Holocene seasonal temperature evolution and spatial variability over the Northern Hemisphere landmass

Abstract

The origin of the temperature divergence between Holocene proxy reconstructions and model simulations remains controversial, but it possibly results from potential biases in the seasonality of reconstructions or in the climate sensitivity of models. Here we present an extensive dataset of Holocene seasonal temperatures reconstructed using 1310 pollen records covering the Northern Hemisphere landmass. Our results indicate that both summer and winter temperatures warmed from the early to mid-Holocene (~11–7 ka BP) and then cooled thereafter, but with significant spatial variability. Strong early Holocene warming trend occurred mainly in Europe, eastern North America and northern Asia, which can be generally captured by model simulations and is likely associated with the retreat of continental ice sheets. The subsequent cooling trend is pervasively recorded except for northern Asia and southeastern North America, which may reflect the cross-seasonal impact of the decreasing summer insolation through climatic feedbacks, but the cooling in winter season is not well reproduced by climate models. Our results challenge the proposal that seasonal biases in proxies are the main origin of model–data discrepancies and highlight the critical impact of insolation and associated feedbacks on temperature changes, which warrant closer attention in future climate modelling.

Holocene summer temperature record based on branched tetraethers in Northeast China

“…As for the mean annual temperature, brGDGTs records from Gushantun and Hani peat in NE China (Zheng et al, 2017, 2018) show a cooling trend during Holocene (Figure 4e and f). In addition, the MAT records based on terrestrial mollusk assemblages from North China (Dong et al, 2022) and based on an extensive pollen dataset from the Northern Hemisphere (Zhang et al, 2022) (Figure 5d) suggested a trend of warming during the early-middle Holocene and cooling during the middle-late Holocene. The brGDGTs records from Gushantun and Hani peat contradicted the records based on mollusk and pollen probably because the brGDGTs records from NE China carried more summer-inferred temperature information rather than the MAT.…”

“…(c) BrGDGTs-based mean annual temperature from Gushantun peat (Zheng et al, 2018). (d) Pollen-based annual temperature anomaly based on an extensive pollen dataset (Zhang et al, 2022). (e) Pollen-based mean warmest month (July) temperature sequence from Sihailongwan maar lake (Stebich et al, 2015).…”

“…The frozen condition restrains the growth of brGDGTs production bacteria (Zhu et al, 2021). Therefore, the MAT change trend during Holocene probably is warming during the early-middle Holocene and cooling during the middle-late Holocene as shown by Dong et al (2022) and Zhang et al (2022).…”

“…Pinus pollen percentage in Sihailongwan maar lake ((c) dark blue line, Stebich et al, 2015) and Lake Moon, which is the same lake with Kielguo crater lake ((d) light blue line, Wu et al, 2019), are proxy records for the variation of winter temperature (Wu et al, 2019). (e) Pollen-based annual temperature anomaly based on an extensive pollen dataset (Zhang et al, 2022). (f ) BrGDGTs-based mean annual temperature from Gushantun peat (Zheng et al, 2018).…”

“…(c) Pinus pollen percentage in Lake Moon, which as the same lake with Kielguo crater lake (Wu et al, 2019). (d) Pollen-based annual temperature anomaly based on an extensive pollen dataset (Zhang et al, 2022). (e) Reconstructed mean annual temperatures for 30°N-60°N from the Temperature 12 k database (Kaufman et al, 2020b).…”