He’s also looking for green nuclear engineers, and says he feels guilty that he and his fellow environmentalists created so much fear of nuclear power. Alternative energy and conservation are fine steps to reduce carbon emissions, he says, but now nuclear power is a proven technology working on a scale to make a serious difference.

“There were legitimate reasons to worry about nuclear power, but now that we know about the threat of climate change, we have to put the risks in perspective,” he says. “Sure, nuclear waste is a problem, but the great thing about it is you know where it is and you can guard it. The bad thing about coal waste is that you don’t know where it is and you don’t know what it’s doing. The carbon dioxide is in everybody’s atmosphere.”

Mr. Brand predicts that his heresies will become accepted in the next decade as the scientific minority in the environmental movement persuades the romantic majority. He still considers himself a member of both factions, just as in the days of the Merry Pranksters, but he’s been shifting toward the minority.

“My trend has been toward more rational and less romantic as the decades go by,” he says. “I keep seeing the harm done by religious romanticism, the terrible conservatism of romanticism, the ingrained pessimism of romanticism. It builds in a certain immunity to the scientific frame of mind.”

Mr. Brand got his first look at the big picture one afternoon in 1966 while sitting on a roof in San Francisco at what he calls an “altitude of three stories and 100 mikes,” meaning micrograms of LSD. He contemplated the skyline and decided the buildings weren’t parallel because he was seeing the curvature of the Earth.

This reminded him of Buckminster Fuller’s theory that people abused the environment because they thought of the Earth as flat and infinite, not as a finite globe. The next day the Earth looked flat again, but the 28-year-old Mr. Brand had a new cause. He printed up buttons asking, “Why haven’t we seen a photograph of the whole Earth yet?”