Pre-industrial Common Era temperature fluctuations in South China inferred based upon bacterial tetraether lipids from Lake Poyang

Abstract

<p>Quantifying past temperature changes during the Common Era (the past 2000 years) is essential for assessing the rates, magnitudes, and consequences of different climate forcings on current warming and projecting future climate change. At present, however, the quantitative evaluation of temperature changes at multi-centennial-to-millennial timescales remains not well understood. In this study, we provide a high-quality mean annual temperature record for the past 2000 years based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) in a well-dated sediment core retrieved from Lake Poyang in the middle and lower reaches of the Yangtze River. Our results show an overall pre-industrial cooling trend in the Poyang Lake region, with clear temperature changes associated with the Medieval Warm Period (MWP) and Little Ice Age (LIA), consistent with local, regional, and global records. The centennial to millennial temperature fluctuations, particularly the pronounced cooling at approximately 1500 CE, generally agrees with changes in total solar irradiance, supporting the importance of solar activity in affecting pre-industrial temperature changes. Further comparisons with other biomarker-based quantitative temperature reconstructions revealed that the temperature offset between the MWP and LIA increased with latitude and elevation, suggesting that centennial-scale temperature fluctuations were amplified at higher elevations and latitudes during the past two millennia.</p>