Climate dynamics of the last Millennium derived from cell structure measurements of pine and oak trees in the temperate lowlands of NE-Germany and N-Poland

根据政府间气候变化专门委员会(IPCC)的评估报告，全球变暖无疑正在发生。此外，区域和季节气候变化的动态将有很大不同。模型比较表明，全球部分地区和某些季节的气温稳定，在某些情况下甚至下降。为了更全面地了解这种特殊的区域和季节趋势，古气候学将注意力集中在长期气候重建上。基于树轮的温度重建是气专委报告所用数据库的主要部分。到目前为止的温度重建表明，在过去的几十年里，气温有所上升。然而，一个主要的批评是，所使用的大部分年轮年表来自生长在纬度或海拔极限附近的树木，例如阿尔卑斯山地区和斯堪的纳维亚半岛北部。对于所有超过500年的年轮年表来说，情况尤其如此。相比之下，在纬度或海拔范围内生长良好的树木所衍生的长期重建图则缺失。因此，它们不是IPCC数据库的一部分，我们认为这是古气候数据库中的一个关键缺口。例如，欧洲温带低地迄今还没有基于树木年轮的千年尺度温度重建。然而，初步研究表明，这种重建可能揭示出与高纬度和高海拔地区的长期趋势有很大不同的长期趋势，从而使人们对有关欧洲温带低地的大型半球和全球重建的代表性产生怀疑。数据库中的这一差距直到今天仍然存在，因为温带低地地点的树状气候学由于三个主要原因而受到干扰，即扩散的气候-生长关系，由于长寿命树木稀有而只有较短的年表，以及由于样本段长度较短可能造成低频信号的损失。这一困境可以通过分析树轮参数而不是宽度来解决，例如稳定同位素或细胞结构，但测量这些参数非常耗时。最近，我们开发了一种应用共聚焦激光扫描显微镜的新方法，它减少了获得细胞结构测量年表的努力。首先，分析表明，这些年表包含强烈的气候信号，表明欧洲温带低地气候重建的巨大潜力。因此，该项目的核心目标是编制德国东北部和波兰北部的细胞结构测量的百年年表，用于长期重建。随后的分析将通过气候模拟来研究气候动力学和基本模式，如北大西洋涛动。

According to the assessment report of the Intergovernmental Panel on Climate Change (IPCC) global warming is undoubtedly occurring. Moreover the dynamics of regional and seasonal climate changes will differ significantly. Model comparisons indicate that some parts of the globe and some seasons experience stable or in some cases even declining temperatures. In order to more comprehensively understand such particular regional and seasonal trends, palaeoclimatology directs its attention towards long-term climate reconstructions. Tree-ring based temperature reconstructions form the major part of the data base used for the IPCC report. Temperature reconstructions so far indicated a rise in temperatures during the last decades. One major criticism, however, is that the bulk of the tree-ring chronologies used were from trees growing near the latitudinal or altitudinal limits, e.g., Alpine regions and northern Scandinavia. This is especially true for all tree-ring chronologies longer than 500 years. In contrast, long-term reconstructions derived from trees growing well within their latitudinal or altitudinal limits are missing. Thus they are not part of the IPCC data base, which we believe is a crucial gap in the palaeoclimate database. For instance, no tree-ring-based temperature reconstructions of millennial scale are available as yet for the temperate lowlands in Europe. Preliminary studies, however, indicate that such reconstructions may reveal long-term trends that substantially differ from those obtained for the high latitudes and altitudes, thus leaving doubts concerning the representativeness of large hemispherical and global reconstructions concerning the temperate lowlands in Europe. This gap in the data base still exists until today because dendroclimatology at temperate lowland sites has been upset for three main reasons, i.e., diffuse climate-growth relationships, only short chronologies because long-living trees were rare and the potential loss of low-frequency signals due to short sample segment lengths. This dilemma can be solved by analysing tree-ring parameters, other than width, e.g., stable isotopes or cell structures, but measuring these parameters is very time-consuming. Recently, we have developed a new method applying confocal laser scanning microscopy which reduces the efforts for obtaining chronologies of cell-structure measurements. First analyses have shown that such chronologies contain strong climate signals indicating the great potential for climate reconstructions for the temperate lowlands in Europe. Therefore, the core objective of this project is to develop multi-centennial chronologies of cell-structure measurements for NE-Germany and N-Poland, which will be utilized for long-term reconstructions. Subsequent analyses will examine the climate dynamics and underlying modes, such as the North Atlantic Oscillation by means of climate simulations.