P2C2: Constraining Mechanisms of Tropical Climate Change Using Simulations and Proxies of the Last Glacial Maximum (LGM)

末次盛冰期（LGM）是21000年前的一段时间，当时地球被冰川覆盖，比现在冷得多，为测试气候环流模型提供了一组独特的边界条件。该提案旨在利用LGM的模拟来确定当时热带太平洋的大气-海洋耦合系统沃克环流是更强还是更弱。该项目将试图解决几个重要问题，包括：1)水文循环、海面温度梯度和巽他大陆架暴露对沃克环流过去强度的影响有多重要？2)模型偏差在这些机制之间的相互作用中有何影响？3)对热带太平洋地区过去气候的不同重建是否可以调和并用于约束这些机制？4)最先进的气候模式如何很好地模拟了Walker环流对LGM期间由于海平面降低而暴露的巽他陆架的响应。研究中使用的模型还用于生成关键的古气候模拟，这些模拟将在IPCC第5次评估报告中讨论。因此，评估不同模型的性能对气候研究界来说是非常有价值的。

The Last Glacial Maximum (LGM), that period of time 21,000 years ago when the earth was glaciated and significantly colder than today, provides a unique set of boundary conditions to test climate general circulation models. This proposal aims to use simulations of the LGM to determine if the Walker Circulation, a coupled atmosphere-ocean system in the tropical Pacific, was stronger or weaker at that time. The project will attempt to address several important questions including: 1) How important are changes in the hydrological cycle, sea surface temperature gradients, and exposure of the Sunda shelf in affecting past intensity of the Walker Circulation? 2) What is the impact of model bias in the interaction among these mechanisms? 3) Can the different reconstructions of past climate in the tropical Pacific be reconciled and used to constrain each of these mechanisms? 4) How well do state-of-the-art climate models simulate the response of the Walker circulation to the exposure of the Sunda shelf due to lower sea level during the LGM.The models to be used in the study were also used to produce key paleoclimate simulations that will be discussed in the IPCC AR5 reports. Thus the evaluation of the performance of the different models will be very valuable to the climate research community.