The challenge for the International Geosphere-Biosphere Programme (IGBP) in 1999 was how to integrate the evidence of humans transforming Earth’s functioning as a system into a coherent overview of global environmental change. The IGBP report Global Change and the Earth System: A Planet Under Pressure (2004) identified a dramatic mid-20th-century step-change in anthropogenic global environmental change, which would come to be called ‘The Great Acceleration’. ‘The Great Acceleration’ outlines the complex, multi-causal, system-level set of processes that have altered the Earth system, from domestication of land to human alterations of the atmosphere, hydrosphere, and biosphere. It also discusses tipping points that result in relatively rapid, non-linear, and potentially irreversible ‘step-changes’ in Earth’s climate system.