No Emergency Brake: Slow Ocean Response to Abrupt Stratospheric Aerosol
Injection
Abstract
Given the possibility of irreversible changes to the Earth system,
technological interventions such as solar radiation management (SRM) are
sometimes framed as possible climate emergency brakes. However, little
knowledge exists on the efficacy of such disruptive interventions. To
fill in this gap, we perform Community Earth System Model 2 (CESM 2)
simulations of a SSP5-8.5 scenario on which we impose either gradual
early-century SRM to stabilise surface temperatures or a rapid
late-century cooling, both realised via stratospheric aerosol injection
(SAI). While both scenarios cool Earth’s surface, we find that ocean
conditions differ drastically. The rapid-cooling scenario fails to
dissipate sub-surface ocean heat content (OHC), ends up in a weaker AMOC
state and does not restore an ailing North Atlantic deep convection.
Furthermore, the weakened AMOC state mediates the climate response to
rapid SAI, thus inducing an interhemispheric temperature asymmetry. Our
results advise caution when considering SAI as an emergency
intervention.