NOAA/WDS Paleoclimatology - European Alps, 755-2004 AD, maximum latewood density temperature reconstruction, European Larch, PAGES Euro-Med 2k Version

Annually resolved summer temperatures for the European Alps are described. The reconstruction covers the a.d. 755-2004 period and is based on 180 recent and historic larch [Larix decidua Mill.] density series. The regional curve standardization method was applied to preserve interannual to multicentennial variations in this high-elevation proxy dataset. Instrumental measurements from high- (low-) elevation grid boxes back to 1818 (1760) reveal strongest growth response to current-year June-September mean temperatures. The reconstruction correlates at 0.7 with high-elevation temperatures back to 1818, with a greater signal in the higher-frequency domain (r = 0.8). Low-elevation instrumental data back to 1760 agree with the reconstruction's interannual variation, although a decoupling between (warmer) instrumental and (cooler) proxy data before 1840 is noted. This offset is larger than during any period of overlap with more recent high-elevation instrumental data, even though the proxy time series always contains some unexplained variance. The reconstruction indicates positive temperatures in the tenth and thirteenth century that resemble twentieth-century conditions, and are separated by a prolonged cooling from 1350 to 1700. Six of the 10 warmest decades over the 755-2004 period are recorded in the twentieth century. Maximum temperature amplitude over the past 1250 yr is estimated to be 3.1C between the warmest (1940s) and coldest (1810s) decades. This estimate is, however, affected by the calibration with instrumental temperature data. Warm summers seem to coincide with periods of high solar activity, and cold summers vice versa. The record captures the full range of past European temperature variability, that is, the extreme years 1816 and 2003, warmth during medieval and recent times, and cold in between. Comparison with regional- and large-scale reconstructions reveals similar decadal to longer-term variability.

本数据集提供了欧洲阿尔卑斯山区逐年分辨率的夏季温度序列。该温度重建序列的时间跨度为公元755年至2004年，基于180条近现代与历史时期的欧洲落叶松（Larix decidua Mill.）密度序列。研究采用区域曲线标准化（regional curve standardization）方法，以保留该高海拔代用资料集（proxy dataset）中从年际到百年尺度的气候变率信号。对1818年（1760年）以来的高（低）海拔网格盒的器测数据（instrumental measurements）分析显示，树木生长对当年6-9月平均温度的响应最为显著。该重建序列与1818年以来的高海拔器测温度的相关系数为0.7，其中高频域信号更强，相关系数达0.8。1760年以来的低海拔器测温度数据与重建序列的年际变率较为吻合，但1840年之前存在器测数据（偏暖）与代用资料（偏冷）之间的解耦（decoupling）现象。该偏差幅度大于所有与近期高海拔器测数据重叠时段的偏差，尽管代用资料序列始终存在部分无法解释的方差。重建结果显示，公元10世纪与13世纪的夏季温度偏高，其水平与20世纪相当，而1350年至1700年的长期降温将这两个暖期分隔开来。公元755-2004年间最热的10个十年中有6个出现在20世纪。过去1250年间的最大温度振幅（temperature amplitude）出现在最热的1940年代与最冷的1810年代之间，估算值为3.1℃。不过，该估算结果受器测温度数据校准过程的影响。暖夏似乎与太阳活动（solar activity）高值时段相吻合，冷夏则反之。该重建序列完整记录了欧洲过去的温度变率范围，包括1816年与2003年这两个极端年份，中世纪及近现代的暖期，以及其间的冷期。与区域及大尺度温度重建序列的对比显示，二者在十年到更长时间尺度上的变率特征相似。