Chemistry and Impact of Stratospheric Aerosol Injection

Overview 
Stratospheric Aerosol Injection (SAI) is a proposed solar geoengineering strategy that introduces reflective particles into the stratosphere to reduce sunlight reaching Earth and mitigate global warming. Our research investigates how these proposed materials—such as calcite, aluminum oxide, titanium dioxide, and other solid inorganic aerosols—behave once injected into the stratosphere. 

We aim to determine how these particles interact with stratospheric gases and whether they could unintentionally trigger polar stratospheric clouds (PSCs) that accelerate ozone depletion. 

Why It Matters 
If SAI materials promote PSC formation, they could amplify ozone loss and delay recovery of the ozone layer. By understanding the chemistry and cloud-forming ability of candidate particles, our work provides the scientific foundation needed to evaluate the risks and feasibility of solar geoengineering before large-scale deployment. 

The results will also improve atmospheric models and inform international ozone protection policies. 

Key Questions 
• Can solid inorganic aerosols used for SAI nucleate PSCs under polar conditions? 
• How does atmospheric aging (oxidation or H₂SO₄ coating) change surface chemistry and cloud-nucleating ability? 
• What are the timescales over which coatings suppress PSC formation? 
• At the molecular level, what surface features promote or inhibit ice and nitric-acid hydrate nucleation? 

Approach / Methods 
We combine cold-temperature laboratory experiments and molecular simulations to explore PSC formation mechanisms: 
• Particle characterize with mass spectrometry, spectroscopy, and electron microscopy. 
• Simulate months–years of stratospheric aging in environmental chambers and oxidative flow reactors. 
• Examine PSC formation with optical and infrared microscopy in low-temperature flow cells and cold-stage assays. 
• Use molecular dynamics simulations to study how water and nitric acid interact with aerosol surfaces at the atomic scale. 

Selected Publications 

• Huynh, H. N. and V. F. McNeill (2024). The potential environmental and climate impacts of stratospheric aerosol injection: a review. Environmental Science Atmospheres, 4(2).
• Keith, D. W., et al. (2016). Stratospheric solar geoengineering without ozone loss. Proceedings of the National Academy of Sciences of the United States of America, 113(52), 14910–14914.

Collaborators / Partners

• Gren Patey, University of British Columbia
• Nadine Borduas-Dedekind, University of British Columbia
• Russ Algar, University of British Columbia