Pliocene contrasted climate conditions in space and over time: A unique pollen dataset from the NW Mediterranean Region for comparison with climate models

A set of 62 Pliocene pollen records and reconstructed climate parameters across the Northwestern Mediterranean Region, together with palaeoclimate simulations from the IPSL earth system model, provide a unique opportunity to study the Pliocene, especially the early Piacenzian Cooling (ePC) and the mid-Piacenzian Warm Period (mPWP). Vegetation reconstructed from pollen records documents strong spatial contrasts in the area. It reveals a retreat of the subtropical broad-leaved evergreen forest to the advantage of Mediterranean sclerophyllous ecosystems. This study is a first attempt to compare observation-based data with model simulations in the Northwestern Mediterranean Region. It reveals substantial discrepancies with encouraging results, pointing out the need to expand the work of data – model comparisons to other regions. The mid-Piacenzian warm period appears to be an interesting past analogue for the ongoing anthropogenic global warming, including its regional impacts. We observe that two areas (Northern Catalonia and the Southern Alps–Liguria) were affected by increased precipitation during brief episodes in the mid-Piacenzian, while the Roussillon–Languedoc–Provence area experienced drier conditions. Such a spatial pattern seems comparable with the present-day context. The significance of ecosystems composed of some Cupressaceae ( Cupressus-Juniperus -type) is interpreted partially as subtropical forest, and partially as Mediterranean vegetation. This regional study provides valuable data and interpretations to improve the contribution of past records to such evaluations, and inspires future palaeoclimate simulations with finer resolution.