Can Linear Optimization Methods be used for Regional Risk Mitigation with Solar Geoengineering?

Abstract:

Although a growing body of literature examines the use of solar radiation management, or geoengineering, to achieve large-scale objectives like global mean temperature reduction, less research has investigated the regional ramifications of geoengineering practices. We utilize the output of seasonally and regionally variant solar reduction simulations conducted in the HadCM3L global climate model and the CESM2 climate model to analyze the ability of linear optimization methods to modify regional climate objectives. We use the regional climatology obtained in the different HadCM3L forcing scenarios to define an “optimized” forcing. We then conduct a series of experiments in the higher-resolution CESM2 climate model to investigate whether regionally optimized geoengineering patterns built from a simpler model can predict local effects in a more complex climate system, examining impacts on both mean temperature and precipitation effects and regional climate extremes. This is an analogy to using our most complex, comprehensive climate models at present to try to optimize forcing patterns for improved regional outcomes in the real world. We show that a regionally-optimized solar reduction strategy from a simple model does succeed in achieving better temperature outcomes, but fails at creating the desired precipitation outcomes, and in some cases exacerbates the problems caused by global warming. This suggests that trying to predict regional hydrological outcomes with geoengineering may be extremely difficult, and controlling these regional hydrological outcomes by optimizing forcing is unlikely to succeed.