Beginning of the Miocene Climatic Optimum in Central Europe in sediment archive of the Most Basin, Czech Republic

represents a time of global warming within the persistent Cenozoic cooling (Zachos et al. 2001). The MCO brought thermophilic vertebrate species into central Europe (Böhme 2003), and was terminated by an abrupt return to global cooling. In spite of considerable research efforts, climate evolution in the pre-MCO and early MCO periods has not been fully understood. The southern polar ice cap (Antarctic Ice Sheet, AIS) was considerably reduced during the MCO (Gasson et al. 2016, Levy et al. 2016), perhaps due to a coincidence of particular paleogeographic (Gasson et al. 2016) and orbital settings (De Vleeschouwer et al. 2017), and possibly acting in coincidence with long carbon cycles (Liebrand et al. 2016, Valero et al. 2016). The global pre-MCO climate could also have responded to some specific, yet unidentified trigger(s). A volcanic hypothesis was proposed (Courtillot & Renne 2003), tested, rejected based on a critical discussion on Ar-Ar dating precision (Barry et al. 2010, Armstrong McKay et al. 2015), and finally revoked after new dating and upon addressing all uncertainties of the Miocene time scales (Kasbohm & Schoene 2018). An increase in atmospheric CO2 was assumed to have been the MCO trigger; evidence for this was searched for in