Conceptualisations of tipping points across diverse disciplines

The genealogy of the tipping point concept in social sciences can be traced to the 1950s when it was used to understand and describe unintentional social transitions (Nuttall, 2012). Political scientist Morton Grodzins (1957) originally described the process of ‘tipping’ and the ‘tip points’ at which 14 large cities in the United States experienced rapid and largely irreversible changes in their racial composition (for a critique of the racist origins of the ‘tipping point’ concept, see Nerlich, 2022). In contrast, the re-emergence of the notion of social tipping points in the 2000s involved a decided opening as to whether what came after the tipping point was positive or negative (desirable or not; Franzke et al., 2022): the term ‘social tipping points’ was used to reflect on deliberative social and political transformations related to climate tipping points (Milkoreit et al., 2018; Skrimshire, 2008).

In considering social–climatic tipping points, social research goes beyond trying to predict the timing and nature of tipping points, as occurs in the natural sciences, to identifying what social changes have the potential to affect the dynamics of the whole system. This involves focusing on ‘conscious interventions of human agency’ (Otto et al., 2020, p. 2356) informed by collective understandings on what desirable social–environmental states entail, where collective includes the perspectives of those who are often marginalised, such as Indigenous communities or youth (Christensen & Krogman, 2012). Such intentional tipping interventions may include the spreading of technologies, behaviours and social norms, and the creation of new institutions that contribute to the achievement of more just and equitable carbon-neutral societies (Fünfgeld, 2017; Otto et al., 2020; Whyte, 2020; Winkelmann et al., 2022). Yet, social research is not only concerned with possible interventions, but also how they are implemented and experienced, which actors are instrumental in mobilising and resisting change and the (unequal) impacts they might have (e.g. Pelling & Dill, 2010). In the following, we explore the contributions of different (interdisciplinary) research fields to the understanding of the elements of desirability and intentionality in social–climatic tipping points.

Within human geography are studies on climate adaptation tipping points or adaptation limits, that is conditions under which an adaptation solution ceases to be effective (van Ginkel et al., 2020). Within this discipline, it is often assumed that there exists a set of social and environmental conditions that meet local social values and needs (Barnett et al., 2014; Juhola et al., 2022), that is, a desirable stable state or status quo (Fünfgeld, 2017). Changes in the desirable stable state occur as a result of global anthropogenic climate change, for example, increased coastal flooding resulting in salinisation of farming lands (Juhola et al., 2022) or inundation of essential infrastructure (Barnett et al., 2014). While such local impacts may be addressed incrementally through adaptation, such as building new protective infrastructure, at some point no new adaptation options will be available and social reorganisation is required, for example, abandonment of farm land or relocation of inundated coastal towns. Some geography scholars therefore make a distinction between incremental adaptation and transformative adaptation. Transformative adaptation assumes that it is possible for social actors to identify alternative desirable stable states, which are not achievable through incremental adaptation, and then intentionally mobilise to shift social values, expectations and behaviours towards those transformative solutions through institutional tipping points. For example, feed-in tariffs may aim to move to a different energy regime by changing individual behaviours and market incentives (Fünfgeld, 2017). Where incremental adaptation is assumed to involve a smooth and linear transition that operates within tolerable limits (Dow et al., 2013; Garschagen & Soletzki, 2017), transformational adaptation is recognised as being a non-linear process that involves negotiating conflict among diverse actors at multiple scales (O’Brien & Sygna, 2013), often challenging concentrations of elite power and the status quo.

Critical human geography and environmental justice studies highlight how the desirability of alternative stable states, and the intentionality of actions that might prevent, maintain or establish certain social–climatic states, are not uncontested but rather the result of ongoing conflict and struggle in society (Cote & Nightingale, 2012; Whyte, 2020). Different value systems are not equally represented in decision-making processes, depending on power/knowledge dynamics in society. Not everyone has the same agency to have their values, beliefs and interests reflected in mainstream or hegemonic discourses about what is desirable action, or with what intentionality. For example, Pelling and Dill (2010) discuss how disasters can provide opportunities for social tipping points. Post-disaster responses often create new resource flows and social networks that can change relations between citizens and the state resulting in political regime changes where the state and elites are unable to maintain power and uphold their legitimacy. However, the likelihood for such transformative change is strongly related to pre-disaster power relations and inequalities based on class, ethnicity, etc. (Pelling & Dill, 2010). Thus, desirability and intentionality of transformative adaptation raises questions about whose values and vulnerabilities are included in scoping desirable stable states, which actors are able to exert influence at various scales, how existing social relations can be disrupted and the consequences of such radical change (Cote & Nightingale, 2012; Fünfgeld, 2017; Juhola et al., 2022).

To our conceptualisation of social–climatic tipping points, social ecology contributes an understanding of societies which lends itself to the integration of knowledge across disciplinary boundaries: societies are socio-cultural and biophysical hybrids, subject to both natural and cultural spheres of causation (Fischer-Kowalski & Weisz, 1999). In studying social metabolism—the material and energy inputs, transformation and outputs required for societal reproduction—socio-ecological research has long been conducted in the tipping-point neighbourhood. Socio-metabolic transitions, regime shifts or metabolic reconfigurations (Schindler & Demaria, 2019) occur when a society’s material and energetic basis changes fundamentally (e.g. from solar energy and biomass to fossil energy) and coincides with an equally fundamental change in societal organisation and power relations. These large-scale shifts are, in and of themselves, not intentional. However, the far-reaching change in the societal resource base that they require is only achievable through what social ecology refers to as colonisation, that is, ‘the intended and sustained transformation of natural processes, by means of organized social interventions, for the purpose of improving their utility for society’ (Fischer-Kowalski & Weisz, 1999, 234, emphases added).

From deforestation and tillage to the construction of roads or dams, these interventions render the environment more useful to specific social actors (Hausknost et al., 2016) but they also require labour and energy and generally have (unintended) consequences such as erosion, habitat loss, pollution, etc. The linking of socio-metabolic with environmental justice research (Martinez-Alier, 2007; Temper et al., 2015) has been instrumental in highlighting how the consequences of such interventions are considered undesirable by many, giving rise to ecological distribution conflicts (Scheidel et al., 2018). For example, in examining socio-metabolic transitions on small islands, social ecology has explicitly identified the role of social and ecological tipping points in explaining observed occurrences of socio-metabolic collapse (Petridis & Fischer-Kowalski, 2016; Singh et al., 2022). Although the authors explicitly acknowledge that tipping points must not necessarily signal an undesirable change, the outcome of crossing the tipping points in these cases was undesirable for the local population.

Industrial ecology considers the flows of energy and matter between human activities and nature. One of the first definitions of industrial ecology points to its contribution to the study of social–climatic tipping points: ‘Industrial ecology is the study of the means by which humanity can deliberately and rationally approach and maintain a desirable carrying capacity’ (Graedel & Allenby, 1995, p. 9, italics added). Industrial ecology quantifies the environmental impacts and pressures of human activities and evaluates strategies that might help approach desirable sustainability targets. In general, sustainability assessments (e.g. life cycle assessment) determine the damage of systems on certain areas that should be protected over time, such as human well-being, ecosystems and natural resources, but balancing the impacts and benefits of human activities on these areas remains a challenge (Schaubroeck & Rugani, 2017). What is considered a desirable outcome is often constrained by intentional policy targets guiding global, national or local actions (e.g. Sustainable Development Goals) or science-based targets with a widespread public acceptance (e.g. planetary boundaries). Thus, intentionality and desirability can contradict each other through trade-offs and rebound effects. For example, the much-contested ‘circular economy’ concept, which intendsto close material loops and slow down material consumption, can increase overall production of primary materials and thus lead to undesirable effects (Zink & Geyer, 2017). To account for the ‘absolute’ benefits and impacts of intentional actions, the concept of ‘planetary boundaries’, stemming from Earth sciences (Rockström et al., 2009), is being increasingly integrated into these assessments. This involves evaluating the environmental impacts and pressures of regions and sectors, to understand to what extent they operate within or beyond humanity’s safe operating space (Rockström et al., 2009), that is a sustainable stable state, and provide target (intentional and desirable) recommendations for policy and practice (e.g. Sandin et al., 2015). However, conducting such assessments invariably raises questions of ethics and values: which ethical principles should be used to divide emission budgets across nations and regions? Whose values guide the allocation of impacts across individuals, regions or market segments? (Sandin et al., 2015).

Incorporating intentionality and desirability into the definition of tipping points

Common across the social sciences and social–environmental research on tipping points described above is a recognition that social tipping points cannot solely be identified by and understood through the description of system changes used in natural sciences, for example, what the initial and final (stable) states are, what sustains or reinforces changes (feedbacks) and whether the changes are reversible or abrupt. To understand and navigate social–climatic tipping points, intentionality and desirability must be explicitly considered. Intentionality translates into regulations, adaptation processes and paradigm shifts (e.g. deep transformations) that aim to take action in light of past or future (impending) damage. Whether these intentions are desirable (i.e. acceptable or just) depends on the current and historical social context and on who interprets what is (un)desirable. Thus we not only need to consider the extent to which human agency can bring about transformative change (as per Milkoreit, 2023), but if such human agency exists, whether it is possible to disrupt existing social networks and resources to ensure that intentional actions do not further exacerbate existing vulnerabilities and injustices. This requires recognition that navigating social–climatic tipping points challenges the power of those with vested interests in maintaining the status quo, and paying close attention to who are the winners and losers.

Future interdisciplinary research on social–climatic tipping points needs to consider (1) whether the new stable states are desirable and by whom, taking into account the often unequal impacts of changes on human societies and (2) the role that individuals, groups and institutions have, either intentionally or unintentionally, in generating the changes and feedbacks, and who is excluded from such action. Thus, we propose that a conceptual framework needs to consider six constitutive features: desirability, intentionality, stable states, feedbacks, abruptness and irreversibility (Figure 1). Incorporating the concepts of desirability and intentionality into the general definition of tipping points proposed by Milkoreit et al. (2018) results in an expanded definition of social–climatic tipping points that can inform interdisciplinary research on climate change:

Through our framework and definition, we recognise that social and environmental systems are linked through co-evolutionary dynamics (Otto et al., 2020), that is that there are co-determining drivers that lead to cascading feedbacks in such coupled systems (van Ginkel et al., 2020). An interdisciplinary approach needs to consider the links between multiple climate and social tipping points and other non-tipping changes and their cumulative impacts.

Stable social–climatic states

The AMOC slowdown is likely to be a response to anthropogenic warming, associated ice melting and changes in the water cycle (e.g. Caesar et al., 2018; Thornalley et al., 2018). The AMOC, a key component of global ocean circulation, was relatively active over at least 1400 years, and possibly 10,000 years (Spooner et al., 2020). AMOC reconstructions show an anomalous slowdown since the mid-1800s that accelerated from the 1960s (Caesar et al., 2018, 2021; Thornalley et al., 2018). AMOC-slowdown simulations indicate an increased frequency of winter storms in some European coastal areas (e.g. Jackson et al., 2015) while climate predictions depict an increase in storm intensity (e.g. Feser et al., 2015). Projections indicate that the AMOC will weaken further, although its tipping point and collapse are unlikely during the 21st century (IPCC, 2013).

Anthropogenic forcing of global warming and the AMOC slowdown has co-evolved with economic and societal power structures. The stability of the current social state is evident internationally in the Conference of the Parties (COP) deliberations and the limited progress on reducing global carbon emissions (Carattini & Löschel, 2021). At the local level, implementation of climate change mitigation has also been slow. Yet, concern about future undesirable social–climatic states continues to bring communities and governments together to deliberate and attempt to negotiate a path towards limiting temperature increases to 1.5°C above pre-industrial levels and preventing a tipping point from occurring. Social research about these negotiations points to questions of justice in terms of whose voices count in negotiations, and how those most responsible for contributing to global warming can help those most affected by and least able to cope with climate change impacts (Okereke, 2010). Indeed, in the COP27 deliberations in November 2022, there was a breakthrough agreement to establish a dedicated ‘loss and damage’ fund for the countries most affected by climate disasters.

With respect to the AMOC specifically, concern about the undesirability of future social–climatic states is driving calls for action and adaptation. There is a growing recognition that increased storminess combined with ecological changes will have ramifications for all aspects of social life: health, relationships, livelihoods and recreation (Figure 2). In Germany, rising concern about increased frequency and intensity of extreme weather events triggered by the 2021 Ahr valley flood has reinforced calls by the climate movement for better mitigation and adaptation. One policy change currently being considered involves amendments to national construction laws to facilitate faster reconstruction of residential areas in higher grounds after flooding disasters (Lang, 2023). Thus, concern about undesirable future climatic states at a global scale is driving changes in social behaviours and policies at national and local scales. Further empirical research is needed to determine the desirability and equality of such social changes and whether they result in new social–climatic states.

Abruptness

While the AMOC slowdown is gradual (century scale; Caesar et al., 2021; Lenton et al., 2008), changes in storminess and related impacts are being recorded at pluri-annual and shorter scales among scientists and citizens alike (Lozano et al., 2004). At its worst, storms result in significant decline in human welfare, loss of life and damage to infrastructure (Ciavola & Jiménez, 2013), transformation and permanent displacement of coastal communities, resulting in significant disruptions to social, cultural and economic practices (Galappaththi et al., 2019; Zhang, 2012). The Ahr valley flood, for example, was an unusually abrupt event due to the concentration of rainfall (100 L/m² of rain falling over a 24-h period) in a critical part of the basin.

While such abrupt climatic changes have significant ecological consequences, they have also been shown to push social systems to surpass tipping points (Pelling & Dill, 2010). The Ahr valley flood is considered to have triggered a social tipping point because it marked a turning point in the public awareness and concern about the effects of climate change and shaped new discussions about adaptation. As in the case of other disasters resulting in social tipping points, the flood reconfigured social networks and resources (Möller, 2023). The federal and state governments provided 30 billion euros for reconstruction in the area, the largest post-flood package ever given in Germany. For the residents of the region, the experiences of living through the flood have affected their relationships with one another and expectations of the State. Citizens have formed working groups to develop new proposals on how government infrastructure should be rebuilt differently (Möller, 2023). While this example shows how abrupt social–climatic tipping points can result in deliberations about and intentional actions towards desirable developments, questions remain about whether humans are likely to engage as readily with less abrupt changes.

Reversibility

While there is no consensus on the irreversibility of the AMOC collapse, scientists anticipate that changes to marine ecosystems are potentially reversible depending on whether the change is non-linear (Schmittner, 2005). With respect to reversibility of impacts on infrastructure and social systems, the potential for reversibility depends on the efficiency, intensity and soundness of the policies, strategies and plans that local authorities develop and implement about land use, land take and local resources use (Kim et al., 2017). For example, Helderop and Grubesic (2019) note that there is an irreversible tipping point for infrastructure damage associated with hurricane storm surges that occurs between category III and IV hurricanes. A category IV hurricane results in a significantly greater number of households and businesses becoming flooded, more roads washed out, including official evacuation roads and roads that provide access to hospitals. The cutting off of access to hospitals is associated with higher morbidity and mortality (Helderop & Grubesic, 2019). The reversibility of the impacts also depends on strengthening the capacities of vulnerable communities and working across public sectors like housing, water and sanitation, parks, and health departments while centring the equity and affordability of measures (Graham et al., 2016; Shi et al., 2016).

In the case of the Ahr valley, reconstruction is progressing slowly. While much is able to be rebuilt, there are limitations on availability of building materials, tradespeople, engineers and capacity of the local government to process applications. While over the long-term, the communities may be rebuilt, many roads remain damaged and many buildings remain uninhabitable (Möller, 2023). The slow reversibility of impacts of the AMOC may have significant social consequences. For example, in the United States, post-disaster neighbourhood vacancy has been found to impact the mental health of those remaining and their quality of life (e.g. Newman et al., 2022). Elsewhere, extreme climatic events have resulted in community abandonment (Zhang, 2012), often because post-disaster recovery resources are inadequately and inequitably distributed to help already marginalised groups rebuild. And so, the speed with which, where and for whom, infrastructure and housing can be rebuilt may ultimately affect who stays and who leaves, with ramifications for local networks, community dynamics and capacities to respond to future climatic changes.

Feedbacks

Social responses to cascading feedbacks associated with the AMOC have the potential to further exacerbate or ameliorate the slowdown. For example, care needs to be taken when building new infrastructure and adapting industries, for example, tourism and fisheries, to avoid maladaptation and accommodate changing climatic and ecological conditions. The materials and energy needed for their implementation have a carbon footprint dependent on their life cycle (Wiedmann & Minx, 2008). Similarly, while implementing flood adaptation measures, such as traditional dikes or novel green infrastructure, requires an investment in material and energy resources, their impacts might be offset if damage is avoided, for example, to vehicles, houses or urban infrastructure (Hennequin et al., 2018; Petit-Boix et al., 2017). Further shifts in our production and consumption patterns can reduce or create risks for additional cascading effects.

In the case of Germany’s Ahr valley, changes triggered by the 2021 floods conform to an emerging new stable social–climatic state in which extreme climatic events are primarily perceived, and responded to, as a consequence of climate change, thus moving away from pre-existing ‘natural disaster’ or ‘anthropogenic hazard’ rationales. Such changes at the local (Ahr valley) and national (Germany’s emergency/disaster mechanisms) level resonate and are amplified by long-ranging processes associated with the ongoing transformations in the European political system. Several national Western European Green Parties received strong electoral support in the May 2019 European Parliamentary Elections in the constituencies of Belgium, Germany, Finland, France and Luxembourg, trends influenced by the Fridays For Future movement. In Germany specifically, opinion polls indicate an abrupt increase from 5% to 40%–60% in just 1 year (autumn 2018 to autumn 2019) in concern for the environment. Polling data indicated that the Green Party had become effectively equal with the conservative party as the preferred political party of German voters in the latter half of 2019. Such developments in the European Union’s electoral scene and public opinion have been interpreted as constitutive of a potential ‘social tipping element’ in the European political system (Winkelmann et al., 2022) that may result in cascading network dynamics and positive feedback mechanisms when coupled with extreme events, such as the Ahr valley flood in 2021.