1 Introduction

In many ways, Earth system science (ESS) and modelling have given rise to a new conceptual framework in the recent decades, which goes much beyond climate science. Indeed, Earth system science and modelling have the ambition “to build a unified understanding of the Earth”, which involves not only the “interacting physical, chemical, and biological processes between the atmosphere, cryosphere, land, ocean, and lithosphere” (Steffen et al., 2020, 54)––a daunting task in itself––but also all the relevant human and social processes interacting with these Earth system components. Recent developments in Earth system modelling make this last point very explicit: for instance, Donges et al. (2021) introduce the term “World-Earth system” in order to highlight that “human societies, their cultures, knowledge and artefacts (the “World”) should now be included on equal terms in a new family of models” (1116). “World-Earth system” aims to contrast with “Earth system”, for instance as it is commonly used in climate modelling. Indeed, Earth system models––e.g. within the context of the reports of the Intergovernmental Panel on Climate Change (IPCC)––tend to be focused mainly on the dynamics of the physical components of the Earth system, with only limited consideration for the social dynamics of the human societies––something that can be considered somewhat paradoxical in a field (ESS) that aims provide a conceptual framework for understanding the planetary-scale impacts of human activities (see Lövbrand et al., 2015, § 2.2).

The unified understanding that ESS aims to achieve should involves many different disciplines both from the natural and social sciences, and fundamentally requires some level of interdisciplinarity in the broad sense of “integrating information, data, techniques, tools, perspectives, concepts, and/or theories” (National Academy of Sciences, 2005, 2) from different disciplines and interactions among them. This need for interdisciplinarity is explicitly acknowledged by Earth system scientists; for instance, in the first paragraph of an introductory textbook on the topic, Tim Lenton writes that “Earth system science is thus a deeply interdisciplinary field” (2016, 1) and similarly, Steffen et al. (2020, 56) note that in the early days of Earth system science (i.e. 1980s), “[r]eports, workshops and conferences all agreed that ESS, given the very nature of its object, should be interdisciplinary”.

Now, the very notion of interdisciplinarity and how exactly the interdisciplinary interactions should concretely be implemented in a given context raise many epistemological and methodological questions, and there is indeed a substantial philosophy of science literature on interdisciplinarity.Footnote 1 However, there is little philosophical discussion of interdisciplinary interactions in Earth system science and modelling, despite the fundamental epistemological and methodological issues that arise in this context between the natural sciences on the one hand, and the social and human sciences on the other. In this paper, we consider the conceptual framework of Earth system science in the light of recent philosophy of science work on interdisciplinarity and values in science, highlighting the interconnections between the two. In particular, the paper puts current critical social science discussions of core ESS concepts (Anthropocene, planetary boundaries and tipping points) in an epistemological perspective about interdisciplinarity. The aim is to provide a better understanding of the ESS framework, its strengths and limitations, in view of addressing the climate and environmental challenges.

Section 2 introduces the global ESS articulation of the influential concepts of Anthropocene, planetary boundaries and tipping points. These concepts have been subject to a social science critique, which we relate to the way interdisciplinarity is implemented in ESS. Indeed, we argue that the interdisciplinary relations in ESS between natural and social / human sciences are best characterized in terms of what is called ‘scientific imperialism’ in the literature on interdisciplinarity (Sect. 3). We will see that this imperialistic nature of interdisciplinarity in ESS has some detrimental epistemic and non-epistemic effects, notably when addressing the issue of values in ESS (Sect. 4). Seriously acknowledging the interconnections between interdisciplinarity and values suggests ways for ESS to move forward in the face of the climate and environmental challenges (Sect. 5).

2 Three core concepts of Earth system science and a common critique

Three interrelated concepts are especially representative of the global conceptual framework of ESS (see Steffen et al., 2020, 59–62). First, the concept of Anthropocene aims to denote a new geological epoch characterized by the planetary-scale impact of human activities, putting the Earth system on a trajectory away from the conditions of the Holocene. Second, the concept of planetary boundaries aims to identify a “safe operating space for humanity” in terms of “boundaries for anthropogenic perturbation of critical Earth-system processes” (Steffen et al., 2015). Third, the concept of climate tipping points “refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or the development of a system” (Lenton et al., 2008, 1786), such as the climate system or other subsystems of the Earth system.Footnote 2 The more formal definitions of tipping points in ESS exploit the mathematical framework of dynamical systems theory, and require that the parameters characterizing the system can be combined in single control parameter (or a small number of control parameters), whose critical values corresponds to tipping points (Lenton et al., 2008).

The concepts of Anthropocene, planetary boundaries and tipping points encode the global perspective of ESS in the sense that they can be understood in terms of trajectories or features of the Earth system as a whole. In many ways, this global nature is closely related to a common critique that these concepts have been subject to, mainly in the social science literature: one of the main worries is that this global conceptual framework tends to promote a homogenising perspective that is blind to the various different historical, socio-political and ethical aspects that are connected to these concepts and that are key to understand the (diversity of) climate and environmental challenges.Footnote 3 According to this critique, the Earth system narrative of the Anthropocene tends to contract “the social diversity and difference into a single path for humanity”, which can lead to losing “sight of the situated conflicts, warped distribution of wealth and unequal power relations that engine the ‘great acceleration’ characterizing this new epoch” (Lövbrand et al., 2015, 213–214). Concerning the concept of planetary boundaries, Biermann and Kim (2020) similarly stress that it “was not designed to account for the regional distribution of causes and consequences of earth system transformations, historical patterns, or societal issues broadly defined” (502), so that the related discourse is “seen in the South as unfair given past colonialism and current Northern overconsumption” (514). The concept of a planetary threshold generated by a cascade of interacting climate tipping points, which are understood in terms of a relatively small number of control parameters, naturally invites what Lövbrand et al. (2015, 217) call “techno-managerial planning and expert administration”––often expressed in terms of Earth system stewardship in the ESS literature, as in Steffen et al. (2018)––and the worry is that this global and top-down stance might come “at the expense of democratic debate and contestation” (Lövbrand et al., 2015, 217).

In the last decade, there has been a substantial literature in social sciences discussing these concepts––in particular the Anthropocene and planetary boundaries concepts––and the comments above are not meant to do justice to the richness of these works. What we want to highlight is that a broad common critique can be identified in these social science analyses: the concepts of Anthropocene, planetary boundaries and tipping points, as articulated within the global ESS framework, can have homogenising and depoliticizing effects with undesired (e.g. undemocratic, unfair, counterproductive) consequences in view of addressing in a just way the climate and environmental challenges.

This critique is all the more relevant given the fact that these concepts play a central role in the (political) narrative that aims to highlight the threats posed by climate change and/or to show a certain level of commitment to the issue. For instance, António Guterres, the Secretary-General of the United Nations (UN), has on several occasions referred to the threat of climate tipping points in high-profile speeches, such as in the opening of the 2022 UN Climate Change Conference (COP27), where he warned that “our planet is fast approaching tipping points that will make climate chaos irreversible”. Similarly, concerns about climate tipping points and planetary boundaries underlie the notion of climate emergency,Footnote 4 which has been officially acknowledged by an increasing number of governments around the world. In this emergency context, the worry is that the concepts of tipping points and planetary boundaries (with the Anthropocene in the background) can help justify controversial technologies such as solar radiation management and, more generally, non-democratic forms of environmental governance (Sillmann et al., 2015).

In the next sections, we consider these core ESS concepts and their social science critique in the light of recent philosophical discussions on interdisciplinarity and values, with the aim to suggest a better articulation of these important notions and of the conceptual framework of ESS more generally.

3 Earth system science: interdisciplinarity as scientific imperialism

3.1 Three aspects of scientific imperialism

Interdisciplinarity as a field of study is extremely broad, and we do not intend (and do not need) to enter the intricate debates around interdisciplinarity. We are here rather interested in a specifically epistemological perspective on interdisciplinarity, and in particular we will exploit the notion of scientific imperialism, which can be broadly understood “as a type of interdisciplinary relation in which one scientific discipline occupies or enters into another discipline’s domain” (Mäki et al., 2017). In this broad descriptive sense, scientific imperialism does not necessarily have a negative connotation, as for instance in Durpé (1994):Footnote 5 it is first taken as a tool to characterize and understand certain interdisciplinary relations. In a second step, cases of scientific imperialism can then be evaluated in a normative perspective.

ESS is fundamentally an interdisciplinary field, which at its core involves “elements of geology, biology, chemistry, physics and mathematics” (Lenton, 2016, 1). Moreover, as we have highlighted in Sect. 1, the field has in recent years developed the ambition to “fully integrate human dynamics, as embodied in the social sciences and humanities, with biophysical dynamics in a truly unified ESS effort” (Steffen et al., 2020, 61). So, ESS involves a variety of different interdisciplinary relations, among the natural science disciplines themselves, but also between the natural science disciplines on the one hand and the social and human science disciplines on the other hand. We focus on the latter, arguing that this type of interdisciplinary relations within ESS can be understood as a case of scientific imperialism. In the context of ESS, it is really about the specific (‘imperialistic’) stance of the natural sciences with respect to the domain(s) of the social and human sciences (rather than one specific discipline invading the domain of another specific discipline).

To this aim, we consider three aspects of scientific imperialism as defined by Mäki (2013); these distinct but interrelated aspects will help us to characterize and evaluate the interdisciplinary relations at work within the framework of ESS––in particular those at work between the natural and social science domains as well as those articulated in the core ESS concepts discussed in the previous section.

“Imperialism of scope. An expansionist discipline seeks to explain phenomena that belong to the perceived domain of another discipline. This is the pursuit of explanatory unification that is disrespectful for disciplinary boundaries.

Imperialism of style. The styles and strategies of research, such as the techniques and standards of inquiry and communication, characteristic of one discipline, are transferred to, or imposed on, other disciplines.

Imperialism of standing. The academic and non-academic prestige, power, and resources as well as the acknowledged technological and political relevance of one discipline increase at the expense of those of another.” (Mäki, 2013, 334).

3.2 Imperialism of scope

Imperialism of scope entails one (set of) discipline(s) encroaching on the usual domain of another (set of) discipline(s), such that the explanations provided by the ‘invaded’ discipline(s) may be de facto superseded by those of the ‘invading’ discipline(s). This encroachment is a matter of degree, and indeed ESS clearly involves some level of imperialism of scope, in particular on the domain of the social sciences.Footnote 6 For instance, as mentioned above, recent developments in ESS explicitly have the ambition to understand (and to a certain extent, to explain) “the dynamics of human societies” (Steffen et al., 2020, 61) as well as their interactions with nature (Donges et al., 2021), which typically constitute central topics in social sciences (as a paradigmatic example, consider the Marxist analyses of the evolution of societies).

According to Mäki (2013), a central (“ontological”) constraint for a legitimate imperialism of scope is the pursuit of explanatory and ontological unification, where the former relies on the latter and where ontological unification is broadly understood as the “discovery of the extent to which there is unity in the world itself” (336). Unification understood in this sense is indeed a common objective in the natural sciences, where it has very often a normative (positive) connotation (although not all unification accounts of explanation are ontological). In this perspective, achieving some degree of unification is an important condition for an imperialism of scope to be legitimate and even desirable.Footnote 7

Now, we want to emphasize that unification understood as a normative constraint is debated in philosophy of science. Following Longino (1996), it can be argued that unification may contribute to “ontological homogeneity” by way of giving priority to a privileged class of entities, which are the product of a historically and institutionally determined disciplinary culture, and whose broader legitimacy can be disputed. Beyond the metaphysical aspects, the important point here is that this ontological homogenisation may lead to overlook relevant differences between different types of entities. From this point of view, ontological heterogeneity can be seen as a legitimate value, since “[o]ntological heterogeneity permits equal standing for different types, and mandates investigation of the details of such difference” (Longino, 1996, 47). As a consequence, according to Mäki’s ontological constraint, whether or not imperialism of scope is seen as legitimate in a given context depends on whether or not unification is seen as legitimate in that context.

In many ways, this unificatory move is at the very heart of the ESS project, since ESS aims to encompass under a single umbrella both the relevant natural and social systems composing the Earth system. This endeavour finds a motivation in the very concept of Anthropocene, where the planetary impact of human activities is often conceived to imply the “end of nature”, that is, the irrelevance of the nature/society dichotomy, hence favouring a form of explanatory and ontological homogeneity. As we just mentioned, evaluating the legitimacy of the imperialism of scope at work in ESS is then a matter of evaluating the legitimacy of such homogenisation within the framework of ESS. We have seen in Sect. 2 that one of the main critiques from the social sciences precisely concerns various aspects in which such a homogenisation can be problematic when it comes to social systems.

3.3 Imperialism of style

Let’s now consider the two other aspects of scientific imperialism. Imperialism of style refers to the transfer from one discipline to another of what is sometimes broadly called “epistemic culture” in the social sciences (Knorr Cetina, 1999).Footnote 8 Within the framework of ESS, the ambition is explicitly to transfer the global research strategy that is characteristic of climate science (e.g. in terms of global numerical models) from the domain of the natural subsystems of the Earth system (such as the atmosphere or the ocean) to the domain of social systems (such as “human societies, their cultures, knowledge and artefacts” as Donges et al., 2021, 1116 put it).

Of course, the use of modelling methods from the natural sciences to understand social systems and their interactions with their environment is widespread. Indeed, various approaches in social sciences make heavy use of computational modelling, such as agent-based modelling, typically involving game-theoretic and complex systems methods.Footnote 9 These computational approaches could be seen as involving an imperialism of style to a certain extent––it is a matter of degree––in the sense of a transfer of modelling techniques from the natural sciences to the social sciences––of course, this depends on how ‘social sciences’ are understood in the first place (and we have already commented above that they may be hard to construe as a homogeneous discipline).

In the context of ESS and its recent developments (e.g. in terms of ‘World-Earth system’, see Sect. 1), the understanding of social systems and processes (only) through the modelling lens amounts to an imperialism of style from the perspective of the critical and interpretative social science traditions.Footnote 10 For instance, ‘World-Earth system’ modelling within ESS aims to include socio-cultural aspects such as “individual and collective opinions, behaviours, preferences and expectations, and their social network dynamics” as well as “social norms and value systems” (Donges et al., 2021), together with feedback loops between these socio-cultural features and environmental ones. From the critical social science perspective, the exclusive focus on modelling studies in ESS leads to what O’Brian and Barnett (2013, 381) describe as a situation in which there is “little room within Earth system framings for critical research on the social context and unequal consequences of [the global environmental] changes for different places and groups.”

Imperialism of style within ESS not only concerns the transfer of (numerical) modelling methods, but also of concepts and mathematical tools. Indeed, the recent and growing interest in social tipping points in ESS constitutes a good example where conceptual, mathematical and modelling methods from the natural sciences are transferred to the study of the dynamics of social systems. The very definition of a social tipping point within ESS––to the extent that it is explicit––is often directly inspired by the definition of a climate tipping point. For example, the following definition of Milkoreit et al. (2018), which is based on a literature review, is very similar to the standard definition of a climate tipping point (see Lenton et al., 2008): “a social tipping point can be defined as a point within [a socio-ecological system] at which a small quantitative change inevitably triggers a non-linear change in the social component of the [socio-ecological system], driven by a self-reinforcing positive feedback mechanisms, that inevitably and often irreversibly lead to a qualitatively different state of the social system.” As this definition illustrates, the conceptual framework within which the notion of social tipping point is articulated in ESS is very much inspired by the mathematical theory of dynamical systems theory. This conceptual framework also enables the application of mathematical and modelling techniques that are characteristic of the natural sciences in view of modelling both climate and social tipping points on an equal footing in the unified ESS perspective (see Donges et al., 2020).

This imperialism of style can be normatively evaluated in the light of Mäki’s epistemological constraint, which recommends a “great deal of epistemic caution” (2013, 336); according to Rolin (2018, 54), this constraint requires that “imperialists make explicit the uncertainties involved in their attempts to apply concepts and models to topics traditionally studied in other disciplines”. The extent to which such epistemic caution is implemented within ESS is best discussed on a case-by-case basis. In the social tipping point example, it is acknowledged in the ESS literature that in general social tipping processes display “greater complexity” and are “less predictable” than climate tipping points (Winkelmann et al., 2022, § 4.4). However, a recent review on the topic highlights a trend to overuse the concept of social tipping point, mainly as a consequence of a lack of epistemic caution: Milkoreit (2023) identifies in the literature a series of epistemically detrimental patterns in the application of the concept of social tipping points (such as premature labelling, definitional vagueness, lack of evidence). Moreover, part of the work on social tipping points is characterized by an overconfidence in our ability to understand the complexity of social systems and processes in terms a few control parameters (an attitude that Milkoreit, 2023 finds “puzzling”).

3.4 Imperialism of standing

Finally, the third aspect of scientific imperialism identified by Mäki (2013) concerns in particular the higher standing within ESS (in terms of prestige, power and political relevance) of certain quantitative methods (characteristic of the natural sciences) over more qualitative ones (typically found in the critical social sciences). This imperialism of standing is closely connected to the hegemony of what Heymann et al. (2017) call the “cultures of predictions”––an expression that aims to capture the various (political, cultural, economic,…) aspects linked to the production of predictive knowledge that relies on computer models.Footnote 11 Indeed, within these dominant cultures of predictions, they note that “[n]umbers generated with sophisticated scientific means such as computer models carry authority and represent powerful arguments in their own right”, and this may lead to “the marginalization of the humanities vis-à-vis predictive scientific knowledge based on computer models and simulations” (Heymann et al., 2017, 8). This characterizes well the imperialism of standing at work within ESS, where modelling techniques play such a central and authoritative role, especially when it comes to policy making; for instance, Donges et al. (2020) are quite explicit about this role when they claim that “[c]omputer simulation models are pivotal tools for gaining scientific understanding and providing policy advice for addressing global change challenges such as anthropogenic climate change or rapid degradation of biosphere integrity” (396), where this modelling effort needs to extend to social processes in all their complexity in the new generation of World-Earth models (see Sect. 1).Footnote 12

Within the ESS framework, this imperialism of standing, as instantiated in these cultures of predictions, often implicitly involves a sort of epistemic injustice against social scientists (and against the humanities more generally), in the sense of a “credibility deficit […] making it more difficult for these scientists to function as a scientific expert” (Rolin, 2018, 59), in particular when it comes to informing policy makers.Footnote 13 To some extent, there is an acknowledgement in parts of the ESS literature of the greater complexity of social processes (compared to physical ones) and of the challenges that mathematical representation and modelling face when it comes to human behaviour and social dynamics (Donges et al., 2020, 398; see also Winkelmann et al. 2022). However, the underlying assumption in ESS––which is little debated––still is that social processes can be quantified and predicted, and moreover that modelling is the best way to inform policy––at the expense of other forms of relevant scientific knowledge, in particular from the social sciences and the humanities. O’Brien and Barnett (2013, 384) thus argue that models in Earth system science (and a fortiori ‘World-Earth system models’) “do not accommodate lives, values, needs, rights, desires, loves, interests, and the workings of power in all its forms” and that “[t]hese cannot be subsumed into mathematical models and are instead unique forms of knowledge” about important features of social processes. They further highlight that “[t]he things that models do not account for are at best subordinate (or to be factored in if possible), at worst not matters of science, and hence, invisible in the science-policy process” (2013, 384). This invisibility in the science-policy process clearly constitutes a case of epistemic injustice in the sense of a credibility deficit (or unfair distribution of credibility)Footnote 14 towards the social scientists that produce and work on these “forms of knowledge”. As a concrete example, we consider the fact that the ESS analyses of social tipping points (see § 3.3) “tend to ignore existing social theories” (Milkoreit, 2023) as exemplifying a form of epistemic injustice in the above sense, which itself can be understood as a consequence of an imperialism of standing of dynamical systems theory (among other related natural science disciplines) on critical theories of social changes.

In a first descriptive approach, we have seen in this section that the notion of scientific imperialism captures important features of the interdisciplinary relations at work within the ESS framework, in particular between natural and social sciences. We have also suggested how to apply in the ESS context various normative criteria that have been proposed in the philosophy of science literature on interdisciplinarity (we will come back to this normative aspect in the last section). We now turn to the way the imperialistic nature of interdisciplinarity in ESS affects the articulation of values in this context.

4 Values in Earth system science

The role of so-called non-epistemic values in science, such as social, ethical, political and economic values, has been largely discussed in philosophy of science, in particular in relation to the value-free ideal of science and the challenge from inductive risk.Footnote 15 More specifically, the role of non-epistemic values in climate science has more recently attracted some increasing attention.Footnote 16 Within the framework of climate modelling, non-epistemic values have been convincingly argued to enter the picture at different stages in model development and model (output) assessment. For instance, non-epistemic values can have an influence in shaping model purposes and priorities, in selecting the entities and processes being represented as well as the way to represent them. Indeed, building and developing climate models involve numerous choices that are not fully constrained by theory or observation, thus leaving ample room for the influence of non-epistemic values. This influence has also started to be explicitly acknowledged in climate science in general (the role of non-epistemic values is explicitly discussed in the latest Working Group I report of the IPCC, see IPCC, 2021). In this perspective, a crucial issue concerns the concrete management of non-epistemic values in climate science. Despite the fact that, in many ways, this issue has only been rather recently acknowledged, in particular at the concrete level of operational climate science, and thus requires further work, certain general features such as transparency and diversity have been argued to be key to legitimate value management in climate science (see, e.g., Intemann, 2015, Jebeile & Crucifix, 2021, Pulkkinen et al., 2022). In this context, transparency is about making explicit the underlying values and value judgements, while diversity concerns the plurality of values and perspectives (that is, also in terms of actors and communities).Footnote 17

Now, we want to stress that, within the framework of ESS, the imperialistic nature of the interdisciplinary relations between the natural and social science domains may pose new challenges for implementing these features and for value management more generally. Indeed, transparency and diversity about values may be more difficult to achieve in a context of scientific imperialism, since certain values prevailing in the ‘invading’ discipline may be (more or less implicitly) imposed on the domain of the ‘invaded’ discipline. Within the framework of ESS, the hegemony of computer modelling methods for understanding both natural and social systems and the related cultures of prediction (which partake of both imperialism of style and imperialism of standing, see § 3.3 and § 3.4) may lead to the implicit imposition of certain technocratic values, according to which, for instance, climate and environmental challenges are best dealt with in exclusively techno-scientific and depoliticizing terms. As noted in Sect. 2, this technocratic stance naturally “invites techno-managerial planning and expert administration at the expense of democratic debate” (Lövbrand et al., 2015, 217)––that is: at the expense of value diversity and transparency.

This lack of value diversity and transparency, which is strengthened by the scientific imperialism at work in ESS, lies at the heart of the homogenisation and depoliticization critique of the conceptual framework of ESS, and more particularly of the concepts of Anthropocene, planetary boundaries and tipping points (see Sect. 2). It is for instance quite telling that the planetary boundaries framework still relies to a large extent on a value-free ideal of science where science alone is expected to unambiguously define a “safe operating space for humanity”. However, the planetary boundaries framework clearly involves non-epistemic values at different levels, for instance when it comes to the various attitudes that can be adopted towards risks––defining what ‘safe’ means clearly involves values––or when it comes to the different possible trade-offs (or hierarchies) that need to be articulated between the different planetary boundaries (see Biermann & Kim, 2020, Brand et al., 2021).

Proposals to expand the framework to include social boundaries––in order to define a “safe and just space for humanity” (Raworth, 2012, 2017)––only strengthen the role of non-epistemic values, in particular when it comes to defining what counts as ‘just’ in this context. It is interesting to note that in recent years the ESS community has started to explicitly include a justice perspective in its approach to planetary boundaries (see recently Gupta et al., 2023, Rockström et al., 2023). In this context, an Earth system justice framework is adopted and operationalized in terms of three justice criteria, namely interspecies justice, intergenerational justice and intragenerational justice (see Gupta et al., 2023 for a discussion of Earth system justice in the ESS context). Rockström et al. (2023) convert these justice criteria into biophysical units in order to quantify “safe and just ESBs [Earth system boundaries] that minimize human exposure to significant harm […] from Earth system change”. Non-epistemic values play an important role in the concrete articulation of these justice considerations, for instance in balancing between the different justice criteria; if this role is somewhat implicitly acknowledged in the recent ESS literature, it is however explicitly put aside.Footnote 18 This move does not help managing values in this context; rather, it runs the risk of making their role (more) opaque and impeding value diversity, since value judgements are then made implicitly (or ‘by default’) and by a small number of experts.

To be clear: the issue here is not that non-epistemic values play a role in the planetary boundaries framework (this is to be expected), but rather the issue is the lack of value diversity and transparency, which raises a legitimacy question. Indeed, the value judgements (implicitly) made by the small number of experts––mostly natural scientists––designing the planetary boundaries framework may not be representative of the values and interests of the majority (or of the relevant stakeholders).Footnote 19 In the context of the operationalization of Earth system justice for planetary boundaries, Gupta et al. (2023) indeed “recognize that [they] have not adequately addressed recognition justice by including a broader representation of scholars or interested people in [their] selection of boundaries and research” (where recognition justice means including “the excluded and marginalized––women, indigenous people, local communities and developing countries, accounting for their views and ways of knowing”).

This lack of value diversity and transparency leads to the implicit––and, in a sense, ‘imperialistic’––imposition of certain values ‘by default’ that are embedded in the ESS planetary boundaries framework, such as those of the experts––who, as we have seen, are mostly natural scientists. Discussing this ESS framework from a critical social science perspective, Brand et al. (2021) thus argue that “the planetary boundaries concept limits its consideration to a rather narrow spectrum of values and worldviews” (268), and that it “risks reinforcing not only the invisibilization of other forms of knowledge […], but also the suppression of solution paths embedded in a plurality of ways of inhabiting the world […] by suggesting top-down technocratic solutions such as large-scale climate engineering” (273). This narrowing down of the space of possibilities (“solution paths”) and of the space for debate is strengthened by the ‘imperialistic’ dominance of the natural sciences within ESS,Footnote 20 which tends to leave unquestioned the linear model of the relationship between science and policy (according to which science provides value-free information for the policy-makers to follow). This linear model is contested in the social sciences (in particular in science and technology studies, e.g. see recently Jasanoff, 2021a, b; Oreskes, 2022) and in the next section we will consider alternatives that rely on more balanced interdisciplinary relationships (in particular between natural and social sciences) and on better value management (in particular promoting––rather than impeding––value diversity and transparency).

5 Perspectives

So far, we have investigated the nature of interdisciplinarity and the role of non-epistemic values in Earth system science (ESS), and we have argued in this context that the interdisciplinary relations between the natural and social science domains constitute a form of scientific imperialism. More specifically, we have seen in Sect. 3 that the very global and unified ambition of ESS involves some degree of scientific imperialism from the natural sciences on the social sciences, in its dimensions of scope, style and standing. In this sense, this paper clearly identifies a novel and important case of scientific imperialism, which has not been discussed in the literature so far––Mäki (2013, 334) actually notes that the “empirical identification [of scientific imperialism] tend to be […] difficult”.

This identification of scientific imperialism in ESS then raises the difficult question of its normative assessment. We have seen that certain normative criteria have been suggested in the literature on scientific imperialism (mainly in relation to the case of economics imperialism, see Mäki, 2009, 2013, Clarke & Walsh, 2009)––even if they do not all apply equally well to the ESS context. Various aspects of scientific imperialism as implemented in recent ESS developments can be epistemically harmful––and are therefore neither (epistemically) legitimate nor adequate––according to at least two normative dimensions: first, imperialism of style can lead to a lack of epistemic cautiousness (violation of Mäki’s epistemological condition, see § 3.3) and second, imperialism of standing may involve some level of epistemic injustice (see § 3.4). Indeed, we have seen in § 3.3 that the incautious application of mathematical and conceptual tools from climate science to social systems (e.g. concerning tipping points) can have epistemically detrimental consequences (see Milkoreit, 2023). Similarly, we have argued in § 3.4 that the cultures of predictions at work in ESS impose a credibility deficit on social scientists, which can lead to “impoverished accounts” of social systems and dynamics (see Rolin, 2018).Footnote 21 These considerations point to the need for more balanced interdisciplinary relationships within ESS, in particular between the natural and social science domains, that is, to the need for a more legitimate scientific imperialism in ESS.Footnote 22

One strategy to move towards a more balanced interdisciplinarity within ESS is to explicitly take into account value management alongside other normative criteria that are relevant for scientific imperialism in ESS (such as Mäki’s epistemological condition and Rolin’s fair distribution of credibility).Footnote 23 As already mentioned, providing a full set of necessary and sufficient conditions for scientific imperialism to be legitimate (and adequate) in ESS seems rather difficult since much depends on the concrete details of the specific situation under consideration (so that a detailed evaluation is very much a case-by-case issue). The suggestion here is to highlight value management as a central aspect of balanced interdisciplinary relationships in ESS:Footnote 24 interdisciplinary relations––including imperialistic ones––must help promoting––instead of impeding––legitimate value management, which may typically involve value diversity and transparency (see Sect. 4).

Recent work in philosophy of science on values (see Elliott, 2022 for an overview) can help to shed some light on ways to implement (legitimate) value management within ESS. For instance, Elliott (2017, 2022) suggests three conditions for guiding value management in science:Footnote 25

 (1) Transparency: “scientists should be as transparent as possible about their data, methods, models, and assumptions so that others can identify the ways in which their work supports or is influenced by particular values” (2017, 14).

 (2) Representativeness: “scientists and policymakers should strive to incorporate values that are representative of major social and ethical priorities” (2017, 14).

 (3) Engagement: this condition “focuses on generating engagement between different scientists, community members, and scholars from range of different fields” (2022, 46). In particular, this condition involves promoting diversity.

According to Elliott (2022, 46–47), condition (3) emphasises the importance of “generating communication between an interdisciplinary array of scholars in order to promote critical reflection on values in science”––in particular, such a reflection is typically pursued within critical social sciences, as we have noted in Sect. 3 (see footnote 10). So, our suggestion here that the issues of value management and interdisciplinarity are interconnected and best addressed together is thus very much in line with Elliott’s account of value management. Now, to concretely implement Elliott’s conditions (1)-(3) within the framework of ESS raises a number of tricky questions (some of which being related to general issues identified by Elliott himself, independently of the ESS context). For instance, to what extent and how exactly should transparency be implemented? (As Elliott, 2022, 47 puts it: “[t]ransparency can never be achieved perfectly, and it has costs as well as benefits […], so it is important to specify more precisely how to achieve the kinds of transparency necessary for managing values appropriately.”) When it comes to the representativeness condition, identifying “major social and ethical priorities” in the global context of ESS is extremely challenging. And similarly, identifying who is entitled to take part in the engagement effort and under what conditions is not easily answered at the scale of the entire planet (for instance, power relations among stakeholders need to be carefully considered at this scale, see also footnote 27). More specifically, how to engage with indigenous and other subaltern communities around the world, their priorities and values is indeed extremely challenging. All these questions relate to difficult and open issues about values in science that are subject to intense on-going research (see Elliott, 2022 for an overview), and addressing them in depth would go much beyond the scope of this paper (but constitutes an important task for future work).

What we want to stress is that fostering legitimate value management within ESS in the sense of implementing Elliott’s conditions of transparency, representativeness and engagement involves recalibrating interdisciplinary relations––including imperialistic ones––within ESS. Indeed, implementing condition (3) above requires ESS to engage with a “range of different fields”, in particular including (critical) social sciences when it comes to generate “critical reflection on values” in ESS. This engagement can take many different forms and take place at different levels. As an example, the international science initiative Future Earth precisely aims to provide an institutionalized framework for such an interdisciplinary engagement.Footnote 26 This latter puts severe constraints on scientific imperialism in ESS: while great epistemic caution is required along the dimensions of scope and style, imperialism of standing seems incompatible with value diversity and interdisciplinary engagement (in particular so as to avoid all forms of epistemic injustice, see § 3.4). In this perspective, the pursuit of explanatory unification and the transfer of concepts and methods form one discipline to another within ESS need to make explicit their limitations and allow for critical reflection on values in ESS––but should not lead to a higher standing or any form of hegemony of the ‘imperialist’ concepts and methods.

We would like to end with a few considerations about ways forward inspired by recent works in science and technology studies (STS) on how science should best address the global climate and environmental challenges. Indeed, Inkpen and DesRoches (2019) emphasize interdisciplinarity and values as central features of what they call “science in the Anthropocene”, since the Anthropocene confronts natural and social scientists with “problems and systems that transgress traditional disciplinary boundaries” and since, at the same time, the Anthropocene also “increasingly involve[s] discussions that inextricably link the normative and the scientific”. This latter link is also at the heart of Jasanoff’s co-production framework, which rests on “the observation that how we acquire and organize our knowledge of the world is always entangled with ideas of how we should govern it” (Jasanoff, 2021a)––ideas which of course fundamentally involve value issues. Co-production in this sense is a central feature of knowledge production within the framework of ESS: as a paradigmatic example, the global ESS perspective naturally involves the concept of Earth system stewardship, that is, the idea of steering the Earth system on a ‘safe’ planetary trajectory (in an abstract planetary state space), away from dangerous potential planetary tipping points (see Steffen et al., 2018). Of course, such a planetary stewardship fundamentally involves value considerations, as the value-laden notions of ‘safe’ and ‘dangerous’ clearly illustrate; it also raises the issue of legitimate value-management in a particularly acute manner, since the values of the experts involved in steering the Earth system may play a disproportionate and illegitimate role.

From a co-production perspective, the issues of values and of value management are therefore central to the enterprise of scientific knowledge production: in the context of climate science, Jasanoff (2021b) recently argues for questions of justice to be at the heart of the climate knowledge-making process (according to her, it is crucial to ask questions such as: “how might knowledge-making be made more compatible with society’s demand for just climate policies?”). In the context of ESS, acknowledging co-production similarly entails seriously (and openly) debating over the (ethical, political, social, economic,…) values to be promoted, and interdisciplinary engagement (in Elliott’s sense) provides favourable conditions for such a debate.Footnote 27 As Inkpen and DesRoches (2019) put it: “[m]oving forward, natural scientists need to more fully embrace their colleagues in the social sciences and humanities who are specifically trained to deal with such [value] issues.”Footnote 28 We have argued that this very much applies to ESS.

Much work remains to be done within ESS to address the issue of value management and to recalibrate interdisciplinary relations accordingly, including in their imperialistic dimensions inherent to ESS. Given the scientific ambitions of the field (e.g. fully integrating social systems into the Earth system description) and its normative ramifications (e.g. in terms of planetary stewardship), the interrelated value and interdisciplinarity challenges are especially acute and pressing in ESS, in particular when it comes to articulate the influential––in the co-productionist sense––concepts of Anthropocene, planetary boundaries and tipping points. As Brand et al. (2021, 280) put it, “[n]o one discipline or approach is afforded the luxury anymore of pretending that its findings are not political”.