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.

With development of coal-fired electric generation stopped cold over greenhouse gases, the only alternative to nuclear power for producing continuous energy at the levels needed is natural gas. But climate change isn't the only reason to move away from fossil fuels.

Fossil fuels also are a major health threat. "Coal causes the worst health impacts of anything we are doing today," Moore said.

Plus, uranium can be found within the United States and also comes in large quantities from Canada and Australia. Nuclear Power reduces the reliance on supplies in dangerous places including the Middle East, he said.

Moore spoke at the chamber breakfast after an appearance in Idaho Falls Tuesday night that attracted 300 people. He also spoke to the Idaho Environmental Forum in Boise, all sponsored by the Partnership for Science and Technology.

He represents the Clean Air and Safe Energy Coalition, a nuclear energy-backed group promoting reactors for electric energy generation. He began his career as a leaders of Greenpeace fighting nuclear testing and working to save whales.

In recent years, he has taken on causes unpopular with his former group, like old growth logging, keeping polyvinyl chlorides and now nuclear energy.

He says his change of heart comes from his background in science and a different approach to sustainability.

He sees a need for maintaining technologies that are not harmful while fixing or replacing those that are harmful.

"We don't believe we have been making too much electricity," he said. "We believe we've been making energy with the wrong technologies."

His critics, like Andrea Shipley, executive director of the Snake River Alliance, say he has simply sold out.

"The only reason Patrick Moore is backing something as unsafe and risky as nuclear power is he is being paid by the nuclear industry to do so," Shipley said.