Overlooked Long‐Term Atmospheric Chemical Feedbacks Alter the Impact of Solar Geoengineering: Implications for Tropospheric Oxidative Capacity

For the scenarios considered, stratospheric ozone was depleted by 5-15% depending on latitude, and the increased transmission of UV-B radiation caused a reduction of ambient ground-level ozone of about 1-3 ppbv.

“For the scenarios considered, stratospheric ozone was depleted by 5–15%, depending on latitude, and the increased transmission of UV-B radiation caused a reduction of ambient (ground-level) ozone of about 1–3 ppbv (parts per billion by volume, equal to ca 2 μg m−3 at sea level).”

The reduction of ambient ozone would avoid ca 67,000 premature deaths per year from its inhalation.

“However, the reduction of ambient ozone would avoid ca 67,000 premature deaths per year from its inhalation.”

Moch and colleagues estimated that globally the increase in UV-B radiation would cause an additional 950 premature deaths per year from skin cancer, and the increase in PM2.5 would lead to an additional 6400 premature deaths from air pollution.

“Moch and colleagues [69] estimated that globally the increase in UV-B radiation would cause an additional 950 premature deaths per year from skin cancer, and the increase in particulate matter smaller than 2.5 μm (PM2.5) would lead to an additional 6400 premature deaths from air pollution.”

Our re-evaluation supports the established view that increases in UV-B radiation lead to a detrimental net effect on human health, and is at odds with the suggestion by Moch et al. that stratospheric ozone depletion may have net benefits.

“Our re-evaluation supports the established view that the increases in UV-B radiation lead to a detrimental net effect on human health, and is at odds with the suggestion by Moch et al. [69] that stratospheric ozone depletion may have net benefits.”

Previous studies on health impacts of SAI due to air quality changes have either relied on more idealized modeling frameworks and/or simplified mortality estimation methods.

“Previous studies have looked into the health impacts of SAI due to air quality changes (Eastham et al., 2018; Visioni et al., 2020; Moch et al., 2023; Harding et al., 2024). These efforts have either relied on more idealized modeling frameworks and/or simplified mortality estimation methods.”

Our use of CESM2(WACCM6) enables interactive coupling between aerosols, chemistry, and climate, unlike previous CTM studies that imposed stratospheric aerosols without capturing feedbacks on dynamics and transport.

“Unlike previous studies using CTMs (e.g., Eastham et al., 2018; Moch et al., 2023), which imposed stratospheric aerosols without capturing feedbacks on dynamics and transport, our use of CESM2(WACCM6) enables interactive coupling between aerosols, chemistry, and climate.”