Simulating the warmth and equability of past hothouse climates has been a challenge since the inception of paleoclimate modeling. The newest generation of Earth system models (ESMs) has shown substantial improvements in the ability to simulate the early Eocene global mean surface temperature (GMST) and equator-to-pole gradient. Results using the Community Earth System Model suggest that parameterizations of atmospheric radiation, convection, and clouds largely determine the Eocene GMST and are responsible for improvements in the new ESMs, but they have less direct influence on the equator-to-pole temperature gradient. ESMs still have difficulty simulating some regional and seasonal temperatures, although improved data reconstructions of chronology, spatial coverage, and seasonal resolution are needed for more robust model assessment. Looking forward, key processes including radiation and clouds need to be benchmarked and improved using more accurate models of limited domain/physics. Earth system processes need to be better explored, leveraging the increasing ESM resolution and complexity. ▪Earth system models (ESMs) are now able to simulate the large-scale features of the early Eocene.▪Remaining model-data discrepancies exist at regional and seasonal scales and require improvements in both proxy data and ESMs.▪A hierarchical modeling approach is needed to ensure relevant physical processes are parameterized reasonably well in ESMs.▪Future work is needed to leverage the continuously increasing resolution and complexity of ESMs.

中文翻译：

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对过去的温室气候进行建模，作为评估地球系统模型和提高对温暖气候的理解的一种手段


自古气候建模开始以来，模拟过去温室气候的温暖和平等性一直是一项挑战。最新一代的地球系统模型 （ESM） 在模拟始新世早期全球平均表面温度 （GMST） 和赤道到极点梯度的能力方面有了实质性的改进。使用社区地球系统模型的结果表明，大气辐射、对流和云的参数化在很大程度上决定了始新世 GMST，并负责改进新的 ESM，但它们对赤道到极点温度梯度的直接影响较小。ESM 仍然难以模拟某些区域和季节性温度，尽管需要改进时间、空间覆盖范围和季节分辨率的数据重建才能进行更稳健的模型评估。展望未来，包括辐射和云在内的关键过程需要使用更精确的有限域/物理模型进行基准测试和改进。需要更好地探索地球系统过程，利用不断提高的 ESM 分辨率和复杂性。▪地球系统模型 （ESM） 现在能够模拟始新世早期的大尺度特征。▪在区域和季节尺度上存在剩余的模型-数据差异，需要在代理数据和 ESM 方面进行改进。▪需要一种分层建模方法来确保在 ESM 中合理地很好地参数化相关的物理过程。▪未来的工作需要利用 ESM 不断提高的分辨率和复杂性。