Learning from climate change news: Is the world on the same page?

in Table 1. Only newspapers classified as left-center or right-center made it to the final selec- tion. Although the goal was to represent political opposites, the labels from the five-class scale were left intact. One extra left-center newspaper was selected for Australia, considering the right-center The Australian has a substantially larger circulation than any left-center Australian newspaper. As a second step, the search keywords on climate change were determined, considering that not every article that covers the subject literally mentions “climate change”. To generate a broader search query and prevent bias due to human-driven selection, the contents of 230 pages on Wikipedia (en.wikipedia.org) were retrieved and computationally analyzed using tf-idf scores to find climate change keywords. Tf-idf represents an established method for uncovering words that demonstrate relative singularity within a specified subject matter or document [43]. This involved the pages on United Nations Climate Change conference and Global warming, those for each COP meeting, and all pages linked by non-capitalized phrases on the former two pages. By defining tf-idf and document frequency thresholds, the final result was a list of 24 unigrams and 2 bigrams: (1) agreement, (2) air, (3) atmosphere, (4) carbon, (5) carbon dioxide, (6) climate, (7) climate change, (8) co2, (9) dioxide, (10) earth, (11) emissions, (12) gas, (13) global, (14) greenhouse, (15) heat, (16) ice, (17) land, (18) nations, (19) ocean, (20)

protocol, (21) sea, (22) solar, (23) species, (24) surface, (25) temperature and (26) warming. As a third step, the time frames for collection were defined, based on the occurrence of COP meetings. Keller et al. [14] have shown that news publications on climate change peaked around COP meetings. These meetings are (usually) held annually, as the main gathering of the Conference of the Parties (COP) from the United Nations Framework Convention on Cli- mate Change (UNFCCC) (unfccc.int/process/bodies/supreme-bodies/conference-of-the- parties-cop). The time frames around all 26 COP meetings that have taken place between 1995 and 2019 (COP 1 until 25, including the additional COP6a) were included. For each COP meeting, col- lection started one week before the official start and ended one week after the official ending. The average time frame covered 25 days, varying from 23 up to 27 days. The articles were collected on a per-time frame basis. A search string was formed to retrieve full matches of one or multiple keywords, as can be seen in Fig 1 in S2 Appendix. Unfortunately, Nexis Uni did not offer functionality to download more than 100 articles at once and only provided articles as formatted files (PDF). Since each time frame featured thou- sands of search results, collection was automatized using Python, relying on Selenium (selenium-python.readthedocs.io), ChromeDriver (chromedriver.chromium.org) and Chro- mium (chromium.org/Home). Due to hard- and software limitations, only the first 75% of

articles were downloaded for the majority of COPs. With the articles already being sorted by relevance in the search results, this was not considered an issue. Table 1. Overview of countries and newspapers selected for data collection and their share of articles in the dataset. Country Newspaper Political orientation Number of art. Australia The Australian Right-Center 6,547 Sydney Morning Herald Left-Center 5,590 The Age Left-Center 4,321 Canada The Globe and Mail Right-Center 5,556 The Toronto Star Left-Center 4,871 United Kingdom The Times Right-Center 6,770 The Guardian Left-Center 9,917 https://doi.org/10.1371/journal.pone.0297644.t001 PLOS ONE Learning from climate change news PLOS ONE | https://doi.org/10.1371/journal.pone.0297644 March 20, 2024 8 / 27