The Special Report "Renewable Energy Sources and Climate Change Mitigation (SRREN)" aims to provide a better understanding and broader information on the mitigation potential of renewable energy sources: technological feasibility, economic potential and market status, economic and environmental costs & benefits, impacts on energy security, co-benefits in achieving sustainable development, opportunities and synergies, options and constraints for integration into the energy supply systems and in the societies. It will also assess resources by region and impacts of climate change on these resources. The report is structured with technology chapters - bio-energy, direct solar energy, geothermal energy, hydropower, ocean energy and wind energy - which will feed into the overarching chapters. A system integration chapter will be a key one, bringing all different aspects of energy demand and supply together. The report will finally consider the policy options, outcomes and conditions for effectiveness, and how the accelerated deployment could be achieved in a sustainable manner. Capacity building, technology transfer and financing in different regions will be assessed. The Special Report is prepared under the responsibility of Working Group III (Mitigation of Climate Change) and will be completed in early 2011. The first order draft of the SRREN underwent an expert review in December 2009 and has now been revised by the authors. The second order draft is available for simultaneous Government and Expert Review from June 18, 2010 to August 16, 2010.