欧亚大陆中世纪暖期与小冰期温度变化的区域差异分析

REGIONAL DIFFERENCES FOR TEMPERATURE CHANGES IN MEDIEVAL WARM PERIOD AND LITTLE ICE AGE OVER EUROPE AND ASIA

根据集成多来源代用资料新建的欧洲过去1500年和亚洲过去1200年温度变化数据集,采用旋转经验正交函数分解方法将欧亚大陆划分为11个温度变化区;分析了各区在中世纪暖期和小冰期期间的显著温暖、寒冷时段和温度变幅以及中世纪暖期以来各区的百年最大升温速率。结果显示:1)在800~1350年间欧亚大陆各区均存在显著的温暖时段,但其起讫时间及暖峰出现年代和温暖程度却存在显著差异;其中欧洲、亚洲中部各区多始于9世纪前期,亚洲东部各区则多始于10世纪中前期,印度南部最迟(始于13世纪),且多数区域曾被其间的多年代际转冷而分割为2~3个温暖时段;偏暖区域最多的时段为1001~1020年,11个区域中有9个显著偏暖;温暖程度最显著的区域出现在欧洲北部和亚洲中部及东亚东部,其暖峰的年代温度距平皆达相应区域20世纪最暖10年的一半以上。2)在1400~1900年间欧亚大陆各区均存在显著的寒冷时段,尽管其起讫年代也存在差异,但各区寒冷时段出现的时间较中世纪暖期更为同步,其中1581~1610年所有11个区均显著寒冷,1830s也有10个区域表现为气候寒冷。寒冷程度最显著的区域出现在欧洲西部、亚洲中部及东亚,其冷谷年代的温度皆比过去千年各区平均温度低1.5倍标准差以上。3)20世纪增暖在欧亚大陆的所有区域几乎同步,且多数区域现代暖期的百年最大升温速率高于此前至中世纪暖期。上述区域差异可能是因历史冷、暖期主要受太阳、火山活动和气候系统内部变率等自然因素驱动,而20世纪暖期则受人为导致的温室效应增强主控。然而,受代用资料对温度变化响应的时空敏感度不一和时空分布不均等影响,现有研究结果仍存在显著不确定性。

Investigating the regional characteristics of temperature changes during the Medieval Warm Period(MWP)and Little Ice Age(LIA)can help to understand the spatial differences of Current Warm Period(CWP)and assess it in the context of the past millennium.Based on the latest gridded temperature reconstructions in Europe and Asia from multi-proxies over the past 1500 and 1200 years,Europe and Asia are divided into 11 sub-regions by rotated empirical orthogonal function method.We analyzed the characteristics of temperature change over MWP and LIA,including significant warm and cold periods and magnitude.We also compared the maximum 100-year warm rate from MWP to CWP.The main conclusions are as follows:(1)Significant warm periods exist in all regions of Europe and Asia between 800 A.D.and 1350 A.D.,while there are differences in their durations,time and anomaly of the warm peaks.The starting time of MWP is the earlier 9 th century for regions in Europe and Central Asia,the first half of the 10 th century for regions in East Asia,and the 13 th century for South India.The MWP is separated into 2~3 warm periods by multi-decadal cooling intervals for most regions.The warmest period is during 1001~1020 A.D.when 9 out of 11 regions have significantly warm anomalies.The temperature of the warmest decade in MWP is higher than half of that in the 20 th century for North and West Europe,Central Asia and east part of East Asia.(2)Significant cold periods also exist in all regions of Europe and Asia between 1400 A.D.and 1900 A.D.Although there are differences in their time and anomaly of the cold valleys,the coherence of temperature change in LIA is better than MWP.All 11 regions have significantly cold anomalies in 1581~1610 A.D.and 10 of them have significantly cold anomalies in 1830 s.The temperature of the coldest decade in LIA is lower than-1.5 standard deviations of the past millennium for West Europe,Central Asia and East Asia.(3)The coherence of regional warming is great in the 20 th century and the 100-year warming rate in CWP is higher than that between MWP and pre-CWP for most regions.(4)The regional difference of temperature change could be mainly attributed to the mechanism driven by different external forcings.The warming in CWP is due to emission of anthropogenic greenhouse gases.The temperature changes in MWP and LIA are dominated by solar and volcanic activities and associated changes of internal variability in climate system.However,there are still uncertainties in the current results due to the inconsistent spatial and temporal sensitivity and uneven distribution of climate proxies.More works are needed to address these problems in the future.