The legal field of Climate Change Litigation is in constant motion. The German Constitutional Court’s decision from March 2021 has now given rise to a new category of climate-related lawsuits: Private individuals filed lawsuits against companies that are among the largest greenhouse gas emitters in order to intensify the companies’ climate protection obligations. This article analyzes whether these horizontal climate actions can be successful under German private law. Further, the lawsuits are put in an international context, comparing them to the famous Shell case from the Netherlands and examining whether the Aarhus Convention is going to influence the judicial assessment of the lawsuits.