Greenpeace founder Patrick Moore says there is no proof global warming is caused by humans, but it is likely enough that the world should turn to nuclear power - a concept tied closely to the underground nuclear testing his former environmental group formed to oppose.

The chemistry of the atmosphere is changing, and there is a high-enough risk that "true believers" like Al Gore are right that world economies need to wean themselves off fossil fuels to reduce greenhouse gases, he said.

"It's like buying fire insurance," Moore said. "We all own fire insurance even though there is a low risk we are going to get into an accident."

The only viable solution is to build hundreds of nuclear power plants over the next century, Moore told the Boise Metro Chamber of Commerce on Wednesday. There isn't enough potential for wind, solar, hydroelectric, and geothermal or other renewable energy sources, he said.