Carbon Cycle Response to Stratospheric Aerosol Injection With Multiple Temperature Stabilization Targets and Strategies

Abstract We analyze the global carbon cycle response to a set of stratospheric aerosol injection (SAI) simulations performed by the CESM2(WACCM6‐MA) model. The simulations are performed under the specified SSP2‐4.5 CO 2 concentration pathway. It is found that both the temperature stabilization target and the SO 2 injection strategy have important effects on the global carbon sink. Relative to the SSP2‐4.5 scenario, averaged over the last 20 years of our simulations (year 2050–2069), simultaneous multi‐location SO 2 injection causes an increase in cumulative land carbon uptake of 45 and 23 PgC, and an increase in cumulative ocean carbon uptake of 6 and 2 PgC for temperature stabilization targets of 0.5°C and 1.5°C respectively. For a temperature stabilization target of 1.0°C, SO 2 injections increase land and ocean carbon sinks by 22–42 PgC and 4–7 PgC, respectively, depending on the strategies of SO 2 injections (low latitude, mid‐to‐high latitude, and multi‐objective injection). Relative to SSP2‐4.5, by year 2069, SAI increases diagnosed cumulative CO 2 emissions by 25–53 PgC (3%–6%), implying a decrease in atmospheric CO 2 if SO 2 injections were performed under a prescribed CO 2 emission pathway. Stratospheric SO 2 injections slow permafrost thaw, but do not restore permafrost to the previous extent at the same warming level for all injection strategies. An abrupt termination of SO 2 injection weakens both the ocean and land carbon sink, and causes a rapid decline of permafrost extent. A gradual phaseout of SO 2 injection slows sharp decline of permafrost and delays the rebound of carbon sink.