The El Niņo Southern Oscillation (ENSO) is the main source of interannual climate variability in the modern climate system. It is driven by a coupling between oceanic and atmospheric circulation in the tropical Pacific Ocean. The future of ENSO is subject to controversy as climate models provide different results as to its development in a warming world. Past reconstructions test the sensitivity of ENSO to different background conditions and climate forcings. This project aims to reconstruct ENSO variability during two key periods of the past: the last Glacial period and the Holocene, using giant clams (Tridacna sp.) from Papua New Guinea.