Earth system science (ESS) is now over 30 years old. It is an interdisciplinary field originating in various environmental sciences, such as climatology and ecology. It has grand, integrative ambitions. It aims to understand and, where possible, predict continuities and changes in the relationships between the various “systems” that together govern the character of Earth surface phenomena. Originating in the United States, ESS is now an international enterprise with practitioners in Australia, Britain, Germany, Sweden, and elsewhere. Over time it has extended its reach beyond complex biophysical systems to incorporate the human drivers of, and responses to, global environmental change. Geographers have been involved in ESS since the 1990s, though some have been critics – with many geographers simply ignoring it. ESS is now in an important new phase, given that humans appear to be altering the Earth system in unprecedented ways. Interesting questions arise as to what sorts of contributions geographers will in future make to the enterprise.