To shift the global economy from fossil fuels to renewable energy will require the construction of wind, solar, nuclear, and other installations on a vast scale, significantly altering the face of the planet. Can these new forms of energy approach the scale needed to meet the world’s energy demands?

The U.S. has invested billions of dollars trying to create a controlled form of nuclear fusion that could be the energy source for an endless supply of electricity. But as a federal laboratory prepares for a key test, major questions remain about pulling off this long-dreamed-of technological feat.

As utilities seek to build new nuclear power plants in the U.S. and around the world, the latest generation of reactors feature improvements over older technologies. But even as attention focuses on nuclear as an alternative to fossil fuels, questions remain about whether the newer reactors are sufficiently foolproof to be adopted on a large scale.

When the founder of the Whole Earth Catalog embraces nuclear power, genetically engineered crops, and geoengineering schemes to cool the planet, you know things have changed in the environmental movement. In an interview with Yale Environment 360, Stewart Brand explains how the passage of four decades — and the advent of global warming — have shifted his thinking about what it means to be green.