Multilevel intergroup conflict at the core of climate (in)justice: Psychological challenges and ways forward

Although developed countries have been historically responsible for causing climate change, developing countries are more vulnerable to its current and future effects and being asked to commit to levels of climate action that exceed their responsibilities and capabilities. Climate change exacerbates existing social inequities by disproportionately impacting certain groups (including women, racial minorities, and the poor) more than others. Powerful institutions such as the government and the academy have a responsibility to alter this course and advance climate justice but are themselves marred by inequities. Given these disparities, the question of how the burden of climate change mitigation should be justly distributed amongst stakeholders is of paramount importance to international and domestic climate negotiations. Insights from the social identity and group processes literatures explain how experiences of inequity along geographical and sociodemographic dimensions generate identities and groups. As group members, people are sensitive to threats to the ingroup, experience collective emotions on behalf of the group, and differentially apply morality to in‐ versus outgroups. Members are also incentivized to protect and further their group's interests relative to outgroups. Social psychology offers some promising avenues of research for potential solutions to mitigate the multilevel intergroup conflict posing as a barrier to climate justice. Climate governance recommendations to policymakers and negotiators include incentivizing integrative solutions and fully considering the justice implications of climate policy. Climate scholars are encouraged to pursue interdisciplinary collaborations, improve diversity within the academy and in research samples, and prioritize climate adaptation in developing contexts.


| INTRODUCTION
Despite increasing calls to action from academics, activists, politicians, civil society, professional organizations, and business organizations to combat climate change with urgency and unity, organizing our response to this existential global crisis remains a persistent challenge. The required response demands sustained and coordinated efforts from international organizations, local and federal governments, the private sector, and individuals-both as consumers and voters. While consumer behavior is an important cog in the wheel of climate action, the most significant changes can arguably only be implemented by policy, technology, and investments. In solidarity with principles of equity and justice, major historical polluters and current global superpowers have a responsibility to rectify the course of their past actions that have contributed most to climate change. However, while there may be some growing consensus that the burden of mitigating future damage should be assigned as a function of said responsibility, achieving a distribution of climate burden that is deemed as truly fair by all involved parties is in many ways an impossible problem. Because they function as forums for countries and leaders to spearhead collaborative and integrative supply-side solutions (e.g., climate finance; contrasted with individual-level behaviors that fall under demand-side solutions), international climate negotiations are an important tool in aid of climate justice and therefore a main contextual focus of this article.
Decades of international climate change negotiations have debated the question of who should be primarily responsible for leading efforts against climate change, for example, industrialized versus developing countries. At the core of these debates are issues of responsibility and justice, as well as capacity and efficiency of action. When it comes to justice, politicians, climate ethicists, and the general public have yet to converge on how to approach procedural, distributive, and contextual justice in climate action at both the international and intranational levels. Distributive justice emphasizes the fair distribution of mitigation and adaptation burden across stakeholders based on a multitude of factors including historical contributions to climate change, current needs, and capabilities. Procedural justice requires that the processes of determining distribution also be equitable. Contextual justice considers social and historical inequities that have rendered certain communities more vulnerable and less equipped to adapt to climate change (Foster et al., 2019;McDermott et al., 2013). Finding resolution in this matter is not easily achieved for many sociopolitical and psychological reasons, at the core of which, we argue, lies intergroup conflict.
In Section 2, we describe how climate change is shaped by inequalities along at least four dimensions, both internationally and intra-nationally (see Table 1 for a summary). Specifically, we identify that different groups: (a) have contributed unequally toward causing climate change throughout history, (b) are impacted by climate change to different degrees and with varying urgency, (c) are incentivized to defend contrasting principles guiding the global response to climate change, (d) are unequally represented and hold varying levels of influence in various important positions of power in both governments and academia. These disparities represent multiple levels of intergroup conflict, which poses as a key barrier to cooperation in domestic and international climate negotiations. In Section 3, we briefly review the implications of intergroup conflict for climate justice through the lens of psychology and outline some promising areas of psychological research aimed at mitigating intergroup conflict. In Section 4, we suggest a few systemic changes warranted within the scientific community and the government. We conclude by discussing some policy measures that would propel climate justice forward.

| Unequal contributions
An important aspect of inequality in climate change is the variance-both inter-and intranational-in historical contributions to carbon emissions (Althor et al., 2016). Internationally, economically developed countries (e.g., the United States, Japan, the United Kingdom) have benefitted from decades of unrestricted economic growth resulting in their responsibility for a major portion of global carbon emissions to date. The United States has been a top emitter annually for many decades in the past (Friedrich & Damassa, 2014) 1 and is also the overall top historical emitter, accounting for as much as 25% of cumulative global emissions (Ritchie, 2019) 1 . Consequently, the United States ranks high in economic development as well as human development indices tracked by the United Nations (#17 overall in 2020, United Nations Development Program [UNDP], 2020) 1 . In general, early industrializers display a pattern of high historical emissions relative to countries that are at less advanced stages of economic and human development.
Meanwhile, countries that are still in an earlier developmental stage (e.g., India, China, Brazil) have not been major historical contributors, but rather have emerged as present-day top emitters (Friedrich & Damassa, 2014) 1 due to their large and growing populations. India has contributed about 3% of cumulative global emissions (Ritchie, 2019) 1 and currently contributes roughly 7% annually, ranking third in total annual emissions in recent years (Ritchie & Roser, 2020) 1 . Despite its large present-day economy, India consistently ranks low in terms of other development indices (#131 overall in 2020, UNDP, 2020) 1 .
While the above statistics may already suffice in demonstrating that some countries have contributed much more significantly to climate change than others and have benefitted by developing more quickly in the process, the inequalities are much more apparent when we consider per capita statistics. As an illustration of this point, the average Indian consumes only one-tenth of the energy of the average American, per the World Bank's electric power consumption data (2014).
In addition to international inequalities in contributions to climate change, there also exist significant domestic variations in energy consumption. In the United States, affluent Americans have 25% bigger carbon footprints than lower-income residents (Goldstein et al., 2020). Similar trends exist all over the world (Oswald et al., 2020). Residents of higher income classes in developing countries also consume disproportionately more energy than lower income classes. For example, in several developing Latin American and Caribbean countries, the wealthiest (top 10% in income) residents' per capita carbon footprint was more than 12 times that of the poorest (bottom 10% in income) residents (Zhong et al., 2020). In some cases, urban elites in developing countries consume almost as much energy as residents in developed countries (Michael & Vakulabharanam, 2016). Similarly, minority groups (e.g., women, people of color) are generally less responsible for global emissions in both developing and developed countries. For example, Goldstein et al. (2022) found that Caucasian neighborhoods have the highest per capita emissions, and studies have shown how private transportation patterns are gendered, with men's lifestyles and choice of vehicles contributing to their higher emission rates compared to women (Pearse, 2017).
T A B L E 1 Overview of the multilevel inequalities and inequities in climate change.

Subnational
Affluent residents have bigger carbon footprints than lower-income residents.

International
Early developers (e.g., United States, Japan) have much higher cumulative emissions than developing countries (e.g., India).

Subnational
Lower-income residents, women, and nonwhite minorities are disproportionately impacted by climate change and are more concerned about it.

International
Lower-income countries have less climate mitigation and adaptation potential and are more vulnerable to poor social and health outcomes associated with climate change compared to higher-income countries.

Subnational
Women, nonwhite minorities, and young people tend to display more pro-environmental behaviors and higher support for proclimate policies.

International
Developed countries with high cumulative emission rates prefer to discount historical emissions in favor of current emissions in determining how the burden of climate action should be distributed between countries.

Subnational
Women and other minorities are underrepresented in powerful positions within government and academia and are thus less influential in shaping the discourse around climate change.

International
Rich, developed countries hold more power and often act as foot-draggers in international climate negotiations.

| Unequal impacts
Not only have countries and segments of the population within countries contributed unequally to climate change but, to add injury to insult in some cases, are unequally impacted by it. For one, climate change risks are higher for countries or regions within countries with certain geographical characteristics (e.g., coastlines) that make them more prone to extreme weather events related to climate change (e.g., coastal flooding). Geographical realities aside, climate change also disproportionately impacts poorer, developing countries more than developed countries, which are more immune to its effects. Low-income countries are especially vulnerable to increases in poor social and health outcomes due to climate change (Forman et al., 2016) and have overall less mitigation and adaptation potential, i.e., they lack the resources required to cope with the more adverse physical effects of climate change (Burke et al., 2015;IPCC, 2014). Comparing the top ten countries that are least and most vulnerable to climate change, Williams (2021) observes that the former category generally comprises majority-white populations while the inhabitants of the most vulnerable countries are people of color.
Even within countries, climate change disproportionately burdens the poor and those in minority groups including women and people of color (Berberian et al., 2022;Brulle & Pellow, 2006;Bullard & Johnson, 2000;Jones & Rainey, 2006;Pearse, 2017;Terry, 2009). These groups are more impacted by climate change, for example, higher climate-related mortality rates in women compared to men (Sorensen et al., 2018). Traditional societal roles adopted by women also sometimes put them at greater risk to climate impacts. For instance, women and girls who have to walk long distances to procure water in regions with scarce water supplies suffer more health problems as a result of this familial duty (World Health Organization [WHO], 2014). Further, statistics from the WHO (2014) show that more women die from natural disasters caused by climate change-plausibly because they tend to be more homebound when caring for children and their families-and experience worse mental health outcomes after disasters. Berberian et al. (2022) report on studies that have found racial disparities in health outcomes including mortality, respiratory and cardiovascular disease, heat-related illness, and mental health attributable to climate change.
Not surprisingly then, women and racial and ethnic minorities also accurately perceive greater risks from climate change and tend to be more concerned about it (Dietz & Whitley, 2018b;Flynn et al., 1994;Leiserowitz, 2006;Macias, 2016). Despite these reports, the climate concerns of vulnerable groups may be underestimated due to cultural stereotypes policymakers and the general public have about environmentalists. For example, Americans (both white and nonwhite from different income categories) misperceived nonwhite, lower-income Americans as being less concerned about the environment than white, higher-income Americans . This is on top of the fact that people severely underestimate the prevalence of pro-climate beliefs in general (Mildenberger & Tingley, 2019;Sparkman et al., 2022). These misperceptions hinder climate justice by restricting individual support for pro-climate policies and action.
Importantly, these unjust variations in climate vulnerability are also exacerbated by power differentials across sociopolitical groups. Garcia et al. (2022) review the role of power in shaping resilience capacities, noting how resilience intersects with historically entrenched patterns of inequity. They conceptualize resilience as "a socio-political process that is continuously negotiated between a range of actors with diverse needs, interests, and levels of authority." Given that many of the top historical emitters are now global superpowers, they continue to possess the ability to skew international climate negotiations in their favor while maintaining their advantage over more vulnerable, less resilient countries. We elaborate on these issues further in the following subsections.

| Unequal responses
There are three categories of distributive justice policies discussed in the literature that can guide the allocation of greenhouse gas reduction requirements: (1) "grandfathering" in previously unequal emissions, (2) correcting historically higher with lower current emissions in the "polluter-pays principle," and (3) accounting for and correcting percapita inequalities. Grandfathering, the idea that future emission allowances should be higher for major past emitters, is largely dismissed by scholars as patently unjust, yet de facto appears to serve as the basis for many current environmental policies (Knight, 2013). Some scholars oppose this dismissal with an instrumental justification for at least moderate grandfathering, arguing that emission allowances provide more utility to high emitters than to low emitters, who are already adapted to lower emission rates and that high emitters have higher dependence on emissions which are more difficult to reduce (Knight, 2014).
In direct contrast, the polluter-pays principle centers on the idea that higher emitters should proportionally reduce their emissions (Neumayer, 2000). However, there remains a debate as to whether historical emissions should be emphasized over current emissions or vice versa. Developed countries that have relatively larger historical footprints compared to the present-day top emitters have generally disfavored the consideration of historical emissions when distributing the burden of climate action across countries, since that would place a higher burden on them (Bechtel & Scheve, 2013;Muller, 2001). Instead, there is a major incentive for early industrializers to support distributive policies based on current emissions ( Figure 1). In general, however, there seems to be an international consensus that per capita emission inequalities are unjust and should not persist (Roberts, 2001). Developing economies with large populations, on the other hand, are now heavily scrutinized and believe that they face a tradeoff between economics and the environment (Fisher & Jorgenson, 2019). Due to having lower per-capita and historical emission rates, they typically favor distributions of burdens that account for inequalities along these dimensions.
Economic logic would argue that past emissions are sunk costs, which therefore should not enter into any determination of future emission allowances, which in turn ought to be determined only based on marginal costs of emission reductions (Intergovernmental Panel on Climate Change [IPCC], 1996). Nonetheless, we know that human decision makers rarely dismiss sunk costs (Parayre, 1995), and in this case moral arguments for correcting historic inequities seem to prevail on the normative side (i.e., see what moral philosophers suggest), while realpolitik seems to win out empirically (i.e., see what arguments are winning in negotiations).
Again, within-country differences likely persist in who assumes the most responsibility of reducing (personal) emissions. Some work has shown, for example, that women take on disproportionately more of the burden by acting more pro-environmentally (in the Global North, Arora-Jonsson, 2011). In the US, nonwhite minorities report higher climate activism behaviors compared to Whites (Ballew et al., 2019;Pearson et al., 2017). Similarly, young people are more enthusiastic about climate action and climate justice, presumably because they perceive greater risks to their own futures compared to older people (Corner et al., 2015;Sabherwal et al., 2021). Additionally, Bliuc et al. (2015) suggest that sociopolitical conflict best explains the divide between climate change "believers" and "skeptics," whose distinct social identities motivate behaviors to further their group's position on the issue. They also suggest that transforming such conflict-ridden intergroup relations will be important in maximizing public support for climate mitigation policies.

| Unequal representation and power imbalances
An important contributor to the perpetuation of inequities in climate change is the disproportionate underrepresentation of climate-vulnerable populations (e.g., women, people of color, developing countries) in positions of power in climate governance, academia, and activism (Pearse, 2017). In international climate negotiations, procedural justice is limited by the fact that rich, developed countries enjoy more power over proceedings and agendas and thus have the ability to restrict distributive policies that are not aligned with their incentives.
However, it is worth mentioning that countries differ in ideology and action when it comes to negotiating climate responsibilities. European countries are regarded as leaders while other countries are deemed "foot-draggers"-the United States in particular maintains a "stranglehold over any progress" related to global climate change mitigation negotiations (Roberts, 2001). Overall, however, the incentive structure is such that rich countries retain negotiation power, while poor countries have a greater vulnerability to climate change, more motivations to arrive at some agreement through compromise, while being the least equipped to deal with climate change impacts in terms of resources and adaptive technologies.
Even at the individual level, it is much less costly for higher-income people to act pro-environmentally and engage in climate activism (Dietz & Whitley, 2018a). Insofar as patterns of income inequality track with patterns of racial inequity, people of color will be generally less able to participate in protests and lobbying efforts given the opportunity cost of missing work. Eom et al. (2018) find that climate change beliefs predict support for pro-environmental action more strongly for people of higher compared to lower socioeconomic status, because their higher socioeconomic status affords these individuals a greater sense of control over life outcomes.
In the United States, the climate activism movement is also predominantly white (Curnow & Helferty, 2018), again exemplifying that the most vulnerable populations are not well-represented in positions of power in shaping the narrative around climate justice. Taylor (2015) reports on a study reviewing diversity in environmental institutions, noting that while these organizations are hiring more women, men are still much more likely to occupy the top leadership positions, i.e., presidents, chairs, directors, and so on, within said organizations. Notably, this is also true for government environmental agencies. Similar trends persist for ethnic minorities as well. Not only are there a very small percentage of minority members in these organizations, but also, they are largely restricted to lower-ranking positions. Even recruitment practices at environmental institutions perpetuate biases against hiring minorities and instead favoring those with access to greater social (and economic) capital. Parallelly, on an intragovernmental level, policymakers are often members of the majority within their cultural contexts, for example, most United States politicians are white men (Choi, 2011;Lawless, 2015;Sabharwal & Geva-May, 2013). Politicians also tend to be much wealthier than the average citizen (Thompson et al., 2019). Women, racial minority members, and the poor are therefore generally not equitably represented in positions of power in the climate change discourse.
Similar imbalances persist within academia, with Garcia et al. (2022) observing that the Global North is treated as the de facto "epicenter of climate change knowledge production." Academics from WEIRD (western, educated, industrialized, rich, and democratic) countries are consistently overrepresented in research positions and hence publications (Tam et al., 2021). In addition, the samples they study are also lacking in diversity. Much of the research on behavioral interventions to aid climate change mitigation also focuses on affluent populations in the West, but these findings cannot be applied to pre-industrial contexts where households still do not have reliable access to electricity or cannot afford major appliances, energy-efficient or not (Composto & Weber, 2022). Academia, therefore, is mostly concerned with innovating exclusively for the developed world, which indeed does not align with the ideals of global cooperation it simultaneously preaches. Importantly, a lack of diversity in climate science limits academic contributions toward progress on climate justice by amplifying already prominent WEIRD perspectives instead of drawing insights from understudied vulnerable populations.

| CHALLENGES AND SOLUTIONS FROM SOCIAL PSYCHOLOGY
At its core, the climate crisis is in many ways about multiple levels of group processes and intergroup conflict. 2 Psychological mechanisms of social identity formation and group dynamics can help explain why arriving at a compromise during negotiations on allocating the burden of climate action, for example, is a particularly challenging problem.

| Social identity and self-categorization
Most of the papers in a recent review of the social identity approach (SIA) to climate psychology by Mackay et al. (2021) focus on outcomes such as pro-environmental or mitigation behaviors and engagement in climate activism generally. However, the psychological mechanisms described can also be applied to explain why arriving at a compromise during negotiations on allocating mitigation action is a particularly challenging problem, given that powerful group processes and intergroup conflict are at the core of the climate crisis.
The key ideas of the SIA as described by Mackay et al. (2021) and Fielding and Hornsey (2016) are that people selfcategorize themselves into groups based on their identities, but given that multiple identities are typical, identification depends on which identity is made salient. In addition, the strength of one's identification with an ingroup determines how likely one is to align with group norms, experience collective emotions on behalf of the group, and act to protect the group's interests (Ellemers et al., 2002).
When thinking about climate, group identifications 3 generally arise from physical or geographical borders (both inter-and intranational), or sociodemographic dimensions including race, gender, class, income, ideology, and so on. In-versus out-group formation is also implicit along the dimensions of inequality and inequity covered in the previous section. For example, historical top emitters are collectively incentivized to defend the version of the polluter pays principle that is the least disruptive to them and more disruptive to present-day top emitters. Wealthy citizens of any country are likely predisposed to protect their high standards of living rather than sacrifice comfort, while the poorest and most vulnerable communities often have the least power in influencing domestic climate policies. Similarly, men and other majorities who are better represented in positions of power within government and academia are incentivized to maintain group status, thus impeding justice by making it more difficult for minority voices to be heard in the climate change discourse. The following subsections elaborate on the psychology of group dynamics in the context of climate justice.

| Group dynamics: Threat
It is known that individuals who strongly identify with a group work harder to further the group's interests, protect its status, and prevent harm to ingroup members (Ellemers et al., 2002;Mackay et al., 2021) and efforts to meet these goals often involve a focus on outgroups, for example, responding to perceived threats from them or even causing them harm (Halevy et al., 2015). Like most stable psychological phenomena, these behavioral tendencies triggered by (self-)identification to groups are likely generated by multiple mechanisms that operate in parallel (Jachimowicz et al., 2019), including zero-sum thinking , system justification (Jost et al., 2004), and social dominance orientation (Pratto et al., 1994).
Zero-sum thinking-perceiving one's gain as another's loss-can arise from viewing climate change as an intergroup conflict rather than a collective action problem. Under these orientations, policies aimed at improving distributive justice in climate change could be perceived as entryways for economic threats from other nations. For example, many policies are designed to achieve international distributive justice by aiming to equalize or level current emissions between more and less developed countries while balancing pertinent factors like historical emissions and population demands. Such policies would inevitably mean a relative reduction in consumption for developed countries. Seen as a loss for the ingroup and a win for the outgroup, this could lead to zero-sum orientations through feelings of personal relative deprivation (Goya-Tocchetto et al., 2020). This could explain why residents of WEIRD countries typically favor discounting historical emissions in conversations about distributive climate justice despite placing importance on fairness norms (Bechtel & Scheve, 2013). In general, zero-sum outlooks on climate negotiations inhibit integrative solutions from emerging.
In addition to zero-sum thinking that explains why higher status groups are incentivized to resist lower status groups from making relative gains, lower status groups may also solidify existing hierarchies due to system justification, a theory about how disadvantaged groups are motivated to bolster the status quo even if it disfavors them (Jost, 2019). Redistributive climate policy can be perceived as a potential threat to the power wielded by wealthy countries by creating a relative disadvantage for their economies. If citizens of wealthy countries feel threatened by such policies, system justification helps explain why they might block the implementation of said policies to protect their higher status. Lower status groups might also refrain from supporting potentially disruptive policies, instead favoring the status quo and maintaining the social hierarchy. These tendencies have also been linked to social dominance orientation-a measure of support for group-based hierarchies and preference for one's ingroup to hold the dominant position. Swim and Bloodhart (2018) underscore the implication rooted within these system-maintaining ideologies, that disadvantaged groups are somehow deserving of their suffering and that these group-based inequalities then "must be warranted, thus, allowing advantaged… groups to legitimize the system in which these inequalities exist."

| Reducing zero-sum thinking
For climate negotiations to be successful in finding cooperative and equitable solutions for the climate crisis, positivesum thinking is of vital importance. Governments could permit, encourage, and train their international climate negotiators to consider the needs of other countries and focus on finding integrative or "win-win" solutions. Although much more research on ways to reduce zero-sum thinking is warranted, Johnson et al. (2022) have promisingly shown that one way to do so is to merely remind people that other parties have reasons for their stances. Following up on that, understanding that the demands of other groups are reasonable opens the door to the exploration of integrative bargaining solutions that allow multiple parties to achieve their underlying interests. Plous (1993) showed in the context of the nuclear arms race that negotiators' assumptions of the nature of the payoffs to both sides can be dangerously wrong, for example, assuming the presence of a prisoners' dilemma when one does not exist.

| Reducing perceived economic threat
As another example of erroneous assumptions, efforts should also be focused on changing the narrative that pro-climate action can only come at the cost of economic development. This narrative has been adopted both by laypeople and decision makers in government, who tend to disproportionately focus on the economic costs of pro-climate policy while paying little attention to the often-significant co-benefits (of pro-climate action) as well as the costs of inaction (Pralle, 2009). Sustainable economic development is indeed possible (Rietig, 2020). Bain et al. (2016) showed, in a largescale study spanning 24 countries, that economic and other co-benefits can motivate climate action regardless of ideology or concern about climate change. Pointing out that a particular climate policy could advance economic and scientific development or promote a more benevolent community was especially motivating. Therefore, politicians can garner support for pro-climate policies by illuminating co-benefits that their constituencies would value, such as the creation of jobs, revenue increase for relevant stakeholders, lower energy costs and health risks (Mayrhofer & Gupta, 2016). For example, emphasizing that a transition to renewable energy sources would help secure energy independence from foreign exporters of fossil fuels could appeal to conservative voters in the United States.

| Group dynamics: Emotion
Strongly identifying members of a group can also experience collective emotions on behalf of the group (Mackay et al., 2021). Owing partly to natural selection, emotions favoring the formation and maintenance of groups are preserved through generations (Davidson & Kecinski, 2022). Under zero-sum thinking, others' gains are seen as the ingroup's losses, which could heighten negative emotions like anger toward and fear of outgroups and impede progress toward climate justice. Importantly, advances in equality are also perceived as minority gains and ingroup losses by majority members (Eibach & Keegan, 2006). Pronounced emotional responses to the ingroup's losses are increased by loss aversion (Kahneman & Tversky, 1979) from developed countries or privileged groups, who compare the result of distributive climate justice measures to their current status and power. As an added consequence, feelings of anger may be heightened in response to less powerful groups' efforts to increase their status and power. Power dynamics also determine the differential distribution of negative emotions such as shame and fear across groups (Davidson & Kecinski, 2022).
Relatedly, less privileged groups may also experience negative collective emotions in the form of anger toward outgroups they perceive as acting in unjust ways (Halevy et al., 2015;Mackay et al., 2021). These feelings often stem from people's moral appraisals of themselves and others, i.e., there is a general expectation of fairness in social exchanges and groups who violate these expectations can be perceived as immoral by others, giving rise to anger (Davidson & Kecinski, 2022;de Vos et al., 2013). Since climate change is a long-term collective action problem, it can be viewed as an infinitely repeated game. Because players in such games cannot know how many rounds of negotiations there will be between them, they should consider maintaining a good reputation through rounds of negotiation. Negative emotions like anger and retaliatory attitudes can reduce trust and make good resolutions unattainable through negotiations on climate justice.

| Harnessing group emotions productively
Certain negative collective emotions have been shown to result in positive outcomes in certain situations. For example, individuals have been shown to feel guilty on behalf of the group, especially when they believe their group to be causally responsible for injustice (Doosje et al., 2006;Halevy et al., 2015). Feelings of group-based guilt and concern for others can increase support for redistributive climate policies favoring developing countries and minorities. Similarly, group-based anger can cause people to retaliate against the unjust outgroup (Cheung-Blunden & Blunden, 2008), and members of the offending group may respond with increased empathy in response to the anger demonstrated by the protesting group (de Vos et al., 2018).
Feelings of in-group pride can also be harnessed for pro-climate intentions (Harth et al., 2013). For example, governments may garner mass support for more drastic or redistributive climate policies by framing the campaign as symbolic of their country's international leadership in fighting climate change or spearheading climate justice. The environmental NGO Rare has long used collective ingroup-pride campaigns to motivate the conservation of many public goods, from endangered birds in the Caribbean and coastal fisheries in the Philippines (Jenks et al., 2010;Veríssimo et al., 2018). The environmental consulting company Evidn has been similarly successful with campaigns that make groups anticipate the pride of being part of the solution (rather than the guilt of being part of the problem), for example, preservation efforts for the Great Barrier Reef with the help of cane farmers in Queensland, Australia (Pickering et al., 2017(Pickering et al., , 2018. Regret is another powerful motivating emotion, where actions that had negative outcomes ("commissions") are typically more regretted (and elicit more anticipated regret) in the short term (Gilovich & Medvec, 1995) than inactions with negative outcomes ("omissions"; Ritov & Baron, 1992), presumably because actions attract greater attention than inactions. Belatedly however, government officials have been found to be particularly regretful of "errors of omission," also known as false negatives or Type II errors (Gilovich & Medvec, 1995;Roberts & Wernstedt, 2019). Motivated by reputational concerns, they are incentivized to avoid criticism for not acting in response to a disaster event. More climate conscious or justice-oriented voters could pressure politicians concerned about upholding their reputations to support legislation that reflects the constituency's values. This requires, of course, that politicians are aware of the values and concerns of their constituents, which is not always the case (Geiger & Swim, 2016;Sokoloski et al., 2018).
Climate action also has an intergenerational dimension, with current generations being aware of the actions (or rather, inactions) of preceding generations, and future generations being at the mercy of current generations' actions (Böhm et al., 2020). Studies that have examined the impact of predecessors' choices to contribute or not to a public good like climate have identified intergenerational reciprocity as a powerful heuristic in intergenerational decisions (Bang et al., 2017;Wade-Benzoni, 2002). Intergenerational reciprocity is the tendency to match the action of the previous actor in the intergenerational chain and thus dynamically amplifies low past efforts by decreasing subsequent generations' rates of contribution. However, Bosetti et al. (2022) identified a simple intervention that motivates decision makers who themselves failed to receive a contribution to still contribute to the public good, namely by asking decision makers to forecast future generations' actions before making their own decision, increasing the rate of contribution from 46% to over 60%. The intervention worked by shifting decision makers' attention from the immediate negative past (and its effect on them) to a more optimistic future (and positive actions of others) in light of the collectively beneficial effect of contributing to a public good.

| Group dynamics: Morality and altruism
Group memberships can also dictate toward which groups people feel morally obligated (Pearson et al., 2021;Swim & Bloodhart, 2018). Ingroup members are likely to be included within one's scope of justice (or moral circle) while outgroup members are not. Those inside the scope of justice are considered deserving of the same rights, opportunities, and privileges as oneself. However, people are less likely to apply the same justice principles to those outside their moral circle. This means that even convincing people that climate injustice is a problem in the first place can be a difficult hurdle to cross. Indeed, if people are unable to perceive climate injustice toward morally and/or psychologically distal outgroups, they are unlikely to endorse redistributive climate policies aimed at ameliorating the problem even if they are otherwise moral individuals who value justice. For example, a study on public support for various mitigation cost distribution policies in WEIRD countries found that while citizens seem to care about fairness, they fail to account for their own country's historical contributions to climate change and developing countries' inability to shoulder mitigation burden when judging said policies (Bechtel & Scheve, 2013). This myopia can be attributed to the fact that impressions of fairness are colored by group membership and the self-serving emotions the average group member experiences toward their ingroup.

| Expanding the moral circle
Abstracting away from narrowly defined groups expands the moral circle ( Figure 2) to consider more others as deserving of justice (Crimston et al., 2016;Reese, 2016). When a group is viewed as part of one's moral circle, one is predisposed to extending justice toward it. Priming a global identity of humanity may prompt individuals in privileged groups to see the climate justice debate from the perspective of vulnerable groups. Shared identity can be created by focusing on shared values and narratives (e.g., fairness, securing a habitable planet for future generations), or enemies (e.g., climate change; Patterson, 2022).

| Sacred values
Support for redistributive climate policies can be guided by sacred values or moral imperatives (Halevy et al., 2015). Judgments about intergroup conflicts and their outcomes are often made based on ideas of righteousness, and exposure to sacred rhetoric makes listeners "think differently and care more" (Marietta, 2008). Political (or other) leaders can therefore utilize sacred values to elicit self-sacrificial behaviors from their constituents, garner public approval for their political actions, and benefit their own public image (Marietta, 2009). For example, Roser-Renouf et al. (2016) 1 report that most Americans value caring for the environment, future generations, and the poor, but they do not necessarily understand that mitigating climate change would benefit all three entities. By "reframing, repositioning, and reprioritizing" sacred values in relation to climate justice, politicians, activists, and negotiators can flexibly manage them to garner more support for altruistic or redistributive climate policies (Argo & Ginges, 2015). Even religious leaders like the Pope have been successful in swaying public opinion in favor of pro-climate action. Coined "The Francis Effect," messaging from the Catholic Pope Francis about his own position on global warming resulted in more American Catholics (and Americans in general) believing that climate change is a moral issue, a social fairness issue, and a religious issue (Maibach et al., 2015) 1 .

| Empathy
Learning about the suffering of ingroup members also heightens empathy and willingness to help. The suffering of outgroup members, however, does not instill as much empathy (Halevy et al., 2015). In the context of climate justice, abstracting to larger groups based on shared identities can motivate people to empathize with and help the most vulnerable subgroups (Devine-Wright & Batel, 2017). Help could be in the form of voting on redistributive justice policies or supporting political candidates with justice-oriented platforms.
However, some have argued that increasing ingroup empathy promotes intergroup harm and inhibits intergroup helping (Bruneau et al., 2017). Therefore, while abstracting to a higher level can help those who have been included as part of the group-identity expansion, it can also make matters worse for remaining outgroups. For example, priming a national group identity in a particular country could benefit vulnerable groups within said country while diminishing empathy for other countries. It is therefore important for psychologists studying climate justice to be weary of recommending solutions that might improve domestic matters while enhancing international conflict.

| Altruistic competition and hero projects
A frame of altruistic competition could help ameliorate intergroup conflict based on national boundaries. Competitive altruism is when one acts cooperatively or to the benefit of others in competition for an altruistic reputation (Roberts, 1998). Compared to individuals, group representatives dealing with intergroup conflict, such as political leaders or negotiators, tend to adopt a competitive stance in tackling said sociopolitical conflicts (Van Lange & Joireman, 2008).
F I G U R E 2 Expanding the moral circle to different levels of abstraction. Moral circles can be expanded to broadly defined groups based on commonalities. The scope of (climate) justice may even be extended to all sentient beings insofar as climate change threatens all people, ecosystems, and biodiversity generally, albeit to differing degrees.
They are very concerned with securing better outcomes relative to their counterparts, whom they also assume to share the same, competitive mindset. Instead of being incentivized to "win" in distributive negotiations, encouraging climate negotiators to champion global sustainability and fairness objectives could be very productive. Recognizing and rewarding good sustainable leadership could incentivize leaders to prioritize climate justice while appearing "moral and global in orientation" (Van Lange et al., 2018) in climate negotiations.
Another way to motivate climate justice-aiding behaviors in private individuals and organizations is to culturally validate certain endeavors as altruistic and deserving of praise and celebrity. Insights from the Terror Management Theory literature suggest that in some cases, we strive to maintain self-esteem as a defense against the notion of mortality made salient by climate change. This self-esteem striving can be harnessed toward motivating climate justice-aiding behaviors in private individuals and organizations by culturally validating certain endeavors, termed "hero projects," as socially important and worthy of being celebrated (Wolfe & Tubi, 2019). Examples include engaging in philanthropy and using one's fame or status to further sacred causes to enhance self-esteem. Evidence from social psychology also supports the value of leveraging self-regard to motivate prosocial behaviors. Humans often act pro-socially not necessarily in service of others but rather to derive external validation for their altruism. This is especially true when the benefactors are distant and unknown, as is often the case with climate justice (e.g., future generations, people in faraway, vulnerable countries, etc.). People vary in their responses when faced with their own mortality in the face of climate change, but interventions aimed at reducing worry about oneself have been successful in leveraging positive self-regard to increase prosocial behaviors (Schneider & Weber, 2022).

| THE ROAD TO CLIMATE JUSTICE
Section 3 discussed research-based ways in which psychological interventions might mitigate intergroup conflict and, in the process, contribute to climate justice. However, such interventions are effective at the margin, and the best avenue toward greater climate justice is to improve representation of underrepresented groups in important social and political institutions, governing and research bodies, to increase funding toward climate change (social) science and climate justice research, and to demand the adoption of policies that catalyze climate justice.

| Increasing representation in academia and politics
Diversifying voices in climate science and climate policy will help advance climate justice by underscoring the goals, motivations, and preferences of climate-vulnerable populations. Without research about and by these populations, the conversation around climate justice will continue to be shaped by intentionally or inadvertently self-interested privileged groups. The first step toward making climate science more just is to increase diverse representation in both authorship and populations studied. This involves trying to foster more cross-institutional, cross-cultural, or international collaborations to study samples in non-WEIRD countries and/or samples that are more locally or nationally representative of important sociodemographic variables (race, gender, sexual orientation, income, class, education, etc.). Simultaneously, trying to increase diversity in more influential positions (e.g., researchers, professors, journal editors, etc., who are all also potential candidates to be employed as advisors to climate policymakers and international bodies like the IPCC, etc.) within climate science also remains important. Pearson and Schuldt (2014) write about the urgent problem of representational disparities in positions of power, solving which demands not only major organizational reform but also social science-based solutions to understand and mitigate its social psychological origins.
Similarly, diversifying the government is a prerequisite to achieving procedural fairness by way of amplifying voices representing more vulnerable groups in domestic and international climate negotiations. Taking steps toward procedural justice in the determination of climate policy should in turn help advance distributive justice (Maestre-Andrés et al., 2019;Pearson et al., 2021). While achieving equality and fairness in representation is arguably an intrinsically valuable end in itself, increasing diversity can also sometimes be a means to achieve other instrumentally valuable ends. Interestingly, some work has shown that increasing female representation in government has the effect of lowering emissions through the implementation of more stringent climate policies (Mavisakalyan & Tarverdi, 2019;McKinney & Fulkerson, 2015).

| Recommendations for researchers and policymakers for non-WEIRD countries
Researchers designing and testing climate and environment-related behavioral interventions in developing countries should not be pressured into focusing on curtailment behavior (which is the focus in the West). Instead, it may be more productive to shift focus onto the adoption and diffusion of energy-efficient technology throughout these populations. This is because most residents in developing countries, on average, are not consuming as much energy as their WEIRD counterparts (Oswald et al., 2020). As a co-benefit, investing in energyefficient technology should guide developing economies toward sustainable growth and greater economic independence.
Additionally, researchers should place a renewed focus on climate adaptation strategies alongside mitigation efforts. Many climate-related adversities are now inevitable due to past and minimally required future emissions (IPCC, 2022;Parry et al., 1998). Furthermore, developing countries and other vulnerable groups have less adaptation potential or resilience in response to these adversities (Garcia et al., 2022;IPCC, 2014;Mertz et al., 2009). Prioritizing adaptation would help build infrastructural resilience in these communities.

| Aiding climate justice through policy
Although academia has and can make many meaningful contributions to climate justice, these insights cannot be effective unless put into practice through policy. Importantly, climate action is not the same as climate justice action; they each have different goals that warrant equal consideration. While climate action is generally focused on optimizing efficiency, climate justice is concerned with achieving equity. Pearson et al. (2016 point out that social science research has tended to focus on the social impacts of climate change rather than understanding the individual-and group-level processes that shape climate engagement. The latter is increasingly essential as countries work toward meeting their climate goals, which will need cooperation and attitudinal and behavioral changes from individuals and groups. The bottom-up approach to climate action that emphasizes demand-side solutions, while important, should complement but not substitute top-down measures or supply-side solutions pursued by governments and big businesses (Bataille, 2020;Batel et al., 2016;Newell, 2010). A chapter in the IPCC's 6th Assessment Report (2022) focuses on providing better energy services that reduce energy poverty and make energy access more equitable while minimizing greenhouse gas emissions through technological innovations. Governments and industries must ultimately spearhead investments in sustainable adaptation technologies and strategies and treat climate change like the collective action crisis that it is. Further, as Patterson (2022) warns, the introduction of new technologies must be accompanied by careful consideration of how they might be received by different groups with varying worldviews, values, and conceptualizations of the human-nature relationship. This ties back to the notion of contextual justice and the need for cultural sensitivity in the implementation of drastic climate policy so as not to be perceived as unjust and giving rise to political backlash and instability (Box 1).

BOX 1 The Yellow Vest movement: A cautionary tale in climate governance
The Yellow Vest protests in France present a cautionary tale in implementing a policy aimed at climate change mitigation without first considering its justice implications. The protests started in late 2018 after French President Macron communicated plans for further increases in fuel taxes he described as necessary to fight climate change at a time when fuel prices were already soaring. Lower-income citizens living in rural areas and small towns initiated the movement, and hundreds of thousands of demonstrators of various occupations joined in on the protests over time. The outrage stemmed from perceptions that the President's policies were burdening the poor while favoring the elite. Ultimately, when the protests turned increasingly violent and the economy began to suffer, the government was forced to repeal the proposed tax increases. Jetten et al. (2020) analyze the rise of the Yellow Vest movement and political instability in France using the framework of inequality and intergroup processes.

| CONCLUSION
Climate justice is a particularly challenging dilemma to solve owing to a cascade of reasons, the first of which is the existence of a multitude of different stakeholder groups that are formed on the basis of geographical boundaries, shared identities and interests, and also shared experiences of inequity. Indeed, certain groups are more or less responsible for causing climate change and vulnerable to its effects than others and have a higher or lower proclivity for ensuring that these differences are factored into the distribution of burden of climate action amongst stakeholders. Meanwhile, longstanding power imbalances and lacking representation in international political forums, domestic governments, other environmental organizations, and academia only serve to perpetuate these inequities. Crucially, inequity is simultaneously a cause and consequence of the inevitable intergroup conflict between the different stakeholder groups, members of which are incentivized to protect and further their group's interests. Group identity dictates the way members interact with others by sensitizing them to perceptions of threat toward the ingroup, instilling collective emotions that favor group maintenance, and modulating their scopes of justice and morality. Consequently, it is difficult to envision climate justice without first ameliorating the widespread inequity and intergroup conflict in the climate change space.
Fortunately, social psychology offers a number of promising avenues of research with the potential to mitigate intergroup conflict and advance climate justice. Interventions should attempt to reduce zero-sum thinking, dispel the incorrectly assumed tradeoff between economic security and pro-climate (justice) actions, harness group emotions productively to bolster pro-climate justice intentions, build optimism for a better future, expand moral circles based on common goals and enemies, increase empathy for distal outgroups, and increase altruistic behavior by leveraging tools such as sacred values and social validation. Further, research aimed at mitigating inequities that exacerbate climate injustice along racial, gender, and income differences should remain prioritized as well. In addition, scholars also have a responsibility to address the unjust power dynamics and diversity issues within the branch of the academy that deals with climate change and climate justice. Voices representing non-WEIRD groups need to be amplified in the discourse if procedural justice is to be accomplished. Not only will it be important to fix the problem of non-WEIRD authors being underrepresented in climate-related publications, but also, we must generate the demand for original research in and increased visibility of non-WEIRD populations in the literature instead of treating them as sites to replicate effects first identified in WEIRD contexts. Similar power dynamics apply to the jockeying for prominence and influence of academic disciplines, with economics and the law being the incumbent disciplines of influence in the climate justice space. Achieving climate justice unquestionably requires transdisciplinary cooperation and it is of vital importance that scholars be open to collaborating and sharing insights and credit with each other.
Finally, we acknowledge the roles of government, the private sector, and individuals in the road to climate justice. It is important for climate negotiators and policymakers to remember that climate negotiation is an infinitely repeated game but that while forward focus on efficiency targets is needed, so is a backward focus that takes into account historical patterns of inequity in pursuit of contextual, procedural, and distributive justice. Innovation from the private sector and cooperation from individuals are also necessary complements (but not substitutes) to policy efforts. We must be wary of single action bias in our response to climate change and climate injustice which are both very complex issues that demand coordinated efforts from all stakeholder groups.

CONFLICT OF INTEREST STATEMENT
The authors have declared no conflicts of interest for this article.

DATA AVAILABILITY STATEMENT
Data sharing is not applicable to this article as no new data were created or analyzed in this study.
ORCID Rohini Majumdar https://orcid.org/0000-0003-0189-9911 Elke U. Weber https://orcid.org/0000-0002-1678-3631 RELATED WIREs ARTICLES From environmental to climate justice: Climate change and the discourse of environmental justice Culture and identity in climate policy ENDNOTES 1 This is sourced from gray literature. See References for full citations. 2 For an excellent, in-depth review of cognitive and social psychological literatures on the intergroup foundations of climate justice, see Swim and Bloodhart (2018). 3 See Patterson (2022) an extended account of how identities may be created in relation to climate policy.