This Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) impartially assesses the scientific literature on the potential role of renewable energy in the mitigation of climate change for policymakers, the private sector, academic researchers and civil society. It covers six renewable energy sources “ bioenergy, direct solar energy, geothermal energy, hydropower, ocean energy and wind energy “ as well as their integration into present and future energy systems. It considers the environmental and social consequences associated with the deployment of these technologies, and presents strategies to overcome technical as well as non-technical obstacles to their application and diffusion. The authors also compare the levelized cost of energy from renewable energy sources to recent non-renewable energy costs.