The data consists of transcribed recordings of classroom dialogues in a grade 8 classroom during a weeklong «Climate project» lasting 18 lessons. All data is in Norwegian. The data was collected during a school development project, denoted the Argument project, run by the school authority at the local municipality and involved all science and math teachers at three lower secondary schools. It was run in cooperation with six researchers and four outreach staff at the University of Bergen and the Western Norway University of Applied Sciences as part of an R&D project (see argument.uib.no/) funded by the Norwegian Research Council under grant number 275835 and was running from January 2018 until June 2022. Data from the Climate project were collected using non-participatory participation and included whole-class video recordings (camera pointing towards the front of the classroom from behind) and audio recordings of group discussions. Recordings from each lesson were transcribed verbatim, and the data set in this database consists of these transcriptions.