中国中世纪气候异常期温度的多尺度变化特征及区域差异

中世纪气候异常期（MCA,约950-1250年）是地球气候变化史上距今最近的长达数百年的典型温暖气候阶段,因此常被作为研究温暖气候及其影响与适应问题的主要历史相似型而备受瞩目。综合利用近年所发表的长度超过千年的中国4个区域（东北、西北、东中、青藏高原）高分辨率气候变化重建结果,结合历史文献的冷暖记载,采用集合经验模态分解的方法,对MCA期间中国温度的年代—多年代—百年尺度波动特征及其区域差异进行了分析。结果显示：从全国总体看,尽管在12世纪中后期存在数十年的相对冷谷,但在百年尺度上,10-13世纪是过去2000年中持续时间最长的显著暖期,且这一温暖期的起讫时间和温暖程度存在区域差异。各个区域温度变化序列的集合经验模态分解表明：在准30年尺度上,950-1130年间中国区域的温度波动位相基本同步;但在其后的1130-1250年,各区温度波动幅度变小,也存在位相差异。在准百年尺度上,各个区域均自10世纪前期起显著转暖,在MCA期间总体温暖背景下,出现2次冷波动;但除西北与东中部在整个MCA期间的百年尺度温度变化基本同步外,东北和青藏高原地区在MCA期间与其他区域存在显著的波动位相差异,且其温暖气候结束时间也较西北与东中部早40~50年。在百年以上尺度的趋势变化上,东北部和东中部2个区域均显示MCA和其后出现的小冰期（LIA）2个阶段温度差别较显著,而西北、青藏高原2个区域则均显示MCA和LIA的阶段温度差别不大。综合各种尺度的波动特征显示：MCA温暖程度在东中部与20世纪相当,在东北部较20世纪略低,在西北和青藏高原则显著低于20世纪。

Evidences and regional differences on multi-scales in Medieval Climate Anomaly over China

Medieval Climate Anomaly (MCA, 950-1250 A.D.) was the most recent and lasting hundreds of years warm period, which has aroused more attention from climate scholars, because MCA provided similar patterns to research on the impact and adaption of global and regional warming. In this study, we investigate the characteristics of temperature variation on inter-decadal to centennial scale during MCA in four regions (including Northeast, Northwest, Central-east and Tibetan Plateau) in China based on high-resolution temperature reconstructions longer than 1000 years and related warm-cold records from historical documents. Ensemble empirical mode decomposition method is used to analyze the cycles and fluctuations of four regional temperature series. The results show that the longest warm period during the last 2000 years occurred in the 10th-13th centuries over the whole country, although there existed several cold decadal intervals in the mid to late 12th century, different starting-ending warming periods and warming magnitudes in four regions. On quasi-30-year scale, regional temperature variations were similar during 950-1130 A.D. while their amplitudes became smaller and the phases did not match well each other in 1130-1250 A.D. On centennial scale, all the four regions began a warm period in the early 10th century and experienced two cold intervals during MCA. However, temperature variations of Northwest and Central-east kept in phase each other, but out phase in Northeast and Tibetan Plateau, where the ending of the warm period was earlier about 40-50 years than that of Northwest and Central-east. On multi-centennial scale, the mean temperature difference between MCA and Little Ice Age in Northeast and Central-east is significant, but did not appear in Northwest and Tibetan Plateau. Compared with the mean temperature of the 20th century, Central-east had a comparable warming level, Northeast was a little cooler, and both Northwest and Tibetan Plateau had significantly lower temperatures in MCA.