ABU DHABI (Reuters) - Governments approved on Monday a U.N. report projecting that renewable energies such as solar, wind or hydropower could leap to supply almost 80 percent of the world's demand by 2050, with the right policies.

The study broadly matched a draft written by scientists before the meeting, but environmental group Greenpeace said some findings were watered down due to opposition by OPEC heavyweight Saudi Arabia and also by Brazil.

The report by the U.N.'s Intergovernmental Panel on Climate Change (IPCC) also said that a shift to cleaner energies would help cut greenhouse gas emissions, which it blamed for climate change including floods, droughts, heat waves and rising sea levels.

"Close to 80 percent of the world energy supply could be met by renewables by mid-century if backed by the right enabling public policies," it said in a statement after government delegates approved a special report at talks in Abu Dhabi.

"This will be the standard book for renewables," said Sven Teske of Greenpeace, one of the authors.

He said he was happy with the overall report but that the summary for policymakers had toned down, for instance, formerly clear statements that renewable energies were often already cost effective.

"Parts have been watered down," he said of the report, which was agreed at the IPCC meeting in Abu Dhabi which began on May 5. The final session lasted through the night.

Ottmar Edenhofer, who chaired the report, said there were few limits to the theoretical potential for renewable energies. "However, the substantial increase of renewables is technically and politically very challenging," he said.

In 2008, renewable energy production was about 12.9 percent of global primary energy supply, dominated by bioenergy such as firewood in developing nations and followed by hydro, wind, geothermal, ocean energy and solar power.

A review of 164 scenarios for the shift to renewable energies showed that they could make cumulative carbon dioxide savings of 220-560 billion tonnes from 2010 to 2050, aiding the fight against global warming, it said.

That compares with 1.53 trillion tonnes of cumulative fossil and industrial carbon dioxide emissions in a reference scenario for the same years.

(Writing by Alister Doyle in Oslo, editing by Jane Baird)

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