P2C2: Estimating Climate Sensitivity from Temperature Reconstructions of the Last Glacial Maximum

这是一个利用末次冰盛期(LGM：21,000年前)的古气候重建和各种气候模型来评估平衡气候敏感性的项目。Schmittner-Boesch在2011年发表了一篇有影响力的论文，提出地质证据表明，气候对大气二氧化碳倍增1.4至2.8摄氏度的平衡敏感性低于IPCC4可能的2至4.5摄氏度范围，地质数据排除了对二氧化碳倍增非常高的敏感性。然而，还有几个问题尚未解决。例如，对末次盛冰期的几种不同的古气候重建产生了不同的全球气温平均降幅，这对灵敏度估计有很大影响。此外，古气候恢复的误差范围很大，这种误差对气候敏感性的影响需要更好地量化。最后，利用“降低复杂性”气候模型进行了初步研究。目前尚不清楚模型选择对结果的影响程度。该项目将进一步评估这些问题，方法是扩大研究中使用的古气候重建，并纳入末次盛冰期气候模式完全耦合模拟的结果。已经出版了几个新的大冰盖重建图，现在可以进行分析。有了新的CMIP5/PMIP3模型--具有特定的LGM边界条件/重建--现在可以通过使用CMIP5/PMIP3模型结果的输出来约束降低复杂性的模型，以更严格的方式执行平衡气候敏感性分析。该项目将支持俄勒冈州立大学的一名气候建模人员，他将与普林斯顿大学伍德罗·威尔逊公共和国际事务学院的统计学家合作。该项目包括对一名博士后研究员的指导和培训。

This is a project to use paleoclimate reconstructions of the Last Glacial Maximum (LGM: 21,000 years ago) and a variety of climate models to evaluate equilibrium climate sensitivity. Schmittner-Boesch published an influential paper in 2011 suggesting that the geological evidence implied an equilibrium climate sensitivity to a doubling of atmospheric CO2 of 1.4 to 2.8 C, lower than the IPCC4 likely range of 2 to 4.5 C and that the geological data ruled out very high sensitivities to doubling of CO2. However there were several issues left unresolved. For instance, several different paleoclimate reconstructions of the LGM produce different average reductions in global temperatures, which have a big effect of the sensitivity estimates. In addition, the range of error on the paleoclimate reconstructions is large and the effects of this error on the climate sensitivity need to be better quantified. Finally the initial study was performed with a "reduce-complexity" climate model. It was not clear the extent to which the result was affected by choice of model. This project will further evaluate these issues by expanding the paleoclimate reconstructions used in the study and incorporating the output from fully coupled climate model simulations of the LGM. Several new reconstructions of the LGM have been published and are now available for analysis. With access to the new CMIP5/PMIP3 models - with specific LGM boundary conditions/reconstructions - it is now possible to perform the analysis of equilibrium climate sensitivity in a more rigorous way by constraining the reduced-complexity model with output from the CMIP5/PMIP3 model results.This project will support a climate modeler from Oregon State University, who will collaborate with a statistician from the Woodrow Wilson School of Public and International Affairs at Princeton University. Mentoring and training of a postdoctoral researcher is included in the project.