Towards a better understanding of the physical risks and tradeoffs of solar geoengineering.

Solar climate intervention using Stratospheric Aerosol Injection (SAI) is a proposed method of reducing global-mean temperatures to temporarily offset some of the effects of global warming while we cut greenhouse gas emissions and remove CO₂ from the atmosphere. While the scientific, moral, and ethical questions surrounding solar geoengineering are undoubtedly complex, rigorous and unbiased information on its advantages and pitfalls will help us make better decisions in the future. Recent research has shown that some of the negative physical side-effects of SAI can be moderated by designing a better intervention strategy. I will present a comparison between a previously published ensemble of climate model simulations using the Community Earth System Model 2 (CESM2) and a new ensemble using the United Kingdom Earth System Model 1 (UKESM1). This set of simulations is based on a moderate greenhouse gas emission scenario and start injection of stratospheric aerosols in year 2035 to keep the global-mean surface temperature at 1.5 degrees above preindustrial. The injection occurs at four different latitudes and a controller algorithm is used to maintain the latitudinal gradient and inter-hemispheric difference in surface temperature, thus moderating the side effects of previous injection methods. We compare the behavior of the algorithm between the two models, as well as the climate response, with a particular focus on tropical precipitation.