This study examines the level of politicization and polarization in COVID-19 news in U.S. newspapers and televised network news from March to May 2020. Using multiple computer-assisted content analytic approaches, we find that newspaper coverage is highly politicized, network news coverage somewhat less so, and both newspaper and network news coverage are highly polarized. We find that politicians appear in newspaper coverage more frequently than scientists, whereas politicians and scientists are more equally featured in network news. We suggest that the high degree of politicization and polarization in initial COVID-19 coverage may have contributed to polarization in U.S. COVID-19 attitudes.

Despite concerns about politicization and polarization in climate change news, previous work has not been able to offer evidence concerning long-term trends. Using computer-assisted content analyses of all climate change articles from major newspapers in the United States between 1985 and 2017, we find that media representations of climate change have become (a) increasingly politicized, whereby political actors are increasingly featured and scientific actors less so and (b) increasingly polarized, in that Democratic and Republican discourses are markedly different. These findings parallel trends in U.S. public opinion, pointing to these features of news coverage as polarizing influences on climate attitudes.

Scholars have recently suggested that communicating levels of scientific consensus (e.g. the percentage of scientists who agree about human-caused climate change) can shift public opinion toward the dominant scientific opinion. Initial research suggested that consensus communication effectively reduces public skepticism. However, other research failed to find a persuasive effect for those with conflicting prior beliefs. This study enters this contested space by experimentally testing how different levels of consensus shape perceptions of scientific certainty. We further examine how perceptions of certainty influence personal agreement and policy support. Findings indicate that communicating higher levels of consensus increases perceptions of scientific certainty, which is associated with greater personal agreement and policy support for non-political issues. We find some suggestive evidence that this mediated effect is moderated by participants' overall trust in science, such that those with low trust in science fail to perceive higher agreement as indicative of greater scientific certainty.

Concerning gender, 48.2% of our sample self-identified as men (n = 964) and 51.8% as women (n = 1034).71.3% of our respondents identified as White, 12.1% identified as Black or African American, 8.2% as Hispanic, 5.1% as Asian, and 3.4% identified as belonging to other ethnic groups.We measured age with an 8-point scale ranging from "18-24" to "85 or older." The median response was "35-44" (Mean (M) = 3.55, Standard Deviation (SD) = 1.67).Education was measured on an 8-point scale from "Less than high school diploma" to "Doctorate (e.g. PhD)." The median response was "Some college, no degree" (M = 3.73, SD = 1.52).

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