Eocene to Oligocene terrestrial Southern Hemisphere cooling caused by declining pCO2

The greenhouse-to-icehouse climate transition from the Eocene into Oligocene is well documented by sea surface temperature records southwest Pacific and Antarctic margin, which show evidence of pronounced long-term cooling. However, identification a driving mechanism depends on better understanding whether this cooling was also present in terrestrial settings. Here, we semi-continuous record spanning middle to early (~41–33 million years ago), using bacterial molecular fossils (biomarkers) preserved sequence southeast Australian lignites. Our results that mean annual temperatures Australia gradually declined ~27 °C (±4.7 °C) during ~22–24 late Eocene, followed ~2.4 °C-step across Eocene/Oligocene boundary. This trend comparable other Southern Hemisphere, suggesting common mechanism, likely $$p{{\rm{CO}}_{2}}$$ . We corroborate these with suite model simulations demonstrating only including decline lead consistent our proxy record. data form an important benchmark for testing performance, sea–land interaction climatic forcings at onset major glaciation. Terrestrial Hemisphere through Eocene–Oligocene points decreasing atmospheric CO2 dominantly global change, according biomarker coals palaeoclimate modelling.