RENEWABLE energy won't save the planet so it's time to go nuclear, according to one of world's most high-profile climate scientists.
"We should undertake urgent focused research and development programs in next generation nuclear power," said atmospheric physicist James Hansen, head of NASA's Goddard Institute for Space Studies and adjunct professor at Columbia University's Earth Institute in New York.
While renewable energies such as solar and wind were gaining in economic competition with coal-fired plants, Professor Hansen said they wouldn't be able to provide baseload power for years to come.
Even in Germany, which pushed renewables heavily, they generated only 7 per cent of the nation's power.
"It's just too expensive," said Professor Hansen, an expert in climate modelling, planetary atmospheres and the Earth's climate.
"Right now, fossil fuels are the cheapest form of energy,
except for operating nuclear plants," he said on the first day of a lecture tour in Australia.