Hansen et al. are evenhanded in their assessment of nuclear and renewables; they don’t throw renewables under the bus, and they’re upfront about the safety and waste issues associated with the nuclear fuel cycle. However, they make the simple, realistic and obvious point that is understood by every single human being in the energy world, and that is that renewables have one fundamental flaw of nature that is problematic for energy systems in society: Renewables are intermittent.