclear supplying over half of final energy. I show that the principal limitations on nuclear fission are not technical, economic or fuel-related, but are instead linked to complex issues of societal acceptance, fiscal and political inertia, and inadequate critical evaluation of the real-world constraints facing low-carbon alternatives. (C) 2011 Elsevier Ltd. All rights reserved.