Shifting Semantics: A longitudinal study of keywords in climate change reporting

News reporting is a key source of public information on climate change. Over the past three decades, public communication about climate change has intensified, contributing to ongoing public negotiation over the meanings of climate change. This systematic longitudinal study uses computational methods to explore the semantic shifts in climate reporting. We examine three common terms — greenhouse effect, global warming, and climate change — as a means to trace the development of climate news. Our findings indicate that each keyword is associated with distinct semantics, and media coverage of climate change varies according to the prevailing term. While the greenhouse effect dominated early climate reporting, the term "global warming" was used as a transitional term before "climate change" became the predominant term. These variations have significant epistemological, political, and methodological implications. They demonstrate how media reporting on climate science is constantly evolving; indicate how public discussions of climate change are informed by climate news; and highlight the importance of aligning sampling methods with the changing semantic landscape of public climate communication.