This report from the International Resource Panel provides a comprehensive comparison of the greenhouse gas mitigation potential of various energy generation technologies, including hydro, solar, geothermal and wind. It also examines the environmental and human health impacts of these options, and their implications for resource use. Their impacts are compared with those of fossil fuels, including coal- and gas-fired power, with and without carbon capture and storage (CCS). The report provides strong evidence that electricity generated from renewable sources causes substantially less pollution than that generated from fossil fuels. A business-as-usual expansion of fossil fuel-based generation would lead to increased pollution, with serious impacts on human health and the environment, and a doubling of GHG emissions by 2050. Meanwhile, renewable electricity generation produces only 5-6% of the GHG emissions of coal-fired power plants and 8-10% of those of gas-fired power plants.