Late Holocene brGDGTs-based quantitative paleotemperature reconstruction from lacustrine sediments on the western Tibetan Plateau

We present a quantitative mean annual air temperature (MAAT) record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from a sediment core from Xiada Co, an alpine lake on the western Tibetan Plateau (TP). The record indicates a relatively stable and warm MAAT until 2200 cal yr BP; subsequently, the MAAT decreased by ∼4.4°C at ∼2100 cal yr BP and maintained a cooling trend until the present day, with centennial-scale oscillations centered at ∼800 cal yr BP, ∼600 cal yr BP, and ∼190–170 cal yr BP. MAAT decreased abruptly at ∼500–300 cal yr BP and reached its minimum for the past 4700 years. We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past ∼5000 years. The results show divergent temperature variations, including a gradual cooling trend, a warming trend, and no clear trend. We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies, the length of the freezing season of the lakes, the choice of proxy-temperature calibrations, and chronological errors. Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance, clear seasonality, site-specific calibration, and robust dating, to better understand the processes, trends, and mechanisms of Holocene temperature changes on the TP.