MAARTEN KROL is professor Air Quality and Atmospheric Chemistry at Wageningen University in the Netherlands. He also holds a position at the Institute for Marine and Atmspheric Research a Utrecht university and at the Netherlands Institute for Space Research SRON. After being trained as a theoretical chemist, he entered the field of atmospheric chemistry in 1992. He is involved in modelling the atmospheric composition, and studies subjects like air quality, climate change, the carbon cycle, and the oxidizing capacity of our atmosphere. As a member of the mission advisory group for sentinel 4/5 (MAG4/5) he is involved in planned missions to study the atmospheric composition from space. He is also director of the Buys Ballot Research school, a research network for PhD students that study physical aspects of the climate system. Since 2015 is member of the Earth Sciences group within the ESSC.