1. General comments

This manuscript examines the current state of knowledge around climate tipping points in the general population of Norway. The two research questions raised in the manuscript are highly relevant and require urgent answers. The methodology that is used to address the research questions is principally solid. A major strength of the study is the large and diverse sample that has been recruited. The results of the study appear to be quite informative. In some ways, the present findings may even help understand previous findings in the field. Thus, the present research has the potential to make a significant contribution to this emerging research area.

However, in the current form, it is difficult to fully assess the quality of the manuscript and the underlying research given that critical information on the experimental treatment, questionnaire, codebook, and the data is missing. Some sections of the manuscript seem half-finished (e.g., some headers and sentences appear twice). There are also plenty of unclear statements and formatting errors. I hope the following comments will help the authors improve the manuscript.

2. Specific comments

Introduction

• Lines 28-30: “Among the many reasons for his [sic!] inadequate response to the climate challenge (Stoddard 2021), public risk perceptions and the corresponding support for climate action have been paramount.” First of all, I would not use the term ‘paramount’ – other factors can be considered as equally important as policy support and risk perceptions. Secondly, if the authors wish to invoke the concept of policy support, then I would encourage them to explain the interrelationships between policy adaption, policy support, and public perceptions of climate change more clearly while citing recent sources such as Yeganeh et al. (2020) and Bergquist et al. (2022).
• Lines 30-33: “[Lenton et al. (2008] argued that the persistent lack of climate urgency, i.e., insufficiently high-risk perceptions, stems from a “false sense of security” (p. 1792) founded in smooth, gradual projections of climate change.” Lenton et al. (2008) merely say that “Society may [!] be lulled into a false sense of security by smooth projections of global change” (p. 1792). The ‘may’ should be included in the indirect citation as well -> may stem from… Aside from this, I encourage the authors to be more careful when invoking concepts such as risk and urgency (not to equate them). A person who perceives climate change as a significant threat may not necessarily perceive it as an urgent threat. Communicating the risks associated with climate tipping points may affect both types of perceptions. This could be further explored in the introduction or discussion section.

Literature review

• Sections 2.1 and 2.2 contain a lot of information, not all of which is relevant to the focus of the present study. The sections could be shortened to create a more consistent and clear narrative structure. For instance, when the tipping point risk characteristics are explained, the authors should focus on the main points; each of the characteristics could be explained in only three or four sentences. To structure this section, it could also help to first highlight that the reorganization/state shift is the focal process and the remaining characteristics merely describe how this process unfolds (i.e., in a nonlinear, potentially abrupt fashion) and what it entails (i.e., potential for severe, long-term impacts…).
• This brings me to the next point: there is not a clear consensus as to whether ‘irreversibility’ should be considered a CTP characteristic (e.g., Armstrong McKay et al., 2022). After all, irreversibility is a high standard that is extremely difficult to prove. The authors acknowledge this in some parts of the manuscript when they use alternative terms such as ‘limited reversibility’ and ‘irreversible at human timescales’. For reasons of consistency, I would choose a single term, perhaps limited reversibility (or another term that carries the same meaning). From a risk analysis perspective, this can also be framed as a question of controllability: once a tipping point has been crossed, it becomes much more difficult for humans to control exactly how a natural system operates. This is because the regime shift comes with a certain degree of stability/persistence.
• Section 2.1: The authors may want to engage with more recent publications from the field of public perceptions of climate change. Importantly, some of these publications show that in many countries climate change is not perceived as a distant risk anymore (e.g., van Valkengoed et al., 2023; I strongly recommend this review).
• Sections 2.1-2.3: The summary of the previous literature contains statements that are imprecise and potentially misleading. For instance, the authors state that “[Bellamy and Hulme (2011)] found that climate tipping points increased concern only among participants with an egalitarian value set […]” (lines 196-198). The study that is cited here is a cross-sectional study, not an experimental study. Bellamy and Hulme (2011) merely found that egalitarians were most concerned about climate tipping points. It cannot be concluded that there was an ‘increase’ in concern or any other variable.
• In their short summary of the study by van Beek et al. (2022), the authors write that “[van Beek et al. (2022)] observed an increase in concern and perceived seriousness of climate tipping points” (line 190f). However, it should be noted that the changes that van Beek et al. (2022) registered on their quantitative measures of concern and seriousness were nonsignificant. That is, the present summary of van Beek et al. (2022) seems to disregard the quantitative findings and only reports the results from the qualitative analysis.
• Line 204f: “[…] a study by Formanski et al. (2022) found no difference between climate risk perceptions related to linear versus non-linear climate change”. Given that the present study is in many ways similar to the Formanski et al. (2022) study – e.g., in terms of the design and the dependent variables (for RQ-2) – it would make sense to briefly describe the methodological approach and explain the main findings of this previous study. In general, I encourage the authors to pay particular attention to the most recent publications in this field that directly relate to their research questions – e.g., Bellamy (2023, -> RQ-1) and Formanski et al. (2022, -> RQ-2).

Methodology

• “In part 1a, all participants were asked a series of questions about their climate change risk perceptions” (line 256f). The authors need to provide a list of all questions that were asked here, as well as an explanation for how the responses to these questions were processed/aggregated.
• The authors also need to disclose all questions that were part of the “tipping point knowledge test”. In the results section, the authors present statistics about which tipping point characteristics were most frequently identified. However, from the method section, it is not clear which question stimulated these answers. Section 3.1 only states that participants were asked to name an example of a CTP.
• Appendix A – which is said to present the stimulus materials (i.e., information packages) – is missing in the document.
• Sample composition: “A nationally representative sample was recruited […]” (line 275f). The authors need to specify in which sense the sample is ‘representative’. To me, it looks like the sample is a quota sample, not a probabilistic sample. That would, however, mean that the sample is only representative of the Norwegian general population in terms of selected demographic characteristics (e.g., sex, age, region). If that is the case, the authors need to state this explicitly and provide the quota plan.
• Data analysis (knowledge): Is a qualitative categorization necessary? The authors could just present the familiarity ratings and the frequencies for correct/incorrect CTP examples – and then they could probably draw the same conclusions from this data. Yet, this would not require the presentation of a category system. However, if the authors still wish to use a categorization procedure, then I would advise them to avoid the category label “no knowledge” and to use “no demonstrated knowledge” (see Figure 3, p. 13) instead.
• Data analysis (risk perception): Instead of conducting separate independent-sample t-tests on the test scores for t1 and t2, it would be better to conduct an ANCOVA on the post-test scores, with the pre-test scores as a covariate. This is an elegant way to test whether there are differences between the experimental groups at the post-test stage while taking the pre-test scores into account. The paired-sample t-tests (from line 383 onwards) can then be presented as simple ‘follow-up analyses’.

Results

• Section 4.1, 4.4: The authors should try to meet the journal article reporting standards for empirical research articles in psychology and social sciences. That is, mean values and standard deviations should be reported for each experimental condition (e.g., in a table), as well as exact p-values and standardized effect sizes.
• Section 4.1: The authors find that only a few survey respondents rated the information on climate tipping points as “new to them” (see lines 339-341). It is concluded that this indicates socially desirable responding. However, the authors should keep in mind that the free recall of memorized information is generally more difficult than the recognition of memorized information. It is possible that many survey respondents had previously heard of specific tipping elements but were unable to recall that information during the free recall task (“name an example…”). The authors should therefore not simply dismiss their findings on this measure as socially desirable responding. While social desirability could certainly play a role, the present findings could also be an indication that laypeople may be more aware of CTPs and the consequences of unmitigated climate change than researchers often assume (even though that CTP knowledge might not be highly accessible, as it was only activated through the confrontation with specific stimulus materials). The authors should also consider the possibility that many laypeople may be aware of the catastrophic consequences of unmitigated climate change, but they may not associate these impacts with the concept of tipping points or simply do not know the relevant terminology. This tends to be a principal weakness of studies that only ask people ‘whether they have heard of climate tipping points’. Thus, the present results give us limited insights into laypeople’s expectations about how climate change will unfold in the future. This is yet another reason why the authors need to be cautious in their interpretation of the present results.

Discussion

• Lines 418-421: “Our results contrast with recent findings by Formanski et al. (2022) […]. One explanation for this difference might be that Formanski et al focused on a single characteristic of tipping points (non-linearity), which might not be the feature that generates most concern”. The treatment materials by Formanski et al. (2022) also highlighted another feature – severe impacts. However, it is true that other features such as the limited reversibility of the impacts were not explicitly mentioned, which is a valuable observation. At the same time, the authors could also consider the fact that there were other differences in terms of the specificity, scope, and length of the materials - Formanski et al. (2022) acknowledged that the length and simplicity of the materials could explain their null findings. A simple reframing of climate change as a dynamic phenomenon (with the help of the CTP concept) may not be enough to increase concern; yet the current study indicates that a more elaborate discussion of CTPs and the associated risk characteristics could help!
• Lines 426-429: “We did not observe any effect of information of climate tipping points on beliefs about whether or not it is too late to act on climate change. This could be attributed to the public's tendency to downplay the seriousness of these risks due to certain cognitive biases, and that systematic risk associated with climate tipping points pose unique learning challenges that is not easily grasped by participants”. First of all, the authors could point out that the null finding on this item is consistent with the results that Formanski et al. (2022) report for the dependent variable ‘efficacy beliefs’. Secondly, the explanation that the authors offer for the null finding would only seem plausible to me if the text presented to participants had, in some way, suggested that the crossing of multiple CTPs is inevitable – why else would they be prompted to believe that it is too late to act on climate change?

Conclusion

• The excurse on social tipping points (from line 475 onwards) comes a bit out of nowhere. The authors may want to consider deleting this part or embed it more deliberately, so that it fits into the conclusion.

3. Technical corrections

• “Stoddard (2021)” is missing in the references
• Some publications that are listed in the references section are not cited in the text (e.g., Trope & Liberman, 2010)
• Authors names -> correct spelling errors (e.g., Russil -> Russill)
• Throughout the manuscript the authors frequently use phrases such as “could be affected by climate tipping points” (line 58). And when they introduce the concept in line 35, they state that “Climate tipping points refer to dynamics in the Earth system […]”. Technically, tipping points are not ‘dynamics’ within the climate system – they are thresholds; hence, tipping points do not ‘affect’ countries – only the impacts that the crossing of tipping points has can affect countries. I presume that the authors mean the processes that are initiated by tipping events, not the ‘tipping point’ itself?
• The authors use formulations such as “the effects of climate tipping points on” (line 70). I presume that the authors mean the effects of the ‘presentation of’ or ‘exposure to’ information on climate tipping points?
• Line 323: “50% indicated little or no familiarity” – in case two categories were combined here, the authors should provide frequencies for each category (“little familiarity” and “no familiarity”)

This paper reports on the findings of a nationally representative survey of citizens in Norway on the topic of climate tipping points. In particular, it seeks to examine the role of knowledge as a foundation for risk perceptions. It finds low awareness of tipping points and that information on climate tipping points increases concern about climate change. The paper is for the most part well written and contributes to a very important topic that, as the authors highlight, is extremely under-researched compared to work on perceptions of climate change more generally. The unprompted elicitation of tipping point knowledge is particularly novel (although not entirely unproblematic), as is the conduct of the study in Norway. It is a pleasure to recommend this paper for publication, pending some minor comments.

The paper provides excellent background on risk perceptions of climate change in general and climate tipping points, as well as on the Norwegian context for the study. The section on risk-relevant characteristics of tipping points, however, seems a little too long. The main points could be made more succinctly.

At the same time, this section also seems a little too prescriptive. It is rightly noted that definitions of climate tipping points are varied, but it would be worth unpacking the divergences in more detail and adopting either a more flexible understanding of the concept, or alternatively being prescriptive about only those features that are common to all climate tipping points. For example, irreversibility is identified as one of the key features (and by the public themselves), but this is in fact not a feature of many climate tipping points, e.g., Arctic sea ice, Atlantic Meridional Overturning Circulation, ocean acidification, etc. So, it can be contested as to whether identifying ‘irreversibility’ would contribute towards a ‘correct’ understanding of climate tipping points. In other words, it would be good to see some reflection on the problematic nature of ‘knowledge’ about climate tipping points, and what the implications are for the present (and future) research.

A more minor point is that in some places, notably lines 100 to 106, there are repetitions of the text.

First of all, I think its important to recognise the importance of this work. Understanding climate risk perceptions, specially about tipping points is fundamental to build resilience and reduce shifting vulnerabilities.

With regards to the introduction, it is quite hard to discern what is the research question that the study is exploring. It only comes until line 45-55 (4^th and 5^th paragraph) where readers finally understand the intention of the manuscript. The introduction would significantly benefit if the research question is brought earlier on in the first paragraph and then provide information on what has been done and why it is important to explore climate risk perceptions of tipping points from the public in Norway.

There are three issues I would like to raise on the literature review on climate risk perceptions (section 2). First, I would like to suggest including a brief overview of the literature that studies affective dimensions of climate risk perceptions, as this is another growing field in the literature that significantly influences how individuals perceive climate risks. Second, I don’t understand the difference between section 2.1 and 2.2 that both talk about risk perceptions (it may be a typo). This needs attention. Three, section 2.2 “Risk-relevant Characteristics of Climate Tipping Points” and 2.3 “Perceptions of Climate Tipping Point Risk” are far too long and can be summarised. I think it’s important to remember that the study is about the public in Norway and how they perceive climate risks about tipping points. The literature review and background information should provide enough context for this, so this section can significantly be summarised to be more specific about what readers need to know (think about the audience for this piece and what they may already know).

With regards to the description of the study participants, it would be interesting to provide more information (if possible) to know which audience may have not been able to be represented with this method. It is important to be clear about the limitations of our studies, and this is one where it is likely that some publics within Norway remained invisible (e.g., immigrants, international students, refugees, people with some disability, non-binary, etc.). Also, what is the level of study from study participants?

Where the results of the t-tests independently verified? And if so, how?

Finally, on the conclusions, the manuscript fails to provide meaningful recommendations to other potential audience of this study (e.g., government and academia). If the authors believe that the public in Norway need to know about tipping points, then it would be important to explain this. In other words, the conclusion should describe why this knowledge is necessary and what is needed or recommended to disseminate this knowledge. For example, if people in Norway understand the risks of tipping points, could we expect some sort of change? In what way? This takes me to my next comment. The manuscript should provide future research opportunities and also be clear about the limitations of the study.

Minor comments:

Page 1 line 25: Incorrect factual statements are made in the introduction when referring to “internationally agreed-upon targets”. Nationally determined contributions are the opposite of internationally agreed. The Paris Agreement is based on a bottom-up self-determined approach.