Seasonal injection strategies for stratospheric aerosol geoengineering

Simulations of stratospheric aerosol geoengineering have typically considered injections at aconstant rate over the entire year. However, the seasonal variability of both sunlight and the stratosphericcirculation suggests seasonally dependent injection strategies. We simulated single‐point injections of thesame amount of SO2in each of the four seasons and atfive different latitudes (30°S, 15°S, equator, 15°N, and30°N), 5 km above the tropopause. Ourfindings suggest that injecting only during one season reduces theamount of SO2needed to achieve a certain aerosol optical depth, thus potentially reducing some of the sideeffects of geoengineering. Wefind, in particular, that injections at 15°N or 15°S in spring of thecorresponding hemisphere results in the largest reductions in incoming solar radiation. Compared to annualinjections, by injecting in the different seasons we identify additional distinct spatiotemporal aerosol opticaldepth patterns, thanks to seasonal differences in the stratospheric circulation.