emissions. Some options, such as wind power and solar power, produce low quantities of total life cycle carbon emissions, using entirely renewable sources. Other options, such as nuclear power, produce a comparable amount of carbon dioxide emissions as renewable technologies in total life cycle emissions, but consume non-renewable, but sustainable materials (uranium). The term low-carbon power can also include power that continues to utilize the world's natural resources, such as natural gas and coal, but only when they employ techniques that reduce carbon dioxide emissions from these sources when burning them for fuel, such as the, as of 2012, pilot plants performing Carbon capture and storage. Because the cost of reducing emissions in the electricity sector appears to be lower than in other sectors such as transportation, the electricity sector may deliver the largest proportional carbon reductions under an economically efficient climate policy. Technologies to produce electric power with low-carbon emissions are in use at various scales. Together, they accounted for almost 40% of global electricity in 2020, with wind and solar almost 10%. Technologies The 2014 Intergovernmental Panel on Climate Change report identifies nuclear, wind, solar and hydroelectricity in suitable locations as technologies that can provide electricity with less than 5% of the lifecycle greenhouse gas emissions of coal power. Hydroelectric power Hydroelectric plants have the advantage of being long-lived and many existing plants have operated for more than 100 years. Hydropower is also an extremely flexible technology from the perspective of power grid operation. Large hydropower provides one of the lowest cost options in today's energy market, even compared to fossil fuels and there are no harmful emissions associated with plant operation. However, there are typically low greenhouse gas emissions with reservoirs, and possibly high emissions in the tropics. Hydroelectric power is the world's largest low carbon source of electricity, supplying 15.6% of total electricity in 2019. China is by far the world's largest producer of hydroelectricity in the world, followed by Brazil and Canada. However, there are several significant social and environmental disadvantages of large-scale hydroelectric power systems: dislocation, if people are living where the reservoirs are planned, release of significant amounts of carbon dioxide and methane during construction and flooding of the reservoir, and disruption of aquatic ecosystems and birdlife. There is a strong consensus now that countries should adopt an integrated approach towards managing water resources, which would involve planning hydropower development in co-operation with