Preprints
https://doi.org/10.5194/egusphere-2023-117
https://doi.org/10.5194/egusphere-2023-117
02 Mar 2023
 | 02 Mar 2023

Introducing a Comprehensive Set of Stratospheric Aerosol Injection Strategies

Yan Zhang, Douglas G. MacMartin, Daniele Visioni, Ewa Bednarz, and Ben Kravitz

Abstract. Stratospheric aerosol injection (SAI) comes with a wide range of possible design choices, such as the location and timing of the injection. Different injection strategies can yield different climate responses; therefore, making informed future decisions on SAI requires an understanding of the range of possible climate outcomes. Yet to date, there has been no systematic exploration of a comprehensive set of SAI strategies. This limits the ability to determine which effects are robust across different strategies and which depend on specific injection choices, or to determine if there are underlying trade-offs between different climate goals.

This study systematically explores how the choice of SAI strategy affects climate responses. Here, we introduce four hemispherically-symmetric injection strategies, all of which are designed to maintain the same global mean surface temperature: an annual injection at the equator (EQ), an annual injection of equal amounts of SO2 at 15° N and 15° S (15N+15S), an annual injection of equal amounts of SO2 at 30° N and 30° S (30N+30S), and a polar injection strategy that injects equal amounts of SO2 at 60° N and 60° S only during spring in each hemisphere (60N+60S). We compare these four hemispherically-symmetric SAI strategies with a more complex injection strategy that injects different quantities of SO2 at 30° N, 15° N, 15° S, and 30° S in order to maintain not only the global mean surface temperature but also its large scale horizontal gradients. We find that the choice of SAI strategy notably affects the spatial distribution of aerosol optical depths, injection efficiency, and various surface climate responses. Among other findings, we show that injecting in subtropics produces more global cooling per unit injection, with the EQ and the 60N+60S cases requiring, respectively, 59 % and 50 % more injection than the 30N+30S case to meet the same global mean temperature target. Injecting at higher latitudes results in larger equator-to-pole temperature gradients. While all five strategies restore September Arctic sea ice, the high-latitude injection one is more effective due to the SAI-induced cooling occurring preferentially at higher latitudes.

Yan Zhang, Douglas G. MacMartin, Daniele Visioni, Ewa Bednarz, and Ben Kravitz

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-117', Anonymous Referee #1, 11 Mar 2023
    • AC1: 'Reply on RC1', Yan Zhang, 14 Jun 2023
  • RC2: 'Comment on Zhang et al. egusphere-2023-117', Anonymous Referee #2, 23 Apr 2023
    • AC2: 'Reply on RC2', Yan Zhang, 14 Jun 2023
  • RC3: 'Comment on egusphere-2023-117', Anonymous Referee #3, 02 May 2023
    • AC3: 'Reply on RC3', Yan Zhang, 14 Jun 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-117', Anonymous Referee #1, 11 Mar 2023
    • AC1: 'Reply on RC1', Yan Zhang, 14 Jun 2023
  • RC2: 'Comment on Zhang et al. egusphere-2023-117', Anonymous Referee #2, 23 Apr 2023
    • AC2: 'Reply on RC2', Yan Zhang, 14 Jun 2023
  • RC3: 'Comment on egusphere-2023-117', Anonymous Referee #3, 02 May 2023
    • AC3: 'Reply on RC3', Yan Zhang, 14 Jun 2023
Yan Zhang, Douglas G. MacMartin, Daniele Visioni, Ewa Bednarz, and Ben Kravitz

Data sets

Data from: Introducing a Comprehensive Set of Stratospheric Aerosol Injection Strategies Yan Zhang, Douglas G. MacMartin, Daniele Visioni, Ewa Bednarz, and Ben Kravitz https://zenodo.org/record/7545452#.Y9QqLnbMK3A

Yan Zhang, Douglas G. MacMartin, Daniele Visioni, Ewa Bednarz, and Ben Kravitz

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Latest update: 24 Feb 2024
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This study provides an intercomparison of different Stratospheric Aerosol Injection strategies. The strategy choice affects the distribution of aerosol optical depth, the injection efficiency and, crucially, the surface climate response. These results lay the foundation for future trade-off analyses and design strategy optimization.
Short summary
Injecting SO2 into the lower stratosphere can temporarily reduce the global mean temperature and mitigate some of the risks associated with climate change, but injecting at different latitudes and seasons would have different impacts. This study introduces a comprehensive set of SAI strategies and systematically explores the importance of the choice of SAI strategy, demonstrating that it notably affects the distribution of aerosol cloud, injection efficiency, and various surface climate impacts.