The 21st century is characterized by the increase of information technologies, whose environmental impacts are now well documented. The consequences of these impacts, their nature but also the difficulty for the users to identify them make IT services to be an interesting case study for environmental assessments. The proposed methodology aims at retrieving both local and global effects of a given IT activity, taking into account both the direct and indirect impacts. The final objective is to establish an environmental dashboard based on a set of indicators, in order to assess environmental impacts of a service-based activity at different scales.