Can We Really Run the World on 100% Renewables?

Some studies suggest we can easily drop nuclear and fossil fuels, but they raise serious questions.

Every once in a while someone will publish a roadmap for running the world (or a state) on 100 percent renewable energy by some date, say 2030 or 2050. The latest considers what it would take to run New York State with sources such as wind and solar. The resulting headlines look great, and a lot of people walk away with the general impression that, if we wanted to, we could easily drop fossil fuels and nuclear power.