Paolo Laj, born 1966, is senior scientist at Université-Grenoble-Alpes (France) and visiting professor at University of Helsinki (Finland) since 2015. Since more than 10 years, he is actively contributing to developing the in-situ component of the Earth Observation system, dedicated to the long-term observations of short-lived climate forcers, aerosol, cloud and reactive gases. He is one of the coordinators of the European Research Infrastructure ACTRIS (Aerosol, Cloud and Trace Gases Research Infrastructure) dedicated to integrating observations of short-lived species in Europe. He is currently chairing the Scientific Advisory Group on Aerosol of the Global Atmosphere Watch (GAW) of the World Meteorological Organization which overlook and coordinates the network of observing stations in the different WMo regions. One of the main tasks of his current responsibilities is to ensure sustainability of the current ground-based network for atmospheric composition, its interoperability with other networks and to promote usage of date by a wide community of users. Since 2017 he serves in the scientific advisory panel of GEO-6, Global Earth Outlook, organized by UNEP. Between 2010-2015 he served as director of the Laboratoire de Glaciologie and Geophyique de l’Environnement in Grenoble, one of the leading institutes for the studies of cold and polar regions. Paolo Laj has published more than 130 peer-reviewed scientific papers on subjects such as aerosol-cloud interactions, atmospheric composition trends and variability, aerosol formation.