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

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.