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.