A quantitative temperature reconstruction of the ‘Little Ice Age’ in southern China

We present a branched glycerol dialkyl glycerol tetraethers (brGDGTs)–based mean annual temperature reconstruction covering the last millennium from a subtropical lake in Guangxi Province, southern China (23°N). We demonstrate that the pattern and absolute values of mean annual temperatures reconstructed using the eastern African lake brGDGTs calibration based on the methylation of 5-methyl branched tetraethers index provided the most reliable and accurate temperature estimates from the site. The results resemble regional and Northern Hemisphere changes over this period. The pattern shows a general cool period between ca. AD 1450 and 1950, including cooling minima centred at ca. AD 1600, 1750 and 1900, coeval with the ‘Little Ice Age’ temperature fluctuations in the Northern Hemisphere, followed by a warming trend from the mid-20th century to the present. The results suggest that both solar forcing and high-latitude Northern Hemisphere climate fluctuations play a role in influencing the terrestrial temperatures in southern China, possibly on different timescales. In addition, our results support the hypothesis that changes of the East Asian summer monsoon are primarily driven by the land–sea thermal gradient change between terrestrial southern China and the Indo-Pacific Warm Pool regions during the last millennium, owing to external radiative and/or volcanic forcings.