Abstract In radiative-convective equilibrium (RCE), radiative cooling of the troposphere is roughly balanced by the vaporization enthalpy set free by precipitating moist convection. Many earlier studies restricted the investigation of RCE to the dynamics of the atmosphere with constant boundary conditions including prescribed surface temperature. We investigate a GCM setup where a slab ocean is coupled to the atmosphere, and we explore a wide range of CO2 concentrations. We obtain reliable statistical quantities from thousand-year-long simulations. For moderate CO2 concentrations, we find unskewed temporal variations of 1–2 K in global mean surface temperature, with an almost constant climate sensitivity of 2 K. At CO2 concentrations beyond four times the preindustrial value, the climate sensitivity decreases to nearly zero as a result of episodic global cooling events as large as 10 K. The dynamics of these cooling events are investigated in detail and shown to be associated with an increase in large-scale low-level stratiform cloudiness in the subsiding region, which is a result of penetrative shallow convection being capped by an inversion and thus not ventilating the lower troposphere. These dynamics depend on the CO2 concentration: both through the effect of temperature on stratification and through the changing spatial scale of organization of the flow, which determines the spatial scale and temporal coherence of the stratiform cloud sheets.

中文翻译：

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在大范围的 CO2 浓度下，板块海洋的辐射-对流平衡的全球变化

摘要 在辐射-对流平衡（RCE）中，对流层的辐射冷却大致由湿对流沉淀释放的蒸发焓平衡。许多早期的研究将 RCE 的研究限制在具有恒定边界条件（包括规定的表面温度）的大气动力学上。我们研究了一个 GCM 设置，其中平板海洋与大气耦合，我们探索了广泛的 CO2 浓度。我们从长达千年的模拟中获得了可靠的统计量。对于中等 CO2 浓度，我们发现全球平均地表温度有 1-2 K 的不偏斜时间变化，气候敏感性几乎恒定为 2 K。当 CO2 浓度超过工业化前值的四倍时，由于高达 10 K 的偶发性全球变冷事件，气候敏感性降低到接近于零。详细研究了这些变冷事件的动力学，并表明与大尺度低层层状云度的增加有关下沉区，这是穿透性浅对流被逆温覆盖，因此对流层低层不通风的结果。这些动态取决于 CO2 浓度：通过温度对分层的影响以及通过流动组织的变化空间尺度，这决定了层状云片的空间尺度和时间连贯性。详细研究了这些冷却事件的动力学，并表明与下沉区域大规模低层层状云度的增加有关，这是穿透性浅对流被逆温覆盖并因此不通风的结果低对流层。这些动态取决于 CO2 浓度：通过温度对分层的影响以及通过流动组织的变化空间尺度，这决定了层状云片的空间尺度和时间连贯性。详细研究了这些冷却事件的动力学，并表明与下沉区域大规模低层层状云度的增加有关，这是穿透性浅对流被逆温覆盖并因此不通风的结果低对流层。这些动态取决于 CO2 浓度：通过温度对分层的影响以及通过流动组织的变化空间尺度，这决定了层状云片的空间尺度和时间连贯性。