Which science reaches the IPCC? Expert recruitment and evidence selection

Abstract

Expert assessments shape the evidence presented to policymakers, and their citations increasingly inform evaluations of research impact, but the scientists who assemble this evidence also contribute to the literature they assess. I examine how journal standing, scholarly visibility and expert recruitment relate to evidence selection, using more than 27,000 references from the 2014 and 2022 climate-mitigation assessments of the Intergovernmental Panel on Climate Change (IPCC). Specialist journals, rather than the most prestigious ones, supply much of the evidence, largely from venues in which assessment authors publish. Within the same journal, year and topic, prior scholarly attention predicts inclusion, while papers coauthored by appointed lead authors have more than three times the odds of inclusion after accounting for prior citations and author geography. In all 14 chapters matched across the two assessments, bibliographies shift towards research by experts joining the writing team and away from research by those leaving it. Experts appointed for a chapter’s subject are cited more in it than elsewhere in the report, but those who write the chapter are cited there more than twice as intensively. The selection of experts is therefore part of the selection of evidence, and assessment citations reflect institutional choices as well as research uptake.