„The GMOS-TRAIN winter school on modelling (6th Feb – 3rd Mar, 2023) was a great success. The Hereon experts on numerical modeling, Dr. Johannes Bieser and Dr. Martin Ramacher, hosted a four week winter school in Hamburg for eight early stage researchers (ESR) of the Marie Sklodowska Curie ITN. In the first week lectures on basic concepts of numerical modeling were held by the likes of Hans v. Storch and other renown experts in the field. This was followed by a 3 week hackathon, in which the ESRs applied these concepts to numerical modeling projects focusing on their research on mercury in the environment. After the 4 week course, the GMOS-Train annual meeting (6th Mar – 8th Mar 2023) was hosted by Hereon at the ZMAW in Hamburg. There, the ESRs presented their modelling studies with presentations and a poster session to about 30 participants. The highly promising modelling projects that started in the GMOS-TRAIN winter school are now being followed up, used for further research in the ESRs PhD research and prepared for publications.”