Reconstructions of ancient partial pressures of carbon dioxide (pCO2) provide a window into Earth’s past climate and are essential for understanding the future impacts of anthropogenic carbon cycle perturbations. Direct measurements taken from air bubbles within ice cores constitute the most robust carbon dioxide record but these are only able to span the last ~800 ka. Beyond these measurements, reconstructions rely on the use of proxy methods. The aim of my research  is to refine the phytane-based pCO2 proxy and apply it to periods of key climatic change.