Temporary stratospheric aerosol injection (SAI) using sulphate compounds could help avoid some of the adverse and irreversible impacts of global warming, but comprises many risks and uncertainties. Among these, the direct financial cost and carbon emissions of potential SAI delivery systems have hitherto received only modest attention. Therefore, this paper quantifies the initial and operating financial costs and initial and operating equivalent CO2 (CO2eq) emissions of the specialised aircraft-based SAI delivery system developed with relatively high-fidelity tools in part 1 of this series. We analyse an interval of operating conditions, within which we devote special attention to four injection scenarios outlined in part 1: Three scenarios where H2SO4 vapour is directly injected at several dispersion rates and one SO2 injection scenario. We estimate financial cost through Raymer’s adjustment of Rand Corporation’s Development and Production Costs for Aircraft (DAPCA) model, augmented by additional data. CO2eq emission is computed from existing data and the computed fuel consumption for each of the scenarios. The latter estimates include an emission weighting factor to account for non-CO2 aircraft combustion products at altitude. For direct H2SO4 injection, both financial cost and CO2eq emission are sensitive to the design dispersion rate. For scenarios where higher dispersion rates are achieved, the delivery system’s cost and CO2eq are relatively small compared with the presumed benefits of SAI. The most optimistic H2SO4 scenario is found to have a financial cost and CO2eq emission similar to that of SO2 injection, while potentially allowing for reductions in the annual mass of sulphur injected to achieve a target negative radiative forcing. The estimates of financial cost and CO2eq emission were subjected to sensitivity analyses in several key parameters, including aircraft operational empty weight, engine specific fuel consumption, fuel price and aerosol price. The results indicate that the feasibility of the considered scenarios is robust.

中文翻译：

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平流层硫酸盐气溶胶的专门输送系统（第 2 部分）：财务成本和等效的 CO2 排放

使用硫酸盐化合物临时注入平流层气溶胶 (SAI) 有助于避免全球变暖的一些不利和不可逆转的影响，但包含许多风险和不确定性。其中，潜在的 SAI 传输系统的直接财务成本和碳排放迄今为止仅受到适度关注。因此，本文在本系列的第 1 部分中量化了使用相对高保真工具开发的基于飞机的 SAI 交付系统的初始和运营财务成本以及初始和运营等效二氧化碳 (CO2eq) 排放量。我们分析了运行条件的间隔，在此期间我们特别关注第 1 部分中概述的四种注入场景：H2SO4 蒸气以多种分散速率直接注入的三种场景和一种 SO2 注入场景。我们通过 Raymer 对 Rand Corporation 的飞机开发和生产成本 (DAPCA) 模型的调整来估计财务成本，并辅以其他数据。CO2eq 排放量是根据现有数据和计算出的每种情景的燃料消耗计算得出的。后者的估计包括一个排放权重因子，以说明在海拔高度的非 CO2 飞机燃烧产物。对于直接 H2SO4 注入，财务成本和 CO2eq 排放对设计扩散率很敏感。对于实现更高分散率的场景，与 SAI 的假定收益相比，输送系统的成本和 CO2eq 相对较小。发现最乐观的 H2SO4 方案具有与 SO2 注入相似的财务成本和 CO2eq 排放，同时可能允许减少每年注入的硫质量，以实现目标负辐射强迫。财务成本和二氧化碳当量排放量的估计在几个关键参数上进行了敏感性分析，包括飞机运行空重、发动机特定燃料消耗、燃料价格和气雾剂价格。结果表明，所考虑情景的可行性是稳健的。