Fundamental limits and trade-offs of stratospheric aerosol geoengineering

平流层气溶胶地球工程的基本限制和权衡

• 批准号: 2038246
• 负责人: Douglas MacMartin
• 金额: $ 39.81万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2038246&HistoricalAwards=false
• 关键词: Fundamental; limits; trade; offs; stratospheric

Reducing net emissions of CO2 and other greenhouse gas (GHG) is essential to any response to climate change, but may not occur fast enough to avoid significant climate impacts. Model projections of stratospheric aerosol geoengineering suggest that it could reduce some climate impacts, and thus might potentially become an additional element of a comprehensive climate change strategy. However, current knowledge is insufficient to support informed decisions. A critical question in evaluating geoengineering is what are the fundamental limits or trade-offs in how well geoengineering can manage the climate response from increased GHG? That is, what can geoengineering do, and what can it not do? Building on recent research, this project will address this essential question. The fundamental motivation for this research is to understand a potential option to reduce future climate impacts. Better information is needed both to support future decisions around deployment, and support the development of governance capacity that will be needed to make these decisions. This research will enable a more complete view of the impacts of deploying geoengineering than has previously been possible, by generating simulations that capture a more comprehensive set of deployment options rather than just one or two; and furthermore will assess the extent to which different objectives can or cannot be simultaneously met.This project will generate a set of climate model simulations that each make different choices for which climate goals to prioritize relative to others, and use this to identify potential tradeoffs (sets of objectives that are mutually exclusive) and boundaries (which objectives are achievable and which are not). Throughout this process, the research team will engage policy and governance experts, regarding the potential range of climate goals that might motivate different actors, and on the governance implications of identified trade-offs. The full range of possible strategies has never been explored, in part because optimization over the space of available degrees of freedom – primarily latitudes and seasons of aerosol injection – is complicated by uncertainty and nonlinear interactions (from both microphysics and aerosol-heating-induced changes in stratospheric circulation), and compounded by combinatorial computational complexity. To address these challenges, the research team will combine three innovations. First, the key enabler to this research is an initial assessment on the “size” of the design space; how many usefully-independent degrees of freedom are there? This reduces the combinatorial problem. Second, the computational burden can be reduced by separating the simulations needed to understand the spatial- and seasonal- distribution of stratospheric aerosol optical depth (AOD), which can be short but require a complete stratosphere model, from those needed to assess the climate response to a specified aerosol distribution, which require multi-decadal simulations but not an accurate stratosphere. And third, nonlinearities and uncertainty can be managed through feedback that adjusts injection rates; this enables comparing simulations based on specified objectives rather than specified injection rates. The research team will design a suite of simulations that individually meet different objectives and collectively span the space of possible outcomes. From this, the key tool in evaluating and visualizing trade-offs is through Pareto-optimal surfaces: how do strategies and their responses change as a function of the optimization criteria. Although the simulations will be focused on understanding physical science tradeoffs, social and governance dimensions play a critical role in understanding which objectives may be most important to achieve or which strategies are simply politically infeasible, thus limiting the space in ways not revealed by climate modeling. Therefore, the research team will interface with governance experts throughout to ensure research informs policy. Simulations will also be made available to the wider international community.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

减少二氧化碳和其他温室气体（GHG）的净排放对于对气候变化的任何反应至关重要，但可能不足以避免严重的气候影响。平流层气溶胶地球工程的模型预测表明，它可以减少某些气候影响，因此可能成为综合气候变化策略的另一个要素。但是，当前的知识不足以支持明智的决定。评估地球工程的一个关键问题是，地球工程能够从GHG增加的气候反应能够管理气候反应的基本限制或权衡是什么？也就是说，地球工程可以做什么，它不能做什么？在最新研究的基础上，该项目将解决这个基本问题。这项研究的基本动机是了解减少未来气候影响的潜在选择。需要更好的信息来支持有关部署的未来决策，并支持制定这些决定所需的治理能力的发展。这项研究将通过生成模拟来捕获更全面的部署选项，而不仅仅是一两个，从而使对部署地球工程的影响更完整地看待部署地球工程的影响。此外，将评估不同的目标可以或不能简单地实现的程度。本项目将生成一组气候模型模拟，每个项目都做出不同的选择，以相对于他人优先考虑气候目标，并使用此方法来识别潜在的权衡（一组相互排斥的目标）和边界（哪些目标是成功的）。通过此过程，研究团队将与可能激发不同参与者的气候目标的潜在气候目标以及确定的权衡的治理含义有关。从未探索过各种可能的策略，部分是因为在可用的自由度（原发性纬度和气溶胶注入的季节）上的优化使不确定性和非线性相互作用（来自微物理学和气溶胶加热诱导的平流层循环变化）变得复杂。为了应对这些挑战，研究团队将结合三项创新。首先，这项研究的关键推动力是对设计空间“大小”的初步评估。有多少方便独立的自由度？这减少了组合问题。其次，可以通过将平流层气溶胶光学深度（AOD）的空间和季节性分布分开，可以减少计算燃烧（AOD），这可以很短，但需要完整的平流层模型，从而评估需要对特定的气溶胶分布的气候响应的模拟，该模型需要多核模拟，但不是精确的模拟。第三，可以通过调整注入率的反馈来管理非线性和不确定性；这可以根据指定目标而不是指定的注入率进行比较模拟。研究团队将设计一套模拟，这些模拟单独符合不同的目标，并统一跨越了可能的结果空间。由此，评估和可视化权衡的关键工具是通过帕累托最佳表面：策略及其响应如何随着优化标准的函数而变化。尽管模拟将集中在理解物理科学的权衡上，但社会和治理维度在理解哪些目标可能最重要的目标或哪些策略在政治上是不可行的，因此以无法通过攀爬建模揭示的方式限制空间。因此，研究团队将与治理专家进行互动，以确保研究为政策提供信息。该奖项也将提供给更广泛的国际社会。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来评估被认为是宝贵的支持。

项目成果

How large is the design space for stratospheric aerosol geoengineering?

平流层气溶胶地球工程的设计空间有多大？

• DOI: 10.5194/esd-13-201-2022
• 发表时间: 2022
• 期刊: Earth System Dynamics
• 影响因子: 7.3
• 作者: Zhang, Yan;MacMartin, Douglas G.;Visioni, Daniele;Kravitz, Ben
• 通讯作者: Kravitz, Ben

Potential Non‐Linearities in the High Latitude Circulation and Ozone Response to Stratospheric Aerosol Injection

高纬度环流和臭氧对平流层气溶胶注入的响应中潜在的非线性

• DOI: 10.1029/2023gl104726
• 发表时间: 2023
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Bednarz, Ewa M.;Visioni, Daniele;Butler, Amy H.;Kravitz, Ben;MacMartin, Douglas G.;Tilmes, Simone
• 通讯作者: Tilmes, Simone

The Overlooked Role of the Stratosphere Under a Solar Constant Reduction

太阳常数减少下平流层被忽视的作用

• DOI: 10.1029/2022gl098773
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Bednarz, Ewa M.;Visioni, Daniele;Banerjee, Antara;Braesicke, Peter;Kravitz, Ben;MacMartin, Douglas G.
• 通讯作者: MacMartin, Douglas G.

Reduced Poleward Transport Due to Stratospheric Heating Under Stratospheric Aerosols Geoengineering

• DOI: 10.1029/2020gl089470
• 发表时间: 2020-09
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: D. Visioni;D. MacMartin;B. Kravitz;W. Lee;I. Simpson;J. Richter

Comparison of UKESM1 and CESM2 simulations using the same multi-target stratospheric aerosol injection strategy

使用相同的多目标平流层气溶胶注入策略的 UKESM1 和 CESM2 模拟比较

• DOI: 10.5194/acp-23-13369-2023
• 发表时间: 2023
• 期刊: Atmospheric Chemistry and Physics
• 影响因子: 6.3
• 作者: Henry, Matthew;Haywood, Jim;Jones, Andy;Dalvi, Mohit;Wells, Alice;Visioni, Daniele;Bednarz, Ewa M.;MacMartin, Douglas G.;Lee, Walker;Tye, Mari R.
• 通讯作者: Tye, Mari R.