Hydropower emits less carbon dioxide than fossil fuels but the lower albedo of hydropower reservoirs compared to terrestrial landscapes results in a positive radiative forcing, offsetting some of the negative radiative forcing of hydroelectricity generat ion. The cumulative effect of this lower albedo has not been quantified. Here we show, by quantifying the difference in remotely sensed albedo between globally distributed hydropower reservoirs and their surrounding landscape, that 19% of all investigated hydropower plants required 40 years or more for the negative radiative forcing from the fossil fuel displacement to offset the albedo effect. The length of these break-even times depends on the specific combination of climatic and environmental constraints, power plant design characteristics and country-specific electricity carbon intensities. We conclude that future hydropower plants need to minimize the albedo penalty to make a meaningful contribution towards limiting global warming.

与化石燃料相比，水力发电排放的二氧化碳更少，但与陆地景观相比，水力发电水库的低反照率导致正辐射强迫，抵消了水力发电的一些负辐射强迫。这种较低反照率的累积效应尚未量化。在这里，我们通过量化全球分布的水电站水库与其周围景观之间的遥感反照率差异表明，所有调查的水电站中有 19% 需要 40 年或更长时间来抵消化石燃料置换产生的负辐射强迫以抵消反照率效应. 这些收支平衡时间的长短取决于气候和环境限制、发电厂设计特征和特定国家电力碳强度的具体组合。