Carbon isotope fractionation during low temperature carbonization of foxtail and common millets

► Foxtail and common millet are ideal materials for palaeoclimate carbon isotope studies. ► δ13C trends of modern millets carbonized at varying temperatures were defined and explained. ► The observed 13C carbonization fractionation of only 0.2‰ in millets is much lighter than in wood. ► δ13C in carbonized millets can serve as an effective indicator for paleoclimatic reconstruction.