Argumentative discourse aims at influencing the opinions, attitudes or behaviour of an interlocutor or an audience by making a statement credible or acceptable" (Adam, Les textes : types et prototypes, Paris : Nathan, 1992:116). There are however different ways of reaching this goal as will be shown in a collection of varied internet videos on climate change. Ecological discourses may be of an expositive nature, i.e. rely on explanations of processes, but can also be closer to exhortation as environmentalists wish to urge people and governments to act on the issue of global warming. A difference in multimodal complexity and/or intensity is observed between the two genres, which are expressed through various multimodal constructs involving gesture, object handling and use of diverse visual resources, but also different verbal strategies and prosodic variations (in terms of intonation, stress, rhythm, etc).