Simulated Effect of Carbon Cycle Feedback on Climate Response to Solar Geoengineering

Most modeling studies investigate climate effects of solar geoengineering under prescribed atmospheric CO 2 , thereby neglecting potential climate feedbacks from the carbon cycle. Here we use an Earth system model to investigate interactive feedbacks between solar geoengineering, global carbon cycle, and climate change. We design idealized sunshade geoengineering simulations to prevent global warming from exceeding 2°C above preindustrial under a CO 2 emission scenario with emission mitigation starting from middle of century. By year 2100, solar geoengineering reduces the burden of atmospheric CO 2 by 47 PgC with enhanced carbon storage in the terrestrial biosphere. As a result of reduced atmospheric CO 2 , consideration of the carbon cycle feedback reduces required insolation reduction in 2100 from 2.0 to 1.7 W m −2 . With higher climate sensitivity the effect from carbon cycle feedback becomes more important. Our study demonstrates the importance of carbon cycle feedback in climate response to solar geoengineering.