COHMAP -- Cooperative Holocene Mapping Project

评估我们对气候系统的了解的一种方法是将过去气候的模型模拟与根据那些时间段可用的数据重建的气候进行比较。这是COHMAP项目(合作全新世测绘项目)的方法，该项目是一个多机构(布朗、哥伦比亚、明尼苏达、俄勒冈和威斯康星州)的工作，重点是研究过去18,000年的气候。这一时间间隔包括最后一次冰盛期、冰川期的终止和现在的全新世间冰期。研究人员正在根据花粉、湖泊水位和海洋浮游生物重建气候。全球数据集以3000年为间隔组织，包括冰盖高度区域、浮游生物化石、花粉和植物微化石的分布，以及湖泊水位的状况。该项目包括用国家大气研究中心的社区气候模型模拟全球气候模式的平行工作。这些模拟实验是气候的“快照”，时间间隔为3000年，时间跨度为1.8万年，并纳入了地球轨道参数变化和冰盖高度和面积等缓慢变化的边界条件的影响。未来几年的拟议工作包括(1)完成对观测到的古气候的全球分析并与最近的数值模拟实验进行比较，(2)启动海洋模型的新工作并将模拟与浮游生物化石分布进行比较，(3)测试模式模拟对过去18,000年来伴随气候变化的大气二氧化碳和气溶胶变化的敏感性；(4)解释来自北美、北大西洋和欧洲的数据，以定量重建过去的气候。这项工作应有助于改进对冰川/间冰期(即大范围)气候变化动态的理解和理论，对气候模型的优点和缺点有更好的认识，并对生物圈和气候之间关系的性质有新的认识。

One method to evaluate our understanding of the climate system is to compare model simulations of past climate with reconstructions of the climate from the data available for those time periods. This is the approach of the COHMAP project (Cooperative Holocene Mapping Project), a multi-institutional (Brown, Columbia, Minnesota, Oregon and Wisconsin) effort focused on examination of the climate of the last 18,000 years. This time interval encompasses the last glacial maximum, the termination of the glaciation, and the present Holocene interglacial. The investigators are reconstructing climate from pollen, lake levels, and marine plankton. The global data sets are organized in 3,000 year intervals and include ice-sheet height area, distributions of fossil plankton, pollen and plant microfossils, and status of lake levels. The project includes a parallel effort to simulate the global patterns of climate with the Community Climate model of the National Center for Atmospheric Research. The simulation experiments are "snapshots" of the climate at 3,000 year intervals spanning the same 18,000 year period and incorporating the effects of changes in earth's orbital parameters and slowly changing boundary conditions such as ice- sheet height and area. Proposed work over the next several years includes (1) completion of global analysis of the observed paleoclimate and comparison with recent numerical simulation experiments, (2) initiation of new work with ocean models and comparison of simulations with fossil plankton distributions, (3) test the sensitivity of the model simulations to variations in atmospheric carbon dioxide and aerosol that have accompanied climate changes over the past 18,000 years, (4) intrepretation of data from North America, North Atlantic, and Europe for quantitative reconstructions of past climates. This work should lead to an improved understanding and theory of the dynamics of glacial/interglacial (i.e., large scale) climatic change, to an appreciation of the strengths and weaknesses of climate models, and to new insights about the nature of the relationships between the biosphere and climate.