In the ENVRI-Hub NEXT project, environmental Research Infrastructures (RIs) collaborate to improve access to observation datasets related to Essential Climate Variables (ECVs) as defined by the Global Climate Observing System (GCOS). The main goal is to enable users from any Virtual Research Environment (VRE) to access, process and analyse ECV-related data from ENVRI RIs using ENVRI-Hub components in a simple and unified manner. Similar to other multidisciplinary environments, in practice, working on dataset discovery and access federation for the ENVRI RIs is challenging due to heterogeneous machine-to-machine services and diverse metadata and vocabularies for observed variables used in the source collections. To work towards a practical solution, an ECV Working Group was established within ENVRI-Hub NEXT. Test the ENVRI-Hub