 Since large amounts of 16O water are being stored as glacial ice, the 18O content of oceanic water is high.Water up to 5 °C (9 °F) warmer than today represents an interglacial, when the 18O content of oceanic water is lower.A plot of ancient water temperature over time indicates that climate has varied cyclically, with large cycles and harmonics, or smaller cycles, superimposed on the large ones.