Description: The Pliocene is often regarded as a suitable analogue for future climate, due to an overall warmer climate (2-3 °C) coupled with atmospheric CO2 concentrations largely similar to present values (∼400 ppmv). Numerous Pliocene sea surface temperature (SST) records are available, however, little is known about climate in the terrestrial realm. Here we generated a Pliocene continental temperature record for Northwestern Europe based on branched glycerol dialkyl glycerol tetraether (brGDGT) membrane lipids stored in a marine sedimentary record from the western Netherlands. The total organic carbon (TOC) content of the sediments and its stable carbon isotopic composition (δ ^13^C~org~) indicate a strong transition from primarily marine derived organic matter (OM) during the Pliocene, to predominantly terrestrially derived OM after the transition into the Pleistocene. This trend is supported by the ratio of branched and isoprenoid tetraethers (BIT index). The marine-terrestrial transition indicates a likely change in brGDGT sources in the core, which may complicate the applicability of the brGDGT paleotemperature proxy in this setting. Currently, the application of the brGDGT-based paleothermometer on coastal marine sediments has been hampered by a marine overprint. Here, we propose a method to disentangle terrestrial and marine sources based on the degree of cyclization of tetramethylated brGDGTs (#rings) using a linear mixing model based on the global soil calibration set and a newly developed coastal marine temperature transfer function. Application of this method on our brGDGT record resulted in a 'corrected' terrestrial temperature record (MATterr). This latter record indicates that continental temperatures were ∼12-14 °C during the Early Pliocene, and 10.5-12 °C during the Mid Pliocene, confirming other Pliocene pollen based terrestrial temperature estimates from Northern and Central Europe. Furthermore, two colder (Δ 5-7 °C) periods in the Pliocene MATterr record show that the influence of Pliocene glacials reached well into NW Europe.

Description: Despite widespread use of branched glycerol dialkyl glycerol tetraethers (brGDGTs) for paleo-temperature reconstruction, no global calibration for their application in lakes has been generated since improved analytical methods have allowed for the separation of the structural isomers [Hopmans et al., 2016]. This is a substantial obstacle for the application of this tool as soil calibrations underestimate temperature values when applied to lake sediments. In order to generate a global calibration, we present a comprehensive dataset (N = 272) of lacustrine brGDGT distributions, consisting of both new and previously reported samples [Boldt et al., 2015; Dang et al., 2018; 2016; Li et al., 2017; Stefanescu et al., 2021], spanning a wide range of geographical locations. In addition, we compiled environmental information from these locations through in situ measurements [Li et al., 2017] and literature search for pH, conductivity, and nutrient content. For parameters such as mean annual air temperature (MAAT), temperature of months above freezing (MAF), mean annual precipitation (MAP), we estimated values from either the CRU [Osborn and Jones, 2014] or PRISM [https://prism.oregonstate.edu/] products depending on the location. Our new calibration [Martínez-Sosa et al., 2021] facilitates the use of lacustrine brGDGTs to reconstruct continental temperatures, a vital piece of information for understanding past climates.