Data_Sheet_2_Centennial-Scale Temperature Change During the Common Era Revealed by Quantitative Temperature Reconstructions on the Tibetan Plateau.xlsx

Quantitative palaeotemperature reconstruction is crucial for understanding the evolution of Earth’s climate and reducing uncertainty in future climate predictions. Clarifying the temperature change over the Tibetan Plateau (TP) during the Common Era is critical because it plays a vital role in the prediction of cryosphere changes in such regions under a future warming climate. In this paper, we report a comprehensive synthesis of currently available quantitative temperature records to refine the temperature history of the TP during the Common Era. To date, Common Era quantitative temperature reconstructions are sparse and mainly concentrated in the northeastern TP. Considering seasonal bias of the available quantitative temperature reconstructions, three different composite temperature records for TP were derived, namely the “Standardization” composite, the “Mean annual air temperature anomaly” composite, and the “Mean summer temperature anomaly” composite individually. All the integrated temperature series reveal the Medieval Climate Anomaly and the Little Ice Age, but the start and end timings of these multi-centennial-scale periods and their temperature amplitudes differ. There is strong seasonality in temperature variations on this high plateau, and the 20th century warming was characterized by rapid winter temperature increases, while summer temperatures displayed weak variations. Spatial analysis suggests a relatively consistent signal marking a warm TP during 600–1400 CE and a cold plateau during 1400–1900 CE. Large-scale trends in temperature history for the TP resemble those for China and the Northern Hemisphere. Many factors, such as seasonality of temperature proxies, might lead to uncertainty in the reconstructed series. The results highlight that it is of crucial importance to develop more seasonal temperature reconstructions to improve the reliability of quantitative paleoclimatic reconstructions based on geological records across the TP.

定量古温度重建（quantitative palaeotemperature reconstruction）对于理解地球气候演化、降低未来气候预测的不确定性至关重要。明确公元纪年（Common Era）期间青藏高原（Tibetan Plateau, TP）的温度变化尤为关键，因为这对未来变暖气候背景下该区域冰冻圈变化的预测具有重要意义。本研究综合整理了当前已公开的定量温度记录，以细化公元纪年期间青藏高原的温度演化历史。截至目前，公元纪年阶段的定量温度重建数据较为匮乏，且主要集中于青藏高原东北部区域。考虑到现有定量温度重建结果存在季节偏差，本研究分别构建了三类不同的青藏高原温度合成序列：即"标准化"合成序列、"年平均气温距平"合成序列以及"夏季平均气温距平"合成序列。所有整合后的温度序列均揭示出中世纪气候异常期（Medieval Climate Anomaly）与小冰期（Little Ice Age）的存在，但这些多年代际尺度气候阶段的起止时间以及温度振幅均存在差异。该高原的温度变化存在显著的季节特征：20世纪变暖以冬季温度快速升高为典型特征，而夏季温度波动相对微弱。空间分析结果显示，存在较为一致的温度信号：公元600–1400年青藏高原处于偏暖状态，而1400–1900年则整体偏冷。青藏高原温度演化的大尺度趋势与中国及北半球的温度趋势较为相似。诸多因素（如温度代用指标（temperature proxies）的季节特征）可能会导致重建序列存在不确定性。本研究结果表明，构建更多基于季节分辨率的温度重建序列，对于提升青藏高原区域基于地质记录的定量古气候重建结果的可靠性至关重要。