| 16 Jul 2026
An Up-HILL Battle: Towards clearer terminology for High-Impact Climate Possibilities, including tipping points
Abstract. Climate science terminology increasingly shapes public and policy discussion, yet shared understanding of commonly used terms is often assumed. This study examines how people make sense of language associated with High-Impact Climate Possibilities (HICPs), sometimes referred to as high‑impact low‑likelihood climate events. Its aim is to inform the development of a glossary to support clearer and more consistent communication across and between specialist, policy and public contexts.
Using qualitative evidence from focus groups, we explored how participants interpreted key terms, how meanings were negotiated through interaction, and how emotional responses emerged. We found that meaning is frequently left implicit, with participants relying heavily on everyday language, personal experience and familiar metaphors when interpreting scientific terminology. As a result, everyday meanings often dominate sensemaking, diverging from scientific intent. Emotional responses were shaped less by the terms themselves than by the context in which they were encountered, including assumptions about timescale, likelihood and certainty that were not explicitly stated.
These findings highlight the risks of relying on assumed shared understanding when communicating HICPs. In response, we propose an evidence‑informed glossary and communication guidance developed through iterative engagement with scientists, policy‑facing colleagues and communicators. The glossary is intended as a practical framework to support clearer, more transparent and more consistent use of language, and as a foundation for further empirical work.
Working in this field, I find this an important study in how science messages are conveyed to non-specialist audiences. I can understand a lot of recent confusion, particularly about the AMOC when definitions appear to be altered between journal articles. It seems a useful effort to get messaging on the same page, and this work presents a great foundation to build upon.
While I do not have a lot of experience with the style of workshop that has been organised for this research, it appears to have been carried out well with the caveats mentioned in the article. I would also be interested in responses from the general public, or at least those that have an interest in climate which is not necessarily associated with their job.
My main concern is that at the end, the glossary is presented as the product of the work but there is no information on how it has been perceived by any of the workshop participants, especially if the definitions provided clear up any of the confusion. This would give proof that the glossary is a useful tool worth expanding upon. Linked to my point above, devising further workshops that include a wider range of participants and introducing the glossary I think would be an important step to measure the impact of this research.
I also think the way the results are presented could be improved. Individual suggestions are detailed below alongside other comments:
Line 30/31: ‘and misinformation’ is not needed.
Line 55: While I know this work focuses more on Earth system tipping points, there are mentions of positive/social tipping points, as well as in the glossary, and this work by Manjana Milkoreit might fit nicely in this paragraph: https://doi.org/10.1002/wcc.813 but this is just a suggestion.
Line 74: Bracket missing.
Line 153: Why was a smaller subset of key government stakeholders used? How were they chosen?
Line 218: I do not understand about the non-probability sampling approach. Is this a caveat to say that the groups were not randomly chosen?
Line 257 and throughout: Link to figure not working.
Fig 2: I think that just showing these altogether without splitting them up into (a) and (b) would be good. Then once you get to the results section you should show how many times each one was chosen as another figure such as a bar chart with a thumbnail of each one. Perhaps bigger version of the images could be placed in the SI so they are easier for the reader to see too.
Line 268: The definition for ‘collapse’ is from a blog article but all of the other definitions are from scientific literature. Was there any reason for this?
Line 273: I assume they did not have a list of the focus terms for this part?
Line 350: Going back to my previous point about the images, I would be good to see some graphical presentation of which were chosen etc.
Line 371: Is there any way to graphically represent this, maybe as a bar chart of terms?
Section 7: I think it’s important to acknowledge that a lot people are not siloed into being a scientist or a communicator and that these roles act on a continuum. While all important points, a lot of these recommendations are very dependent on the audience each time and that line between scientist and communicator starts to blur depending on who the target audience is.
Section 8: Future work should include other Earth system tipping elements for sure. There is a strong focus here on the AMOC but there are a lot of terms associated with the Amazon rainforest which are also poorly defined, for example.
I have a few thoughts on the glossary too, although I do not know if it is my place to comment on it. For the Earth system tipping element’s plain language explainer, the phrase ‘changes which can start to drive themselves’ sounds quite confusing for plain language. Could it be linked to ‘self-accelerating change’ on the next page? Also, if these changes do drive themselves then the tipping point has already been passed and is not ‘close to or at a tipping point’ and the explainer suggests and would avoid confusion with the explainer for Earth system tipping point below it.