Mid-to-late Holocene temperature variability in southwestern China

Southwestern China has been a significant area for human development during the mid-to-late Holocene, with human activities such as pastoralism, dairy farming, population migration, and population expansion being well documented. Climate change is considered a crucial factor that has influenced these developments. However, the overall pattern of temperature variations during this period remains unclear. Here we present a well-dated, high-resolution, quantitative temperature reconstruction based on a branched glycerol dialkyl glycerol tetraether (brGDGT) proxy for the last ∼5000 years from a high-elevation peatland in southwestern China. Our record reveals a general warming trend during the mid-to-late Holocene. It also captures multicentennial-scale climate events, including the Medieval Warm Period (MWP) and the Little Ice Age (LIA). To better understand the pattern of mid-to-late Holocene temperature changes from existing paleoclimate records in southwestern China, we further compiled and analyzed 19 high-quality quantitative paleotemperature records in this region and the nearby Tibetan Plateau. The results reveal that temperature records from high-elevation sites (>3000 m above sea level) generally display an overall warming trend, whereas temperature records from low-elevation sites (<3000 m above sea level) generally show an overall cooling trend. We speculate that the reconstructed temperature records from low-elevation areas might be affected by human activities. In addition, we analyzed 9 records from a sub-region of southwestern China with adequate temporal-resolution and chronological controls to evaluate multicentennial-scale fluctuations over the past millennium. We find that most records show pronounced shifts during the MWP and LIA. Our results emphasized that human disturbances may affect the seasonal bias of reconstructed temperature, highlighting the necessity of carefully evaluating the effects of potential human influences on paleoclimate proxies.