Renewable sources such as solar, wind and hydropower could fulfil almost 80 percent of the world's energy demand by 2050 with the right policies, according to a UN report which won backing from governments.

The 26-page study, by the UN's Intergovernmental Panel on Climate Change (IPCC), broadly matched a draft written by scientists. It was approved by government delegates at talks in Abu Dhabi.

Environmental groups hailed the report as a guide to the shift from fossil fuels to combat climate change, a process set to cost trillions of dollars. But they said some draft findings were watered down, partly due to opposition by oil exporters.

"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," the IPCC said.

The report said moves to cleaner energies including geothermal or ocean energy would help cut greenhouse gas emissions, which it blamed for global warming including floods, droughts, heat waves and rising sea levels.
   
Growth in renewables has already surged in recent years, and costs are falling, it said. "We see a rapid increase in wind and solar PV (photovoltaic) especially," Rajendra Pachauri, chair of the IPCC, told a news conference.

"It underscores the irreplaceable potential of renewable energies to reduce greenhouse gas emissions and improve the lives of people around the world," said Christiania Figueres, head of the UN Climate Change Secretariat in Bonn.

The UN says governments' pledges for cuts in greenhouse gases are insufficient so far to meet an agreed UN goal of limiting rises in global temperatures to below 2 degrees Celsius (3.6 degrees F) above pre-industrial times.

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.

Scenarios for the share of renewables in world supplies by 2050 ranged widely, from just 15 per cent to 77 per cent. Renewables now account for about 12.9 per cent of world energy supplies and are dominated by bioenergy such as firewood in developing nations, and followed by hydropower, wind, geothermal, solar power and ocean energy.

Environmentalists said some language favourable to renewables was toned down, partly by Opec nations led by Saudi Arabia.   

"There are all sorts of 'mights' and 'mays' introduced," said Jean-Philippe Denruyter, manager of global renewable energy policy for the WWF conservation group. "It's not a big problem. We are quite positive about the outcome."    

Sven Teske of Greenpeace, an IPCC author, said the summary had muted, for instance, clearer statements that some renewable energies were already cost effective. Still, he added that the underlying findings "will be the standard book for renewables".   

The underlying IPCC report, of about 1,000 pages, was written by about 120 experts. The Abu Dhabi talks were to get governments to endorse the summary for policymakers, a step meant to give its conclusions global legitimacy.

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