The purpose of this research project is based on three fundamental aspects: <p>1. To enrich the historic knowledge about an increasingly important issue of sociological and public interest.</p><p>2. Environmental phenomena have suffered several transformations of classification, which are important to understand, not only in terms of their current, urgent and novelty dimensions, but also as facts that frequently hide their true background factors.</p><p>Environmental phenomena, in addition to the spontaneous way through which they are identified, often result from processes whose identification will be very useful to better understand their current character. </p><p>3. To carry out a precise chronology of events will be extremely important to assess the meanings disseminated by the media and to understand its current dynamics in Portuguese public opinion.</p>