Germany has decided to pursue ambitious greenhouse-gas reductions — while closing down its nuclear plants. Can a heavily industrialized country power its economy with wind turbines and solar panels?

What’s coming next won’t be so easy. In 2010, the German government declared that it would undertake what has popularly come to be called an Energiewende—an energy turn, or energy revolution. This switch from fossil fuels to renewable energy is the most ambitious ever attempted by a heavily industrialized country: it aims to cut greenhouse-gas emissions 40 percent from 1990 levels by 2020, and 80 percent by midcentury.