Abstract. This paper presents the ’Media Watch on Climate Change’, an interactive Web portal that combines a portfolio of semantic services with a visual interface based on tightly coupled views. The interface enables users to access a repository of environmental knowledge, built by crawling about 300,000 news media articles in weekly intervals. Tagging services annotate each article to create a contextualized information space. A system component for automatically extending ontologies helps structure the knowledge repository, and feeds an ontology-based visualization module. The Web portal is intended to facilitate the access of complex datasets, help users navigate large collections of Web documents based on similarity, geospatial context and underlying concept, and provide annotations via standardized interfaces for third-party applications. 1 Motivation The widespread acceptance of three-dimensional virtual globes such as Google Earth and NASA World Wind advances the vision of ...