Global Cooling Hiatus Driven by an AMOC Overshoot in a Carbon Dioxide Removal Scenario

Abstract The reversibility of global mean surface temperature was examined by a transient CO 2 reversibility experiment using an Earth system model. The results showed that after CO 2 ramp‐up toward CO 2 quadrupling and ramp‐down returned to the present‐day level, the global mean surface temperature kept decreasing but stopped to change for ∼40 years in the early net‐zero CO 2 emission period. This period, referred to a cooling hiatus, resulted from a compensation between Southern Hemisphere cooling and Northern Hemisphere warming. The Northern Hemisphere warming was centered over the North Atlantic. This localized warming was caused by an excessive heat advection by a delayed and surpassed Atlantic Meridional Overturning Circulation (AMOC) to CO 2 forcing. During the progression of CO 2 change, the meridional salinity gradient between subtropic and subpolar regions was enhanced, and the…