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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.

The logarithmic forcing relation implies decreasing incremental forcing per additional ppm, explaining the two annual-increment results. It does not imply that a higher total carbon dioxide burden requires less compensation relative to a fixed original climate. The chosen reference and whether an end-of-year, mean-year or steady maintained aerosol burden is intended must remain explicit.

The numerical mass estimates use an unusually simple, stipulated constant albedo-per-mass calibration. Real particle size and lifetime change with loading, aerosol coagulation, injection altitude/latitude and circulation. Sulfate absorbs radiation as well as scattering it and changes stratospheric chemistry. A global-mean shortwave/longwave radiative forcing balance also need not reproduce regional temperature, rainfall or transient ocean heat uptake; it does not undo CO2-driven acidification. Chemistry–climate simulations explicitly resolve some of these competing aerosol-size, temperature and ozone effects.^[ref]