NOAA/WDS Paleoclimatology - Brauning - Mainling - JUTI - ITRDB CHIN044

Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period ad 1971-2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.

全球既往气候变化呈现出强烈的区域分异特征。为阐明其时空格局，本研究对过去1至2千年间的7个大陆尺度区域开展了过去温度序列重建工作。几乎所有区域温度重建结果中最一致的特征为长期降温趋势，该趋势于19世纪末期终结。在数十年至百年尺度上，温度变率呈现出显著的区域分异模式，两个半球各自内部的相似性高于半球之间的相似性。并不存在可定义全球性中世纪暖期或小冰期的全球同步数十年尺度暖/冷时段，但所有重建结果均显示，公元1580年至1880年间整体处于偏冷状态，部分区域在此期间被18世纪的暖期十年段所打断。向偏冷状态的转型在北极、欧洲和亚洲发生的时间早于北美或南半球各区域。近期的变暖逆转了长期降温趋势；在公元1971-2000年期间，经面积加权平均的重建温度较近1400年来的任何其他时期均更高。