In the 1970s, Buckminster Fuller proposed superconducting global-scale electrical grids to wheel solar energy collected on the daylight hemisphere halfway around the earth to the nighttime hemisphere.

Given the potential for catastrophic climate change, a question must be asked: What has happened to such far-out and disruptive -- but not necessarily unfeasible -- visions for a renewable-energy future? Right now, hundreds of new coal plants are on drawing boards around the world (see "The Dirty Secret").

Today, the world uses about 13 terawatts of power, approximately 80 percent of it from carbon-dioxide-emitting fossil fuels. If we want to keep Earth's average temperature low enough to prevent eventual large sea-level rises (see "The Messenger") -- and also accommodate continued 3 percent annual economic growth -- we will need between 10 and 30 terawatts of new carbon-free power by 2050.

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