Governments with science research budgets should be spending their cash on finding new ways to gather, store and distribute energy from sources like the Sun, wind and waves, he said on the sidelines of a UN conference tasked with clinching a climate rescue pact.
"The essence of the thing is that it should be cheap," the acclaimed documentary-maker told AFP.
"Goodness me... If we could catch one five-thousandth part of the energy that the Sun sprays onto the Moon, onto this globe every day, we would supply all the energy requirements of humanity.
Attenborough is one of the public faces of an initiative dubbed the Global Apollo Programme, which seeks to make renewable energy cheaper than coal within 10 years.
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Supporters of the scheme include Lord Nicholas Stern -- author of a landmark 2006 report on the economics of climate change -- and Lord Martin Rees, a leading astronomy and former head of the Royal Society, Britain's prestigious academy of science.
The goal would be achieved by convincing governments to invest USD 15 billion (14.2 billion euros) a year in research and development -- a patch, the programme says, on the USD 100 billion spent annually on defence-related R&D.
The incentive?
"Only saving the world," said Attenborough. "It's a small thing, but that's what it is."
While humans cannot survive without Earth, he added, "the planet will survive, the planet will do very much better" if we disappeared.
Making renewables cheaper than energy from coal, oil and gas was the only answer, added Attenborough.
"Then the nations of the world, developed or undeveloped, would choose to use that rather than carbon-derived fuel so that the coal and oil which has caused so much trouble now will stay in the ground where it's out of trouble.