Evaluation of the Stratospheric Impacts of Stratospheric Aerosol Injection With Solar-Powered Lofting

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JD042813?af=R

Authors

Ye Lu, Cheng-Cheng Liu, Yifeng Peng, Karen H. Rosenlof, Jianchun Bian, Pengfei Yu

16 July 2025

https://doi.org/10.1029/2024JD042813

Abstract

Stratospheric aerosol injection (SAI) introduces aerosols or their precursors into the stratosphere, reflecting sunlight and mitigating global warming. However, delivering these materials to the stratosphere at the required altitudes (18–25 km) poses practical challenges. Here, we evaluate a novel delivery method called solar-powered lofting (SPL), inspired by self-lofting during extreme wildfires. SPL coinjects a small amount of black carbon (BC) with SO2 at lower altitudes accessible to commercial aircraft (∼13 km), allowing the SO2 to self-loft into the stratosphere. Using the Community Earth System Model, we compare SPL simulations with traditional SAI simulation that injects equivalent SO2 mass at 20 km at the same locations, but without BC. SPL and SAI scenarios generate similar global aerosol optical depths and effective radiative forcing. BC induces an additional 1.5 K annual mean warming in the tropical stratosphere, raising stratospheric water vapor by 0.42 ppm. The coinjected BC accounts for 20% of the annual mean temperature and water vapor anomalies. Furthermore, the BC strengthens the polar vortex and enhances the Brewer-Dobson circulation. As a result of the changes in dynamics and chemistry, the coinjected BC results in a 5% increase in Antarctic ozone depletion in October. The SPL method at aircraft-accessible altitudes offers comparable cooling efficiency but requires careful evaluation of additional BC impacts.

Key Points

Solar-powered lofting (SPL) with black carbon (BC) at 13 km lifts 80% sulfate to the stratosphere, achieving radiative forcing comparable to 20-km SO2 injections

Coinjected BC causes 1.5 K warming and 0.42 ppm water vapor in the lower tropical stratosphere, contributing 20% of the overall SPL effect

Coinjected BC amplifies Antarctic ozone depletion by 5% in October through BC-enhanced strengthening of the polar vortex

Plain Language Summary

Stratospheric aerosol injection (SAI) involves injecting particles or precursors (such as SO2) into the stratosphere to enhance its aerosol loading, thereby increasing the reflection of solar radiation with the aim of mitigating global warming. Traditional SAI simulations inject SO2 at altitudes between 18 and 25 km, beyond the reach of current commercial aircraft. To address this challenge, scientists have proposed a novel method called solar-powered lofting (SPL). SPL involves introducing a small amount of black carbon (BC) aerosol into the troposphere to assist in lofting large quantities of SO2 into the stratosphere. In our study, we use the Community Earth System Model to assess the climate effects of this method. We find that SPL leads to a similar global aerosol optical depth and effective radiative forcing compared with the traditional SAI. However, the coinjected BC causes additional warming in the tropical stratosphere, increases water vapor, and slightly intensifies the circulation patterns in the atmosphere. These changes also result in a higher rate of ozone depletion in Antarctica during October. Our findings suggest that while SPL can be effective in reflecting sunlight without requiring the development of high-altitude, heavy-load aircraft, it also produces climate impacts that need careful consideration in discussions of climate intervention strategies.

Source: AGU