An Up-HILL Battle: Building consensus on terminology for high impact climate events and tipping point risks.

Unclear and inconsistent terminology for high impact climate phenomena, including concepts such as tipping points, irreversibility, ‘collapse’ and ‘shutdown’, presents a substantial barrier to clear understanding of Earth system risks. These terms are frequently used in assessments of major subsystem shifts in ocean circulation, ice sheets and forest biomes, yet they are often applied without shared definitions across scientific, policy and public contexts. This inconsistency affects how scientific results are interpreted, including perceptions of how quickly changes may unfold and whether different parts of the climate system might influence one another. It also has important psychological and emotional impacts. Language that sounds dramatic or alarming may be intended to motivate action, but it can instead lead to desensitisation, message fatigue, denial or even the spread of misinformation. These reactions can weaken engagement and undermine societal preparedness for potential climate driven transitions.

Government science and policy teams, rely on clear and consistent terminology for effective decision making in situations where thresholds and impacts remain uncertain. To support this need, we – as communication specialists work extensively at the interface between science and policy - are developing an evidence-based glossary and guidance for terminology related to tipping points and other high impact climate concepts. The aim is to improve internal communication and to support clearer interpretation of scientific assessments used in national risk planning.

The project is grounded in social science and uses a mixed methods design. It began with a review of existing definitions and research on the psychological effects of climate language. We carried out semi-structured interviews and workshops with scientists and government officials, and this highlighted how linguistic ambiguity affects policy development and the evaluation of uncertain risks. Utilising ta broad cross section of Met Office staff, we carried out focus groups to explore how different definitions were perceived and understood. Participants, including those with strong scientific backgrounds, showed substantial disagreement about the meaning and implications of key terms. This indicates that confusion around terminology linked to tipping point research is not limited to public audiences but also exists within expert communities.

Insights from this analysis are guiding the co creation of a public facing glossary developed with an expert working group of twelve multidisciplinary specialists at the Met Office. Completion is planned for March 2026, alongside continued engagement with international bodies including WCRP and IPCC. By strengthening shared understanding of terms related to climate system transitions and critical thresholds, this work aims to support more coherent communication of high impact climate concepts, improve public and policy interpretation of uncertain risks and reduce unintended emotional and behavioural responses that can undermine, and distract from effective, and much needed climate action.