聯合國新報告：再生能源可望成為主流

Renewable sources of energy could meet 77 percent of the world's energy supply by mid-century if backed by enabling public policies, finds a new report endorsed by the member countries of the Intergovernmental Panel on Climate Change. By contrast, renewables met 13 percent of the world's total primary energy supply in 2008.

The rising adoption of renewable energies could lead to cumulative greenhouse gas savings equivalent to 220 to 560 gigatonnes of carbon dioxide (GtC02eq) between 2010 and 2050, the report finds.

The upper end of the scenarios assessed - a one-third cut in greenhouse gas emissions from business-as-usual projections - could help keep concentrations of the heat-trapping gases at 450 parts per million.

This could contribute towards a goal of holding the increase in global temperature below 2 degrees Celsius - an aim recognized in the United Nations Climate Convention's Cancun Agreements.

"The IPCC brought together the most relevant and best available information to provide the world with this scientific assessment of the potential of renewable energy sources to mitigate climate change," said IPCC Chairman Rajendra Pachauri, introducing the report. "The Special Report can serve as a sound knowledge basis for policymakers to take on this major challenge of the 21st century."

Professor Ottmar Edenhofer, a German economist who serves as co-chair of Working Group III, said, "With consistent climate and energy policy support, renewable energy sources can contribute substantially to human well-being by sustainably supplying energy and stabilizing the climate."

"However," he cautioned, "the substantial increase of renewables is technically and politically very challenging."

Over 160 existing scientific scenarios on the possible penetration of renewables by 2050, with environmental and social implications, were reviewed for the report.

The report concludes that renewables will take an increasing slice of the global energy market.

Despite global financial challenges, renewable energy capacity grew in 2009, the report finds. Most of the reviewed scenarios estimate that renewables will contribute more to a low carbon energy supply by 2050 than nuclear power or fossil fuels using carbon capture and storage.

Though in some cases renewable energy technologies are already economically competitive, the production costs are currently often higher than market energy prices.

But if environmental impacts, such as emissions of pollutants and greenhouse gases, were monetized and included in energy prices, more renewable energy technologies may become economically attractive, the report notes.

For most renewable technologies, costs have declined over the past several decades and the authors expect significant technical advancements and further cost reductions in the future, resulting in a greater potential for climate change mitigation.

Public policies that recognize and reflect the wider economic, social and environmental benefits of renewable energies, including their potential to cut air pollution and improve public health, will be key for meeting the highest renewables deployment scenarios, according to the report.

Ramon Pichs, a Cuban economist who serves as co-chair of the Working Group III, said, "The report shows that it is not the availability of the resource, but the public policies that will either expand or constrain renewable energy development over the coming decades."

"Developing countries have an important stake in this future," said Pichs. "This is where most of the 1.4 billion people without access to electricity live yet also where some of the best conditions exist for renewable energy deployment."

This report on renewables will feed into the broader work of the Intergovernmental Panel on Climate Change as it prepares its Fifth Assessment Report, scheduled for finalization in September 2014.