Amongst Norwegians he is known as "the voice from Africa",[2] through his job as news correspondent, based in Harare 1990–1994 and Cape Town 2002–2006.

After two years as adviser to Salva Kiir, the president of South Sudan, Kristiansen was Communications Officer for ACT Alliance by World Council of Churches in Geneva from 2006 to 2008.

Kristiansen openly criticized the United Nations system for being inefficient in the South-Sudan conflict.

He has introduced "constructive journalism" as a tool for changing journalist's work in a solution oriented direction.

Kristiansen was married to the South African Sharon Coetzee and lived both in Oslo and Cape Town.