Earth system response

Surface Air Quality

Changes in PM2.5 and surface ozone and associated imapct on human health

Uncertainty

Low

Decision relevance

Low

Resolvability scale

Discernible surface climate impact

Metric purposely leaves out mortality increase due to increase in PM2.5 due to offset warming as SAI should be looked at through the lens of comparing to equivalent emissions reduction. Potentially resolvable at 'Discernible' not because we could discover mortality, but could constrain magnitude of composition changes.

Metric

Direct impacts of SAI cause a sufficient net increase in PM2.5 and surface ozone to increase global annual mortality by 10,000

Uncertainty

Low

Combined values of mortality impacts due to surface ozone and PM2.5 changes are well less than 10,000 (Eastham et al., 2018)

Decision relevance

Low

10,000 annual deaths is equivalent to that caused by jet fuel sulfur, and is an order of magnitude less than shipping impacts ([Barrett et al., 2012](https://pubs.acs.org/doi/10.1021/es203325a), [Corbett et al., 2007](https://pubs.acs.org/doi/10.1021/es071686z)).

References

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Impacts of stratospheric sulfate geoengineering on tropospheric ozone(Xia et al., 2017)

Quantifying the impact of sulfate geoengineering on mortality from air quality and UV-B exposure(Eastham et al., 2018)

What goes up must come down: impacts of deposition in a sulfate geoengineering scenario(Visioni et al., 2020a)

Public Health, Climate, and Economic Impacts of Desulfurizing Jet Fuel(Barrett et al., 2012)

Mortality from Ship Emissions: A Global Assessment(Corbett et al., 2007)