The Helmholtz Climate Initiative REKLIM (Regionale Klimaänderungen/Regional climate change) is a consortium of nine research centres within the Helmholtz Association. REKLIM is using its unique combination of competence in regional observations and process studies (in situ observations, airborne and satellite remote sensing) coupled with model simulations to improve regional and global climate models, which provide a solid basis for climate-related decision support. Moreover, global climate simulations are used to determine the effects of climate variability and change on the regional scale with improved modelling tools for attribution and impact studies. On the other hand, process modules and parameterisations from these regional studies serve to improve global climate models. The Climate Initiative will facilitate various scientific opportunities for improving knowledge of the regional Earth System, in particular with respect to impacts. Via the Helmholtz Regional Climate Offices and the Climate Service Centre policymakers and other decision makers will be supported in assessing risks and opportunities and designing mitigation and adaptation strategies.