A climate model's ability to reproduce observed historical warming is sometimes viewed as a measure of quality. Yet, for practical reasons it cannot be considered a purely empirical result of the modeling efforts because the desired result is known in advance and so is a potential target of tuning. Here we report how the latest edition of the Max Planck Institute for Meteorology Earth System Models (MPI‐ESM1.2) atmospheric component (ECHAM6.3) had its sensitivity systematically tuned in order to improve the modeled match with the instrumental record. In practice, this was done by targeting an equilibrium climate sensitivity of about 3 K, slightly lower than in the previous model generation (MPI‐ESM), which warmed more than observed, and in particular by addressing a climate sensitivity of about 7 K in an intermediate version of the model. In the process we identified several controls on cloud feedback, some of which confirm recently proposed hypotheses. We find the model exhibits excellent fidelity with the observed centennial global warming. We further find that an alternative approach with high climate sensitivity compensated by strong aerosol cooling instead would yield colder than observed results in the second half of the twentieth century.

中文翻译：

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调整 MPI-ESM1.2 全球气候模型，通过降低其气候敏感性来改善与仪器记录变暖的匹配。


气候模型重现观测到的历史变暖的能力有时被视为质量衡量标准。然而，出于实际原因，它不能被视为建模工作的纯粹经验结果，因为预期结果是提前已知的，因此是潜在的调整目标。在这里，我们报告了马克斯·普朗克气象研究所地球系统模型 (MPI-ESM1.2) 大气成分 (ECHAM6.3) 的最新版本如何系统地调整其灵敏度，以改善模型与仪器记录的匹配。实际上，这是通过将平衡气候敏感性设定为约 3 K 来实现的，略低于上一代模型 (MPI-ESM)，该模型的变暖程度比观测到的要高，特别是通过解决 7 K 左右的气候敏感性来实现。模型的中间版本。在此过程中，我们确定了对云反馈的几种控制，其中一些证实了最近提出的假设。我们发现该模型与观测到的百年全球变暖表现出极好的保真度。我们进一步发现，通过强气溶胶冷却补偿的具有高气候敏感性的替代方法反而会产生比二十世纪下半叶观察到的结果更冷的结果。