He is a climate change expert and researcher at the Australian National University Climate Change Institute, where he was also the inaugural director (2008-2012). His other positions have included;

• Commissioner at Australia’s disbanded Climate Commission
• Councillor at Australia’s independent Climate Council.
• Senior Research Fellow at the Stockholm Resilience Centre
• Executive Director of the International Geosphere-Biosphere Program in Stockholm (1998-2004).

His authored books and articles include;

• “A Safe Operating Space for Humanity,” Nature 461, 2009, 472-475 – in which he was the second lead author after SRC director Johan Rockström to introduce the seminal concept of planetary boundaries
• The Crucial Decade (2011) – for which he was the principal author of the government climate report
• Planetary Boundaries: Guiding Human Development on a Changing Planet” (Science, 13 Feb 2015, 1286-1287),
• “The Trajectory of the Anthropocene: The Great Acceleration” (The Anthropocene Review, 2:1, 2015, 81-98), a remarkable dashboard of 24 indicators on environmental and socio-economic trends—most of them moving sharply upward in recent decades.