International audience.
The Roman Warm Period (from ≈300 BCE to ≈300 CE) is a climatic optimum, which had a key role in the development of the Roman civilization. This study provides new Mean Air Temperatures (MATs) inferred from the oxygen isotope composition of 80 bones and teeth apatite from 8 humans and 8 animals of the Gallic site of Th ́ezy-Glimont, Picardie, France, dated between the 3rd and 2nd century BCE. Various bones from the cephalic, axial and appendicular skeleton of three human individuals were sampled. All bones have similar phosphate δ18O values for each individual, showing that the oxygen isotope signal of phosphate groups may be homogeneously recorded in bones. The sampled individuals were assumed to drink water from the nearby Avre river collecting local meteoric waters. The MATs were reconstructed combining (1) oxygen isotope fractionation equations be- tween phosphatic tissues (δ18Op) and drinking water (δ18Ow), and (2) relationships between MATs and δ18Ow. Depending on the used MAT-δ18Ow relationship, the reconstructed MATs are 10.2 ◦C ± 1.4 ◦C and 10.5 ◦C ± 1.7 ◦C, which are comparable to present days (10.9 ◦C). This study shows that the Gallic civilization also experienced relatively high temperatures since the initiation of the Roman Warm Period.
