The selected textbooks were published or last revised in the years 2015–2024. We measured the space devoted specifically to climate change issues in three different ways: number of pages, keywords count, and position of the material within the book. Regarding the number of pages, we count in absolute terms or as in percentage of all pages in the book, pages that specifically covered climate change either as the main topic, as the application of a general concept, or simply as passing mention.
We also identified the frequency with which seven keywords are mentioned: Climate, Carbon, GHG, Greenhouse, Global warming, Atmospher*, and temperature. Finally, we considered the order of presentation of climate-related material within the book, in terms of median position: a textbook front-loaded with climate change content is different from one that relegates everything to a final chapter or to an appendix with extra material.
More in detail, to calculate the number of pages devoted to climate change we first have identified and sorted the textbook material according to the following three categories depending on how the material has been presented in the textbooks:
A. Parts centering on a climate change issue without linking it to other concepts; usually found when talking about the science of climate change. In addition, parts about using climate-related issues as an illustration of a broader issue; typically, carbon pricing shows up when introducing externalities, or climate mitigation when presenting social dilemmas.
B. A brief passage, usually limited to a keyword or a line, which mostly refers to passing mentions of “climate change” or “global warming”; the simple presence of a keyword would not suffice. In addition, a mention of climate change topics in a section title, in a question or in an exercise at the end of a chapter.
C. A table, box or graph with content about climate change.
The next step has been to calculate a weighted sum of all components, as follows: Number of pages devoted to climate change = A + 0.1*B + 0.5*C.