CMG COLLABORATIVE RESEARCH: Development of Bayesian HierarchicalModels to Reconstruct Climate over the Past Millennium

曲棍球棒争议是对北半球在过去一千年中经历的平均表面温度变化的重建估计的科学争议。该项目由统计、科学计算、古气候代用物、温度场重建和气候建模方面的专家团队合作完成，目的是更好地评估过去温度重建的不确定性，如曲棍球棒图所示（该图显示了20世纪前的平缓，随后是过去100年的强烈变暖趋势）。曲棍球棒图表争议的社会政治意义集中在它被用作明确的、人为造成的全球变暖的证据的一部分。更广泛的社区争议的几个方面集中在对统计方法和用于创建图表的数据集的有效性的批评和辩护上。这项工作将寻求将几个已知具有不同时间特征和不确定性的代用气候记录合并到使用贝叶斯层次模型（BHM）的古温度重建中。BHM框架有利于将代理数据（如树木年轮宽度）中的观测误差与潜在的感兴趣的物理过程（如过去的地表温度）隔离开来，从而改善上一千年的气候重建。

The hockey stick controversy is a scientific dispute over reconstructed estimates of the mean surface temperature changes experienced in the Northern Hemisphere over the past one thousand years. This project is a collaboration between a team of experts in statistics, scientific computation, paleoclimate proxies, temperature field reconstruction, and climate modeling to better evaluate the uncertainty of past temperature reconstructions, as exemplified by the hockey stick graph (which shows an arguably flat pre-20th century followed by a strong warming trend over the past 100years). The socio- political significance of the controversy over the hockey stick graph centers on its use as part of the evidence for unambiguous, anthropogenically caused, global warming. Several aspects of the broader community dispute centered on criticism and defense of both the statistical methodologies and the validity of data sets used in creating the graph. This work will seek to incorporate several proxy climate records, which are known to have differing temporal characteristics and uncertainties, into paleotemperature reconstructions by combining their information using Bayesian Hierarchical Models (BHM). A BHM framework is favorable in isolating observational errors in proxy data (e.g. tree ring widths) from the underlying physical processes of interest (e.g. past surface temperature) thus improving climate reconstructions of the last millennium.