全新世中期中国气候格局定量重建

QUANTITATIVE CLIMATE RECONSTRUCTION IN CHINA DURING THE MID-HOLOCENE

古气候要素的定量化，是认识气候变化规律的关键节点之一。以往对于我国的古气候要素定量化重建，主要基于孢粉一气候的统计学方法。由于该方法难以有效区分温度、降水和大气CO2浓度等环境因子对植物生长的影响，因而导致重建结果可能存在不确定性。本次研究，我们基于植物生理过程、新一代古气候定量重建的植被反演方法，考虑环境因子对植被生长的影响，利用新完善的中国第四纪孢粉数据库中的孢粉数据，定量化重建了我国全新世中期（6±0．5ka14C）的古气候要素空间格局。结果表明，全新世中期我国年均温度比现在略高约0．7℃，东部区域增温明显，尤其是东北地区，而西北地区可能略有降温；最冷月温度增温较大，达约1℃，而最热月温度增温较小，为约0．5℃。全国年降水量整体比现在多约230mm，主要是夏季降水增多所导致，其中东部地区增加显著。上述结果揭示，全新世中期全球增温将有利于我国降水增加，并导致季节性温度变化明显。本次重建结果增强了与古气候模拟结果的可对比性。

Knowledge of quantitative palaeoclimates is a crucial for the evaluation of climate changes for the earth system. Previous quantitative palaeoclimate reconstruction in China generally used the modern statistic methods between pollen and climate data. The reconstruction methods are built upon the assumption that plant-climate interactions remain the same through time, and implicitly assume that these interactions are independent of changes in the seasonal climate and the atmospheric CO2. This assumption may lead to a considerable bias. In this study, an improved inverse vegetation model that based on a physiological process has been designed to quantitatively reconstruct past climates, with a new China Quaternary Pollen Database. During the mid-Holocene period, mean annual temperature in China were higher ca.0.7℃than present, especially in the Eastern China, but cooler in the northwest China. Winter temperature were generally higher ca. 1.0℃ than today, but summer temperature only higher ca.0.5℃ than present. Mean annual precipitation were wetter ca. 230mm than today, especially in the Eastern China, which was due to the increase of summer rainfall. Our results suggest that the precipitation maybe increase, while the seasonal temperature variation became significant with the global temperature warming. The new reconstructions therefore give a better agreement with PMIP simulations.