Date of Publication: 22 September 2023

One-Line Summary: Spraying tiny particles into the atmosphere, a proposed method of limiting Earth’s warming, may lead to some unexpected global health benefits.

Who did it: An international team of researchers (USA, Hong Kong, Germany, and China).  

What did they study: They calculated the effect of adding sulfate aerosols* high into the atmosphere on pollution levels lower down. 

What they found:  Injection of sulfate aerosols into the atmosphere will increase the amount of ultraviolet (UV) light* hitting Earth’s surface. This result is surprising and has consequences for human health.

Why does this matter:  It was already known that the addition of sulfate aerosols into the stratosphere* will damage the ozone layer, leading to increased UV exposure. This research shows that the increased UV light reaching the lower atmosphere will also improve air quality and reduce greenhouse gases at Earth’s surface. 

What next: We should be mindful of possible atmospheric “side effects” in projects engineered to disrupt climate change. 

Our take:  Geoengineering* will likely have many other surprise impacts (both good and bad). We are already modifying the atmosphere in myriad ways, and with myriad unintended consequences. For now, reducing greenhouse gas emissions remains the best way to prevent additional warming and minimize global mortality from climate change.

*The basics: Aerosols are a suspension of fine solid particles or liquid droplets in air. Ultraviolet (UV) light is the part of sunshine that causes sunburn; this paper showed that it also destroys some of the molecules that form air pollution. The stratosphere refers to the layer of the atmosphere above the clouds. Geoengineering is the subfield of engineering concerned with creating technologies to alter Earth’s climate and modify the negative effects of Climate Change. 

Who to talk to: Dr. Jonathan Moch, AAAS Science and Technology Policy Fellowship Program at U.S. Department of State, Washington, DC, USA, research@jmoch.net. 

The paper: Moch, J. M., Mickley, L. J., Eastham, S. D., Lundgren, E. W., Shah, V., Buonocore, J. J., et al. (2023). Overlooked long-term atmospheric chemical feedbacks alter the impact of solar geoengineering: Implications for tropospheric oxidative capacity. AGU Advances, 4, e2023AV000911. https://doi. org/10.1029/2023AV000911. 

Journal page: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023AV000911

Keywords: geoengineering, Paris Agreement, solar, sulfate, aerosols, climate change, global warming, atmospheric chemistry, greenhouse gases, air pollution, public health