Understanding how the Earth's climate has changed in the past is critical to understanding present and future climate change. My research focuses on climate variability on human timescales, specifically the El Niño Southern Oscillation (ENSO). ENSO is the largest source of interannual climate variability and has profound impacts on human societies. In my research, I look at how ENSO has changed in the past at at the sub-centennial, millennial, and on orbital or glacial-interglacial timescales over the past 1000, 10,000 and 100,000+ years. Deep-sea sediments are valuable archives of past ocean conditions. We can reconstruct past ocean states by examining the geochemistry of the preserved shells (or tests) of tiny creatures called foraminifera preserved in these sediments or by looking at changes in organic molecules left by phytoplankton. These geochemical clues allow us to observe past ocean conditions and to help us better understand the climate system and the complex and varied relationship between overall climatic conditions and climate variability.