Internal feedbacks forced Middle Holocene cooling on the Qinghai-Tibetan Plateau

By Mingda Wang et al.

The nature of Holocene temperature changes is controversial because of the apparent discrepancy between global temperature reconstructions and climate modelling results. Here we present evidence indicating that the discrepancy can be attributed to the combination of seasonal biases in the proxy temperature records and insufficient understanding of the mechanisms within climate models. We obtained independently dated records of mean annual air temperature (MAAT) based on glycerol dialkyl glycerol tetraethers (GDGTs) from Bangong Co in the western Qinghai-Tibetan Plateau (QTP) and two loess-palaeosol sections in the northeastern QTP. One of the most prominent features in the composite MAAT record is the relatively cool Middle Holocene, ~2 °C cooler than the Early and Late Holocene. The MAAT variations are consistent with orbitally forced modelling results that show increasing regional temperatures since the Middle Holocene, but they contrast with global temperature reconstructions that mainly reflect summer temperature variations. Our findings suggest that changes in boreal summer insolation that led to variations in precipitation patterns and vegetation dynamics were the key factor modulating MAAT during the Holocene. Overall, our study sheds light on possible approaches to solving the Holocene temperature conundrum by considering internal feedbacks within the climate system.

The full (paywalled) article appeared on the Boreas website at https://onlinelibrary.wiley.com/doi/10.1111/bor.12531?af=R