As young people rightly demand real solutions to climate change, the question is not what to do — eliminate fossil fuels by 2050 — but how. Beyond decarbonizing today’s electric grid, we must use clean electricity to replace fossil fuels in transportation, industry and heating. We must provide for the fast-growing energy needs of poorer countries and extend the grid to a billion people who now lack electricity. And still more electricity will be needed to remove excess carbon dioxide from the atmosphere by midcentury.