Holocene temperature variability in China

The patterns and mechanisms of Holocene temperature variability in China remain highly controversial, possibly due to the lack of sufficient high-resolution records and few systematic compilations and reviews of published records. Here, we used branched glycerol dialkyl glycerol tetraethers (brGDGTs) to generate a Holocene mean annual air temperature (MAAT) record from Lake Yangzonghai (YZH) in southwest (SW) China. Our record, largely ruling out the effect of seasonal bias, displays a long-term cooling of ∼1.5 °C since 10 cal ka BP, indicating that the discrepancy of Holocene temperature records (such as long-term cooling vs warming trends) in China cannot be attributed to the seasonal bias in temperature proxies. We compiled 67 published Holocene temperature records from China. These temperature records exhibit a mathematically consistent pattern with a relatively warmer mid-Holocene and colder late Holocene in the Asian summer monsoon (ASM) domain, whilst records show a relatively colder mid-Holocene and warmer late Holocene in the westerlies domain. This spatial heterogeneity of Holocene temperature variability is attributed to the modulation of monsoon systems, including the warming effect of ASM and the cooling effect of the East Asian winter monsoon (EAWM). In the ASM domain, the dominant pattern with the relatively warmer mid-Holocene and colder late Holocene is primarily controlled by the persistent weakening of the warming effect of the ASM and the concurrent strengthening of the cooling effect of the EAWM during the mid-to-late Holocene. In the westerlies domain, the warming effect of the ASM disappears, the cooling effect of the EAWM is confined to the north of the Tibetan Plateau due to the blocking effect of the Tibetan Plateau. This dominant pattern with the relatively colder mid-Holocene and warmer late Holocene is driven by the increases in atmospheric greenhouse gases (GHG) radiative forcing and Northern Hemisphere Annual Insolation (NHAI) forcing during the mid-to-late Holocene.