During that time, he also served as a visiting professor at the Academy of Administrative Sciences in Speyer, and consulted several countries on development policy, among them Egypt, Brazil and Jordan.

In 1987, Töpfer became Federal Minister for the Environment, Nature Conservation and Nuclear Safety under Chancellor Helmut Kohl.

Among the milestones of his eight-year tenure are a number of important environmental agreements, including the Cartagena Protocol on Biosafety and the Stockholm Convention on Persistent Organic Pollutants.

As director of UNEP, he had a key role in gauging and attempting to remedy the environmental costs of the 2004 Asian tsunami.

From 2013 Töpfer headed the project "DEMOENERGY – The Transformation of the Energy System as the Engine for Democratic Innovations"[4] together with Claus Leggewie and Patrizia Nanz (both Institute for Advanced Study in the Humanities Essen, Germany).