He is a former chief scientific adviser to the Ministry of Defence and Department of Trade and Industry (now Department for Innovation, Universities and Skills.
After completing his PhD, O'Nions took up a postdoctoral fellowship at the University of Oslo, before moving to lecture at the University of Oxford in 1971, Columbia University in 1975, University of Cambridge in 1970 and back to Oxford in 1995.
In 2000 he was appointed chief scientific adviser to the Ministry of Defence and then in 2004 became director general, science and innovation and chief scientific adviser to the Department of Trade and Industry (now Department for Innovation, Universities and Skills.
- Adviser, Nu Instruments Ltd, May 2008
- Director, Institute of Homeland Security, Imperial College, June 2008
- Non-executive director, Finmeccanica UK, October 2008
All three appointments were approved by ACOBA "subject to the condition that, for 12 months from his last day of service, he should not become personally involved in lobbying UK Ministers or Crown servants, including Special Advisers, on behalf of his new employer".
- Member of advisory board, Serco Defence, Science and Technology, July 2008. Approved by ACOBA "subject to a three-month waiting period from his last day of service and the condition that, for 12 months from the same date, he should not be personally involved in lobbying UK Ministers or Crown servants, including Special Advisers, on behalf of his new employer".
Joined the college in July 2008 to set up and direct a new Institute for Security Science and Technology. He succeeded Roy Anderson as rector in January 2010 and became president and rector in April 2012.
- Member, Council of Science and Technology, 1998 to 2000
- Trustee and then Chairman, Natural History Museum, 1996 to 2005
- Fellow, American Geophysical Union, 1979
- Member, Norwegian Academy of Science and Letters, 1980
- Fellow, Royal Society, 1983
- Honorary Fellow, Indian Academy of Sciences, 1998
- Fellow, Indian National Science Academy, 2001
- Honorary Fellow, Royal Academy of Engineering, 2005
- Geology, University of Nottingham
- PhD Earth sciences University of Alberta, Canada
- Holds honorary degrees from eleven universities
- Knighted for services to earth sciences in the 1999 Queen's Birthday Honours
- Past Rectors Imperial, accessed 25 November 2014
- Tenth Report 2008-2009 Advisory Committee on Business Appointments, accessed 25 November 2014
- Sir Keith O’Nions named Board Chairman of Cambridge Enterprise Enterprise.cam, 7 August 2014, accessed 25 November 2014