NOAA/WDS Paleoclimatology - Borgaonkar - Jangla - CDDE - ITRDB INDI024

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.

全球过往气候变化均表现出强烈的区域分异特征。为阐明其时空分布格局，本研究对过去1至2千年间7个大陆尺度区域的古温度序列进行了重建。几乎所有区域温度重建结果中最一致的特征为一条长期降温趋势，该趋势于19世纪末期终止。在年代际至百年尺度上，温度变率呈现出显著差异化的区域格局，各半球内部的相似性显著高于半球之间。并不存在可定义全球性中世纪暖期（Medieval Warm Period）或小冰期（Little Ice Age）的全球同步性年代际冷暖时段，但所有重建序列均显示，公元1580年至1880年间整体气候偏冷，部分区域在18世纪曾出现持续数十年的暖期。向这类冷期的气候转换在北极、欧洲与亚洲早于北美及南半球各区域。近期的升温逆转了长期降温趋势；在公元1971年至2000年期间，经面积加权平均的重建古温度较近1400年来的任何其他时段均更高。