After much number-crunching, there’s now a clear roadmap for 139 countries to supply all the world’s energy needed in 2050 by using wind, water and sunlight. Researchers at Stanford University and the University of California collaborated to first analyze how much energy each country would need by mid-century, and then to calculate how renewable energy could cover those needs, where it could go, and how much it would cost. Mark Z. Jacobson, director of the Atmosphere/Energy Program at Stanford University, concludes: “These are basically plans showing it’s technically and economically feasible to change the energy infrastructure of all of these different countries.”