Reservoirs are essential for human populations, but their global carbon footprint is substantial (0.73–2.41 PgCO2-equivalent yr−1). Yet the temporal evolution of reservoir carbon emissions and their contribution to anthropogenic radiative forcing remains unresolved. Here we quantify the long-term historical and future evolution (1900–2060) of cumulative global reservoir area, carbon dioxide and methane emissions and the resulting radiative forcing. We show that global reservoir carbon emissions peaked in 1987 (4.4 TmolC yr−1) and have been declining since, due largely to decreasing carbon dioxide emissions as reservoirs age. However, reservoir-induced radiative forcing continues to rise due to ongoing increases in reservoir methane emissions, which accounted for 5.2% of global anthropogenic methane emissions in 2020. We estimate that, in the future, methane ebullition and degassing flux will make up >75% of the reservoir-induced radiative forcing, making these flux pathways key targets for improved understanding and mitigation.
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This study was funded by the UNESCO Chair in Global Environmental Change held by Y.T.P. through which C.S., S.M.-B. and Y.T.P. were funded. J.A.H. was funded by an NSF INFEWS grant (NSF EAR 1639458), an NSF DEB Grant (no. 135211), a GRIL Fellowship Grant and a Stanford University Cox Visiting Professorship.
The authors declare no competing interests.
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Nature Geoscience thanks Xingchen Yan, Lluís Gómez-Gener, Ronny Lauerwald and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Thomas Richardson, in collaboration with the Nature Geoscience team.
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Soued, C., Harrison, J.A., Mercier-Blais, S. et al. Reservoir CO2 and CH4 emissions and their climate impact over the period 1900–2060. Nat. Geosci. 15, 700–705 (2022). https://doi.org/10.1038/s41561-022-01004-2