= Solution
Injected <sulfur dioxide> is oxidized, principally through <hydroxyl radical> chemistry, to <sulfuric acid>, which nucleates or condenses into aqueous <sulfate> particles. A suitably sized, weakly absorbing particle population scatters some incoming sunlight back to space, increasing planetary <albedo> and decreasing absorbed solar energy. The <sulfur dioxide> <molecules> are precursors, not the persistent reflective population.
The <albedo> lifetime reflects <aerosol> formation, growth/<aerosol coagulation>, <sedimentation>, stratospheric transport and eventual return to efficiently scavenged tropospheric air. The <stratosphere> has little <atmospheric precipitation>, so the effect can outlast analogous tropospheric <aerosol>. The assumed year is an effective persistence scale, not a universal lifetime of <sulfur dioxide> <oxidation> or an exact clock for every particle.
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