Regional Response of Land Hydrology and Carbon Uptake to Different Amounts of Solar Radiation Modification

Abstract

Solar radiation modification (SRM) is a proposed method to cool the Earth by intentionally perturbing the Earth's energy balance. One concern about the effect of SRM is disparities in the regional climate response. In this study, we use the Community Earth System Model (CESM1.2) to analyze the regional response of land hydrology and terrestrial carbon uptake to different amounts of SRM. The SRM is implemented by a uniform increase in volcanic-size sulfate aerosols in the stratosphere under a doubling of atmospheric CO2. Our results show that different amounts of SRM could either moderate or exacerbate CO2-induced changes in land hydrology including precipitation, precipitation minus evapotranspiration, and soil moisture (SM), but the effect varies widely across regions and specific variables. An “optimal” amount of SRM that moderates land hydrology changes for one region might exacerbate changes for other regions (or vice versa). Also, our study shows that for quite a few regions, partial SRM moderates CO2-induced change in precipitation minus evaporation but exacerbates changes in CO2-induced SM. The response of terrestrial Net primary productivity (NPP) to different amounts of SRM shows large regional disparities, depending on whether temperature or water availability constrains NPP more. Our study also shows that the effect of CO2 physiological forcing plays a key role in regulating land hydrology response to SRM, especially at the regional scale.