Latent Dirichlet allocation (LDA) topic models are increasingly being used in communication research. Yet, questions regarding reliability and validity of the approach have received little attention thus far. In applying LDA to textual data, researchers need to tackle at least four major challenges that affect these criteria: (a) appropriate pre-processing of the text collection; (b) adequate selection of model parameters, including the number of topics to be generated; (c) evaluation of the model's reliability; and (d) the process of validly interpreting the resulting topics. We review the research literature dealing with these questions and propose a methodology that approaches these challenges. Our overall goal is to make LDA topic modeling more accessible to communication researchers and to ensure compliance with disciplinary standards. Consequently, we develop a brief hands-on user guide for applying LDA topic modeling. We demonstrate the value of our approach with empirical data from an ongoing research project.

Skepticism toward climate change has a long tradition in the United States. We focus on mass media as the conveyors of the image of climate change and ask: Is climate change skepticism still a characteristic of US print media coverage? If so, to what degree and in what form? And which factors might pave the way for skeptics entering mass media debates? We conducted a quantitative content analysis of US print media during one year (1 June 2012 to 31 May 2013). Our results show that the debate has changed: fundamental forms of climate change skepticism (such as denial of anthropogenic causes) have been abandoned in the coverage, being replaced by more subtle forms (such as the goal to avoid binding regulations). We find no evidence for the norm of journalistic balance, nor do our data support the idea that it is the conservative press that boosts skepticism.

We seek to understand the role of the Internet in policy monopolies characterized by a dominant coalition in traditional political venues. In these settings, we identify coalitions and counter-coalitions on the Web and ask how these coalitions differ resource-wise and where these differences come from. To do so, we combine link tracing and quantitative content analysis in the field of climate change in Germany and the United Kingdom. Our results show that online contestation is indeed structured by competing coalitions of climate advocates and skeptics. Moreover, the counter-coalitions of climate skeptics turn out to be the true winners of online communication: they have not only incorporated conservative media as their allies, but also managed to make themselves more visible than climate advocates. This visibility stems from their own link setting activity, which makes climate advocates’ passive online strategy of just ignoring the skeptical camp ineffective.

We study the discursive resonance of online climate skepticism in traditional media in Germany, a country where climate skeptics lack public prestige and thus form a political counter-movement. We thereby differentiate two temporal dynamics: resonance can be continuous or selective, based on the exploitation of specific events. Beyond, we test whether such resonance is higher within the conservative media. We rely on news value theory to shed light on the mechanism facilitating or hindering such resonance and identify three indicators for resonance: frames, positions and actors. Using various computational methods as well as qualitative case studies, we examine the skeptical and traditional media discourses over a period of two years. Our analysis shows that there is no continuous resonance. However, our data reveal selective resonance: skeptics' manage to exploit specific events pushing their frames and positions onto traditional media's agenda. Thereby, conservative media did not give greater resonance to climate skeptical voices whereas they resort to downplaying the issue by allocating less space to it.

The climate of debate: How institutional factors shape legislative discourses on climate change. A comparative framing perspective. Legislative actors and their institutional settings constitute some of the central antecedents of the media's coverage of political issues, not least since they lie at the very heart of the democratic law-making process. Yet, although theories central to the field of political communication have long documented the orientation of the media towards elite policy actors (e.g. Bennett, 1990), we know little about the contexts in which they are embedded. This is particularly the case for those stages that represent the day-today dealings in plenary debates, committee meetings, hearings, etc.-in other words, the courant normal of politics-which make up the bulk of the policymaking process but mostly lie outside the brief peaks of political contest that occur during elections and popular referenda.

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