Challenges and advances in soil tetraether-lipid-based temperature reconstruction in global arid and semi-arid regions: Insights from the pan-third pole
Science China Press
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Figure 1. Global distribution of soil GDGT sampling sites and Holocene loess–paleosol records from the Pan-Third Pole (purple shading). Panels A and B show sampling sites for bacterial brGDGTs and archaeal iGDGTs, respectively. Panel C shows the locations of Holocene temperature records.
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A new review in Science China Earth Sciences examines advances and challenges in reconstructing temperatures from soil microbial lipids across arid and semi-arid regions. Published in Chinese and English, it brings together Academician Fahu Chen’s team at the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, and collaborators from the National Research Center for Geoanalysis, Lanzhou University and the University of Pittsburgh. Drawing on evidence from the Pan-Third Pole, particularly the Tibetan Plateau and arid Central Asia, the review highlights the potential of combining bacterial and archaeal lipids to improve terrestrial temperature reconstructions.
Reliable temperature reconstructions are essential for understanding past climate and testing climate models. Proxy records extend beyond instrumental observations, yet their Holocene temperature histories remain difficult to reconcile with simulations. Over the past approximately 11,700 years, proxy records indicate early- to mid-Holocene warming followed by cooling, whereas simulations generally show sustained warming. Identifying the temperature signals recorded by different proxies is central to resolving this “Holocene temperature conundrum.”
Glycerol dialkyl glycerol tetraethers (GDGTs) are widely used paleotemperature proxies because of their widespread occurrence, structural stability and temperature sensitivity. They comprise bacterial branched GDGTs (brGDGTs) and archaeal isoprenoid GDGTs (iGDGTs). While brGDGTs are widely applied in terrestrial settings, the iGDGT-based TEX86 index, originally developed for marine environments, is increasingly being explored in soils.
The review traces soil brGDGT thermometry from MBT/CBT and MBT′/CBT to MBT′5ME, outlining the empirical calibration framework established using global surface-soil datasets (Figure 1). Expanding datasets have also exposed the limitations of relying on MBT′5ME alone in arid and semi-arid environments.
Climate-specific calibrations, machine learning and bias constraints are improving brGDGT thermometry. Meanwhile, studies across elevation and spatial gradients, supported by molecular ecological evidence, are extending TEX86 to soils and clarifying its temperature response where iGDGT sources are well constrained. The strengths of brGDGTs in humid environments complement the potential of TEX86 in some dryland soils, supporting their combined use (Figure 2). This approach could provide new temperature constraints for proxy–model comparisons and paleoclimate data assimilation.
Expanded sampling across the Pan-Third Pole has extended GDGT research into environmental endmembers characterized by low temperatures, aridity and strong seasonality. These studies reveal complex, regionally variable brGDGT temperature responses and identify temperature sensitivity in TEX86 in some soils where Thaumarchaeota dominate iGDGT production. Together, these findings help establish the regional basis for a dual-proxy approach.
However, divergent Holocene temperature histories from Pan-Third Pole loess–paleosol sequences reflect uncertainties also evident in modern soil studies. Whether GDGT records represent seasonal or mean annual temperatures, and air or soil temperatures, often remains unresolved. Non-temperature influences, response mechanisms and calibration applicability also require better constraints, limiting comparisons among records and with climate simulations.
The review calls for coordinated monitoring of air and soil temperatures and GDGT distributions, alongside integrated analyses of microbial communities, environmental factors and lipid responses. Combined with paleoclimate data assimilation and broader geographical testing of soil TEX86, these efforts could strengthen the mechanistic basis of terrestrial temperature reconstructions and help clarify the proxy–model discrepancies underlying the Holocene temperature conundrum.
Article references
Duan Y, Hao S, Gao Y, Zhou Y, Lu Y, Li Y, Werne J P, Sun Q, Chen F. 2026. Challenges and advances in soil tetraether-lipid-based temperature reconstruction in global arid and semi-arid regions: Insights from the Pan-Third Pole. Science China Earth Sciences, 69: 4071-4087.
Figure 2. Conceptual framework for the joint ecological and physiological controls on GDGT temperature responses
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©Science China Press
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Science China Earth Sciences
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