The outlook could change, of course, if new nuclear plants turn out to be more expensive than expected, or if engineers make breakthroughs in other technologies. (To debate these possibilities, go to www.nytimes.com/tierneylab.) Given the uncertainties, Dr. Metcalf cautions, it would be risky to bet everything on nuclear power as the answer to global warming.

But it seems even riskier to bet on just the soft path, as so many greens are doing, either by flatly opposing nuclear power or by setting so many conditions that no plants could be built for decades, if ever. (Mr. Obama says nuclear power is necessary but should not be expanded until security and safety issues are addressed.)

“The nuclear debate is still stuck back in the 1980s,” says Mr. Tucker, the author of “Terrestrial Energy,” the new brand he’s trying to affix to nuclear power. If people started associating nuclear plants with natural radioactive processes in the Earth instead of atomic bombs, he says, they might be persuaded that it’s the most environmentally benign form of energy, particularly compared with wind farms that cover scenic ridges and the vast solar arrays proposed for “empty” land in deserts.

Mr. Tucker, a journalist who has been debunking environmental alarms for decades, says he has come around to Al Gore’s view on the danger of global warming, and he’d like environmentalists to rethink their views, too.

“Even when greens give grudging support to nuclear power,” he says, “they add the caveat, ‘But first we have to make sure the plants are absolutely safe’ — as if reactors haven’t been operating safely for 25 years. Nobody recognizes the complete overhaul that has occurred in the industry or how it’s now pumping out twice as much electricity from the same plants with a vastly improved safety record.”

By scaring people about the tiny levels of radiation emitted during the normal operation of a nuclear plant, Mr. Tucker says, greens have effectively encouraged the construction of coal plants that actually release more radiation because of the traces of uranium in coal dust. He argues that the risks of terrorist attacks and nuclear waste have been exaggerated, particularly by the environmentalists who objected when the Yucca Mountain nuclear-waste depository was being designed to guarantee a level of safety for only 10,000 years.

They successfully sued to enforce a safety standard extending one million years — which, in an ideal world, would be a very nice standard. But if you believe global warming is a planetary crisis that must be addressed immediately, should you really be obsessing about hypothetical dangers near one mountain in A.D. 1,000,000? If there’s already a proven technology that doesn’t spew carbon dioxide into the atmosphere, why fiddle while coal burns?