BioEd Online

For centuries, humans have powered a growing world by extracting Earth's carbon-rich rocks, peat and liquids and burning them in ever greater amounts, but that trend is beginning to change. A report from the Intergovernmental Panel on Climate Change (IPCC), released on 9 May at a briefing in Abu Dhabi, suggests that an inevitable — if slow — shift towards specialized energy crops, sunlight, wind and other sources of renewable power will mark the next four decades.

In addition to surveying published work on renewable energy potential, production, economics and policy, the IPCC conducted detailed socioeconomic modelling across 164 scenarios, both with and without policies intended to reduce greenhouse-gas emissions. The extent and type of development varies significantly depending on factors such as price and technological progress, and on government policies intended to reduce greenhouse-gas emissions. "Renewables will have a great future even without climate policies, but that does not necessarily lead to an emissions reduction," says Ottmar Edenhofer, chairman of the IPCC's working group on mitigation.

Renewable energy sources, excluding the burning of traditional biomass such as wood, make up roughly 7% of global energy production (see ), and the working group's Summary for Policymakers estimates that by 2050, production could rise to between three and more than ten times its current level. No renewable technology is projected to dominate, but bioenergy, solar energy and wind will be important in the energy mix (see ).This shift towards renewable energy could reduce cumulative greenhouse-gas emissions by 220–560 gigatonnes of carbon dioxide, from a baseline estimate of 1,530 gigatonnes.

In all scenarios, fossil fuel will continue to have an important role for decades to come. The report says that falling prices for renewable energy will drive a gradual deployment of clean energy, but overhauling the global energy system represents a monumental task (see ). The IPCC says there are no technical barriers preventing large-scale deployment of renewable-energy systems over the next few decades. And even in 2050, none of the four main scenarios shows humanity tapping more than 2.5% of the accessible supply of renewable energy.