[3] From 1998 to 2004, he was the executive director of the International Geosphere-Biosphere Programme, a coordinating body of national environmental change organisations based in Stockholm.

[4] Steffen was also prominent advocating along with Paul Crutzen the concept of the Anthropocene,[8] and initiating along with Johan Rockström an international debate on planetary boundaries and the "safe operating space" for humanity and in 2018 on the possibility of uncontrolled climate evolution, which stirred considerable scientific debate (Hothouse Earth).

[9][10] Steffen served as science adviser to the Australian Department of Climate Change and Energy Efficiency.

[4] He was 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 honorary professor at the Copenhagen University's Department of Geography and Geology and visiting researcher at the Stockholm Resilience Centre.