Geir Braathen got his education at the University of Oslo, where he obtained his cand. scient. degree in 1980. He then spent one year at the LAboratoire de Spectrochimie Infrarouge et Raman (LASIR) of the CNRS in France. Back in Norway he obtained his dr. scient. degree in 1986 in the field of physical chemistry (molecular spectroscopy). He then spent two years at the University of California, Berkeley, as a post-doctoral fellow (funded through the Odd Hassel fellowship from the Norwegian Research Council). From 1988 to 2005 he worked as a senior scientist at the Norwegian Institute for Air Research (NILU).
From 2004 he was R & D Director at NILU.
At NILU Braathen had a particular responsibility for stratospheric ozone research. He is an expert on measurements and analysis of observational data on the stratospheric ozone layer. In particular, he worked on ozonesonde observations and he used such data to quantify the degree of ozone loss in the Arctic stratosphere.
He has been a member of the steering committee for the Network for the Detection of Atmospheric Composition Change (NDACC) since 1992 and was co-chair from 2004 to 2013.
From 2005 until 2019, Braathen worked as a senior scientific officer in the Research Department of the secretariat of the World Meteorological Organization in Geneva, Switzerland, responsible for the coordination of stratospheric ozone and solar UV radiation observations carried out in the Global Atmosphere Watch (GAW) Programme.
On his spare time he likes to go hiking, skiing or mountaineering. The camera is always part of the equipment, as he likes to capture photos of the beauty of nature.