Dr Marco Sonnberger
email: marco.sonnberger@zirius.uni-stuttgart.de

Michael Ruddat

Annika Arnold

Dirk Scheer

Wouter Poortinga

Gisela Böhm

Raquel Bertoldo

Claire Mays

Nicholas Pidgeon

Marc Poumadère

Katharine Steentjes

Endre Tvinnereim

Climate concerned but anti-nuclear: Exploring (dis)approval of nuclear energy in four European countries

come   L'archive ouverte pluridisciplinaire

Introduction

Nuclear energy has historically been a highly controversial technology, evoking fears and reservations as well as raising high hopes and expectations among stakeholders and the wider public throughout the world. While some people view nuclear energy production as uncontrollable and highly risky, not least as a result of the Chernobyl and Fukushima Daiichi nuclear disasters, others view it as a stable and almost CO2-free source of energy in terms of power-plant operation [START_REF] Bruckner | Energy Systems[END_REF]. This ambiguity also finds expression in environmental movements.

Among environmentalists, advocates of nuclear energy see it as a "necessary evil" in the fight against anthropogenic climate change, while others strictly rule it out because of its potential environmental risks, particularly those associated with radioactive waste disposal (see e.g. [START_REF] Mccalman | Destabilizing Environmentalism: Epiphanal Change and the Emergence of Pro-Nuclear Environmentalism[END_REF]).

While there is already a comprehensive body of country-specific studies on public perceptions of and support for nuclear energy, cross-national comparisons are lacking [START_REF] Pampel | Support for Nuclear Energy in the Context of Climate Change[END_REF]. Furthermore, as indicated above, the structure of the relationship between public concern about climate change and views on nuclear energy is by no means obvious: either a positive or a negative relationship may be possible. On the one hand, the production of nuclear energy results in close to zero carbon emissions, at least at the point of energy generation, and it could thus in theory be given consideration by anyone favouring robust action on climate change. This reasoning suggests that there should be a positive association between concern about climate change and support for nuclear energy. On the other hand, concern about climate change is often associated with environmentalism, and environmental movements have historically strongly opposed nuclear energy. This argument then leads to the opposing suggestion that there should be a negative association between concern about climate change and support for nuclear energy.

Drawing on survey data collected in June 2016 as part of a cross-European research project, this paper aims to examine the patterns of relationship between climate change concern and public perceptions of nuclear energy in four European countries (France, Germany, Norway, and the United Kingdom [UK]). To our knowledge, this is the first time that such a comparative design has been employed to explore such a relationship; our original research thus falls into the category of "empirically-novel articles" [4, p. 19].

It is particularly worthwhile to compare France, Germany, Norway and the UK, because they represent four key energy-producing nations in Europe with different energy systems, and different histories with respect to nuclear energy [START_REF] Arnold | European Perceptions of Climate Change. Socio-political profiles to inform a cross-national survey in France[END_REF]. France has since the 1970s relied heavily on nuclear energy, and at the time of our survey in June 2016 was operating 58 reactors at 19 nuclear power sites spread across the territory. In 2015, the share of nuclear energy in France's total primary energy supply was 46%, and in its total electricity production, 78% [START_REF]CO2 Emissions from fuel combustion[END_REF]. In the UK, there are currently 15 nuclear power reactors in operation at seven sites distributed across England and Scotland. The share of nuclear energy in the UK's total primary energy supply in 2015 was 10%, and in its total electricity production, 21% [START_REF]CO2 Emissions from fuel combustion[END_REF]. In 2011, in the wake of the Fukushima Daiichi disaster, Germany decided to phase out its nuclear power plants by the end of 2021. Twenty-nine nuclear reactors in Germany have been permanently shut down, and at the time of the study in 2016 seven reactors were in operation at six sites in the north and south of the country. In 2015, the share of nuclear energy in Germany's total primary energy supply was 8%, and in its total electricity production, 14% [START_REF]CO2 Emissions from fuel combustion[END_REF]. Finally, nuclear energy has never played a major role in Norway's domestic energy production; three reactors used only for research purposes were operating in June 2016.

A closer look at the different discourses about nuclear energy in the four countries reveals that there have been some remarkable shifts in the last years. Germany initially planned to use nuclear energy as a so-called "bridging technology" in the transition towards a renewable energy system (the so-called "Energiewende") financing renewables and providing security of energy supply [START_REF] Butler | Nuclear Power After Japan: The Social Dimensions[END_REF][START_REF] Bmwi | Energiekonzept für eine umweltschonende, zuverlässige und bezahlbare Energieversorgung[END_REF]. Thereby, critical voices from politics, environmental organizations and civil society were widely ignored. As mentioned above, this changed dramatically after the Fukushima Daiichi disaster. The reactions in France were in some ways comparable. Although there are no phase out plans for nuclear energy, and an advanced reactor remains under construction, in 2015 the French government decided to reduce France's reliance on nuclear energy to 50% of the overall electricity mix by 2025. In the UK, the picture is different. The UK government remains fully committed to nuclear energy, framing it as highly beneficial.

Norway, in contrast, is a special case. The country's electricity production is based almost entirely on hydropower. In a normal year, Norway exports electricity to neighbouring countries.

The oil and gas industry is a major employer, but plays a subdued role in electricity production, with gas-fired electricity production largely limited to installations on oil and gas platforms in the North Sea. Due to the dominance of hydropower, there are no nuclear plants devoted to energy provision in Norway. Thus, there is no country-specific nuclear energy discourse.

Hence, regarding nuclear energy in particular, these four countries have quite distinct historical and current energy profiles [START_REF] Arnold | European Perceptions of Climate Change. Socio-political profiles to inform a cross-national survey in France[END_REF], which are also associated with respective policies, public debates, and socio-cultural settings. This makes these four countries valuable cases for comparison. At first glance, the country-specific contexts would suggest the existence of different patterns of nuclear energy perception as well as of different forms of association between climate change concern and the perception of nuclear energy across the four countries.

However, due to the existence of universal environmental values typically framing nuclear energy as unsustainable, a pattern consistent across the four countries might also be deemed likely. investigated since the 1980s [START_REF] Capstick | International trends in public perceptions of climate change over the past quarter century[END_REF][START_REF] Engels | Anthropogenic climate change: How to understand the weak links between scientific evidence, public perception, and low-carbon practices[END_REF][START_REF] Wolf | Individual understandings, perceptions, and engagement with climate change: Insights from in-depth studies across the world[END_REF][START_REF] Riffault | Public Opinion in the European Community: Energy[END_REF], through both in-depth academic studies [START_REF] Hagen | European Climate Change Perceptions: Public support for mitigation and adaptation policies[END_REF][START_REF] Leiserowitz | Global Warming's Six Americas[END_REF][START_REF] Lorenzoni | Public Views in Climate Change: European and USA Perspectives[END_REF] and continuous polling surveys [START_REF]TNS Opinion & Social[END_REF][START_REF]TNS Opinion & Social[END_REF][START_REF]TNS Opinion & Social[END_REF]. Public concern about climate change often takes lower priority than other issues of public attention, such as a nation's overall economic situation, unemployment or most recently, migration policies, which people perceive to be more immediate risks and challenges. Scholars attribute this to the psychologically distant character of climate change, asserting that direct personal experience is a crucial factor in people's attention and concern [START_REF] Akerlof | Do people "personally experience" global warming, and if so how, and does it matter?[END_REF][START_REF] O'neill | An iconic approach for representing climate change[END_REF][START_REF] Pidgeon | Climate change risk perception and communication: addressing a critical moment?[END_REF][START_REF] Spence | The psychological distance of climate change[END_REF][START_REF] Tvinnereim | Climate change risk perceptions and the problem of scale: evidence from cross-national survey experiments[END_REF]. Surveys show that concern about climate change has been increasing over the last two decades globally [START_REF] Goldberg | For the first time, the Alarmed are now the largest of Global Warming's Six Americas[END_REF][START_REF] Whitmarsh | Public engagement with carbon and climate change: To what extent is the public 'carbon capable'?[END_REF][START_REF] Corner | Engaging the public on climate risks and adaptation: A briefing for UK communicators[END_REF][START_REF]The Centre for Climate Change and Social Transformations[END_REF][START_REF] Steentjes | British Public Perceptions of Climate Risk, Adaptation Options and Resilience (RESiL RISK): Topline findings of a GB survey conducted in October 2019[END_REF] and that knowledge about the causes of climate change has been increasing as well [START_REF] Shi | Public Perception of Climate Change: The Importance of Knowledge and Cultural Worldviews[END_REF]. Outright scepticism regarding climate change appears to be very low across Europe [START_REF] Engels | Anthropogenic climate change: How to understand the weak links between scientific evidence, public perception, and low-carbon practices[END_REF][START_REF] Poortinga | Climate change perceptions and their individual-level determinants: A cross-European analysis[END_REF], even if some fluctuation over time and across countries can be measured [START_REF] Capstick | International trends in public perceptions of climate change over the past quarter century[END_REF].

State of

Public perception, approval, and (re-)framing of nuclear energy

Public perceptions of nuclear energy in the UK, Germany, and France are well documented.

There is, however, little or no research on the perception of nuclear energy among the public in Norway, which can be attributed to the virtual absence of nuclear power production in that country. For the European Union member states, however, coordinated documentation of public perceptions of nuclear energy dates back to 1982, to one of the first-ever special surveys conducted in the survey series Eurobarometer (no. 17) 1 . This study asked respondents to give their opinion on associated risks and nuclear energy's role in supplying affordable and clean energy [START_REF] Riffault | Public Opinion in the European Community: Energy[END_REF]. Out of all polled countries, approval ratings for nuclear energy were highest in those countries where nuclear energy was developed on a large scale: a substantial proportion of respondents in the UK, Germany [START_REF]Energy Technologies: Knowledge, Perception, Measures[END_REF]. The Fukushima Daiichi nuclear disaster in Japan in March 2011 has led to a further decline in the public's trust in the safety of nuclear power plants, in particular in Japan [START_REF] Poortinga | Public perceptions of climate change and energy futures before and after the Fukushima accident: A comparison between Britain and Japan[END_REF].

However, in the light of climate change and rising global CO2 emissions, some people argue that nuclear energy should be reconsidered [START_REF] Pampel | Support for Nuclear Energy in the Context of Climate Change[END_REF][START_REF] Sundström | Women and nuclear energy: Examining the gender divide in opposition to nuclear power among swedish citizens and politicians[END_REF]. Arlt and Wolling [START_REF] Arlt | Fukushima effects in Germany? Changes in media coverage and public opinion on nuclear power[END_REF] point to the release of the Stern Review in the UK in 2006 [START_REF] Stern | The Economics of Climate Change: The Stern Review[END_REF] as one starting point for various political actors and lobbyists to promote nuclear energy as an effective tool in the fight against climate change.

After some hesitation, public media have cautiously adopted this narrative [START_REF] Doyle | Acclimatizing nuclear? Climate change, nuclear power and the reframing of risk in the UK news media[END_REF][START_REF] Arlt | Danke!?: Eine kommunikationswissenschaftliche Studie zum Einfluss medialer Kommunikation auf Einstellungen gegenüber Atomkraft[END_REF]. In this framing, nuclear energy is presented as an option to ensure stable, affordable, low-carbon energy. If nations want to achieve their CO2 reduction goals, they need to reduce the use of CO2-emitting power production based on natural gas and, notably, coal. Stable and affordable energy supply remain important issues. Following this line of argument, studies have identified a "reluctant acceptance discourse" [START_REF] Corner | Nuclear power, climate change and energy security: Exploring British public attitudes[END_REF][START_REF] Teräväinen | Climate change, energy security, and riskdebating nuclear new build in Finland, France and the UK[END_REF][START_REF] Bickerstaff | Reframing nuclear power in the UK energy debate: nuclear power, climate change mitigation and radioactive waste[END_REF]. Marshall [START_REF] Marshall | Nuclear power. Is the friendly atom poised for a comeback?[END_REF] points to efforts to reframe nuclear energy as climate friendly and "the real green alternative" to renewable and fossil energy sources alike. Bickerstaff et al. [START_REF] Bickerstaff | Reframing nuclear power in the UK energy debate: nuclear power, climate change mitigation and radioactive waste[END_REF] discern an unlikely pro-nuclear coalition of nuclear energy lobbyists and some environmental advocates, two constituencies that traditionally adopt opposing positions with respect to the use and expansion of nuclear energy (see also [START_REF] Kinsella | Rearticulating Nuclear Power: Energy Activism and Contested Common Sense[END_REF] or [START_REF] Greenberg | Nuclear waste management, nuclear power and energy choices: Public preferences, perceptions, and trust[END_REF] for a qualitative study on the discursive struggle in the U.S. American context).

However, while some environmental advocates support the narrative of nuclear energy as a low-carbon, climate-friendly option, at the same time, most of the prominent, powerful environmental advocacy groups and green parties across Europe remain largely opposed, presenting nuclear energy as a high-risk technology that compromises public safety [START_REF] Bickerstaff | Reframing nuclear power in the UK energy debate: nuclear power, climate change mitigation and radioactive waste[END_REF][START_REF] Deluca | Greenpeace International Media Analyst Reflects on Communicating Climate Change[END_REF]. In this context, studies in the UK have examined empirically the effects on public perception of reframing nuclear energy. Bickerstaff et al. [START_REF] Bickerstaff | Reframing nuclear power in the UK energy debate: nuclear power, climate change mitigation and radioactive waste[END_REF] present findings from a mixed-method analysis of public perception of radioactive waste disposal and climate change. Citizen focus groups were, as one part of this study, presented with a climate change frame for nuclear energy. After debating the issue, participants concluded that nuclear energy was not a desirable option, but probably an indispensable component in their country's energy supply in order to deal with climate change. This conditional support sees nuclear energy as the "lesser of two evils" [42, p. 162], while maintaining a general disapproval of the technology. Pidgeon et al. [START_REF] Pidgeon | Climate change or nuclear power-No thanks!: A quantitative study of public perceptions and risk framing in Britain[END_REF] found that while respondents' support for nuclear energy was significantly greater when it was presented as a climate-friendly option, they still preferred alternative options, such as renewables, over nuclear energy. Spence et al. [START_REF] Spence | Public Perceptions of Climate Change and Energy Futures in Britain: Summary Findings of a Survey Conducted in January-March 2010[END_REF] report that higher concern about climate change even decreased the willingness to support nuclear energy as a part of the country's energy mix, although the correlational effects were relatively modest. Wang and Kim [START_REF] Wang | Comparative Analysis of Public Attitudes toward Nuclear Power Energy across 27 European Countries by Applying the Multilevel Model[END_REF] offer an explanation for this UK finding by pointing to a negative relationship in a pan-European study between general environmental awareness (environmentalism) and acceptance of nuclear energy [START_REF] Groot | Morality and nuclear energy: perceptions of risks and benefits, personal norms, and willingness to take action related to nuclear energy[END_REF][START_REF] Vainio | Weighing the Risks of Nuclear Energy and Climate Change: Trust in Different Information Sources, Perceived Risks, and Willingness to Pay for Alternatives to Nuclear Power[END_REF].

The social perception of (nuclear energy) risks

Social science risk research includes multiple theoretical approaches to the social perception of risks. The common ground of these theoretical approaches is the understanding that what people perceive as a risk is always socially constructed. Over the last four decades, theoretical models explaining people's risk perceptions have been developed and tested empirically.

The so-called cultural theory maintains that values or worldviewsthat is, ideas of a desirable social orderfunction as filters for the selection of risks, which are considered by some social groups in society and ignored by others [START_REF] Douglas | Risk and culture: An essay on the selection of technological and environmental dangers[END_REF][START_REF] Wildavsky | Theories of Risk Perception: Who Fears What and Why?[END_REF][START_REF] Thompson | Cultural theory[END_REF]. According to the theory, these different social groups (in cultural theory labelled as egalitarians, individualists, hierarchists, and fatalists) hold different values and thus consider different risks as acceptable or inacceptable.

From a more psychological perspective, the psychometric paradigm also focuses on the subjective meanings of risk [START_REF] Slovic | Perception of Risk[END_REF][START_REF] Slovic | Perceptions of Risk: Reflections on the Psychometric Paradigm[END_REF], but holds that people subjectively assess risk sources on the basis of various qualitative aspects of risks such as voluntariness of taking the risk, benefits, catastrophic potential of the risk, or personal controllability of the risk. According to the psychometric paradigm, responses to risk are determined by the source's perceived profile on such aspects, with the involuntary, uncontrollable profile perceived as particularly risky, or unacceptable.

Another strand of theorizing and empirical research focuses on trust in persons or institutionssuch as regulatory agencies, government, industry, non-government organizations, and science as a major factor influencing risk perception and acceptance [START_REF] Cvetkovich | The attribution of social trust[END_REF][START_REF] Earle | Social trust and culture in risk management[END_REF][START_REF] Renn | Credibility and trust in risk communication[END_REF]. Here, the main assumption is that trust in persons or organizations that are supposed to regulate the specific risk is a core factor in the acceptance of risks. More specifically, high levels of trust are associated with perceiving high benefits and low risks, and consequently with high acceptance rates [START_REF] Siegrist | Salient Value Similarity, Social Trust, and Risk/Benefit Perception[END_REF]. In a similar vein, different general attitudinal constructs such as environmental awareness or cost-benefit perceptions are also used to describe and/or explain risk acceptance [START_REF] Jones | Identifying predictors of attitudes towards local onshore wind development with reference to an English case study[END_REF][START_REF] Perlaviciute | Contextual and psychological factors shaping evaluations and acceptability of energy alternatives: Integrated review and research agenda[END_REF][START_REF] Liebe | Decomposing public support for energy policy: What drives acceptance of and intentions to protest against renewable energy expansion in Germany?[END_REF].

The social amplification of risk framework draws attention to the effects of communication about risk events (e.g., nuclear accidents) [START_REF] Kasperson | The Social Amplification of Risk: A Conceptual Framework[END_REF][START_REF] Kasperson | The social amplification of risk: assessing fifteen years of research and theory[END_REF]. It is based on the assumption "that risk events interact with psychological, social, and cultural processes in ways that can heighten or attenuate public perceptions of risk and related risk behaviour" [64, p. 178-179]. Risk events are observed and communicated by individuals, groups, and institutions (e.g., mass media) using risk signals (e.g., images or symbols). These risk signals can be processed and interpreted in different ways depending on, for example, cultural biases, values, risk heuristics, or qualitative aspects of risks [START_REF] Kasperson | The social amplification of risk: assessing fifteen years of research and theory[END_REF]. The result is either an amplification or an attenuation of the risk event and the risk source.

As this brief overview of the main theoretical approaches in social science risk research has shown, risk has to be understood as a social construct shaped by social and/or psychological factors and processes, in conjunction with specific characteristics of the risk itself. Thus, risks are encoded in interpretative frames that vary across social groups. Empirical research shows too that there are different framings of nuclear energy. These interpretative frames are mainly spread by mass media and have the task of "making sense of relevant events, suggesting what is at issue" [66, p.3]. Examples of such frames that are used for nuclear energy are 'progress'

(great potential for energy production), 'energy independence' (being independent from unreliable oil and gas exporting countries), 'runaway' (nuclear energy use has to be abandoned, since humans cannot control it), or 'devil's bargain' (mix of the progress, energy independence, and runaway frames) [START_REF] Butler | Nuclear Power After Japan: The Social Dimensions[END_REF][START_REF] Gamson | Media Discourse and Public Opinion on Nuclear Power: A Constructionist Approach[END_REF]. Part of the 'devil's bargain' frame is also the characterization of nuclear energy as a low carbon energy source3 that helps mitigate climate change [START_REF] Butler | Nuclear Power After Japan: The Social Dimensions[END_REF][START_REF] Corner | Nuclear power, climate change and energy security: Exploring British public attitudes[END_REF][START_REF] Spence | Public Perceptions of Climate Change and Energy Futures in Britain: Summary Findings of a Survey Conducted in January-March 2010[END_REF][START_REF] Perlaviciute | Contextual and psychological factors shaping evaluations and acceptability of energy alternatives: Integrated review and research agenda[END_REF].

Research scope and research question

Postulating that the perception of nuclear energy is socially constructed, and that there are different social framings of nuclear energy, amongst which there is a framing as a climate friendly energy source, we derive the research question "how is concern about climate change related to perceptions of nuclear energy". As the review above of the state of research indicates, there is as yet no clear basis on which to predict whether the association between climate change concern and perception of nuclear energy will be positive or negative. Moreover, it is unclear whether the association will be uniform across countries. In the presence of the different framings of nuclear energy, it could well be the case that the association between climate change concern and support for nuclear energy differs across countries or may even be inexistent in some countries.

We have used our own data from France, Germany, Norway

Measures

In order to measure climate change concern, we constructed a climate change concern index using six items 4 . Each of these items was answered on a five-point rating scale. The first item (Q1) refers to the general degree of concern people have about climate change. Related to this item is the question as to whether people feel personally affected by climate change (Q2). 4 The wording of the items in the questionnaire was as follows: Q1: How Research suggests that feeling personally affected by climate change brings the issue closer to people and increases the likelihood of favouring policies and behaviour to mitigate climate change [START_REF] Wolf | Individual understandings, perceptions, and engagement with climate change: Insights from in-depth studies across the world[END_REF][START_REF] Lorenzoni | Public Views in Climate Change: European and USA Perspectives[END_REF]. Additionally, emotions have been identified as an influential factor in people's perception of various risks and the related actions they may take [START_REF] Böhm | Emotional reactions to environmental risks: Consequentialist versus ethical evaluation[END_REF][START_REF] Pfister | The multiplicity of emotions: A framework of emotional functions in decision making[END_REF][START_REF] Böhm | Emotion und Moral bei der Risikowahrnehmung[END_REF][START_REF] Böhm | The perceiver's social role and a risk's causal structure as determinants of environmental risk evaluation[END_REF][START_REF] Weber | Experience-Based and Description-Based Perceptions of Long-Term Risk: Why Global Warming does not Scare us (Yet)[END_REF][START_REF] Demski | Experience of extreme weather affects climate change mitigation and adaptation responses[END_REF]. Weber points out that stronger negative emotions such as fear (Q3) and outrage (Q4) serve as motivators to "remove ourselves from a dangerous situation or to change the environment in ways that remove us from risk" [72, p. 104]. Respondents were also asked to assess their willingness to contribute personally to climate change mitigation by reducing their personal use of energy (Q5); this item connects assessments of feelings and beliefs to aspects of actual personal behaviour. Moral responsibility in the face of climate change is a dimension that relates to people's understanding of action and consequences (Q6). Climate change is also an issue of environmental justice [START_REF] Routledge | Translocal Climate Justice Solidarities[END_REF].

Moreover, the degree to which people feel morally responsible for their (personal or societal) behaviour can have real-world impacts [START_REF] Böhm | Emotion und Moral bei der Risikowahrnehmung[END_REF].

These six items can be assigned to three distinct components used in the measurement of attitudes. Social psychological research differentiates between a cognitive component, an affective component and a conativethat is, behaviour-relatedcomponent of attitudes.

Cognition refers to thoughts about a certain topic. Affect denotes the subject's positive or negative feelings towards a certain topic. The conative component finally comprises the will to act in a certain manner with respect to the topic, or the actual behaviour with respect to the topic [START_REF] Eagly | The Psychology of Attitudes[END_REF][START_REF] Maloney | Ecology: Let's hear from the people: An objective scale for the measurement of ecological attitudes and knowledge[END_REF][START_REF] Maloney | A revised scale for the measurement of ecological attitudes and knowledge[END_REF]. According to these definitions, items Q2 and Q6 can be assigned to the cognitive component. Q1, Q3 and Q4 are connected to the affective component. Q5 shows a link to the conative component.

Table 1 shows results of the factor analysis, which was employed to explore the dimensionality of the selected items included in the climate change concern index. The perception of nuclear energy was elicited with an item worded as follows: "What is your general opinion about nuclear power as a method of energy generation for the UK/ Germany/ France/ Norway? Please indicate how positive or negative your opinion is". The item was answered with response categories ranging from 1 = very negative to 5 = very positive. There is a longstanding discussion of whether Likert items with at least five response categories, such as our nuclear perception variable, can be treated as quasi-interval level data (for pro argumentation, see [START_REF] Norman | Likert scales, levels of measurement and the "laws" of statistics[END_REF]; for contra argumentation, see [START_REF] Jamieson | Likert scales: how to (ab)use them[END_REF]). We assume that the categories of our nuclear perception variable are psychologically equidistant in the survey participants' minds, since the response categories are formulated so that they are equally spaced (very negativemainly negativeneither positive nor negativemainly positivevery positive).

Furthermore, in many studies, parametric statistics have been proven to be robust with respect to violations of their basic assumptions when using Likert items as dependent variables (for a comprehensive overview, see [START_REF] Norman | Likert scales, levels of measurement and the "laws" of statistics[END_REF]). Thus, we regard the use of statistical procedures requiring interval level data to be justified.

Results

Climate change concern in cross-national comparison

Table 2 shows the means of the climate change concern index for the four countries involved in the study as well as the results of the comparison of group means. Respondents from France are most concerned about climate change, followed by respondents from Germany, Norway and the UK.

Perception of nuclear energy in cross-national comparison

Figure 1 gives an overview of the percent distribution in each of the four countries of negative and positive opinion concerning nuclear energy (with the two positive and the two negative endpoints of the 5-point scale pooled for better readability).

Nuclear energy is seen in a mainly negative light in France, Germany and Norway. Respondents in the UK were more positive in their opinion towards nuclear energy than their counterparts, with 45% of respondents indicating a very or mainly positive opinion of nuclear energy, and only 33% viewing it mainly or very negatively. The view of nuclear energy is especially negative in Norway and Germany. These descriptive findings are in line with previous research on the topic [START_REF] Engels | Public climate-change skepticism, energy preferences and political participation[END_REF].

Note: Item wording: "What is your general opinion about nuclear power as a method of energy generation for the UK/ Germany/ France/ Norway? Please indicate how positive or negative your opinion is"; response scale: 1 = very negative -5 = very positive. Table 3 shows the distribution characteristics of the perception of nuclear energy for every country as well as the results of a comparison of group means. Significant differences in the perception of nuclear energy between the four countries were identified by running an ANOVA and post-hoc tests. Table 3 shows that respondents in the UK had significantly more positive perceptions of nuclear energy compared with the other three countries. As shown above, UK respondents were also the least concerned about climate change. German respondents, scoring second highest on the climate change concern index, showed more negative perceptions of nuclear energy in comparison with France and the UK. The difference in perceptions of nuclear energy between Germany and Norway was not significant.

The relation between climate change concern and perceptions of nuclear energy

In the next step, we analysed the correlations between the climate change concern index and the perception of nuclear energy in each of the four countries. As shown in Figure 2, negative correlations were found between climate change concern and perceptions of nuclear energy in all four countries, although they differed somewhat in size. That is, considering the four countries in alphabetical order, in France (r = -0.22, p < 0.01), UK (r = -0.12, p < 0.01), Norway (r = -0.09, p < 0.05) and Germany (r = -0.15, p < 0.01), respondents who were more concerned about climate change tended to perceive nuclear energy less favourably.

Fig. 2. Association between climate change concern index and perception of nuclear energy in

France, Germany, Norway and the UK.

To test the robustness of the identified negative relationship between climate change concern and nuclear energy perceptions, we ran multiple linear regression analyses for each country as well as for the overall sample including political orientation 6 , gender, education (university degree yes/no), and age (grouped 25-34, 35-44, 45-54, 55-65, and 65+) 7 as controls. These control variables were derived from the state of research that shows various socio-demographic influences on the support for nuclear energy: women tend to oppose nuclear energy more often than do men [START_REF] Sundström | Women and nuclear energy: Examining the gender divide in opposition to nuclear power among swedish citizens and politicians[END_REF], leftist or liberal political orientation decreases support for nuclear energy [START_REF] Costa-Font | Attitudes as an expression of knowledge and "political anchoring": the case of nuclear power in the United Kingdom[END_REF][START_REF] Edberg | Phasing out or phasing in: Framing the role of nuclear power in the Swedish energy transition[END_REF][START_REF] Latré | The party politics of nuclear energy: Party cues and public opinion regarding nuclear energy in Belgium[END_REF], and higher education increases support for nuclear energy [START_REF] Nguyen | Examination of different socioeconomic factors that contribute to the public acceptance of nuclear energy[END_REF]. Lastly, age has been shown to be positively related to the approval of nuclear energy [START_REF] Wang | Comparative Analysis of Public Attitudes toward Nuclear Power Energy across 27 European Countries by Applying the Multilevel Model[END_REF][START_REF]Public Attitudes to Nuclear Power[END_REF]. We introduced the control variables into the regression models in a first step and then added the climate change concern index in a second step. We believe this provides a more detailed picture of the relationship between climate change concern and perception of nuclear energy than would entering all predictors simultaneously.

As already mentioned above, we regard the dependent variablenuclear energy perceptionas quasi-interval scaled. Thus, we consider running linear regressions as justified. However, we also ran ordinal regressions as the nonparametric equivalent to linear regression, in order to check the robustness of our results (the results of the ordinal regressions can be found in Table 6 in the Appendix). Table 4 shows the results of the linear regression models. A summary of the characteristics of the variables included in the regression models can be found in Table 5 in the Appendix. When we checked the least square assumptions, we found no indication of serious violations of the assumption of normal distribution of residuals, or of the linearity assumption. We also found no indication of multi-collinearity or heteroscedasticity [90, p. 125-140]. Thus, the respective theoretical assumptions of linear regression analysis are fulfilled in each of the regression models. Furthermore, the ordinal regression models (see Table 6 in the Appendix)with only minor deviations concerning the significance of some control variablesyield the same results.

--- --- --- --- --- --- --- --- --- --- --- --- 0.27 0.23 0.09 Germany d --- --- --- --- --- --- --- --- --- --- --- --- -0.95** 0.26 -0.31** Norway d --- --- --- --- --- --- --- --- --- --- --- --- -1.19** 0.24 -0.41** CCC x UK e --- --- --- --- --- --- --- --- --- --- --- --- 0.08 0.07 0.09 CCC x Germany e --- --- --- --- --- --- --- --- --- --- --- --- 0.14 0.08 0.15 CCC x Norway e --- --- --- --- --- --- --- --- --- --- --- --- 0.
The relevant results of the linear regression models therefore can be regarded as robust.

Each of the four national models in Table 4 shows a significant negative relationship of climate change concern to the perception of nuclear energy. Thus, in each of the four countries, higher levels of climate change concern imply more negative perceptions of nuclear energy. That is, there is a uniform association between climate change concern and perceptions of nuclear energy, which is independent of the four surveyed national backgrounds. countries, meaning that the further to the right a respondent places themself on the political spectrum, the more positive is their perception of nuclear energy. Furthermore, women are less positively oriented towards nuclear energy than men, with the exception of Germany, where no gender effect is observed. Having a university degree is related to a more positive perception of nuclear energy in the UK and Norway. In the UK, there are no significant differences between the different age groups. In France, groups of higher ageexcept for ages 45-54 -tend to regard nuclear energy more positively than the reference group (age 15-24), while in Norway the opposite is the case. In Germany, it is only the age groups 45-54, 55-64, and 65+ that consider nuclear energy to be more acceptable than does the reference group. All in all, compared with the strength of the associations between the significant control variables and the dependent variable, the (negative) association between climate change concern and people's views on nuclear energy is more moderate in three of the four countries, with France's more highly negative association being the exception.

We subsequently ran a multiple regression model on the total sample, to which we added the countries as dummy variables and interactions of climate change concern with these dummy variables (see right hand column, Table 4). The model was constructed to test whether the associations of climate change concern with perceptions of nuclear energy are different in the four countries. France, where the (negative) association was the strongest, was chosen as the reference country. Table 4 shows that, when controlling for the other variables, perceptions of nuclear energy are more negative in Germany (B = -0. 4 further shows that across the four countries climate change concern, gender, and political orientation are the most important factors in the perception of nuclear energy, followed by the possession of a university degree. No significant differences were found between the different age groups.

Discussion and conclusion

Our analyses have shown a significant negative association between climate change concern and the public perception of nuclear energy in each of the four surveyed countries (high climate change concern is associated with a negative opinion of nuclear energy). Our results show that this negative association is independent of the national context where it is observed (at least in the four surveyed countries). However, the strength of the relationship varies with national contexts. The results yield several interesting insights and provide suggestions for further research, which we will now reflect upon and discuss against the current state of knowledge.

First, levels of climate change concern and valence of opinion on nuclear energy as an energy source are shown to differ significantly across the four countries. The largest differences are found in the perceptions of nuclear energy: the most positive views of nuclear energy are held in the UK, followed at some distance by France, Norway, and Germany. Somewhat less pronounced differences were found in climate change concern: it is highest in France, followed by Germany, Norway, and the UK. We may surmise that these differing levels are embedded within and differentiated by a country's social, political, and cultural heritage [START_REF] Arnold | European Perceptions of Climate Change. Socio-political profiles to inform a cross-national survey in France[END_REF][START_REF] Slovic | Nuclear Power and the Public[END_REF].

Second, despite their exhibited differences, the four countries nonetheless show an overall similarity in the pattern of relationship between climate change concern and the approval of nuclear energy. Our findings are in line with the findings of previous quantitative studies identifying an inverse relationship between climate change concern and nuclear energy perceptions among the public [START_REF] Spence | Public Perceptions of Climate Change and Energy Futures in Britain: Summary Findings of a Survey Conducted in January-March 2010[END_REF][START_REF] Wang | Comparative Analysis of Public Attitudes toward Nuclear Power Energy across 27 European Countries by Applying the Multilevel Model[END_REF][START_REF] Groot | Morality and nuclear energy: perceptions of risks and benefits, personal norms, and willingness to take action related to nuclear energy[END_REF][START_REF] Vainio | Weighing the Risks of Nuclear Energy and Climate Change: Trust in Different Information Sources, Perceived Risks, and Willingness to Pay for Alternatives to Nuclear Power[END_REF]. Thus, the hypothesis that high climate change concern is associated with negative perceptions of nuclear energy has once again found support. We were able to show that such an inverse relationship exists in four major energy-producing European countries, despite their diversity with respect to their absolute levels of approval of nuclear energy as measured by our survey, and also with respect to the structure of the national energy systems, including the actual and historic extent of nuclear energy use. Our study revealed that nuclear energy is not an unanimously preferred option for mitigating climate change through energy systems: across the four countries, people who are concerned about climate change do not see nuclear energy as a solution. Thus, the negative association between climate change concern and the perception of nuclear energy seems to be independent of national contexts, although the strength of that relationship varies across countries. Here the pattern is differentially shaped by various measured features (gender, political orientation, education). Because the inverse relationship is observed in these four different countries of Northern and Western Europe, it can be hypothesized that it may also exist in other modern, industrialised Western countries; further studies like ours can investigate the particular weight of background features in each context.

Third, our results suggest there may be little likelihood of a successful reframing of nuclear energy as a measure in reducing global CO2 emissions. Public support for nuclear energy seems to be very limited. Furthermore, there is no indication in our results that the narrative of expanding the use of nuclear energy to combat climate change will resonate with those members of the public who are concerned about climate change. The 'climate friendliness of nuclear' narrative (or 'devil's bargain' frame, which would hypothetically show high climate concern to contribute to high approval for nuclear energy) does not appear to be greatly influential and effective in the contexts we studied, nor is it the only frame that exists. The older narrative of 'nuclear as a threat due to its high catastrophic potential' (or 'runaway' frame), which dates to the beginning of the anti-nuclear movement in the early 1970s, seems to retain the upper hand.

Signs that the 'runaway' frame is weakening are apparent only in the case of Norway, where the younger generation displays more positive perceptions of nuclear energy than do older cohorts. All in all, efforts to reframe perceptions of nuclear energy may not be in keeping with the current landscape of public opinions towards this energy source and thus may be unlikely to gain broad public support. Our findings do not necessarily exclude the possibility of a nuclear renaissance from a public acceptance perspective, but they do seriously question the potential of using climate friendliness as a frame for recruiting nuclear energy supporters among persons concerned by climate change. However, an alternative view might be that reframing nuclear energy in terms of climate friendliness could become more persuasive in the light of the prominent 'climate emergency' discourses now beginning to emerge, and considering the declarations being made in so many countries around the globe (see e.g. [START_REF] Ripple | Corrigendum: World Scientists' Warning of a Climate Emergency[END_REF]). Furthermore, since the collective and individual experience of climate change impacts may become more pressingand a significant decrease in electricity consumption is unlikely to be popularreframing efforts may become more successful. Finally, we recognize a weakness in our results due to a restriction in our data collection. The explained variance was relatively low in all four regression models. This corresponds to the fact that, besides the control variables, only one predictor variable (climate change concern) could be included in the models. Our survey mandate was centred on climate change perceptions and the questionnaire could not carry sufficient items to support a multifaceted analysis of nuclear energy perception or, therefore, a comprehensive theoretical model of risk perception to be tested by regression. The regression models may remain underspecified. Other studies have examined nuclear energy perception with a much broader range of predictor variables (e.g., [START_REF] Corner | Nuclear power, climate change and energy security: Exploring British public attitudes[END_REF][START_REF] Peters | The Role of Affect and Worldviews as Orienting Dispositions in the Perception and Acceptance of Nuclear Power[END_REF]). Rather than trying to maximize the amount of explained variance in the perception of nuclear energy by introducing a grand variety of existing questionnaire items, we chose to focus explicitly on the nature of the relationship between climate change concern and approval of nuclear energy across the four surveyed countries with their distinct energy profiles and nuclear energy discourses. However, the climate change concern index is only one little piece in explaining nuclear energy perception. Thus, cross-national examinations of nuclear energy perception drawing on a broader range of potentially relevant predictor variables (see section 2.3) would be a worthwhile endeavour, in order to confirm (or not) our results.

2 . 1

 21 research: climate change concern and public perception of nuclear energy Public perception of climate change Public perception of climate change in the four countries of this study has been extensively

  , and the UK to explore the research question in four national contexts with very different traditions regarding energy generation in general and nuclear energy in particular. The cross-national comparison of perception patterns should yield valuable insights about the nature of the association between climate change concern and (dis)approval of nuclear energy, since the particular characteristics of countries can be taken into account. The question is whether the same pattern holds for all four countries. 4. Dataset and methods 4.1 The European perceptions of climate change study The data for the following analyses came from four nationwide, representative surveys in France, Germany, Norway, and the UK, conducted between June 1st and 17th, 2016, by the international social research company Ipsos MORI. The surveys mainly focused on diverse facets of the public perception of climate change (e.g., relevance of climate change relative to other national issues, images of climate change, concern about climate change, climate change beliefs, psychological distance of climate change, emotions, beliefs about scientific consensus, perception of climate impacts), but also included some few energy-related questions mainly regarding preferences for different energy sources (such as nuclear energy). The survey questionnaire was developed by the full team of researchers in English and subsequently translated into French, German and Norwegian. A double translation process was applied, with one translation provided by the pertinent national research team and another by professional translators from the employed social research company. Pilot interviews were carried out to test respondents' comprehension of the survey questions, check for translation issues, and assess the reliability of answer scales.The French, German and UK surveys ran on a weekly face-to-face omnibus. Interviews were conducted face-to-face at respondents' own homes using Computer-Assisted Personal Interviewing. In each case, the basic population was people aged 15 years and over. The average length of the interviews was around 25 minutes. In each country, stratified random samples were drawn based on country-specific geographical categorisation systems. Depending on the country, quotas were set on age, gender, occupation, rurality, region, town size, employment status, or tenure.The Norwegian survey was carried out by telephone, as face-to-face interviewing is uncommon in Norway due to the highly dispersed population. The interviews were conducted using Computer Assisted Telephone Interviewing. The average interview length was 24 minutes. The official telephone register was used as the sampling source for the study. The official telephone register includes all private non-anonymised numbers, with 30% of registered numbers being landline and 70% being mobile.The final sample sizes were as follows: The UK sample consisted of 1,033 interviews, the German sample of 1,001 interviews, the French sample of 1,010 interviews, and the Norwegian sample of 1,004 telephone interviews. Each national data set was weighted to ensure that each sample was representative of the respective population. The systematic data collection procedure helped to avoid common pitfalls of quantitative survey research (namely sampling error, coverage error, non-response error, and measurement error[67; 4, p. 24-25]). A comprehensive account of the sampling procedure and survey methodology is provided bySteentjes et al. (2017).

  Significant differences in the level of climate change concern between the four countries were identified by running an ANOVA with post-hoc tests. Due to variance heterogeneity, the Brown-Forsythe-Test as global test procedure was applied[80, p. 443-444]. The test result (p < 0.01) indicated existing significant differences in the level of climate change concern among some of the four countries. A Dunnett-T3 as post-hoc test identified significant differences between the groups[80, p. 459]. Norway and the UK score significantly lower (p < 0.05) on the climate change concern index than do France and Germany. The French respondents have the highest score on the index in comparison to the other three countries. Only the difference between Norway and the UK is not statistically significant. All in all, with means ranging from 2.90 to 3.34 on the index, which ranges from 1 (very low concern) to 5 (high concern), climate change concern seems to be moderate in the four surveyed countries.

Fig. 1 .

 1 Fig. 1. Perceptions of nuclear energy in Germany, Norway, France and the UK.

  However, as revealed by the stepwise introduction of the control variables and the climate change concern index into the regression models, the contribution of the climate change concern index to the overall explained variance varies from country to country. While in the case of France the adjusted R 2 value nearly doubles with the introduction of the climate change concern index into the regression model (block 1: adjusted R 2 = 0.043; block 2: adjusted R 2 = 0.081) and in the case of Germany it rises substantially (block 1: adjusted R 2 = 0.028; block 2: adjusted R 2 = 0.037), the contribution of the climate change concern index to the overall explained variance is small in the cases of UK and Norway (UKblock 1: adjusted R 2 = 0.106; block 2: adjusted R 2 = 0.112 / Norwayblock 1: adjusted R 2 = 0.113; block 2: adjusted R 2 = 0.118). Overall, the four regression models show relatively low adjusted R 2 values (France: 0.081, Germany: 0.037, Norway: 0.118, UK: 0.112). The negative association between perceptions of nuclear energy and climate change concern is largest in France (B = -0.31); the other three models show somewhat smaller associations (between B = -0.14 and B = -0.15). Some associations between the control variables and perception of nuclear energy are statistically significant in the different countries. Political orientation is significantly and positively related to perception of nuclear energy in all four

  95) and Norway (B = -1.19) than in France. The positive climate change concern x Norway interaction (B = 0.22) shows there is a weaker negative association of climate change concern with perceptions of nuclear energy in Norway than in France. No significant differences were found in the strength of association between France on the one hand and the UK and Germany on the other. The right-hand column of Table

Fourth, the climate

  change concern index developed in this study expands existing approaches to measuring climate change concern by including and detailing further relevant facets of concern. The climate change concern index presented by McCright [92] consists of three items, including perception that the seriousness of global warming is underestimated in the news, as well as worry about global warming and perception that global warming will threaten one's personal way of life. Our index of six items reflects the latter two components (general concern, expectation of personal consequences) and adds to this basis by including emotions (fear and outrage), behavioural intentions, and moral responsibility. In this way our climate change concern index offers richer and broader coverage of factors influencing lay people's climate change concerns.

  worried, if at all, are you about climate change? Q2: Climate change is likely to have a big impact on people like me. Q3: When you think about climate change and everything that you associate with it, how strongly, if at all, do you feel each of the following emotions? Fear

Q4: When you think about climate change and everything that you associate with it, how strongly, if at all, do you feel each of the following emotions? Outrage Q5: I am prepared to greatly reduce my energy use to help tackle climate change. Q6: Some people have moral concerns about climate change. For example, because they think that its harmful impacts are more likely to affect poorer countries, or because they feel a moral responsibility towards future generations. To what extent, if at all, do you have moral concerns about climate change?

Table 1

 1 Factor loadings and communalities based on a principal component analysis. : n = 3.720; extraction method: principal component; no rotation; 1 component extracted, explained variance = 48.3%; Kaiser-Meyer Olkin = 0.823, Bartlett test of sphericity: p < 0.05, Cronbach's α = 0.80.

	Item

Note

5

and together appear to be a sound instrument for measuring climate change concern. The climate change index was constructed by averaging the scores of the six items, meaning that it ranges from 1 as the lowest score (i.e., very low concern about climate change) to 5 as the highest score (i.e., very high concern about climate change).

Table 2

 2 Cross-country comparison of climate change concern.

	Country	M (SD)	n	France	Mean difference (SE) Germany	Norway
	France	3.34 (0.76)	972
	Germany	3.08 (0.74)	857	0.26** (0.04)
	Norway	2.92 (0.81)	913	0.42** (0.04)	0.16** (0.04)
	UK	2.90 (0.82)	979	0.44** (0.04)	0.18** (0.04)	0.02 (0.04)
	Note: M = mean; SD = standard deviation; n = number of cases; SE = standard error; * p < 0.05, ** p < 0.01; index
	ranging from 1 = no climate change concern to 5 = high climate change concern.

Table 3

 3 Cross-country comparison of nuclear energy perceptions.

				33%
			52%
	68%	67%
				22%
			24%
	18%	15%		45%
	14%	18%	24%
	Germany	Norway	France	UK
	mainly/ very negative	neither -nor	mainly/ very positive

Table 4

 4 Linear regression models predicting perceptions of nuclear energy from climate change concern and various control variables in the UK, France, Germany, and Norway.

				UK			France			Germany			Norway			Overall
	Block Variables	B	SE	ß	B	SE	ß	B	SE	ß	B	SE	ß	B	SE	ß
		Left-right scale	0.13**	0.02	0.20** 0.05*	0.02	0.10* 0.08**	0.02	0.14** 0.06**	0.02	0.12** 0.06**	0.01	0.11**
		Female a	-0.66** 0.08 -0.26** -0.26*	0.08	-0.11*	-0.13	0.08	-0.06 -0.45** 0.08 -0.18** -0.38** 0.04 -0.15**
		University degree b	0.24**	0.09	0.09**	0.09	0.08	0.04	-0.01	0.14	-0.00	0.22*	0.09	0.09*	0.09*	0.05	0.03*
		Age 25-34 c	0.07	0.15	0.02	0.34*	0.15	0.11*	0.19	0.17	0.06	-0.37*	0.16	-0.10*	-0.07	0.08	-0.02
		Age 35-44 c	0.17	0.16	0.05	0.30*	0.15	0.10*	0.28	0.17	0.09 -0.61** 0.15 -0.19** -0.13	0.08	-0.04
	1	Age 45-54 c	-0.06	0.15	-0.02	0.21	0.15	0.07	0.34*	0.16	0.13* -0.85** 0.15 -0.27** -0.26** 0.08 -0.08**
		Age 55-64 c	0.06	0.16	0.02	0.57**	0.15	0.18** 0.46**	0.17	0.16** -0.96** 0.16 -0.26** -0.13	0.08	-0.04
		Age 65+ c	-0.01	0.15	-0.00 0.58**	0.14	0.21** 0.39*	0.16	0.15* -1.00** 0.14 -0.32** -0.18*	0.07	-0.06*
		Adjusted R 2		0.106			0.043			0.028			0.113			0.037
		F statistics		13.75**			5.61**			3.74**			14.34**			17.78**
		n		884			848			848			913			3493
		Climate change concern (CCC)	-0.14** 0.05 -0.09** -0.31** 0.05 -0.20** -0.15** 0.05 -0.10** -0.14*	0.06	-0.09* -0.26** 0.05 -0.17**
		Left-right scale	0.12**	0.02	0.18** 0.03*	0.02	0.07* 0.08**	0.02	0.13** 0.04*	0.02	0.09* 0.06**	0.01	0.11**
		Female a	-0.62** 0.08 -0.24** -0.17*	0.08	-0.07*	-0.09	0.08	-0.04 -0.39** 0.08 -0.16** -0.34** 0.04 -0.13**
		University degree b	0.27**	0.09	0.10**	0.12	0.08	0.05	-0.01	0.14	-0.00 0.24**	0.09	0.10** 0.12**	0.05	0.05**
		Age 25-34 c	0.05	0.15	0.02	0.43**	0.15	0.13**	0.23	0.17	0.07 -0.41** 0.16 -0.12** 0.04	0.08	0.01
		Age 35-44 c	0.17	0.16	0.05	0.38**	0.14	0.13**	0.30	0.17	0.10 -0.65** 0.15 -0.20** 0.02	0.08	0.01
		Age 45-54 c	-0.06	0.15	-0.02	0.28	0.14	0.09	0.37*	0.16	0.14* -0.91** 0.15 -0.28** -0.11	0.08	-0.03
		Age 55-64 c	0.06	0.16	0.02	0.65**	0.15	0.20** 0.50**	0.16	0.17** -1.02** 0.16 -0.28** 0.01	0.08	0.00
	2	Age 65+ c	-0.05	0.15	-0.01 0.63**	0.14	0.23** 0.40*	0.16	0.15* -1.07** 0.15 -0.34** -0.06	0.07	-0.02
		UK d

This survey polled all member states of the then European Economic Community (EEC).

The survey was limited to the then Federal Republic of Germany, excluding the former German Democratic Republic, as Germany was still a divided state in 1982.

This characterization is supported by the Fifth Assessment Report of the IPCC: "The literature reviewed[…] shows that the range of technologies can provide electricity with less than 5% of the lifecycle GHG emissions of coal power: wind, solar, nuclear, and hydropower in suitable locations" [1, p. 540]).

Typically, values for Cronbach's α of .7 and above are classified as acceptable [81, p. 231].

The survey question was worded as follows: "In politics people sometimes talk of left and right. Using a scale from 0 to 10, where would you place yourself on this scale?" (0 representing "left" and 10 "right").

In our data set, the respondents' age was only available as a grouped variable. Thus, we had to include the different age groups as dummy variables into the regression models.

Acknowledgements

This work was supported by the Joint Programme Initiative on Climate Change (JPI), a research programme uniting National Research Councils across Europe. Our "European Perceptions of Climate Change" study, under the leadership of Professor Nick Pidgeon, was co-funded by the UK Economic and Social Research Council (grant number: ES/M009505/1), France's Agence Nationale de la Recherche (grant number: ANR-14-JCLI-0003), the KLIMAFORSK programme of the Norwegian Research Council (grant number: 244904), a cooperation agreement between Equinor (formerly Statoil) and the University of Bergen (Akademiaavtale; project number: 803589) and the German Federal Ministry of Education and Research (grant number: 01UV1403).

Appendix


domain: sde info

text:
Christophe Klopp

André Lasalle

Santiago Di Landro

Denise Vizziano-Cantonnet

RNA-Seq transcriptome data of undifferentiated and differentiated gonads of Siberian sturgeon

Keywords:

RNA-Seq transcriptome data from twenty Siberian sturgeon gonads at different developmental stages is described: ten undifferentiated gonads, six gonads of immature males and four gonads from immature females. Siberian sturgeon, Acipenser baerii , is long-lived, late-maturing fish farmed in 50 countries but its production remains on a craftsman scale when compared to industrial species. Sturgeon genetic and physiological studies are less developed than for industrial fish. The data presented hereafter enables fundamental studies on the regulatory mechanisms of sturgeon gonad development, which can further be applied both in aquaculture and in fundamental research.

Specifications Table

Subject

Biology Specific subject area Transcriptomics, sex determination and differentiation Type of data Raw RNA-Seq data and assembled reference transcriptome assembly How data were acquired Illumina HiSeq 2500 Data format Raw data and assembly information Parameters for data collection Gonads from10 sex undifferentiated fish of 3 to 6 months of age Gonads from 4 immatures males (only spermatogonias) before first maturity and from 6 immatures females (with oogonias and pre-vitellogenic oocytes) Description of data collection Gonads were collected from Siberian sturgeons farmed at Estuario del Plata (San Gregorio de Polanco, Uruguay) under natural conditions. The gonad stage was identified by histology for fish ≥6 months of age. Data

Value of Data

• This data set will benefit the community of scientists working on sex determination/sex differentiation mechanisms and gametogenesis as well as fish evolution. • This data set includes RNA-Seq of gonads at several stages before and after sex differentiation enabling to better understand the control of sex differentiation. • This data will facilitate the development of sex control strategies to increase aquaculture production of Siberian sturgeon.

Data Description

Gonadal development, from sex differentiation to the end of gametogenesis and gamete production is a key process for species perpetuation. Understanding the different regulation steps of gonad development is a key point in reproduction studies. These studies may have an impact at the applied level in the control of sex and production of gametes in aquaculture; and they also can be useful for the understanding of the general mechanisms of sex differentiation and its evolution. The Siberian sturgeon is a long lived and late maturing fish for which mechanisms of sex differentiation and gametogenesis are not well understood [START_REF] Vizziano-Cantonnet | De novo transcriptome analysis to search for sex-differentiation genes in the Siberian sturgeon[END_REF] . The unraveling of the molecular control of sex differentiation and early gametogenesis can profit from gonad RNA-seq data sets at different maturation stages. We provide here a high-quality data set including 10 gonads from sex undifferentiated animals and 10 immature gonads at early stages of gametogenesis.

Gonad samples were taken from fish at several stages of sex undifferentiated period (2.5, 3, 5, and 6 months of age), males at immature stage containing only spermatogonia (8, 9, 14 and 17 months of age), and females with oogonias and different stages of oocyte development previous to vitellogenesis (9 and 17 months of age) [START_REF] Vizziano-Cantonnet | De novo transcriptome analysis to search for sex-differentiation genes in the Siberian sturgeon[END_REF] . The gonads were sequenced individually using Illumina HiSeq 2500, except at 2.5 months for which gonads of 13 fish were collected individually under binocular loupe and pooled before RNA extraction. Raw data correspond to Fastq for RNA-Seq reads and fasta for assembled contigs. The library identification and the corresponding SRA files are given in the Table 1 .

Table 1

Fish identification (Id), library name, SRA files, SAMN files, sequencer and quality of sequences produced Fish Id Tissue samples Library name SRA files SAMN files Sequencer Nb of bases (1) Alignment rate (2) Q20 ratio (3) I1 (1) Number of bases (2) Alignment rate: is the number of sequences aligned on the de novo transcriptome reference divided by the total number of sequences of the sample expressed in percent (3) Q20 ratio is the number of raw read base pairs having a quality score equal or over 20 divided by the total number of read base pairs of the sample expressed in percent.

Experimental Design, Materials, and Methods

Ethics statement

Research procedures involving animal experimentation complied with international principles on the use and care of laboratory animals and Uruguayan regulations on animal welfare (Comisión Honoraria de Experimentación Animal: CHEA). The protocol was approved by the "Comisión de Etica en el Uso de Animales" from the Comisión Honoraria de Experimentación Animal CHEA of Uruguay (Authorization Number 006-11).

Experimental animals and rearing procedures

Siberian sturgeon ( Acipenser baerii ) individuals were obtained from a fish farm (Estuario del Plata, Uruguay). The embryos come from Poland, and were hatched and reared at natural temperature at the sturgeon farm [START_REF] Vizziano-Cantonnet | Sex determination and differentiation of the Siberian sturgeon: morphological and molecular approaches[END_REF] . The fish were sacrificed by spinal transection. Gonad samples for transcriptome studies were used individually for RNA extraction, except for the 2.5-monthold individuals, for which gonads of 13 fish were pooled for RNA extraction due to their minute size. The external gonad characteristics were observed for fish aged 2.5-5 months that were considered as sex undifferentiated following previous studies made in our Laboratory [ 1 , 3 ]. For 6-month-old fish, gonad staging was performed in fish from the same cohort as the fish used for RNA extraction, as the gonads are too small to at this age to allow for RNA extraction and histological gonad staging in the same fish. In fish > 6 months of age, one gonad was frozen in liquid nitrogen and stored at -80 °C until RNA extraction, and the contralateral gonad was stored in 10% formaldehyde for histological analysis). Histological data were reported previously [START_REF] Vizziano-Cantonnet | Identification of the molecular sex-differentiation period in the siberian sturgeon[END_REF] .

RNA extraction, cDNA library construction, and Illumina sequencing

RNA was extracted using the Illustra RNAspin Mini RNA Isolation Kit (GE Healthcare, Little Chalfont, UK) according to manufacturer instructions, and quality was assessed using an Agilent 2100 Bioanalyzer. The cDNA libraries were developed from the total RNA of the individual samples. The RNA samples conformed to the required purity criteria (A260/A230 and A260/A280 > 1.8) and quality levels (RIN > 8) (Agilent 2100 Bioanalyzer) for library preparations for sequencing. The cDNA libraries were constructed on a Tecan EVO200 liquid handler using the Illumina TruSeq Stranded mRNA sample prep kit for RNA analysis. Briefly, the mRNA molecules containing poly (A) were purified using magnetic poly (T) beads from each total RNA sample. A fragmentation buffer was added to break the mRNA into short fragments with an average length of 155 base pairs (bp) (120-210 bp). From these fragments, the first strand cDNA was synthesized using random hexamer primer. The second cDNA strand was synthesized. After purification and end repair, these short cDNA were ligated to the sequencing adapters (60 bp on each side) and enriched by polymerase chain reaction (PCR, 12 cycles). Libraries were checked using an Agilent High Sensitivity DNA Kit and quantified with a KAPA Library Quantification Kit to ensure accuracy. RNA-seq experiments were performed on the Illumina HiSeq 2500 platform (high-throughput mode) with a paired-end read length of 2 × 100 bp and an Illumina TruSeq SBS kit, v3.

Transcriptome assembly

The reads were assembled using the methods presented in [START_REF] Vizziano-Cantonnet | De novo transcriptome analysis to search for sex-differentiation genes in the Siberian sturgeon[END_REF] and released at in NCBI in TSA (Transcriptome Shotgun Assembly): https://www.ncbi.nlm.nih.gov/nuccore/GICD0 0 0 0 0 0 0 0 . The quality assessment results of the assembled transcriptome were presented in [START_REF] Vizziano-Cantonnet | Identification of the molecular sex-differentiation period in the siberian sturgeon[END_REF] and resumed in Table 1 .

  source location Laboratorio de Fisiología de la Reproducción y Ecología de Peces, Facultad de Ciencias, Universidad de la República Oriental del Uruguay.

		Country: Uruguay
		Site of collection: Estuario del Plata sturgeon farm, San Gregorio de Polanco,
		Tacuarembó, Uruguay
	Data accessibility	Raw data of RNA Seq analysis are available on Sequence Read Archive (SRA)
		database and connected with BioProject PRJNA589957

https://www.ncbi.nlm.nih.gov/bioproject/PRJNA589957 Reference transcriptome assembly is available at the NCBI in TSA https://www.ncbi.nlm.nih.gov/nuccore/GICD0 0 0 0 0 0 0 0

Acknowledgements

The authors acknowledge the chief executive officer of Estuario del Plata Facundo Márquez, to Dr. Vet. Andres Ryncowski, Mr. Eduardo Oliver, and all of the Estuario del Plata (Uruguay) staff for their ample support and kindness during the development of this work.

Funding

This work was supported by the Comisión Sectorial de Investigación Científica (CSIC), Universidad de la República Oriental del Uruguay, Grant C225-348-Uruguay; the Agencia Nacional de Investigación e Innovación-Dirección Nacional de Recursos Acuáticos ANII-DINARA -FPA 9975-Uruguay; and Agencia Nacional de Investigación e Innovación -FMV_1_2017_1_135908.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Supplementary Materials

Supplementary material associated with this article can be found, in the online version, at doi: 10.1016/j.dib.2020.105741 .