The Effects of Solar Radiation Management on the Carbon Cycle

Purpose of Review Review existing studies on the carbon cycle impact of different solar geoengineering schemes. Recent Findings The effect of solar geoengineering on terrestrial primary productivity is typically much smaller than that of CO2 fertilization. Changes in the partitioning between direct and diffuse radiation in response to stratospheric aerosol injection could substantially alter modeled plant productivity. Inclusion of the nitrogen cycle would further modify the terrestrial response to solar geoengineering. Relative to a high-CO2 world, solar geoengineering, via cooling the surface ocean, would increase CO2 solubility, enhancing oceanic CO2 uptake. However, the effect from geoengineering-induced changes in ocean circulation and marine biology would be more complicated. Solar geoengineering would have a small effect on surface ocean acidification, but could accelerate acidification in the deep ocean. Solar geoengineering would reduce atmospheric CO2, but the relative contribution from the ocean sink and land sink is uncertain. Summary To date, there are only a few studies on the carbon cycle response to solar geoengineering. Coordinated geoengineering model intercomparison studies are needed to gain a better understanding of the carbon cycle impact of solar geoengineering and feedback on climate change.