Abstract Sulfate geoengineering is a proposed method to partially counteract the global radiative forcing from accumulated greenhouse gases, potentially mitigating some impacts of climate change. While likely to be effective in slowing increases in average temperatures and extreme precipitation, there are known side-effects and potential unintended consequences which have not been quantified. One such consequence is the direct human health impact. Given the significant uncertainties, we take a sensitivity approach to explore the mechanisms and range of potential impacts. Using a chemistry-transport model, we quantify the steady-state response of three public health risks to 1 °C global mean surface cooling. We separate impacts into those which are “radiative forcing-driven”, associated with climate change “reversal” through modification of global radiative forcing, and those “direct impacts” associated uniquely with using sulfate geoengineering to achieve this. We find that the direct (non-radiative forcing driven) impact is a decrease in global mortality of ∼13,000 annually. Here the benefits of reduced ozone exposure exceed increases in mortality due to UV and particulate matter, as each unit of injected sulfur incurs 1/25th the particulate matter exposure of a unit of sulfur emitted from surface sources. This reduction is exceeded by radiative forcing-driven health impacts resulting from using sulfate geoengineering to offset 1 °C of surface temperature rise. Increased particulate matter formation at these lower temperatures results in ∼39,000 mortalities which would have been avoided at higher temperatures. As such we estimate that sulfate geoengineering in 2040 would cause ∼26,000 (95% interval: −30,000 to +79,000) early deaths annually relative to the same year without geoengineering, largely due to the loss of health benefits associated with CO2-induced warming. These results account only for impacts due to changes in air quality and UV-B flux. They do not account for non-mortality impacts or changes in atmospheric dynamics, and must be considered in the wider context of other climate change impacts such as heatwave frequency and sea level rise.

中文翻译：

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量化硫酸盐地球工程对空气质量和 UV-B 暴露导致的死亡率的影响

摘要 硫酸盐地球工程是一种拟议的方法，可部分抵消累积温室气体造成的全球辐射强迫，有可能减轻气候变化的一些影响。虽然可能有效减缓平均气温和极端降水的增加，但已知的副作用和潜在的意外后果尚未量化。其中一种后果是对人类健康的直接影响。鉴于存在重大不确定性，我们采用敏感性方法来探索潜在影响的机制和范围。使用化学传输模型，我们量化了三种公共卫生风险对 1°C 全球平均表面冷却的稳态响应。我们将影响分为“辐射强迫驱动”的影响，通过改变全球辐射强迫与气候变化“逆转”相关联，以及与使用硫酸盐地球工程实现这一目标相关的那些“直接影响”。我们发现直接（非辐射强迫驱动）影响是全球死亡率每年下降约 13,000。在这里，减少臭氧暴露的好处超过了因紫外线和颗粒物而导致的死亡率增加，因为每单位注入的硫所产生的颗粒物暴露量是从地表源排放的单位硫的颗粒物暴露量的 1/25。使用硫酸盐地球工程抵消 1°C 的地表温度上升所产生的辐射强迫驱动的健康影响超过了这种减少。在这些较低温度下形成的颗粒物增加会导致约 39,000 人死亡，而这在较高温度下是可以避免的。因此，我们估计与没有地球工程的同一年相比，2040 年硫酸盐地球工程每年将导致约 26,000 人（95% 区间：-30,000 至 +79,000）过早死亡，这主要是由于与二氧化碳引起的变暖相关的健康益处的丧失。这些结果仅说明空气质量和 UV-B 通量变化造成的影响。它们不考虑大气动力学的非死亡影响或变化，必须在其他气候变化影响的更广泛背景下考虑，例如热浪频率和海平面上升。这些结果仅说明空气质量和 UV-B 通量变化造成的影响。它们不考虑大气动力学的非死亡影响或变化，必须在其他气候变化影响的更广泛背景下考虑，例如热浪频率和海平面上升。这些结果仅说明空气质量和 UV-B 通量变化造成的影响。它们不考虑大气动力学的非死亡影响或变化，必须在其他气候变化影响的更广泛背景下考虑，例如热浪频率和海平面上升。