= Solution
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.<The impact of geoengineering aerosols on stratospheric temperature and ozone by P. Heckendorn and others>[Environmental Research Letters 4 (2009), 045108, Abstract: coupled aerosol-size and chemistry–climate simulations]{ref}
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