Results are presented and compared for the Community Earth System Model version 2 (CESM2) simulations of the middle Holocene (MH, 6 ka) and Last Interglacial (LIG, 127 ka). These simulations are designated as Tier 1 experiments (midHolocene and lig127k) for the Coupled Model Intercomparison Project phase 6 (CMIP6) and the Paleoclimate Modeling Intercomparison Project phase 4 (PMIP4). They use the low‐top, standard 1° version of CESM2 contributing to CMIP6 DECK, historical, and future projection simulations, and to other modeling intercomparison projects. The midHolocene and lig127k provide the opportunity to examine the responses in CESM2 to the orbitally induced changes in the seasonal and latitudinal distribution of insolation. The insolation anomalies result in summer warming over the Northern Hemisphere continents, reduced Arctic summer minimum sea ice, and increased areal extent of the North African monsoon. The Arctic remains warm throughout the year. These changes are greater in the lig127k than midHolocene simulation. Other notable changes are reduction of the Niño3.4 variability and Drake Passage transport and a small increase in the Atlantic Meridional Overturning Circulation from the piControl to midHolocene to lig127k simulation. Comparisons to paleo‐data and to simulations from previous model versions are discussed. Possible reasons for mismatches with the paleo‐observations are proposed, including missing processes in CESM2, simplifications in the CMIP6 protocols for these experiments, and dating and calibration uncertainties in the data reconstructions.

中文翻译：

---

CESM2中CMIP6中间茂和lig127k模拟的比较

呈现并比较了中全新世（MH，6 ka）和最后一次冰间期（LIG，127 ka）的社区地球系统模型版本2（CESM2）模拟的结果。这些模拟被指定为第1层的实验（midHolocene和lig127k）为耦合模式项目阶段6（CMIP6）和古气候模拟项目阶段4（PMIP4）。他们使用的是CESM2的低顶，标准1°版本，可用于CMIP6 DECK，历史和未来的投影仿真以及其他建模比对项目。中全新世和lig127k提供了机会来检查CESM2中对日照的季节和纬度分布的轨道诱发变化的响应。日照异常导致北半球各大陆夏季变暖，北极夏季最低海冰减少，北非季风的面积增加。北极终年温暖。lig127k中的这些变化比中全新世的模拟大。其他值得注意的变化是减少Niño3.4变异性和Drake通道的运输，以及从piControl到中全新世再到lig127k的大西洋子午翻转翻滚环流略有增加。模拟。讨论了与旧数据和先前模型版本的模拟的比较。提出了与古观测不匹配的可能原因，包括CESM2中缺少过程，这些实验中CMIP6协议的简化以及数据重建中的日期和校准不确定性。