Steffen completed a BSc in Chemical Engineering from the University of Missouri in 1970. The University of Florida awarded him an MSc in 1972 and a PhD in 1975. He is widely published on climate science. His research interests range over climate change and Earth system science issues, with a focus on sustainability. He has written on adapting land use to climate change, bringing human processes into the modeling and analysis of the Earth system, and the history of and future prospects for the relationship between the natural world and humans. Steffen has also been prominent in advocating along with Paul Crutzen the concept of the Anthropocene, and initiating along with Johan Rockström an international debate on planetary boundaries and the “safe operating space” for humanity.

Steffen served as science advisor to the Australian Department of Climate Change and Energy Efficiency. He has been a member of the advisory board of the Australian Bureau of Meteorology and worked with the Prime Minister’s Science, Engineering and Innovation Council. He was also on an advisory panel in Colorado with the National Center for Atmospheric Research.

Currently, Steffen is on the Science Advisory Committee of the APEC Climate Centre in Korea. He is honorary professor at the Copenhagen University’s Department of Geography and Geology and visiting researcher at the Stockholm Resilience Centre. He is the chair of the Federal Government’s Antarctic Science Advisory Committee, and advises the Australian Government in further roles as scientific advisor to the Department of Climate Change and Energy Efficiency, and as expert advisor to the Multi-Party Climate Change Committee. Steffen also sat on the Australian Climate Commission.

In 2011, he was the principal author of a government climate report, The Critical Decade, which advocated a tax should be placed on carbon.