DOHA, Qatar — The world's top scientific body concluded that renewable energy in the coming decades will be widespread and could one day represent the dominant source for powering factories and lighting homes, according to a draft report obtained by The Associated Press Thursday.
But the report also warned that such expansion will be costly and policy changes will have to be enacted to ensure that renewable energy can achieve its potential in helping reduce greenhouse gas emissions.
It called for better balancing competing demands for land, addressing "institutional barriers" that prevent the installation of solar energy as well as overcoming the constraints to transmitting renewable energy to users.
The four-day meeting of the U.N. Intergovernmental Panel on Climate Change which began Thursday in Abu Dhabi was largely bullish on replacing fossil fuels.
"It is likely that renewable energy will have a significantly larger role in the global energy system in the future than today," said the report. "The scenarios indicate that even without efforts to address climate change, renewable energy can be expected to expand."
A spokesman for the IPCC refused to comment on the report, saying it was still subject to several days of negotiations.
The report found that renewable energy — including solar, hydro, wind, biomass, geothermal and ocean energy — represented only about 13 percent of the primary energy supply in 2008. But its growth is picking up with almost half of new electricity generating capacity coming from renewables in 2008 and 2009.
That growth will continue through 2050 with 164 different scenarios predicting the use of renewables significantly increasing as the world shifts to a low-carbon economy.
The most ambitious projected it will represent 77 percent of global energy sources in 2050.
Commitments to reduce greenhouse gas emissions coupled with cheaper technology for renewable energies will spur their growth, especially as the increasing shortages of oil and other fossil fuels raises those costs.
But the report made clear there are plenty of challenges that could hamper the growth of renewables as they still need to be better integrated into existing energy supply systems.
Policies also need to be changed to attract massive investment to build the infrastructure and spur the technology innovations needed that make renewables more affordable and dependable.
And despite its rosy predictions for renewable use, at least one environmental group observing the talks say the report falls short of their expectations.
"IPCC delivers a landmark report that shows the rapid growth potential for renewable energy — but unfortunately does not endorse a 100 percent renewable energy pathway until 2050," said Stephan Singer, director for Global Energy Policy at WWF International.
"We need to be fast if we want to tackle pressing issues as varied as energy security and efficiency, and at the same time keep climate change below the danger threshold," he added.