Hans-Christen Hansson is professor in Air pollution at the department of Environmental Science, Stockholm University with a 40 year long carrier in science. His research focus on the life cycle of the atmospheric particles, especially how atmospheric particles influence the climate. Influence on health is also a concern, which drives his involvement connecting urban research with the regional focused research. In this he as been acting as advisor to the Swedish EPA and participated in expert groups e.g. within EMEP/CLRTAP. HC Hansson has an extensive international network through his participation in more than 15 major international projects and has been co-chair of ILEAPS (Integrated Land-Ecosystem-Atmosphere Process Study) a core project within Future Earth. He is also a member of the Swedish Royal Academy of Science National committee on Global Environmental Change and editor in chief for the open access peer-review international journal TELLUS B.