Fluctuations and changes in Africa’s climate are critical to people today and over millennia have had profound impacts on our ancestors. Jessica Tierney, recipient of the 2014 American Geophysical Union Macelwane Medal, uses novel geochemical (leaf wax) techniques to reconstruct past hydrology and climate changes in parts of the continent where other reliable records are limited, and where records of the past are vital for improving predictions of the future. Combining empirical and modelling approaches, this talk sheds new light on the timing, extent and causes of the early Holocene ‘Green Sahara’, and its rapid demise to the extreme arid conditions we are familiar with today.