Expanding the design space of stratospheric aerosol geoengineering to include precipitation-based objectives and explore trade-offs

Previous climate modeling studies demonstrate the ability of feedback-regulated, stratospheric aerosol geoengineering with injection at multiple independent latitudes to meet multiple simultaneous temperature-based objectives in the presence of anthropogenic climate change. However, the impacts of climate change are not limited to rising temperatures but also include changes in precipitation, loss of sea ice, and many more; knowing how a given geoengineering strategy will affect each of these climate metrics is vital to understanding the limits and trade-offs of geoengineering. In this study, we first introduce a new method of visualizing the design space in which desired climate outcomes are represented by 2-D surfaces on a 3-D graph. Surface orientations represent how different injection choices influence that objective, and intersecting surfaces represent objectives which can be met simultaneously. Using this representation as a guide, we present simulations of two new strategies for feedback-regulated aerosol injection, using the Community Earth System Model with the Whole Atmosphere Community Climate Model - CESM1(WACCM). The first simultaneously manages global mean temperature, tropical precipitation centroid, and Arctic sea ice extent, while the second manages global mean precipitation, tropical precipitation centroid, and Arctic sea ice extent. Both simulations control the tropical precipitation centroid to within 5 % of the goal, and the latter controls global mean precipitation to within 1 % of the goal. Additionally, the first simulation overcompensates sea ice, while the second under-compensates sea ice; all of these results are consistent with the expectations of our design space model. In addition to showing that precipitation-based climate metrics can be managed using feedback alongside other goals, our simulations validate the utility of our design space visualization in predicting our climate model behavior under a given geoengineering strategy, and together they help illustrate the fundamental limits and trade-offs of stratospheric aerosol geoengineering.

先前的气候模拟研究表明，在人为气候变化的情况下，通过在多个独立纬度注入气溶胶并进行反馈调节的平流层气溶胶地球工程，有能力实现多个基于温度的同时目标。然而，气候变化的影响不仅限于气温上升，还包括降水变化、海冰减少等等；了解特定的地球工程策略将如何影响每一个这些气候指标，对于理解地球工程的局限性和权衡取舍至关重要。在这项研究中，我们首先引入一种可视化设计空间的新方法，在三维图中用二维曲面表示期望的气候结果。曲面方向代表不同的注入选择如何影响该目标，相交的曲面代表可以同时实现的目标。以这种表示作为指导，我们利用包含全大气社区气候模式的社区地球系统模式（CESM1（WACCM）），对两种反馈调节气溶胶注入的新策略进行了模拟。第一种策略同时控制全球平均温度、热带降水重心和北极海冰范围，而第二种策略控制全球平均降水、热带降水重心和北极海冰范围。两种模拟都将热带降水重心控制在目标的5%以内，后者将全球平均降水控制在目标的1%以内。此外，第一种模拟对海冰补偿过度，而第二种模拟对海冰补偿不足；所有这些结果都与我们的设计空间模型的预期一致。除了表明基于降水的气候指标可以与其他目标一起通过反馈进行控制外，我们的模拟验证了我们的设计空间可视化在预测给定地球工程策略下气候模型行为方面的实用性，并且它们共同有助于阐明平流层气溶胶地球工程的基本局限性和权衡取舍。