He is an author and scientific skeptic, with a special interest in environmental risk assessment, as well as in decision theory and belief revision.
He received a second PhD in practical philosophy at the University of Lund in 1999, and since 2000 he has been a professor at KTH; he became department head in 2005.
[4] He was also a member of two temporary Commissions on environmental policies appointed by the Swedish Government, expert advisor to a 1999–2000 Swedish government committee the kemikaliekommittén, and a member of the board of the MISTRA project New Strategy for the risk management of chemical substances.
Hansson has contributed to the development of belief revision theory, in particular, analysis of application of the AGM postulates.
He was the founding chairperson of the Swedish Skeptics (Vetenskap och Folkbildning),[10] and is still a board member and editor of the organisation's journal Folkvett.