The reversibility of global mean surface temperature was examined by a transient CO₂ reversibility experiment using an Earth system model. The results showed that after CO₂ ramp-up toward CO₂ 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 CO₂ 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 CO₂ forcing. During the progression of CO₂ change, the meridional salinity gradient between subtropic and subpolar regions was enhanced, and the oceanic stratification in subpolar North Atlantic was reduced due to accumulated heat and reduced vertical salt import in the deeper ocean. As AMOC started to recover, consequently, the enhanced salt advection feedback and the relaxed buoyant force resulted in AMOC overshoot.

中文翻译：

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二氧化碳去除情景中由 AMOC 过冲驱动的全球冷却中断

全球平均地表温度的可逆性通过使用地球系统模型的瞬态 CO ₂可逆性实验来检验。结果表明，在CO ₂上升至CO ₂翻两番并下降回到当前水平后，全球平均地表温度在CO ₂净零排放初期持续下降但停止变化约40年时期。这一时期被称为冷却中断，是由于南半球变冷和北半球变暖之间的补偿造成的。北半球变暖集中在北大西洋。这种局部变暖是由延迟并超过大西洋经向翻转环流 (AMOC) 到 CO 的过度热平流引起的₂强迫。在CO ₂变化过程中，副热带和副极地之间的经向盐度梯度增强，由于热量积聚和深海垂直盐分输入减少，北大西洋副极地海洋分层减少。随着 AMOC 开始恢复，因此，增强的盐平流反馈和松弛的浮力导致 AMOC 超调。