気候：地球の炭素貯蔵能力における世界的な限界の確立

The practical planetary capacity for storing carbon emissions in rock formations is estimated at 1,460 gigatons, according to a paper in Nature. This upper limit will likely be met by 2200 under current warming mitigation scenarios, indicating that nations should reconsider the role of carbon storage in their plans to reduce emissions.

To meet the goal of net zero carbon emissions, sources of carbon dioxide must be equal to removal by carbon dioxide sinks. One method of achieving this is to store carbon emissions in geologic formations for centuries or millennia using capture and storage technology. While previous proposals have suggested that the amount of carbon that can be stored is incredibly large, research is needed to clarify any upper limits.

Matthew Gidden, Joeri Rogelj and colleagues quantified the amount of geologic carbon storage Earth can practically support by analysing stable geologic formations while accounting for risk factors such as environmentally sensitive locations, distance to population centres, and lack of government support. They calculate that this more prudent estimate of the planetary geologic storage potential of carbon dioxide lies at 1,460 gigatons, and that this potential could be exhausted by 2200. Adhering to this storage cap, the authors report that geological carbon storage can reverse a maximum of 0.7 °C of global warming in the future. About 70% of this storage capacity is located onshore, and countries with high storage potential include Russia, the USA, China, Brazil, and Australia, who are mostly large-scale extractors of fossil fuels.

The authors note that a key limitation of this analysis is not accounting for the obstacles of scaling up carbon capture and storage technology or considering any other technologies that might be developed in the future. Policymakers should include explicit estimates of how much carbon storage is needed, while also planning strategies to mitigate carbon emissions.