Trade-offs of Solar Geoengineering and Mitigation under Climate Targets.

So far scientific analyses have mainly focused on the pros and cons of solar geoengineering or solar radiation management (SRM) as a climate policy option in mere isolation. Here we put SRM into the context of mitigation by a strictly temperature-target based approach. As a main innovation, we present a scheme by which the applicability regime of temperature targets is extended from mitigation-only to SRM-mitigation analyses. Hereby we explicitly account for a risk- risk comparison of SRM and global warming, while minimizing economic costs for complying with the 2 °C temperature target. To do so, we suggest precipitation guardrails that are compatible with the 2 °C target. Our analysis shows that the value system enshrined in the 2 °C target would be almost prohibitive for SRM, while still about half to nearly two-third of mitigation costs could be saved, depending on the choice of extra room for precipitation. In addition, assuming a climate sensitivity of 3 °C or more, in case of a delayed enough policy, a modest admixture of SRM to the policy portfolio might provide debatable trade-offs compared to a mitigation-only future. In addition, in our analysis for climate sensitivities higher than 4 °C, SRM will be an unavoidable policy tool to comply with the temperature targets. [ABSTRACT FROM AUTHOR]