Sensitivity of Aerosol Distribution and Climate Response to Stratospheric SO2 Injection Locations

Injection of SO2 into the stratosphere has been proposed as a method to, in part, counteract anthropogenic climate change. So far, most studies investigated injections at the equator or in a region in the tropics. Here we use Community Earth System Model version 1 Whole Atmosphere Community Climate Model (CESM1(WACCM)) to explore the impact of continuous single grid point SO2 injections at seven different latitudes and two altitudes in the stratosphere on aerosol distribution and climate. For each of the 14 locations, 3 different constant SO2 emission rates were tested to identify linearity in aerosol burden, aerosol optical depth, and climate effects. We found that injections at 15 degrees N and 15 degrees S and at 25km altitude have equal or greater effect on radiation and surface temperature than injections at the equator. Nonequatorial injections transport SO2 and sulfate aerosols more efficiently into middle and high latitudes and result in particles of smaller effective radius and larger aerosol burden in middle and high latitudes. Injections at 15 degrees S produce the largest increase in global average aerosol optical depth and increase the change in radiative forcing per TgSO(2)/yr by about 15% compared to equatorial injections. High-altitude injections at 15 degrees N produce the largest reduction in global average temperature of 0.2 degrees per TgS/yr for the last 7years of a 10year experiment. Injections at higher altitude are generally more efficient at reducing surface temperature, with the exception of large equatorial injections of at least 12TgSO(2)/yr. These findings have important implications for designing a strategy to counteract global climate change.