Pollen-based Holocene quantitative temperature reconstruction on the eastern Tibetan Plateau using a comprehensive method framework

Quantitative climate reconstruction on long timescales can provide important insights for understanding the climate variability and providing valuable data for simulations. Unfortunately, the credibility of some attempts was hampered by incomplete reconstruction procedures. We here establish a comprehensive framework resting on high-quality Chinese modern pollen database, including modern pollen data screening, calibration set selection, major climate factor analysis, appropriate model selection, strict statistical assessment of results and ecological interpretation. The application of this framework to three high-resolution pollen records from the eastern Tibetan Plateau allows accurate quantitative inferences of Holocene temperature changes, which is the major control of regional vegetation. The results show that the mean warmest month temperature (MTwa) during the early Holocene was ca. 10.4 degrees C and reached the highest value at 8.5-6 ka BP (ca. 11 degrees C). The early and mid-Holocene (11-5 ka BP) warmth was followed by 1.2 degrees C temperature decrease, culminating in the coolest temperatures of the Holocene during the Neoglacial cooling. Superimposing on the general cooling trend, MTwa reveals a significant 500-yr periodicity with varying intensities through time, showing that warm (cold) intervals are in phase with solar maxima (minima) periods. This spectral similarity indicates a possible connection of multi-century scale climate fluctuations with solar forcing.