Visual digital intermediaries and global climate communication: Is climate change still a distant problem on YouTube?

PLOS ONE Visual digital intermediaries and global climate communication across contexts — or, a platform doing the same thing may integrate locally to different effect. On the other hand, what content contributors and audiences do also plays in. The intuition about varied patterns is supported by emerging research. An exploratory cross-platform study identified distinct visual vernaculars associated with climate change across platforms [16]. Related work (not on climate issues) suggests that there is also reason to expect differences within the same platform. In the case of YouTube, a handful of studies show that ranking cul- tures differ across issues (e.g. have a stable or ‘newsy’ morphology [11]), and take different shape around the same issue across language/region contexts [66,67]. Such suggestive find- ings motivate the question whether the conditions for dissolving a green ghetto are the same everywhere on a platform such as YouTube. We specify our second question as follows: (RQ2) What characterises ranking assemblages underpinning top-ranked results on climate change on YouTube Search — and does this differ across region/language search contexts? The multi-sided interactions in ranking assemblages are inherently difficult to pick apart. Nevertheless, we argue that they are still accessible to comparative analysis. In this study, we follow the proposal to address the tangled agencies through API-based large-scale observation [11,66]. This, like most other approaches to algorithm auditing, leverages outside observa-

tion to handle the challenges of access, transparency, comprehensibility and randomisation in dealing with algorithms [50]. We recognise that other approaches could be more power- ful for focusing particular relations (e.g. agent-based audit to focus user-platform dynamics [68]). However, an advantage of API observation for our purposes is that it makes it possi- ble to systematically probe the multi-sided interactions in how they unfold over time, and thereby lends traction to comparative analysis. Since the API for a platform such as YouTube Search runs as close as possible to a baseline search, the API approach is also useful when the analytical focus is the platform-level process rather than what specific users actually see [11,69]. 3 Climate change on YouTube search We focus on YouTube, a video sharing and social media platform that is receiving increas- ing attention for its pivotal position in global online climate discourse. The U.S.-based plat- form is a global destination for climate news, science, entertainment, and education con- tent that spans the spectrum from professional to amateur [70,71]. It is localised in over 100 countries and 80 languages [72]. A sizeable audience is in the U.S., which is the most stud- ied. By 2022, however, YouTube was twice as big in India, and had major markets in countries such as Indonesia, Brazil, Russia, and Japan, followed by others such as Mexico and Germany [73]. The platform offers several popular ways to discover, navigate and consume content,

including Search, following recommendations for related content via the UpNext listing, or subscribing to particular channels. Search is a central affordance on the platform. The default setting ranks results by ‘rele- vance’, displaying thumbnail image, title, views and date uploaded. YouTube prioritises three key considerations in connecting users with content in Search: the relevance of keyword match in titles, thumbnails, video description and content; viewer satisfaction in aggregate signals of engagement such as watch time, likes, and comments; and quality. For quality, the platform surfaces authoritative sources and demotes borderline content, especially for news, politics, science, and medical information. Personal search and watch history contribute to results if a user is logged in [74,75]. As noted, ranking assemblage differences have been observed within and between other issues on YouTube Search [11,67]. PLOS ONE https://doi.org/10.1371/journal.pone.0318338 April 8, 2025 6/ 23