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By reflecting some incoming solar radiation, stratospheric aerosol intervention using SO2 would reduce global mean temperature. Previous research has shown that multiple injection latitudes can be used to maintain not only global mean temperature, but also interhemispheric and equator-to-pole temperature gradients. However, the regional climate response depends not only on where the SO2 is injected, but also on when. We show here that even with these same objectives and same choices of latitudes, injecting in only one season instead of continuously throughout the year results in significant differences in regional climate, for instance in the magnitude of precipitation changes over India. The differential outcomes highlight the potential for underlying trade-offs, with different choices regarding deployment leading to a different distribution of benefits or harms. This aspect of climate engineering should be considered in developing governance and emphasizes the need for a deeper understanding of the mechanisms underlying the regional responses.

Plain Language Summary Injecting sulfate in the stratosphere has been suggested as a quick, temporary solution to the warming produced by the increase in greenhouse gases. This method would however come with some drawback that could become important at a regional scale. We show here that some of what are considered drawbacks of sulfate injection interventions (a reduction in precipitation over India or the Amazon Basin, or an imperfect recovery of sea ice at high northern latitudes) are dependent on the strategy used (injecting all year round versus injecting in only one season per each hemisphere). The presence of regional trade-offs between different strategies indicates that this is an important point when considering an eventual global governance of this method.