Effective radiative forcing (ERF) is evaluated in the ACCESS1.0 General Circulation Model (GCM) with fixed land and sea‐surface‐temperatures (SST) as well as sea‐ice. The 4xCO₂ ERF is 8.0 W m⁻². In contrast, a typical ERF experiment with only fixed SST and sea‐ice gives rise to an ERF of only 7.0 W m⁻². This difference arises due to the influence of land warming in the commonly used fixed‐SST ERF experimental design, which results in: (i) increased emission of longwave radiation to space from the land surface (−0.45 W m⁻²) and troposphere (−0.90 W m⁻²), (ii) reduced land snow‐cover and albedo (+0.17 W m⁻²), (iii) increased water‐vapor (+0.49 W m⁻²), and (iv) a cloud adjustment (−0.26 W m⁻²) due to reduced stability and cloudiness over land (positive ERF) counteracted by increased lower tropospheric stability and marine cloudiness over oceans (negative ERF). The sum of these radiative adjustments to land warming is to reduce the 4xCO₂ ERF in fixed‐SST experiments by ∼1.0 W m⁻². CO₂ stomatal effects are quantified and found to contribute just over half of the land warming effect and adjustments in the fixed‐SST ERF experimental design in this model. The basic physical mechanisms in response to land warming are confirmed in a solar ERF experiment. We test various methods that have been proposed to account for land warming in fixed‐SST ERFs against our GCM results and discuss their strengths and weaknesses.

中文翻译：

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具有固定表面温度的GCM中的有效辐射强迫

在ACCESS1.0通用环流模型（GCM）中评估了有效辐射强迫（ERF），该模型具有固定的陆地温度和海面温度（SST）以及海冰。4xCO ₂ ERF为8.0 W m ^-2。相比之下，典型的仅具有固定的海温和海冰的ERF实验得出的ERF只有7.0 W m ^-2。这种差异是由于在常用的固定SST ERF实验设计中土地变暖的影响而导致的，其结果是：（i）从地面（-0.45 W m ^-2）和对流层向空间发射的长波辐射增加（ -0.90 W m ^-2），（ii）减少陆地积雪和反照率（+0.17 W m ^-2），（iii）增加水汽（+0.49 W m ^-2），以及（iv）由于陆地上的稳定性和混浊度降低（正ERF）而引起的云层调整（-0.26 W m ^-2），而对流层稳定性和海洋上空的云量增加了对海洋的影响（负ERF）。这些对土地变暖的辐射调整的总和是将固定SST实验中的4xCO ₂ ERF降低约1.0 W m ^-2。一氧化碳₂在此模型中，气孔效应被量化，并被发现仅占陆地变暖效应的一半以上，并且在固定SST ERF实验设计中进行了调整。太阳ERF实验证实了响应土地变暖的基本物理机制。我们根据GCM结果测试了建议用于解决固定SST ERF中土地变暖的各种方法，并讨论了它们的优缺点。