Decisions about solar geoengineering (SG) entail risk–risk tradeoffs between the direct risks of SG and SG’s ability to reduce climate risks. Quantitative comparisons between these risks are needed to inform public policy. We evaluate idealized SG’s effectiveness in reducing deaths from warming using two climate models and an econometric analysis of temperature-attributable mortality. We find SG’s impact on temperature-attributable mortality is uneven with decreases for hotter, poorer regions and increases in cooler, richer regions. Relative to no SG, global mortality is reduced by over 400,000 deaths annually [90% CI: (−1.2 million,2.7 million)] for cooling of 1 °C from 2.5 °C above preindustrial in 2080. We find no evidence that mortality reduction achieved by SG is smaller than the reduction from equivalent cooling by emissions reductions. Combining our estimates with existing estimates of sulphate aerosol injection direct mortality risk from air quality and UV-attributable cancer enables the first quantitative risk-risk comparison of SG. We estimate with 61% probability that the mortality benefits of cooling outweigh these direct SG risks. We find the benefits outweigh these risks by 13 times for our central estimates, or 4 deaths per 100,000 per 1 °C per year [90% CI: (−11,23)]. This is not a comprehensive evaluation of the risk–risk tradeoffs around SG, yet by comparing some of the most consequential impacts on human welfare it is a useful first step. While these findings are robust to a variety of alternative assumptions, considerable uncertainties remain and require further investigation.

中文翻译：

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太阳能地球工程对温度归因死亡率的影响


关于太阳能地球工程 （SG） 的决策需要在 SG 的直接风险和 SG 降低气候风险的能力之间进行风险权衡。需要对这些风险进行定量比较，以便为公共政策提供信息。我们使用两个气候模型和温度归因死亡率的计量经济学分析来评估理想化 SG 在减少变暖死亡方面的有效性。我们发现 SG 对温度归因死亡率的影响是不均衡的，较热、较贫穷的地区降低，而较凉爽、较富裕的地区增加。相对于无 SG，2080 年从工业化前的 2.5 °C 冷却 1 °C，全球死亡率每年减少超过 400,000 人死亡 [90% CI：（−120 万，270 万）]。我们没有发现证据表明 SG 实现的死亡率降低小于通过减排实现的等效冷却的降低。将我们的估计与现有的硫酸盐气溶胶注射、空气质量直接死亡风险和紫外线归因癌症的估计相结合，可以对 SG 进行首次定量风险比较。我们以 61% 的概率估计，降温的死亡率益处超过了这些直接的 SG 风险。我们发现，根据我们的中心估计，益处是这些风险的 13 倍，即每年每 1 °C 每 100,000 人中有 4 人死亡 [90% CI： （-11,23）]。这并不是对围绕 SG 的风险-风险权衡的全面评估，但通过比较对人类福利的一些最重要的影响，这是有用的第一步。虽然这些发现对各种替代假设都是稳健的，但仍然存在相当大的不确定性，需要进一步调查。