Palaeo-seasonality of the last two millennia reconstructed from the oxygen isotope composition of carbonates and diatom silica from Nar Gölü, central Turkey

► Comparing δ18O from carbonates and diatoms allows insights into seasonality. ► Use of data from lake monitoring to help interpret down-core isotope variations. ► Severe winters inferred 301-801 AD, 921-1071 AD and 1821-1898 AD.