We describe the approach taken to develop the United Kingdom's first community Earth system model, UKESM1. This is a joint effort involving the Met Office and the Natural Environment Research Council (NERC), representing the U.K. academic community. We document our model development procedure and the subsequent U.K. submission to CMIP6, based on a traceable hierarchy of coupled physical and Earth system models. UKESM1 builds on the well‐established, world‐leading HadGEM models of the physical climate system and incorporates cutting‐edge new representations of aerosols, atmospheric chemistry, terrestrial carbon, and nitrogen cycles and an advanced model of ocean biogeochemistry. A high‐level metric of overall performance shows that both models, HadGEM3‐GC3.1 and UKESM1, perform better than most other CMIP6 models so far submitted for a broad range of variables. We point to much more extensive evaluation performed in other papers in this special issue. The merits of not using any forced climate change simulations within our model development process are discussed. First results from HadGEM3‐GC3.1 and UKESM1 include the emergent climate sensitivity (5.5 and 5.4 K, respectively) which is high relative to the current range of CMIP5 models. The role of cloud microphysics and cloud‐aerosol interactions in driving the climate sensitivity, and the systematic approach taken to understand this role, is highlighted in other papers in this special issue. We place our findings within the broader modeling landscape indicating how our understanding of key processes driving higher sensitivity in the two U.K. models seems to align with results from a number of other CMIP6 models.

中文翻译：

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英国社区地球系统 CMIP6 建模


我们描述了开发英国第一个社区地球系统模型 UKESM1 所采用的方法。这是英国气象局和代表英国学术界的自然环境研究委员会 (NERC) 的共同努力。我们基于耦合的物理和地球系统模型的可追踪层次结构，记录了我们的模型开发程序以及随后英国向 CMIP6 提交的文件。 UKESM1 以完善的、世界领先的物理气候系统 HadGEM 模型为基础，融合了气溶胶、大气化学、陆地碳和氮循环的尖端新表征以及海洋生物地球化学的先进模型。总体性能的高级指标表明，HadGEM3‐GC3.1 和 UKESM1 这两个模型的性能优于迄今为止针对广泛变量提交的大多数其他 CMIP6 模型。我们指出在本期特刊的其他论文中进行了更广泛的评估。讨论了在我们的模型开发过程中不使用任何强制气候变化模拟的优点。 HadGEM3-GC3.1 和 UKESM1 的第一个结果包括新兴气候敏感性（分别为 5.5 和 5.4 K），该敏感性相对于当前的 CMIP5 模型范围较高。本特刊的其他论文强调了云微物理和云-气溶胶相互作用在驱动气候敏感性方面的作用，以及为理解这一作用而采取的系统方法。我们将我们的发现置于更广泛的建模环境中，表明我们对两个英国模型中推动更高灵敏度的关键过程的理解似乎与许多其他 CMIP6 模型的结果一致。