Overview

In reports of the Intergovernmental Panel on Climate Change (IPCC), calibrated language is used to communicate confidence and/or agreement in claims. This language is highly specialised and has developed over time to account for diverse sources of knowledge and types of agreement. Currently, the IPCC uses two typologies for calibrated language – a qualitative confidence scale that assesses the amount of evidence, and expert agreement about that evidence, and a more quantitative scale that measures and expresses uncertainty. IPCC leadership intends for calibrated language to help make their reports scientifically clearer, although the resulting stylised language raises readability challenges. Calibrated IPCC language is also used, cynically, as a diplomatic tool during the report adoption plenaries of the Panel, as government delegates raise questions about the characterisation of climate facts. Uncertainty language in the IPCC, then, signifies both technical advancement in the characterisation of uncertainty and the challenges of communicating climate science in diverse contexts.

17.1 Introduction

In his article, beautifully titled ‘the precautionary principle and enlightened doomsaying’, French philosopher Jean-Pierre Dupuy gets right to the heart of why IPCC authors spend countless hours of volunteer labour pouring over their uncertainty language, carefully calibrated with their chapter group of expert assessors, ensuring that the terms align with the research at hand and the guidance provided by the IPCC. It is work of care and standardisation, precise depictions of what is known and what isn’t, what has been fully investigated and what is emergent as a topic of research, and where and how experts agree about climate science. Uncertainty, in IPCC documents, emerges from managed, calibrated epistemic and authorial processes – processes that the IPCC has taken up with incredible technocratic enthusiasm.

Calibrated language in IPCC reports, specifically in their Summaries for Policymakers (SPMs), is intended to provide scientific clarity and precision to the text. However, this is often perceived to be at the expense of readability, particularly among lay people or non-expert decision makers as the IPCC seeks to expand its audience beyond environmental ministries (Barkemeyer et al., Reference Barkemeyer, Dessai, Monge-Sanz, Renzi and Napolitano2016). The highly stylized language, requiring specific knowledge to comprehend, is a barrier to accessing climate information in IPCC reports.

Uncertainty is also an alibi. Using uncertainty language offers an alternative to providing statements of fact, which may take scientists decades or even centuries (if ever) to come to agreement upon. Formal uncertainty language helps shade in details about knowledge that always comes in the form of ranges of possible future outcomes – like climate modelling – or knowledge that is partial, underway, incomplete or currently in a state of some expert disagreement. Uncertainty allows for plausible hedging. It is protective and, like much of scientific dispositions, it is conservative, offering ranges that may narrow or widen as more becomes known.

Uncertainty is also used cynically. Dupuy contrasts epistemic uncertainty to the uncertainty of random variables in life. Scientists know this well, characterising different types of uncertainty in response to how it is generated – through computer models or through conflicts in expert agreement, to name two examples. But climate contrarians have regularly taken the deployment of uncertainty by scientists to underscore what is not known, suggesting that action cannot be taken until knowledge is complete. This approach does not hold up well in the face of the overwhelming evidence of human-caused climate change.

Instead, the cynical approach to uncertainty is used in increasingly sophisticated ways, including using the careful process of calibrated language in IPCC reports as a tactic for stalling and derailing the adoption of these reports at a political level, as described later. But first, this short chapter will provide an overview of the history and typology of uncertainty language before examining a case study of political re-interpretations of IPCC uncertainty guidance.

17.2 A Brief History and Typology of Calibrated Language in the IPCC

Scientific uncertainty is a means for communicating precision in ranges of outcomes. There are two main types of uncertainty – model uncertainty and socially derived uncertainty – which further encompasses conflict uncertainty, judgement uncertainty and ethical uncertainty. Model uncertainty can reflect parameters of climate models or the structural uncertainty inherent in making decisions about the code (Funtowicz & Ravetz Reference Funtowicz and Ravetz1990; Draper Reference Draper1995; Patt, 2007). Conflict uncertainty (Patt, 2007) is generated by subjective, expert disagreement relating to how to interpret evidence. Judgement uncertainty (O’Reilly et al., Reference O’Reilly, Brysse, Oppenheimer and Oreskes2011), like conflict uncertainty, is socially derived and is generated through the cultural specificity of the group of experts charged with assessing information. The IPCC is just beginning to consider the ethical implications of model choices as Integrated Assessment Models (IAMs) continue to gain power as epistemic and political tools (see Chapter 15). The IPCC communicates model uncertainty and, to an extent, conflict uncertainty. The social act of performing the assessment creates judgement uncertainty, which the IPCC generally does not assess.

The history of uncertainty treatment in the IPCC originates with attempts to standardise the communication of model uncertainty and, over time, develops into more elaborate devices to calibrate socially derived uncertainty (see also Swart et al., Reference Swart, Bernstein, Ha-Duong and Petersen2009). In the First Assessment Report (AR1), only Working Group I (WGI) used uncertainty language and this hewed closely to quantitative, probabilistic statements familiar to earth systems modellers. In the Second Assessment Report (AR2), WGII included qualitative confidence statements in their Executive, Summaries as well (Mastrandrea & Mach, Reference Mastrandrea and Mach2011: 661). The AR3 provided the first attempt to standardise IPCC approaches to assessing and communicating uncertainty, although this was only picked up by WGI and WGII (for an insider’s account, see Petersen, [2006] 2012). Moss and Schneider (Reference Moss, Schneider, Pachauri, Taniguchi and Tanaka2000) wrote the guidance document, a wide-ranging article that offered advice on how to match a style of uncertainty communication with the type of uncertainty being assessed. This guidance was applied interpretively, chapter by chapter, as the expert authors iterated on the guidance to suit the publications they assessed. While this makes intuitive sense from a scholarly perspective, it did not help the report readers more clearly understand the information assessed. AR4 leadership worked towards a more systemised approach, at least within – and for the first time, across all – WGs.

AR4 was written with a four-page guidance document for calibrating uncertainty (IPCC, 2005). This note built upon Moss and Schneider’s advice, along with the substantial proceedings of a 2004 IPCC workshop titled ‘Describing Scientific Uncertainties in Climate Change to Support Analysis of Risk and of Options’ (Manning et al., Reference Manning, Petit and Easterling2004). Each of the three WGs could, in essence, choose one of several approaches to calibrating their confidence language depending on the epistemic traditions of their WG, including how best to communicate uncertainty for the type of literature generally assessed (IPCC, 2005). The InterAcademy Council (IAC) report, an independent assessment of the IPCC, took place after the plaudits and scandals emerging from AR4 (see Chapters 3 and 6). An entire chapter is devoted to ‘IPCC’s evaluation of evidence and treatment of uncertainty’ (IAC, 2010: 27). After analysing the three different WG uncertainty standards, the IAC review authors recommended that the WGIII approach – using a qualitative level-of-understanding scale describing the amount of evidence available and the degree of agreement among experts – was ‘convenient’ and recommended that this become the standard across all three WGs, supplemented with qualitative uncertainty judgements when possible (IAC, 2010: xiv–xv).

The IPCC took this advice into account for AR5 and AR6, both of which used the AR5 guidance note on uncertainty, although they have elaborated their approach slightly. This is because, while ‘level-of-understanding’ language can help readers understand the knowledge basis that guides the authors’ judgement, this language does not communicate their likelihood assessment. Authors communicate their qualitative level-of-understanding and then – depending on the type of knowledge being assessed – calibrate their assessment with formalised, qualitative confidence language or quantified uncertainty language. Specifically, the guidance note (Mastrandrea et al., Reference Mastrandrea, Field and Stocker2010) instructs authors to:

1. 1. ‘evaluate the validity of a finding’: type, amount, quality, consistency of evidence

2. 2. If high agreement and robust confidence, do one of the following:

   1. a. Qualitative level of confidence based on author judgement (very low, low, medium, high, very high) (Mastrandrea et al., Reference Mastrandrea, Field and Stocker2010: 2)

   2. b. Quantitative measure of uncertainty (virtually certain, very likely, likely, about as likely as not, unlikely, very unlikely, exceptionally unlikely) (Mastrandrea et al., Reference Mastrandrea, Field and Stocker2010: 2)

      1. i. Statistical analysis to determine probability distribution

      2. ii. Alternately, a formal, quantitative survey of expert views can determine probability distribution (Mastrandrea et al., Reference Mastrandrea, Field and Stocker2010: 4)

The AR5 (and AR6) uncertainty guidance included a figure and a table to help visualise the ranges of uncertainty, along with the appropriate calibrated language. The qualitative ‘confidence scale’ combines the level-of-understanding along axes of evidence and agreement (Figure 17.1). Confidence, because it is a collective judgement by the authors about the state of the literature being assessed, can be evaluated even when evidence is limited if existing literature is generally in agreement (Mastrandrea et al., Reference Mastrandrea and Mach2011: 679).

Figure 17.1 Confidence scale comparing evidence and agreement.

Adapted from Figure 1 in Mastrandrea et al., Reference Mastrandrea, Field and Stocker2010: 3

When the information at hand allows assessors to make quantitative judgements about uncertainty, another scale of language is used to describe likelihood. Figure 17.2 helps authors align their probabilistic assessment with likelihood language, articulating the numerical range behind the prose. The table’s footnote suggests that some additional likelihood terms from AR4 can be carried forward if that probabilistic estimate is more appropriate for the assessment.

Figure 17.2 Likelihood scale matching terms to probability ranges.

Adapted from Table 1 in Mastrandrea et al., Reference Mastrandrea, Field and Stocker2010

Figure 17.1 and the table in Figure 17.2 function as devices for IPCC authors to align their assessment with the calibrated language expected in the full assessment reports. Along with these reference tools, IPCC authors working on internal IPCC documents – such as uncertainty guidance – often publish more conceptual versions of their IPCC-adjacent work in peer-reviewed journals. This allows for additional scrutiny, as well as ensuring that their work is attributable (read: citable) to a broader audience than the universe of IPCC authors (see Manning et al., Reference Manning, Petit and Easterling2004; Mastrandrea et al., Reference Mastrandrea and Mach2011 for key examples related to IPCC uncertainty). For AR5, the IPCC guidance note – with its clear, stepwise, user-guide style – contrasts with the longer scholarly style of the lengthier concept paper, although the content remains consistent. Significantly, the peer-reviewed concept paper lays out the importance of creating a ‘traceable account’ of all uncertainty statements in the IPCC, moving from individual chapters through to the SPM and Technical Summary. Such traceable accounts are important for rigour and precision, as well as for assisting those representing the IPCC at the approval plenaries (Mastrandrea et al., Reference Mastrandrea and Mach2011). Additionally, these publications provide guidance for assessing uncertainty related to ‘key findings’, which suggests that key findings should be those with robust evidence and agreement along with relatively high levels of confidence or likelihood.

This process has become increasingly legible, transparent and standardised. But the fact that an IPCC ‘key finding’ must be adorned with varying linguistic levels of uncertainty further relegates knowledge that cannot be treated in this way to findings that are not, by default, ‘key’. Adler and Hirsch Hadorn (Reference Adler and Hirsch Hadorn2014) note several critiques about scholarship that is either difficult or impossible to calibrate. This includes scholarship coming from models of linear expertise (Beck, Reference Beck2011a), small scale, holistic studies that are the hallmark of anthropology (Bjurström & Polk, Reference Bjurström and Polk2011), and a lack of inclusion of interpretive social sciences (Hulme & Mahony, Reference Hulme and Mahony2010). The totalising demands of the IPCC’s uncertainty language marginalises entire forms of knowledge and sets of disciplinary expertise, while at the same time paints over the knowledge that is assessed with a veneer of completeness and authority.

What is thereby left out of the IPCC’s ‘key findings’ may well be knowledge that is essential to understanding how to survive the climate crisis. For example, this might be knowledge from the interpretive social sciences that reveals the possibilities or barriers to behavioural, political and cultural change in different contexts, or Indigenous knowledge or otherwise marginalised knowledge (see Chapter 13). What is left in the text is often conceptually vague, either because of slippage in the use of formal uncertainty language or else due to more fundamental misunderstandings. Aven and Renn (Reference Aven and Renn2015) note that the conceptual and theoretical underpinnings of risk and uncertainty in IPCC reports remain unclear, even as guidance over the assessment process has become more directed and authors attempt to take a more standardised approach to calibrated language.

The requirement for deploying rigid uncertainty language raises another concern about what is left out of IPCC texts. This is the way the IPCC communicates low-probability, high-risk events, such as the rapid disintegration of the polar ice sheets (O’Reilly et al., Reference O’Reilly, Oreskes and Oppenheimer2012). In the case of the ice sheets, AR4 authors did not include assessments of ‘rapid dynamical flow’, although they noted the exclusion – a wispy, flagging gesture towards a serious conflict in this part of the report (see Chapter 12 and Box 12.1). For AR5, uncertainty guidance included encouragement to consider such events, exhorting author teams to ‘provide information of the range of possible outcomes, including the tails of distributions of variables relevant to decision-making and risk management’ (Mastrandrea et al., Reference Mastrandrea and Mach2011: 681). Building levees that address the middle range projections for sea-level rise is very different from building levees that account for the higher-end projections.

The users of the IPCC reports – who are sometimes framed as decision-makers, other times as ‘consumers’ of the products of the reports – also have diverse lenses through which they read these apparently clear words. In their literature review categorising IPCC approaches to and critiques of uncertainty, Adler and Hirsch Hadorn (Reference Adler and Hirsch Hadorn2014: 669) included a box about end users titled ‘pluralism of epistemic standards and values of users’. These different standards and values become apparent in the example offered in the following section, as the WGI AR6 report travelled to the report adoption IPCC plenary in July and August 2021.

17.3 When Calibration Veers Off Course: Political Re-interpretations of Uncertainty

Comparing the AR4 and AR5 reports, the use of calibrated language in IPCC texts increased in both frequency and diversity across the three scales: evidence/agreement, confidence and likelihood (Mach et al., Reference Mach and Field2017). Janzwood (Reference Janzwood2020) extended this analysis to note further increases in calibrated uncertainty language use in the Special Reports of the AR6 cycle. Mach et al. – a team of experts who have held roles as IPCC authors, co-chairs, advisors, and Technical Support Unit staff – are clear about the goals underpinning the more sophisticated set of AR5 uncertainty guidance: ‘a harmonised, more broadly applicable approach, enabling consistent treatment of uncertainties in communicating the assessed state of knowledge’ (Mach et al., Reference Mach and Field2017: 3). However, I additionally suggest that the increase in confidence language is not just about institutional decision-making by the IPCC and increased maturity in uncertainty guidance for the authors. It is also in anticipation of – or in direct response to – governmental requests for clarification at the approval plenary stage.

IPCC reports undergo several rounds of expert and government review before taking a final step at the report adoption plenary (see Chapter 11). At this meeting, the governments that form the Panel approve the SPM, sentence by sentence. Delegates come to the meetings ready to intervene on matters of style and substance. Unsurprisingly, these interventions often take up matters of national interest. These interests range from assuring the correct scientific representation of climate change and concerns about due process from various states, to acting as an upholder of particular scientific values, to ensuring that scientific understanding accelerates the energy transition from petroleum to renewables – or not (see De Pryck, Reference De Pryck2021a).

Over the course of the AR6 WGI report adoption plenary – conducted virtually from 26 July to 6 August 2021 – particular delegates offered interventions that were important for their countries to communicate. These interventions became dependable and predictable in their repetition. One illustrative example was the Saudi Arabian delegate’s interventions on calibrated language, the characterisation of statements of facts, and ensuring that textual statements could be associated with quantification. In their opening statement, as reported by the Earth Negotiations Bulletin (ENB), ‘SAUDI ARABIA pointed to instances in the report where non-calibrated language is used, and called for clarifying uncertainties relating to the use of models and projections’ (ENB, 2021: 3). Additional, representative interventions along these lines (and the outcomes) in the ENB report include:

Saudi Arabia was not the only delegation at the approval Plenary to intervene about calibrated language and quantification, but they were the most persistent. Nor was this topic the only point that they brought into the Plenary. Their delegation used quantification – and the IPCC’s turn towards increasing quantification – as a means for slowing down the proceedings, as well for raising doubts about the validity of statements if they were not easily translated in quantifiable – or quasi-quantifiable – prose. As evident from the statements above, sometimes the suggested changes were incorporated into the SPM, sometimes the authors conferred and made small edits, sometimes the authors explained their rationale and the original wording was accepted. And sometimes others – like WGI co-chair Dr. Masson-Delmotte – benchmarked the language against past practice or against the broader narrative of the report.

While the Saudi Arabian delegation regularly urged deletion of text if their concerns could not be quantified, or at least clarified, the German delegation worked on calibrated language from the other end of the spectrum. That is, several times a German representative noted that statements of fact did not need calibrated language attached. For example:

The pull-and-push over uncertainty language at the low- and high-uncertainty ranges shows that the edges of uncertainty continue to matter as points of political and scientific import. The removal of calibrated language represents the point at which a claim becomes fact. The inclusion of low-likelihood, but high-impact, information becomes a point of policy relevance, even policy demand, even as the scientific information at hand remains unresolved. Janzwood (Reference Janzwood2020) notes that authors know that these critiques are imminent at the adoption Plenary and may consider leaving out information in anticipation of the debate that might ensue at the political level. In an interview Janzwood conducted with an IPCC author, this author noted that being made to consider levels of confidence when elevating statements to the level of the SPM constitutes a ‘reality check’ (Janzwood, Reference Janzwood2020) : 1666). Authors decide in advance that some matters are too politically contentious to withstand the scrutiny and the slowing of the approval process, choosing some statements to defend and others to remain only in the main report or the Technical Summary, both of which receive less scrutiny.

17.4 Achievements and Challenges

As an institution, the IPCC has demonstrated enthusiasm for creating and implementing increasingly sophisticated means for calibrating uncertainty language. Most importantly, the move towards systematising qualitative information has encouraged trust and comparison between the quantifiable and probabilistic findings typical of natural and physical sciences and forms of knowledge coming from different disciplinary traditions. In AR6, the concept of risk was also scaled up into rubrics, decision matrices and standardised, calibrated language, building off the apparent success of IPCC uncertainty guidance (Reisinger et al., Reference Reisinger, Howden and Vera2020). IPCC authors, leadership and staff regularly convey that this elaboration of uncertainty guidance reflects community values within the IPCC – values including traceability, transparency, professionalism, rigour and care.

However, this trajectory has some sticking points, both epistemic and political. In terms of knowledge, the process of standardising calibrated language, even as it seeks to be more inclusive of diverse methodological and disciplinary traditions, excludes some forms of knowledge that don’t easily adhere to formal uncertainty calibration due to their descriptive or interpretive nature. As an in-language, frequent use of formal uncertainty calibration can alienate the audience that the IPCC hopes to engage. And in diplomatic spaces, the rhetoric of precision can be cynically deployed to slow the approval process, obfuscate or remove findings that cannot clear the language bar, or else engender debates about the nature of scientific facts.

Overview

In the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC), the chapters of each of the three Working Groups (WGs) are structured with the intention of integrating ‘cross-cutting themes’ and ‘handshakes’ between them. While integration received special emphasis in AR6, it is not new. The IPCC has long considered how to treat issues such as representations of uncertainty and scenario data consistently across WGs. The IPCC’s effort to integrate knowledge across WGs raises important epistemological and ethical questions related to how the humanities, natural sciences and social sciences shape understandings of climate change. To illustrate the theme of integration as applied within the IPCC, this chapter focuses on how risk is integrated across WGI and WGII in the AR6.

18.1 Introduction

The expectation of integration in the AR6 is clear in the vision statement that the IPCC Chair submitted to the IPCC’s 46th plenary session, held in Montreal in 2017:

This integration of social and natural sciences and humanities across WGs – while considering practitioners and focusing on solutions – can be understood as ‘anti-boundary’ work; instead of maintaining boundaries between WGs, they are intentionally bridged (De Pryck & Wanneau, Reference De Pryck and Wanneau2017: 206–207).

The emphasis in the AR6 on integrating knowledge within and between WGs is motivated in part by the imperative to provide policymakers with solutions-focused science. This could lead to reductionist or abstract generalisations. It could potentially strip away political-economic contexts in which climate change is produced and in which solutions might be implemented (Schipper et al., Reference Schipper, Dubash and Mulugetta2021). This problem can be put differently. If different forms of knowledge have different ways of understanding what the problems and appropriate solutions to climate change are, then there may well be disagreement between IPCC authors when it comes to integrating their home disciplines into a common framework (Schipper et al., Reference Schipper, Dubash and Mulugetta2021).

The implications of integration across WGs are discussed in the literature in reference to adaptation, mitigation, and development (Ayers & Huq, Reference Ayers and Huq2009; Nightingale et al., 2020), food security (Porter et al., Reference Porter, Challinor, Henriksen, Howden, Martre and Smith2019; Rivera-Ferre, Reference Rivera-Ferre2020), and Negative Emission Technologies (NETs) (Beck & Mahony, Reference Beck and Mahony2018b). This chapter focuses on the topic of risk, and introduces the theme of integration by tracing the development – through informal and formal venues – of the approved AR6 chapter outline.¹

18.2 A Typology of Integration

The tensions identified above by Schipper et al. (Reference Schipper, Dubash and Mulugetta2021) can usefully be situated alongside the typology developed by Barry et al. (Reference Bazeley2008) in their study of ‘the logics of interdisciplinarity’, which draws from science and technology studies (STS), political theory and empirical case studies. Barry et al. (Reference Bazeley2008) articulate three ideal-typical modes through which a range of actors and organisations have attempted interdisciplinary work: service-subordination, integrative-synthesis and agonistic-antagonistic.

The service-subordination mode integrates knowledge through a ‘hierarchical division of labour’ that subordinates the social sciences and humanities to a framework established by the natural sciences. The expectation is that the social sciences will ‘serve’ the natural or physical sciences. It is plausible that some of the historical tensions between the cultures of the three WGs could be traced to this mode (see Chapter 12). However, the integrative-synthesis mode provides the dominant discourse through which interdisciplinarity is attempted in the AR6. This mode is characterised by the ways that ‘social’ factors (e.g. the economy) and nature are accounted for in the same model. Its prevalence in the IPCC is evidenced in the dominance of concepts of resilience, adaptive capacity and vulnerability, which each draw upon complexity theory and social-ecological systems theory. As Barry et al. (Reference Bazeley2008: 28) point out, the synthesis enacted in this mode can lead to closure, not ‘new heterogeneous fields’. This speaks to the tension identified by Schipper et al. (Reference Schipper, Dubash and Mulugetta2021) between a holism that imposes a totalising unity on the one hand, and the complex and deeply rooted ways that climate intersects with existing relations of power on the other.

The third mode discussed by Barry et al. (Reference Bazeley2008) is the agonistic-antagonistic mode. This draws from Chantelle Mouffe’s concept of the role of opposition as a constitutive element of the political. In this mode, ‘interdisciplinarity springs from a self-conscious dialogue with, criticism of, or opposition to, the intellectual, ethical or political limits of established disciplines or the status of academic research in general’ (Barry et al., Reference Bazeley2008: 29). In other words, the norms and assumptions of different disciplines are challenged as they are brought into conversation with each other. The agonistic-antagonistic mode highlights the potential for creative and novel ways of understanding and responding to climate change to emerge from the intermingling of received ideas. At the same time, it highlights the potential for incommensurability. For example, as discussed in Chapter 13, seeking to integrate Indigenous knowledge into a framework dominated by Western science might diminish the integrity and meaning of Indigenous knowledge by removing it from the context within which it is produced.

18.3 A Historical Snapshot: Networked Relationality, Uncertainty and the TGICA

Treating ‘cross-cutting issues’ consistently between WGs is a long-standing issue in the IPCC. For example, a set of four guidance papers produced over 20 years ago in the lead up to AR3 argued for the ‘consistent use of terms and approaches to the assessment and reporting of information that is relevant to the cross-cutting issues’ (Pachauri et al., Reference Pachauri, Taniguchi and Tanaka2000: 2). The four cross-cutting issues treated in the guidance papers were: costing methodologies; uncertainties; decision analysis frameworks; and development, equity and sustainability. Additional cross-cutting issues that were dealt with in special reports at that time were: integrated assessment; scenarios; biogeochemical/ecological feedback; and sinks (Pachauri et al., Reference Pachauri, Taniguchi and Tanaka2000: 2).

In their guidance paper produced for the AR3, Moss and Schneider (Reference Moss, Schneider, Pachauri, Taniguchi and Tanaka2000: 48) detailed how uncertainties are represented in different ways in previous assessments, and called for ‘more explicit and consistent treatment of uncertainties in future assessments for all working groups’. Despite Moss and Schneider’s (Reference Moss, Schneider, Pachauri, Taniguchi and Tanaka2000) plea, however, uncertainty was not always treated in a uniform manner (see Chapter 17). As reported by the InterAcademy Council (IAC, 2010: xiv), WGs in the AR4 ‘used a different variation on IPCC’s guidance to describe uncertainty’. This hampered the IPCC’s ability to communicate uncertainty and, in the aftermath of the controversies of 2009–2010 (see Chapters 3 and 6), the IAC (2010: 69) echoed statements made in the cross-cutting papers with their recommendation for ‘strengthening coordination across Working Groups where appropriate and productive’.

Despite the evident desire for integration, coordinating this across WGs is no easy task. Each of the three WGs has its own culture, which is not necessarily shared (Beck, Reference Beck2011a; Fløttum et al., Reference Fløttum, Gasper and St. Clair2016). This is due, in part, to the IPCC’s organisational structure. The IPCC has relatively few permanent paid staff members; at the time of writing, the Secretariat headquartered in Geneva had 16 positions, not including three interns. Each WG is supported by a paid Technical Support Unit (TSU) of a similar number, and each of the three TSUs is formed anew by different host nation states for each new assessment cycle. The work of actually writing the assessment reports is undertaken by volunteers who are selected for each specific report. Given this organisational structure, it is helpful to understand the IPCC as a ‘network organisation’ in which change can be mediated through key individuals (Venturini et al., Reference Venturini, De Pryck and Ackland2022). Integration within and between WGs is worked towards through key individuals whose roles span more than one WG; they occupy what Venturini et al. (Reference Venturini, De Pryck and Ackland2022) call ‘multipositional thematic bridges’.

Lead Authors, Coordinating Lead Authors, and IPCC Bureau members, which includes WG Co-chairs, can all provide bridges between and within WGs in both formal and informal spaces (see Figure 18.1). As depicted in the figure, informal spaces allow for interaction to build support for key concepts that can then enter the formal structure of the IPCC at Panel/WG plenaries.

Figure 18.1 Networked integration.

Key actors who occupy multiple positions between and within WGs can communicate thematic framing devices and concepts in informal and formal venues. IPCC processes (Circle 1) include informal venues, such as Expert Meetings (Circle 2), and formal venues, such as WG/Panel Plenaries (Circle 3). This interplay between informal and formal venues takes place on a smaller scale within each type of venue. That is, both informal venues (Circle 2) and formal venues (Circle 3) include informal and formal elements. Thematic bridges, who occupy multiple positions in informal and formal venues, allow for framing devices and concepts, such as the risk framework, to be communicated between and within WGs. As indicated by Circle 4, venues outside of the IPCC can also be connected in this manner.

Figure made by the author

The controversies of 2009–2010 heightened the need for transparency and consistent treatment of issues across WGs. This must have been on the minds of some of the roughly 50 individuals – many of whom act as multipositional thematic bridges – who participated in the 2016 IPCC Expert Meeting on the Future of TGICA (Task Group on Data and Scenario Support for Impacts and Climate Analysis). The meeting was convened to consider how the TGICA should respond to changing conditions, including the massive increase in computing power that had occurred since its inception. The TGICA was formed in 1997 as a reformulation of a similar group that had formed the previous year (Vaughan, Reference Vaughan2016: 1). One of the main tasks of the TGICA was to coordinate and provide consistent scenario data to all three WGs. Another of its tasks was to provide input on ‘cross-cutting issues’ that were thought to be relevant to all three WGs (IPCC, 2018f: 13). As Vaughan (Reference Vaughan2016: 2) states in her report written for the 2016 Expert Meeting: ‘Many current and past TGICA members cite its role in facilitating informal communication between Working Groups that does not have many other avenues for exchange as critically important’.

The Expert Meeting on the Future of TGICA in 2016 was an informal venue (Circle 2 in Figure 18.1) that featured a series of plenary presentations and breakout discussion groups, one of which was titled ‘Collaboration within IPCC – including facilitating interaction between Working Groups’. One participant noted that in AR5, it was left to individual authors to collaborate with other WGs. Several other participants noted that some LAs and CLAs in AR5 ‘had very little or no interaction with TGICA’ (IPCC, Reference Shongwe, Tall and Wratt2016d: 14).

In 2018, two years after the Expert Meeting, the IPCC decided to rename the TGICA as the Task Group on Data Support for Climate Change Assessments (TG-Data) and change its mandate to focus primarily on the management of data and scenarios (IPCC, 2018d: 14–16). The TG-Data is not expected to be a conduit for integration; instead, with AR6, integration is structured into the outline of its chapters.

18.4 Achieving Integration through Informal and Formal Venues

The Scoping meeting for the AR6 was held in Addis Ababa, Ethiopia. There, themes and topics that were first addressed in venues that are outside of the IPCC’s formal processes – specifically the meeting on Integrating Science across the IPCC on Climate Risk and Sustainable Solutions (Stockholm, Sweden, 29–31 August 2016) and the International Conference on Climate Risk Management (Nairobi, Kenya, 5–7 April 2017) – were brought inside the IPCC’s formal processes via thematic bridges (Circle 4 in Figure 18.1). The AR6 Scoping Meeting in Addis Ababa included breakout group discussions that not only included topics and themes addressed in prior venues but that also, according to the Co-Chairs of WGI and WGII, ‘provided a unique opportunity for the three WGs to coordinate the development of their respective assessments, [which is] critical to have early in a cycle where more integration across WGs is expected than in previous cycles, building on the cross-WG Special Reports that are currently underway’ (IPCC, 2017c: 6).

The outline developed at the AR6 Scoping Meeting was approved in Montreal, Canada, in 2017 at the IPCC’s 46th session, where the following cross-cutting issues were discussed in a series of breakout groups: Regions, Scenarios, Risks, Cities, Global Stocktake, Geoengineering, Adaptation and Mitigation, and Approaches and Processes for Integration (IPCC, 2017a: 7–13).

Integration was built into the approved chapter outlines for each of the three WGs. The final chapter of WGI, for example, ‘Chapter 12: Climate change information for regional impact and for risk assessment’ was intended to synthesise hazards identified by WGI for further integration into the risk framework in WGII. As stated by the WGI co-chairs report: ‘this chapter will contribute to the hazard component of a quantitative assessment of present and future climate risks, resulting in a key ‘handshake’ point between WG I and II’ (IPCC, 2017c: 28). Integration is structured into the approved outline for WGII, in which the final cluster of three chapters synthesise previous chapters. The concluding chapter of WGII, ‘Chapter 18: Climate resilient development pathways’, was intended to act as a ‘connection’ to WGIII (IPCC, 2017d: 6). Another key ‘handshake’ was the online interactive atlas that was published in August 2021 (IPCC, 2021b).

After the formal adoption of the AR6 outline, the dynamic process of integration depicted in Figure 18.1 continued through the work of writing the AR6, which can be seen in the case of risk and regionalisation. As stated by the WGI co-chairs in their report for the IPCC’s 46th meeting: ‘Two major areas that require coordination across WGI and II are regional information in the assessment of climate mechanisms and linking climate variability and change and related uncertainties to the risk assessment framework’ (IPCC, 2017c: 9).

The Expert Meeting on Assessing Climate Information for Regions, 16–18 May 2018, was held in Trieste, Italy, several months before the first Lead Author Meeting for AR6 WGI. The Expert Meeting reports:

One of the main recommendations made by the meeting, which was structured around the familiar form of informal breakout groups and formal plenary sessions, was to: ‘Make an improved and consistent use of the risk assessment framework across WGI and WGII, and regions’ (IPCC, Reference Moufouma-Okia, Masson-Delmotte and Pörtner2018g: 9). Indeed, the risk framework is a key way in which WGI and WGII achieve integration.

As made explicit in Figure 1.5 of AR6 WGII report, one of the significant differences between risk framework used in AR5 and that used in AR6 is the addition of ‘response’ along with the trio of hazard, exposure and vulnerability established in previous assessment cycles (Begum et al., 2022: 35; see also Simpson et al., Reference Simpson, Mach and Constable2021). In other words, the risk framework recognises the possibility that maladaptation contributes to the risks that humans experience.

18.5 Achievements and Challenges

To integrate WGs in the AR6, the IPCC explicitly pursues approaches that fall within the integrative-synthesis mode of integration identified by Barry et al. (Reference Bazeley2008) and that guided the risk and resilience frameworks that were structured into the approved chapter outlines. However, the networked quality of the IPCC means that integration cannot be achieved through top-down imposition. Actors occupying multipositional thematic bridges champion the vision for integration in formal and informal venues. But it is up to authors – Lead Authors, Coordinating Lead Authors, Chapter Scientists and Contributing Authors – to actually write the assessments. This means that, in the actual writing of AR6, the service-subordination or agonistic-antagonistic modes discussed by Barry et al. (Reference Bazeley2008) might be attempted by different individuals or groups (see Chapter 12).

The risk framework in AR6 represents an achievement of the IPCC. Several decades ago, the IPCC adopted a risk framework that centred on biophysical hazards. But as discussed earlier, the AR6 updates the risk framework to include human responses to climate change as an additional source of risk. As stated in the AR6 WGII Summary for Policymakers, ‘the risk that can be introduced by human responses to climate change is a new aspect considered in the risk concept’ (IPCC, 2022: 5). This extension of the IPCC risk framework to further include ‘the social’ should be seen as an achievement.

Another achievement accomplished in AR6 is the high degree of cooperation between the Co-chairs of the three WGs, which appears to be greater than that achieved in AR4 or AR5. Similarly, anecdotal information suggests that in AR6 more multipositional thematic bridges participated in LA Meetings for WGs other than their own than was the case in previous assessment cycles. These individuals are key to the success of the IPCC’s attempt for integration, but they are also rare. It takes considerable social, economic and cultural capital to be able to communicate between different disciplinary paradigms. A challenge the IPCC faces is how to support those thematic bridges who better represent geographical and gender diversity. The scope of this challenge for the IPCC increases when Indigenous knowledge is included along with the humanities, and the social and natural sciences.

Some IPCC authors might censor themselves and not include text that they suspect might be opposed by governmental delegates. For example, there may be ample peer-reviewed evidence that political–economic contexts and social relations of power exacerbate the vulnerability of impoverished people to climate change. But it could be a challenge for IPCC authors to include such knowledge into an integrative framework in such a way that retains critical and political clout while also being approved by all government delegates (see Chapter 20).

Considering the challenges described earlier, the IPCC should confront the question of what can and should be done with incommensurable forms of knowledge that come from Indigenous Peoples or critical scholars. This knowledge may provide vital insight into the problem of climate change, but it may remain incommensurable with the IPCC’s chosen integrative frameworks, posing significant ethical and epistemological challenges.

Overview

A widely shared expectation of science is that it speaks authoritatively about how the physical world works and therefore about what the consequences of different human actions and policy interventions are likely to be in that world. Science, and therefore the scientist, is believed to offer public life something different – something more truthful and hence more authoritative – than offered by politicians, journalists, lawyers, priests or celebrities. Scientists ‘reaching a consensus’ and ‘speaking with one voice’ are integral to science’s projection of epistemic authority. This is especially the case with the Intergovernmental Panel on Climate Change (IPCC), where its authority is perceived to rest on its communication of a scientific consensus. This chapter first summarises the nature of consensus-making in science in general, before examining the IPCC’s consensus-seeking practices. It then evaluates some of the arguments for and against the pursuit of consensus by the IPCC and concludes by highlighting some future challenges for the IPCC with respect to its pursuit of consensus.

19.1 Introduction

The pursuit of consensus has been central to the mission, procedures and communication of the IPCC’s knowledge assessments. This pursuit has been grounded in the belief that an intergovernmentally owned and transnational knowledge consensus about climate change is a prerequisite for effective policymaking. From its beginning, the IPCC has sought and delivered a consensus on what is deemed to be known scientifically about climate change. For example, in the foreword to the IPCC’s very first assessment – the Working Group I (WGI) First Assessment Report (AR1) published in 1990 – the Co-Chair Sir John Houghton wrote ‘peer review has helped ensure a high degree of consensus amongst authors and reviewers regarding the results presented’ (IPCC, Reference Houghton, Jenkins and Ephraums1990a: p.v, emphasis added). This aspiration for authority-through-consensus has been evidenced in the rhetoric of IPCC communications. For example, in November 2007, just ahead of the publication of AR4’s Synthesis Report, the IPCC promoted its consensus processes thus: ‘2500+ scientific expert reviewers; 800+ contributing authors; and 450+ lead authors; from 130+ countries; 6 years work; 4 volumes; 1 report. The core findings of the three volumes integrated in the most policy-relevant scientific document on climate change for the years to come’. The sheer weight of expertise compressed into ‘one report’ is offered by the IPCC, tacitly, as evidence of its epistemic authority.

This association between consensus and authority is used by social and political actors and commentators outside the IPCC, whether they be politicians, lobbyists, advocates or critics. The stronger the consensus, it is claimed by advocates, the greater the authority the IPCC has in public or policy debates. Critics on the other hand, seek to challenge the IPCC’s consensus in order to weaken its public authority. Politicians also draw upon the language of consensus. For example, Kevin Rudd, the then Australian Prime Minister, announced in a speech on 6 November 2009, just before COP15 in Copenhagen:

The role of the IPCC’s consensus in public debates and political negotiations about the goals and instruments of climate policy continues to provoke vigorous arguments. Some scientists are critical of consensus-seeking practices in the IPCC because of their ostensibly conservative outcomes. Oppenheimer et al. (Reference Oppenheimer, O’Neill, Webster and Agrawala2007), for example, argued that the IPCC’s search for consensus with respect to future sea-level rise deflected attention from the full exploration of scientific uncertainties, to the detriment of robust policymaking. On the other hand, some political philosophers accuse consensus-driven knowledge assessments of subverting good scientific practice, by masking legitimate epistemic dissensus (Beatty & Moore, Reference Beatty and Moore2010). These arguments about the legitimacy, outcomes and effects of the IPCC’s consensus-seeking practices highlight long-standing debates in the history and philosophy of science about the nature of epistemic consensus (e.g. Fuller, Reference Fuller2002) and in science and technology studies (STS) about the legitimacy of knowledge consensus practices in science–policy interactions (e.g. Jasanoff, Reference Jasanoff2004). They also reflect debates in political science about the role and status of expert representation and deliberation in healthy democracies (e.g. Brown, Reference Brown2009). These academic debates about the nature and impact of consensus in regulatory scientific institutions and knowledge assessments are interesting in general terms. But they become crucially important for public policy with respect to specific concerns such as climate change.

This chapter first summarises the nature of consensus-making in science in general, before examining the IPCC’s consensus-seeking practices. It then evaluates some of the arguments for and against the pursuit of consensus by the IPCC and examines whether such consensus is epistemically appropriate and politically desirable. It concludes by highlighting some future challenges for the IPCC with respect to its pursuit of consensus.

19.2 The Nature of Scientific Consensus

Making and defending a scientific consensus can be understood to fulfil a number of different functions. For example, a consensus can validate specialist knowledge about some physical phenomenon and hence act as a ‘truth claim’. Establishing such a consensus can bring a new epistemic community into being or else consolidate the perceived authority of an existing epistemic community (Haas, Reference Haas1992). A consensus can also offer a pragmatic way of bringing authoritative knowledge into public circulation when important policy decisions loom. Oreskes (Reference Oreskes2019) argues that consensus-making – ‘scientists speaking with one voice’ – is central to the practice of science. On the other hand, none of these functions of consensus-making in science stands unchallenged; there has long been a strand of philosophy that interrogates the nature of consensus in science. Thus Rescher (Reference Rescher1993) argues against the desirability of consensus, claiming that cognitive pluralism in science is inescapable, while Miller (Reference Miller2013) points out that the lack of social diversity in an epistemic community undermines its claim to forge a legitimate consensus. In a similar vein, Stirling (Reference Stirling2010) argues that democratic decision-making is better served by epistemic pluralism – ‘keeping things open’ – than by seeking a knowledge consensus.

The slippery and contested nature of a knowledge consensus prompts STS scholars such as Harry Collins to claim ‘we don’t really know what scientific consensus is’ (quoted in Jomisko, Reference Jomisko2013: 28). And it results in a proliferation of knowledge consensus typologies and the recognition of multiple practices of consensus-making. Scholars also talk about ‘strong’ and ‘weak’ consensuses. Gilbert (Reference Gilbert2002), for example, puts forward a non-summative account of group belief (i.e. consensus), which distinguishes between the group’s collective belief in a claim and the range of beliefs of the individual members of the group. Similarly, Fuller (Reference Fuller2002: 207–232) distinguishes between ‘essential’ (group belief arrived at through deliberation) and ‘accidental’ (convergence of autonomous individual beliefs) consensus. And there seems no consensus about how a scientific consensus should best be arrived at. Guston (Reference Guston, Frickel and Moore2006), for example, proposes the use of voting procedures in scientific assessments, whilst Verheggen et al. (Reference Verheggen, Strengers and Cook2014) enumerate consensus in climate science through expert surveys.

When applied to matters of significant public policy concern – such as climate change – these questions about the nature and legitimacy of a knowledge consensus become important to answer. There may be a general recognition in philosophy of science that cognitive diversity is inevitable, that consensuses are unstable over time, and that what matters for the cultural authority of science is the legitimacy and integrity of the process of consensus-making (Beatty & Moore, Reference Beatty and Moore2010). But this theoretical understanding of consensus in science begs two important practical questions when it comes to pursuing and interpreting knowledge consensus in the IPCC: When is making a knowledge consensus epistemically appropriate? And when is it politically desirable?

In relation to the first question, Miller (Reference Miller2013) asks under what conditions might an epistemic consensus be deemed ‘a mark of knowledge’. He suggests three conditions need to be satisfied:

• the social calibration condition – the use of common evidential standards and ontological schemes;

• the apparent consilience of evidence condition – different lines of evidence seem to converge;

• the social diversity condition – parties to a consensus should have diverse social profiles.

The case of the IPCC presents particularly challenging circumstances for these three conditions to be met. Social calibration and the consilience of evidence are more exacting conditions when dealing with a wide range of disciplinary epistemologies and traditions (Jasanoff, Reference Jasanoff, Dryzek, Norgaard and Schlosberg2011b), such as the IPCC embraces. And the social diversity condition reveals the tension between parties to a consensus being selected on the basis of formal expertise versus national allegiance or other non-epistemic criteria (see Chapter 7).

With respect to the second question – when is a consensus politically desirable – a range of factors come into play. These can broadly be captured by the idea of civic epistemology (see Chapter 23), which challenges the universal legitimacy and efficacy of a knowledge consensus generated by a transnational body such as the IPCC. How a knowledge consensus is made, and whether these processes are perceived as credible and legitimate within any given polity, will then determine how – and how effectively – consensus claims are used in public discourse and policy advocacy. What is politically effective in Germany, for example, may be very different from what is effective in the United States. Policy traps lurk if a singular transnational knowledge consensus is used to guide or justify the design of policy instruments to be applied across different political cultures of risk management (Rothstein et al., Reference Rothstein, Borraz and Huber2012).

19.3 Consensus Practices in the IPCC

Little systematic theoretical or empirical attention has been given to exactly how knowledge consensus within the IPCC is constructed or how these processes have evolved historically. Where such consideration has been given to the nature of the IPCC’s consensus, it has often been poorly grounded in empirical evidence (e.g. exchanges with regard to the early IPCC consensus; see Boehmer-Christiansen, Reference Boehmer-Christiansen1996; Shackley, Reference Shackley1997), or else been approached using insights from limited disciplinary perspectives. For example, Elzinga (Reference Elzinga, Elzinga and Landström1996) reflected from an STS perspective on the shaping of the IPCC’s ‘worldwide consensus’ and Goeminne (Reference Goeminne2013), likewise, using STS and political science. Conversely, Curry and Webster (Reference Curry and Webster2013) examined the IPCC’s consensus in terms of scientific practice, but without drawing upon the insights of STS or philosophy of science. The clutch of studies which have sought to enumerate the strength of the ‘climate consensus’ (e.g. Oreskes, Reference Oreskes2004; Verheggen et al., Reference Verheggen, Strengers and Cook2014) have done so with little engagement with political science (Pearce et al., Reference Pearce, Grundmann, Hulme, Raman, Hadley Kershaw and Tsouvalis2017b).

IPCC reports generate different types of consensus statements. For example, in Summaries for Policymakers (SPMs) there is line-by-line agreement between government representatives and scientists, which is a different form of consensus than that which emerges within chapter teams. For SPMs, IPCC procedures allow for issuing formal ‘minority reports’, although this option is rarely utilised (Livingston et al., Reference Livingstone2018). Central to the IPCC’s consensus practices is how the final assessment products capture and represent uncertainty in scientific knowledge. The IPCC has evolved an elaborate series of guidelines for communicating uncertainty in its knowledge statements (see Chapter 17). Yet among observers and participants of the IPCC, there are ambiguities about whether consensus statements reflect ‘a lowest common denominator consensus view of the vast majority of scientists’ (Edwards & Schneider, Reference Edwards and Schneider1997: 13), or whether the IPCC ‘brings controversy within consensus, capturing the full range of expert opinion’ (Edwards, Reference Edwards, Schneider, Miller and Edwards2010: xvii). Guidance issued ahead of AR6 asked chapter teams to seek the ‘full range of views’, but stopped short of saying exactly what this means or how this should be done. It is also important to recognise the distinction between consensus-as-product – offering the ‘lowest common denominator’ between varying expert opinions – and consensus-as-process – negotiating between different scientific interpretations of theory or evidence (see Box 19.1).

19.4 Arguments in Favour of Consensus

The argument in favour of the IPCC seeking a scientific consensus on climate change is that by doing so it reflects what science supposedly is uniquely disposed to be good at – applying rules of reasoning and inference, which lead unambiguously and universally from evidence to conclusion. The same evidence presented to the same disciplined minds leads to precisely the same conclusion. In this view, a lack of consensus would undermine the authority of science. It might suggest that sufficient effort had not been made to reconcile conflicting views among experts, or else that personal or cultural biases and values had protruded into the reasoning process.

This is the position implicitly assumed by Sir John Houghton in the foreword to the AR1 WGI report cited earlier. His comments on IPCC’s consensus were immediately preceded by the observation that: ‘Although … there is a minority of opinions which we have not been able to accommodate, the peer review has helped ensure a high degree of consensus amongst authors and reviewers regarding the results presented. Thus, the Assessment is an authoritative statement of the views of the international scientific community at this time’ (IPCC, 1990: p. v, emphasis added). The IPCC’s assessment of knowledge is authoritative because it is a consensus. Paradoxically, this is also the view of many critics of the IPCC who assert that science properly conducted – through unbiased and structured reasoning processes – should lead to unanimous consent (Oreskes, Reference Oreskes2019). On such a reckoning, simply pointing to the existence of a minority dissenting position that contradicts an IPCC consensual statement is sufficient to undermine the authority of the IPCC’s consensus. The symbolic and political power that a scientific consensus affords the IPCC would thereby be undermined (Pearce et al., Reference Pearce, Mahony and Raman2018). This view of consensus in science is one that offers a wide variety of protagonists a useful defence against cultural relativists.

19.5 Arguments against Consensus

The earlier defence of consensus reflects a very particular (purist) view of scientific knowledge, which scholars such as Bruno Latour (Reference Latour1993) have described as the ‘modernist illusion of science’. Silberzhan et al.’s (2018) experiment, for example, shows that random groups of similarly qualified experts can reach quite different conclusions when presented with identical empirical evidence.

There are three main groups of arguments against the pursuit of a knowledge consensus by the IPCC. First, the requirement of consensus can be pernicious; in order to protect the authority of a group it encourages premature agreement among experts where there is none (Beatty & Moore, Reference Beatty and Moore2010). Some argue that the IPCC should more openly embrace the idea of expert elicitation, or even expert voting: ‘A scientific body that does not partake in … a politics of transparent social choice – one that hides both its substantive disagreements and its disciplinary and sectoral interests beneath a cloak of consensus – is not a fully democratic one’ (Guston, Reference Guston, Frickel and Moore2006: 401). For example, such an approach to capturing disagreement could usefully have been applied to the case of the sea-level rise controversy in AR4 (see Box 19.1). Expert elicitation makes disagreements explicit and better reflects the quasi-rationality of scientific deliberation.

Second, the presence of officially sanctioned credible minority views – thereby revealing the extent of expert dissensus – can enhance the authority of science in public and political life (Rescher, Reference Rescher1993). It would show that the deliberative procedures of the IPCC were fair and accommodating to the full range of accredited views. The implication of this argument is that the IPCC assessment process should not just allow minority reporting in its rules of procedure, but ensure that minority reporting is actively facilitated. ‘Science would provide better value to politics if it articulated the broadest set of plausible interpretations, options and perspectives, imagined by the best experts, rather than forcing convergence to an allegedly unified voice’ (Sarewitz, Reference Sarewitz2011: 7).

A third group of arguments against the necessity of scientific consensus works by analogy. Majority rule works very effectively in maintaining order in social institutions, such as parliaments and the courts that involve voting MPs and juries. Consensus is not required for a legal ruling or judgement to carry authority in wider public settings. And whatever differences between the nature of scientific enquiry and political (or jury) debate might be insisted on, it must be recognised that scientific assessments such as the IPCC are established explicitly as social (i.e. deliberative) institutions. They scrutinise and evaluate evidence, much like a judicial process (Shapin, Reference Shapin2010). There are many other dimensions beyond just ‘unanimity of view’ if institutions are to become trusted and authoritative amongst members of a polity – for example, fair and agreed procedure, respect for dissent, and acceptance of outcomes.

Even if one accepts that a scientific consensus is desirable, in many fields of climate change consensus is elusive. Agreement – i.e., ‘high confidence’ – exists within some specific research communities, for example among detection and attribution studies leading to affirm the reality of human influence on the climate system. But in other fields relevant to climate change impacts and policy such a consensus does not hold. For example, there is ‘low confidence’ in the magnitude of the contribution of permafrost thawing to carbon cycle feedbacks, on whether – and with what speed – Antarctic ice sheets might contribute substantially to sea-level rise and on whether Arctic sea-ice thawing causes increases in mid-latitude climate variability (IPCC, Reference Masson-Delmotte, Zhai and Pirani2021a).

19.6 Achievements and Challenges

Over its 34-year history the IPCC has brought a substantial degree of ‘epistemic order’ to scientific knowledge about climate change. The founding chairman of the IPCC – Bert Bolin – sought to bring order out of what he perceived in 1988 to be ‘chaos’ in the public perception of climate science (Bolin, Reference Begum, Lempert, Ali and Pörtner2007: 49). Reflecting this desire, the IPCC has managed to organise the scientific community to increasingly approximate a univocal stance on climate change knowledge. As a social accomplishment, this was already recognised nearly 25 years ago by van der Sluijs et al. (Reference van der Sluijs, van Eijndhoven, Shackley and Wynne1998) in their analysis of the IPCC’s consensus statement about the climate sensitivity; this consensus estimate – a range of 1.5–4.5 °C – ‘anchored’ the scientific terms of the policy debate.

However, the IPCC’s search for consensus across all areas of relevant scientific and social scientific knowledge has not always been easy and there are new challenges ahead. As the IPCC seeks to respond to changing political and public expectations about its role, how it establishes and communicates a knowledge consensus on climate change will come under ever closer scrutiny. As future assessments engage more directly with policy solutions to climate change – and as the IPCC furthers its enlistment of more diverse forms of knowledge and expertise – informal modes of consensus-making relying on unstructured deliberation will be found wanting. For example, future engagement by the IPCC with more explicitly value-based forms of knowledge (see Chapter 13) will question whether consensual statements are epistemically, or even ontologically, appropriate or politically desirable. These tensions have already surfaced in previous ARs and will require more direct handling in the future. Formal procedures such as voting, expert elicitation and minority reporting – far from weakening the authority of the IPCC – may in fact be the only way in which the IPCC can remain authoritative and relevant for policy.

Overview

The reports of the Intergovernmental Panel on Climate Change (IPCC) are not produced by scientific experts disconnected from policy. They are produced within a political framework. The governmental endorsement of IPCC reports is a key element of the perceived success of the organisation. In particular, the approval of the Summaries for Policymakers (SPMs) makes the member states of the IPCC active participants in the assessment process and creates ownership of their content. At first sight, the involvement of governments in the IPCC reveals a genuine exercise of co-production between science and politics. It is expected to make the reports more legitimate and policy-relevant. Yet a closer look at the practices through which governmental ownership of IPCC reports is produced shows that governments may in some cases contribute to making them policy-irrelevant.

20.1 Introduction

Presenting the Fourth Assessment Report (2007) (AR4) at the United Nations Summit on Climate Change in 2009, the former chair of the IPCC, Rajendra K. Pachauri (2009) stated that ‘the uniqueness of this mammoth exercise lies in the fact that all the governments of the world – your own governments – approved of this report, and therefore have full ownership of its contents’. More recently, Chris Field and Vicente Barros (Reference Field and Barros2015: 36), two former members of the IPCC Bureau, praised the ‘added value’ of IPCC approval sessions, which ‘generate broadly shared ownership of scientific knowledge on climate change – a key contribution to the influence of IPCC reports’. These quotes are illustrative of the ‘perceived binding force’ (Riousset et al., Reference Riousset, Flachsland and Kowarsch2017: 263) that emerges from governmentally negotiated documents like the SPMs. It is generally expected that, once approved, the summary statements cannot be questioned in other multilateral fora, and in particular in the UN Framework Convention on Climate Change (UNFCCC).

For a long time, the IPCC approval process was presented by its leadership as exempt from political interference. For instance, another Bureau member, Sir John Houghton (Reference Houghton, Hester and Harrison2007: 14), argued that ‘it can be said with confidence that no wording was included or added, and no changes were made [in the SPMs] for political or ideological reasons’. Social scientists, however, have increasingly challenged such views and presented a more complex, social and political analysis of the approval process. It has been argued that such a process, while creating a ‘shared scientific understanding’ of climate change (Lidskog & Sundqvist, Reference Lidskog and Sundqvist2015: 12) can also be conflictual and lead to ‘least-common denominator generalities’ (Vardy et al., Reference Vardy, Oppenheimer, Dubash, O’Reilly and Jamieson2017: 59). It has also been suggested that the approval process offers the member states of the IPCC (i.e. the ‘principals’) much scope to shape the knowledge and policy perspectives put forward in the SPMs (Compagnon & Bernstein, Reference Compagnon and Bernstein2017).

This chapter discusses how governmental ownership is forged through the approval process and ultimately how IPCC member states contribute to shaping the meaning of climate change. In this chapter we understand the IPCC as we would any other UN organisation, i.e., one that remains ‘accountable to governments, its founders and funders, both individually … and collectively’ (Ghaleigh, Reference Ghaleigh, Gray, Tarasofsky and Carlarne2016: 69). This does not mean that IPCC authors and Bureau members do not have agency in shaping the SPMs. Quite the contrary. But IPCC authors do need to take governments’ multiple and sometimes contradictory interests into account while drafting the reports.

This chapter thus explores how the scientific ‘facts’ presented in the SPMs are translated into diplomatic ‘facts’ (Ruffini, Reference Ruffini2017: 120). It shows that the SPM approval process reveals disagreements about scientific interpretations and policy relevance. But it also shows that, crucially, when statements contained in the SPMs become entangled with interstate relations and UNFCCC negotiations, the approval reveals multilateral diplomacy at work. The chapter is based on the available literature, on participants’ accounts, as well as on the author’s own observations of plenary sessions of the Panel (2014–2022). The following sections discuss governmental approval as a process, as a negotiation and as an output.

20.2 Approval as Process

Governmental ownership is not only created at the end of the assessment process, when IPCC authors submit their reports, but through the whole process (see Chapter 3). First, governments agree on whether or not to produce a report and decide on the timeline for its production. Following a scoping meeting – which brings together representatives from governments, observer organisations and academia – a first outline is submitted for approval to the member states of the IPCC. This outline sets the overall narrative of the report and contains chapter titles and indicative bullets. The approval of the outline offers an opportunity for governments to define the mandate of the reports and to suggest policy-relevant questions. It is also a moment in which the messages and terminology proposed in the document are scrutinised and may become enmeshed in controversies.

During the approval of the outline, government representatives may ask for clarifications and changes in the structure and the bullet points. Because they come from diverse national institutions (e.g. from meteorological agencies or ministries of foreign affairs), their interventions can be both scientific and political. Some government representatives may want the IPCC to address specific scientific and technical debates or to discuss issues relevant for their domestic and international policies. Others may also seek to raise issues in the IPCC in order to move forward discussions in the UNFCCC because of the historical proximity between the two institutions (see Chapter 2).

At this stage, much time is already spent ‘weighting’ (Hughes & Vadrot, Reference Hughes and Vadrot2019) the terms and concepts proposed in the outline, by testing how they can be interpreted by different audiences and assessing whether they have a ‘policy context’ – for example, whether they relate to policy documents beyond the IPCC. Governments may also seek to prevent certain topics from being discussed in the IPCC. For example, references to terms such as ‘fossil fuel’ or ‘Nationally Determined Contributions’ (NDCs) have sometimes been opposed, because oil-producing countries wanted to divert attention from the main drivers of climate change or because of unresolved conflicts in the UNFCCC (Hermansen et al., Reference Hermansen, Lahn, Sundqvist and Øye2021). While the outline still leaves much leeway to authors in how they address each topic, its approval reflects struggles over the control of the narrative of the reports and of the assessment process more broadly. These struggles often re-emerge in subsequent meetings of the IPCC.

Following the approval of the outline, authors then work autonomously in their Working Groups (WGs) and draft the reports. Governments get involved in the review process by providing comments on the Second Order Draft (SOD) of the reports, as well as on their SPMs (see Chapters 5 and 11). At that stage, they may ask for clarification and additional information, make suggestions to improve the text, but also express disagreement with certain statements. The governmental review process helps authors and Bureau members identify issues that are likely to become controversial in the approval session of the SPMs. They assess whether each statement or figure is grounded in well-founded and traceable reasoning – and are thus ‘defendable’ – and make sure it does not constitute a ‘red line’. This may lead to self-censorship, but authors and Bureau members may also decide to go forward with their analyses and ‘fight’ for it in plenary (Broome, Reference Broome, Brister and Frodeman2020).

The approval of the SPMs usually takes one week, two weeks when approved online (see Chapter 4, Box 4.1). These sessions are performances of multilateral diplomacy where government delegates scrutinise the document line by line and agree, in dialogue with the authors, on a common position that satisfies them all. The IPCC uses deliberative procedures that have been refined over 30 years and closely follow UN practices. These include the arrangement of the main plenary room (Figure 20.1), where delegates are seated in alphabetical order by country, the use of the track-changes mode to amend the draft documents, and the availability of breakout rooms to pursue parallel discussions in smaller and less formal settings. At the same time, the detailed scrutiny that the SPMs undergo is unique. Few other international institutions give member states such control over their outputs.

Figure 20.1 Plenary Session of the IPCC Member States, UNESCO, 24–28 February 2020.

Photo by IISD/ENB Leila Mead

Sitting on a podium, the authors – usually the Coordinating Lead Authors or Lead Authors, see Chapter 7 – and the Bureau members assess the requests made by governments and suggest more consistent formulations. Arguments put forward concern issues of ‘clarity of the message’, ‘scientific accuracy’, ‘balance’, ‘policy-relevance’, ‘policy prescriptiveness’ and ‘procedural consistency’ (Petersen, Reference Petersen, Gramelsberger and Feichter2011: 3). In other words, statements contained in the SPMs must be clear and consistent with the underlying literature reviewed in the WG reports. Statements also need to be balanced in such a way that they do not single out particular perspectives, and yet are deemed relevant to a wide range of policymakers, while leaving unconstrained the range of development pathways and policy options (to avoid policy prescriptiveness) (see Chapter 21). While government comments are sometimes politically motivated, when their countries’ interests are at stake, most contribute to make the SPM clearer – and provide at times a much needed ‘reality check’ to some of the theoretical and abstract statements proposed by the authors.

The SPMs must be approved in a transparent process that does not leave any country behind. The approval process renders visible the tensions between two views of consensus that coexist more generally in the IPCC (see Chapter 19). On the one hand, is the view in the singular. This type of consensus tends to reduce the diversity of perspectives by converging on the most robust and unanimous conclusions. On the other hand, consensus is also viewed in the plural. This view seeks to accommodate the concerns of all parties and to balance a variety of perspectives. This second type of consensus abides by principles of pluralism to ensure that ‘everybody is on board’ (Kouw & Petersen, Reference Kouw and Petersen2018).

20.3 Approval as Negotiation

Studies of intergovernmental expert bodies like the IPCC – but also of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) – have conceptualised SPM approval sessions as ‘negotiating sites’ (Hughes & Vadrot, Reference Hughes and Vadrot2019: 15). The SPM ‘negotiations’ involve much arguing, a great deal of compromising and some bargaining (De Pryck, Reference De Pryck2021a). The deliberations are generally dominated by a small group of countries (see Chapter 9).

The approval process is complex (Figure 20.2), contingent on the negotiating capabilities of delegates and authors and is influenced by a variety of factors. These include: the epistemic features – for example whether quantitative or qualitative knowledge is under discussion – and ‘controversiality’ of the sentence or figure under scrutiny; the strength of the arguments raised; the scientific and political resources of the delegations supporting/opposing it; and the personality and argumentative skills of the delegates, authors and chairs of the sessions. In general, the modification of a statement without the consent of the authors cannot be accepted without exposing the organisation to severe criticism. Yet, authors are strongly encouraged to seek consensus and accept compromises, even if they might not always want to.

Figure 20.2 Flowchart representing the process of negotiating an SPM sentence or figure.

The shades of grey show the level of controversiality.

Flowchart produced by the author

The authors and Bureau members use various strategies to respond to governments’ comments. They may enjoin governments to respect the voice of the authors or ask for additional time to consider their requests. When an issue cannot be resolved in plenary, the discussion with disagreeing parties is moved to ‘a contact group’, a formal parallel meeting in a dedicated room, whose proceedings are carefully communicated. Or ‘a huddle’ may be formed – an informal meeting, decided on the spot, which generally takes place in the back of the plenary or in the corridors. The choice of one or the other of these devices is made at the discretion of the chair of the session and depends on the number of disagreeing parties. Contact groups are chaired by two government delegates – one from a developed country and one from a developing country – mandated to remain neutral and bring parties to an agreement. They can span several days and generally multiply towards the end of the week. When a consensus is found, it is brought back to the plenary and accepted.

When a compromise consistent with the position of the authors cannot be found, the IPCC procedures allow for the diverging views to be acknowledged in the document, for example in a footnote. Government delegates are, however, reluctant to be publicly named in the SPMs and generally request to see their reservations expressed in the minutes of the session. Governments may also consensually agree to delete the contentious issues from the document, a decision that generally creates great frustration among the authors. John Broome (Reference Broome, Brister and Frodeman2020), for example, recalls a moment in which a paragraph on climate justice in the AR5 Synthesis Report came close to being deleted by governments. Yet, when the authors threatened to resign from the process, ‘this made the delegates suddenly more cooperative. They did not really want us to go. Consequently, agreement was reached following some shuttle diplomacy between the two camps the next day’ (Broome, Reference Broome, Brister and Frodeman2020: 105).

Closure is reached when silence fills the room, in the absence of delegates asking for the floor. It reflects their agreement to let a document stand as the position of the group and the ‘suspension of disagreement … signalled by the absence of objections to a consensus proposal’ (Moore, Reference Moore2017: 127). Once approved, the SPMs become a ‘black box’ that masks the disagreements that went into the deliberations. Their conclusions are widely disseminated in the media, through outreach events in different countries and at UNFCCC side events (see Chapters 22 and 26). In the UNFCCC, they are discussed in the Subsidiary Body of Scientific and Technological Advice (SBSTA) and in other ad hoc mechanisms – for example, in the Structured Expert Dialogue (SED). Yet, agreement on which conclusions to identify as most relevant for the UNFCCC and how they should be integrated in decisions of the Conference of the Parties (COP) is generally difficult to reach (Lahn & Sundqvist, Reference Lahn and Sundqvist2017).

20.4 Approval as Output

In general, the approval of the SPMs is deemed necessary by many participants and researchers for whom such a process reflects a delicate exercise of co-production between scientists and government representatives to produce ‘usable knowledge’ (Haas & Stevens, Reference Haas, Stevens, Lidskog and Sundqvist2011). There is no doubt that it generally helps increase its policy relevance and speak to a wide range of perspectives. At the same time, questions have been raised about the implications of the approval on the framing of climate change. In the early work of the IPCC, observers have documented numerous attempts by Saudi Arabia and the United States to focus the debate on the remaining uncertainties related to anthropogenic climate change in order to delay action (Franz, Reference Franz1998). It has also been suggested that governments may seek to weaken the language of the SPMs by inserting vague and consensual terms, caveats and qualifications that render statements too generic.

Social scientists have also drawn attention to the ‘epistemic selectivity’ (Vadrot, Reference Vadrot2017: 69) at play in intergovernmental expert bodies – the dominance of ‘specific forms of knowledge, problem perceptions, and narratives over others’ – and to the tendency to put forward a global and technical framing of environmental problems. It has been suggested that governments contribute, as much as scientists, to presenting an abstract and global story of climate change, which downplays more regional and local information and asymmetries (Livingston et al., Reference Livingstone2018). Such language also avoids implicating actors or sectors and contributes to framing climate change in a non-political manner (Victor, Reference Victor2015). Researchers have also challenged the tendency of some governments to privilege a technical framing of climate solutions by downplaying the political feasibility and socio-economic implications of certain technologies (Fogel, Reference Fogel2005).

Finally, social scientists have elucidated the challenges that the IPCC faces when introducing issues that have implications for the UNFCCC, because governments are unlikely to accept statements that could compromise their positions. For example, in the approval of the AR5 WGIII SPM, conflicts arose over a graph showing anthropogenic greenhouse gas emissions aggregated by country-income groups (Victor et al., Reference Victor, Gerlagh and Baiocchi2014) and a paragraph on the effectiveness of the Kyoto Protocol (Stavins, Reference Stavins2014). Both examples carried important implications for the ongoing negotiations of the Paris Agreement that several governments did not want reflected in the SPM. In response to the controversy, authors shared this frustrating experience, suggesting that the SPM had become a summary by policymakers rather than a summary for them (Wible, Reference Wible2014).

20.5 Achievements and Challenges

The endorsement of IPCC’s reports by its member states and, in particular, the approval of their SPMs, is a unique institutional feature of the organisation. It is undeniably one of the main reasons for the IPCC’s high legitimacy among policymakers. Because of the perceived success of the IPCC as a science–policy interface, several other global environmental assessments have adopted a similar framework. Both IPBES and UNEP (in its Global Environmental Outlook) submit SPMs for the approval of their member states.

At the same time, as this chapter shows, social scientists have increasingly highlighted the limits of these governmentally negotiated documents. First, the approval of key scientific conclusions does not mean that governments accept them and will take more informed decisions. For instance, following the approval of the Special Report on Global Warming of 1.5 °C (SR15), the United States – under the administration of Donald J. Trump – requested to insert in the report of the meeting a statement noting that the ‘approval of the SPM … should not be understood as U.S. endorsement of all of the findings and key messages included in the SPM’ (IPCC, 2018c: 16). Later, at COP24, the United States, with Saudi Arabia, Kuwait and Russia, opposed ‘welcoming’ the report out of concern that it could be used to call for more stringent action.

Second, despite its intergovernmental nature, the IPCC has increasingly been struggling with meeting the multiple information needs of policymakers. On the one hand, IPCC reports tend to produce decontextualised knowledge that is difficult to translate at the national, regional and local levels. On the other hand, by shying away from some of the most relevant (geo)political aspects of climate change, they may contribute to supporting the international status quo and the ossification of the UNFCCC. In that context, the policy-relevance of the IPCC has been questioned. Interestingly, however, other actors, and civil society groups in particular, have started to leverage the political status of the SPMs, using them for instance as legal evidence in climate change litigation.

Social and political pressure on the IPCC is likely to intensify in the context of an increased interest in solutions to climate change. If the IPCC is to meet these challenges and remain policy-relevant, it will need to rethink how governmental approval is produced. Several researchers have proposed giving more visibility to the individual chapters of the WG reports and to the Technical Summaries, whose language and scope is less likely to have been tuned down (Victor et al., Reference Victor, Gerlagh and Baiocchi2014). Others (Hulme et al., Reference Hulme2010; Victor, Reference Victor2015) have suggested that the most controversial political questions should be addressed in parallel processes independent from the IPCC and from governmental influence.

Overview

This chapter reviews the history of the efforts of the Intergovernmental Panel on Climate Change (IPCC) to achieve and maintain policy relevance while remaining policy-neutral and staying far away from ‘policy prescriptiveness’. The chapter argues that the boundaries between policy relevance, neutrality and prescriptiveness are a practical achievement – they must be constantly negotiated as the science and politics of climate change evolve. The chapter uses historical case studies to illustrate this point, such as the controversy over the so-called ‘burning embers’ diagram. It ends by discussing recent debates about the IPCC’s new role in the post-Paris Agreement policy landscape. While IPCC actors call for greater policy relevance, observers and critics contend that the IPCC will always and inevitably be policy-prescriptive, even if on a tacit and unintentional level. Achieving even greater policy relevance may therefore mean jettisoning or modifying the aspiration to be policy-neutral.

21.1 Introduction

For anyone with an interest in the history of scientific objectivity, authority and science-politics relations, there’s a lot going on in the above self-description of the IPCC’s status and modus operandi. The institution is both scientific and governmental by nature, concerned both with understanding the world and with governing it, and thus must presumably negotiate the occasional contradictions of those natures. The scientific information it offers is both rigorous – it offers the very highest quality of analysis – and balanced – it accounts for various interpretations and arguments, some of which presumably will be less rigorous than others. And the process of governmental endorsement is a performative demonstration of states’ deferment to scientific expertise in offering the most authoritative description of the world under climate change, even where those descriptions may have profound implications that run contrary to some states’ self-interests.

All these sources of potential tension lay behind the IPCC’s oft-quoted mantra of being policy-relevant but policy-neutral, never policy-prescriptive. The IPCC offers a science that describes and predicts potential policy problems, and that increasingly evaluates the impacts of different policy options. But it offers a science that is neutral when it comes to political choice. The IPCC won’t tell you what to do, just that something needs to be done, and that there is a range of possible things that you might do (Havstad & Brown, Reference Havstad and Brown2017). But working at these many interlinking boundaries – between description and prescription, knowing and governing, rigour and balance, scientific authoritativeness and real-world relevance – is neither easy nor straightforward. Indeed, the policing of these boundaries is arguably a defining feature of all the various disputes and controversies that have punctuated the IPCC’s history to date (see Chapter 16).

This chapter reviews and summarises studies of the IPCC’s efforts to navigate the relevance/neutrality boundary. Most of this research is informed by science and technology studies (STS), a field which largely offers its own consensus that science and politics (or policy) cannot be neatly separated and that values, norms and interests structure scientific work in similar ways to how they shape political decision-making. STS scholars would therefore conclude that defining a science–policy boundary is a practical achievement – something which must be continually worked at, as situations and contexts change.

21.2 Beyond ‘Truth to Power’: Fashioning Policy Relevance

From the outset, the IPCC moved beyond a model of science–policy interaction by which an autonomous science ‘speaks truth’ to a separate, political domain of ‘power’ (see Chapter 2). The IPCC has, since its founding, created and operated within a uniquely ‘hybrid’ space of science and policy, where problem framings, the selection of relevant questions and foci, modes of assessing reliability (Chapter 11), expressing uncertainty (Chapter 17) and communicating findings (Chapters 25 and 26) have been the product of negotiation between scientists and policymakers (Chapters 9 and 20). Although much copied since, the IPCC was for many years unique in following this hybrid model in producing regular global environmental assessments. But the nature of this hybridity has changed over time.

Over its first assessment cycle (1988–1990), this science–policy hybridity was particularly intense, and the IPCC was essentially the global setting for negotiating both the science and politics of climate change. In the First Assessment Report (AR1), Working Group III (WGIII) was a space for debating policy alternatives, whereas its next manifestation in 1995 became the more prosaically framed ‘Economic and Social Dimensions of Climate Change’. Several developing countries expressed dissatisfaction at the first report’s ambiguous positioning at the science–policy boundary, and were wary of the IPCC, with its numerical dominance of participants from the global North (see Chapter 7), becoming the chief setting where a climate policy architecture would be worked out (Miller, Reference Miller, Heazle, Griffiths and Conley2009). The Intergovernmental Negotiating Committee (INC) was therefore established in 1990, and was the institutional setting for the drafting of the UN Framework Convention on Climate Change (UNFCCC) (Bodansky, Reference Bodansky, Luterbacher and Sprinz2001). This act of boundary making subsequently strengthened the IPCC’s self-identification as a scientific body, with a clear ‘firewall’ established between policy relevance and policy neutrality.

Beginning with the Second Assessment Report (AR2), new modes of fostering policy relevance were developed. Government representatives took on a larger role in the review process, and the processes for producing a Synthesis Report (SYR) and Summary for Policymakers (SPM) were formalised (see Chapter 3). The SYR offered an interdisciplinary, policy-relevant synthesis of the three WG reports and, Shaw (Reference Shaw2005) contends, acted as a firewall between the science-facing WG chapters and the more policy-oriented SPM. Parts of the assessment process were increasingly pointed towards the requirements of the COP – such as Article 2 of the UNFCCC and the definition of dangerous anthropogenic interference (DAI) with the climate system (Oppenheimer & Petsonk, Reference Oppenheimer, Oreskes and Jamieson2005). In the AR3 report (2001), attempts were made to further enhance the policy relevance of the SYR by including a number of ‘policy-relevant scientific questions’ (PRSQs). The intention was to draw policymakers not just into the review and approval of the provisioned information, but into the process of framing the very questions addressed. But as Shaw (Reference Shaw2005) reports, the process of defining the PRSQs was fairly ad-hoc, involving just a select number of national governments.

This trajectory of the IPCC seeking to further increase the policy relevance of its assessment products, while strengthening both the internal and external boundaries between science and policy, has continued to date. It extends to the much-heralded ‘solution-oriented’ turn (Kowarsch & Jabbour, Reference Kowarsch and Jabbour2017) and to the increased regularity of ‘special reports’, some of which – like that on the implications of 1.5 °C of global warming (SR15) – have been very directly mandated and framed by policymakers (Livingston & Rummukainen, Reference Livingston and Rummukainen2020). Later in this chapter, we will return to these recent developments; what follows next is an exploration of how the pursuit of ever more policy relevance has always been accompanied by contestations and struggles over the boundaries of relevance, neutrality and prescriptiveness.

21.3 Policing the Boundaries

In the Third Assessment Report (AR3), a new way of visually engaging with the possible definition of DAI was developed by the authors of WGII, Chapter 19. The ‘burning embers’ diagram offered a visual depiction of authors’ estimates of when different impacts would occur at different levels of temperature rise (for an example, see Figure 25.3 in Chapter 25). The blurred colours were intended to convey the inevitable uncertainties involved in aggregating already-uncertain knowledge about regional impacts to a global scale, and to convey the role that ‘expert judgement’ (see Mach et al., Reference Mach and Field2017) played in evaluating the significance and meaning of findings in the scientific literature.

The diagram was intended to be policy-relevant in the sense of furnishing policymakers with information by which they could come to their own judgements as to the meaning of DAI. Interviews with the diagram’s creators revealed the complex, and not always consensual, intersection of epistemic, aesthetic and ‘value’ judgements.¹ Ultimately the diagram was designed to separate the primarily epistemic judgements of the authors from the subsequent normative judgements to be made by policymakers with the diagram’s assistance. But this distinction was challenged in the review process, most notably by government representatives. A reviewer for the US government suggested that the implication that there was enough scientific evidence to inform a judgement of DAI was itself far too close to being policy-prescriptive, while other reviewers thought the diagram offered far too conservative a view of when dangerous impacts might begin. The subsequent AR4 version of this chapter met with similar issues. For a US reviewer, the whole thing was far too normative and prescriptive, even verging on the ‘theological’. In contrast, for a German reviewer, the chapter needed to engage much more closely with the emerging political discourse around 2 °C as being an appropriate threshold of DAI, and thus serving as a policy target (Mahony, Reference Mahony2015). In the draft AR5 version of the burning embers figure, a much closer engagement with both 2 °C and 1.5 °C targets was proposed, but at the government plenary where approval was sought for the SPM, the ‘UK, supported by Slovenia, proposed removing all dotted lines so as to appear scientifically neutral’ (IISD, 2014: 12).

Throughout the history of the burning embers diagram, which has become ‘a cornerstone of the IPCC assessments’ (O’Neill et al., Reference O’Neill, Oppenheimer and Warren2017: 28), the authors were praised by some for consistently acknowledging the role of ‘value judgements’. For others, however, the presence of such judgements in any form ran counter to the IPCC’s stated mission to be policy-neutral. For such critics, even venturing a possible definition of DAI constituted unwelcome policy prescriptiveness. These tussles can be interpreted as instances of ‘boundary work’ – the social processes whereby distinctions are drawn between science and non-science (Gieryn, Reference Gieryn1999). Conventionally, ‘boundary work’ has been seen as something done by scientists to maintain their own intellectual authority and autonomy. In boundary organisations like the IPCC however, boundary work is something engaged in by both scientific and policy participants, in struggles to stabilise an ever-moving field of scientific and political facts and arguments, and to retain the respective autonomy of zones of scientific and political reasoning.

One lesson of the burning embers example – and of comparable cases discussed in Chapter 24 – is that different conceptions of where the science/policy (or relevant/neutral/prescriptive) boundary lies exist in different policy communities. In relation to the burning embers, Jasanoff’s notion of civic epistemology can help interpret the wildly diverging views of different government representatives (see Chapter 23). Sociotechnical controversies in the United States and Germany, for example, reveal very different ideas about where science ends and politics begins (also Jasanoff, Reference Jasanoff, Dryzek, Norgaard and Schlosberg2011b). The challenge for an international body like the IPCC is that there is no universally accepted definition of that distinction. The IPCC is a space where international actors engage in constant negotiation over how to bring science and policy together, and how to produce policy-relevant knowledge that does not stray into the realm of policy prescription. IPCC statements and representatives may allude to an apparently universal definition of where the boundaries lie. But the IPCC’s history of practically managing science–policy interactions shows that drawing a line between science and policy, relevance and neutrality, is a product of negotiation within particular contexts. The line can never be settled once and for all, and more negotiation will always be required as contexts change.

21.4 Incredible Futures: From Relevance to Performativity?

The political world after the Paris Agreement of 2015 is very different: countries are busy deliberating their own Nationally Determined Contributions (NDCs) to the mitigation effort, as well as trying to think about adaptation at more local scales (see Chapter 22). Thus, the meaning of policy relevance for the IPCC is undergoing some quite radical changes (Lahn, Reference Kouw and Petersen2018), and the intensification of mitigation debates has put the economics-heavy work of WGIII in the spotlight (Hughes & Paterson, Reference Hughes and Paterson2017). WGIII participants have themselves become active participants in debates about the future of solution-oriented global environmental assessments (GEAs), most notably former WGIII Co-Chair Ottmar Edenhofer in his collaborations with philosopher Martin Kowarsch. They have argued that GEAs have a duty to provide much better knowledge of the implications and co-benefits of different policy choices, and to better accommodate diverse normative viewpoints. These authors say that the IPCC needs to reach out beyond conventional national government audiences to the diverse array of actors that make up the new landscape of polycentric climate governance. They contend that IPCC authors can work as ‘map-makers’ and ‘cartographers of pathways’, helping policymakers to think about different routes to intended policy outcomes – like keeping global warming to 1.5 °C or 2 °C – and to think through the interdependencies of policy goals, means and outcomes (Edenhofer & Kowarsch, Reference Edenhofer and Kowarsch2015).

Edenhofer and Kowarsch’s model recognises that maintaining policy relevance will require the IPCC – or at least parts of it – to engage more readily with thorny normative and political questions. They do not propose that the IPCC become ‘policy-prescriptive’, but rather that policy relevance be maintained through ever-closer engagement with the goals and values of policymakers and diverse stakeholders. Much of the earlier controversial work of the IPCC sought to help policymakers identify policy goals, such as not exceeding a point of DAI. Now, however, knowledge controversies are more likely to rage around pathways to pre-agreed policy outcomes (see Chapter 15).

Following the publication of AR5 several commentators criticised the inclusion of speculative ‘negative emission technologies’ (NETs) like bioenergy with carbon capture and storage (BECCS) in modelled pathways prepared for the assessments. For Oliver Geden, Kevin Anderson and others, this was evidence of the modelling community, which underpinned the work of WGIII, trying to keep policymakers engaged by telling them what they wanted to hear – that their targets were still achievable despite the continued lack of real mitigation effort (Anderson, Reference Anderson2015; Geden, Reference Geden2015). By loading the models with deus ex machina technologies that would, at some point in the future, come along and save the day, policy goals could be retained while the means and outcomes of the pathways to them changed radically. For some, this represented an abnegation of scientific integrity; for others, the presence of speculative technologies in authoritative mitigation scenarios raised another prospect – that of the ‘performativity’ of scenarios and forecasts.

While the inclusion of high levels of BECCS may not have been an overt prescription by WGIII authors – i.e., a statement of ‘this is what the world should do’ – perhaps it could nonetheless become a self-fulfilling prophecy. Sociologists of science and technology have long observed that visions of the future can become self-fulfilling by shaping what is deemed to be possible and desirable, by directing funding decisions, and lending an air of credibility to what otherwise might be considered speculation (Merton, Reference Merton1948). Economic theory and forecasts have been noted to be particularly performative, with public policy used to shape markets and societies such that positive forecasts come true. The real world is increasingly shaped by the concepts and principles of mainstream economics, rather than the other way around. It is the supposed ‘neutrality’ of economics as a science that gives it the authority to exercise such world-making power (MacKenzie, Reference MacKenzie2006).

In the climate context, theoretical technologies like BECCS have, since 2015, increasingly been positioned in national policy scenarios and toolkits (e.g. National Grid, 2021). This seemingly bears out the idea that BECCS, as an illustrative possible means to a certain end in IPCC scenarios, has come to be seen as indispensable to achieving certain ends. It appears as a fully-fledged policy option under consideration by powerful actors, even if the technology may be unproven and lacking societal consent (Beck & Mahony, Reference Beck and Mahony2018b).

The inclusion of BECCS-heavy low-emission scenarios in AR5 was a laudable attempt to keep the possible ‘solution space’ for policymakers as open as possible, in line with the principles proposed by Edenhofer and Kowarsch (Reference Edenhofer and Kowarsch2015). However, Beck and Oomen (Reference Beck and Oomen2021) argue that in pursuing its role as a ‘map-maker’, the IPCC has also functioned as a ‘corridor-maker’. It has limited ideas of possible routes to predefined emissions goals to a series of consensually agreed and scientifically authoritative pathways. The concern is that in relying on technologies that can pass the economic sniff-tests of integrated assessment modelling, other, more radical policy options may be left off the table. Many are now asking how assessments like the IPCC can instead broaden the solution space in a way which goes beyond those solutions deemed feasible within economic models designed to tend towards global economic optimisation (Kear, Reference Kear2016; Pielke Jr, Reference Pielke2018). What if, to deal with decarbonisation properly, the rules of mainstream economics, and of political and social feasibility, need rewriting? What would that mean for the IPCC?

The integrated assessment community is starting to explore scenarios that unsettle the assumption that economic growth should be a default policy goal (O’Neill et al., Reference O’Neill, Carter and Ebi2020). In assessing such scenarios the IPCC could further expand the possible solution space. But with economic growth being such a powerful default public policy (Barry, Reference Barry2021), would this be to the detriment of policy relevance and credibility? By challenging – or at least questioning – some basic political-economic assumptions, the IPCC will inevitably attract criticism for being too normative or prescriptive, or maybe even ‘theological’. But as the IPCC seeks policy relevance in a polycentric climate governance context, and as it aims to pivot from identifying the climate change problem to assessing solutions, it will need to increasingly engage with thorny normative and political questions (Maas et al., Reference Maas, Montana and van der Hel2021). Indeed, Noel Castree and colleagues recently called for a new mode of GEA that is openly political, offering ‘visibility to a wide range of worldviews’, particularly those which would challenge the base assumptions of other worldviews, such as the nature of power, what counts as valid argumentation, and the desirability of endless economic growth (Castree et al., Reference Castree, Bellamy and Osaka2021: 72). Remaining ‘neutral’ in such a context would be impossible – indeed remaining so would itself be an exercise of power, an unspoken backing for a certain way of thinking about and organising the world (Delvenne & Parotte, Reference Delvenne and Parotte2019).

21.5 Achievements and Challenges

The IPCC has often been accused by reviewers and critics of being ‘too political’ and ‘alarmist’, and of not sticking to a sober deliberation of scientific facts (Shaw & Robinson, Reference Shaw and Robinson2004). Others have observed that the push for consensus and rigorous assessment has sometimes undermined the policy relevance of reports. For example, reflecting on the exclusion of more extreme, but highly uncertain, projections of future sea-level rise (SLR) from the AR4 WGI report, Oppenheimer et al. (Reference Oppenheimer, O’Neill, Webster and Agrawala2007) argued that the IPCC was doing policymakers a disservice (see Box 19.1). Surely those charged with governing coastlines and littoral cities would want to know about ‘high-magnitude’ potential events – like an SLR of 7 metres or more – no matter how unlikely the best models may currently say they might be (see also Chapter 17). In a later paper, Brysse et al. (Reference Brysse, Oreskes, O’Reilly and Oppenheimer2013) looked across a range of IPCC projections and argued that the knowledge-making structures and processes of the IPCC mean that the reports tend to ‘err on the side of least drama’. Avoiding scientific and political ‘hot potatoes’, in a bid to preserve scientific credibility and authority, means that information that may be highly relevant to policymakers can be excluded because of its uncertain or controversial nature. As the IPCC strives towards ever more policy relevance, it runs up not only against its own policy of remaining neutral, but also against its other practices for maintaining credibility and authority, such as consensus-seeking (see Chapter 19).

The distinction between policy relevance and neutrality may seem straightforward in theory, but it is something that must be worked out continuously in practice. Stabilising the boundary between science and policy is always a practical, context-bound achievement – a product of ongoing negotiations between IPCC authors, reviewers and government representatives. The IPCC can claim some success in stabilising this boundary sufficiently over time such that its reports continue to be considered a scientific gold standard as well as having demonstrable policy impact. But the IPCC and the communities that constitute it will need to reflect on the new political context of climate change, and on the challenge of the relevance and neutrality of IPCC reports being in more direct tension as the organisation pivots towards a more solution-oriented and risk-management framing of its assessments (see Chapter 18).

• Rather than simply seeking relevance to policy and policymakers, perhaps the IPCC should take as a guiding mantra the enlargement of the solution space, for example through engaging with a wider range of scenarios of, and pathways to, global sustainability (O’Neill et al., Reference O’Neill, Carter and Ebi2020). Through this and other means the IPCC could build relevance with diverse stakeholders and publics, while helpfully laying the foundations for informed democratic debates about the broad suite of policy options available for limiting the trajectory and impacts of global warming. The challenge here would be to reconcile new tensions between relevance and neutrality. Perhaps enlarging the scope of the former is worth the cost of jettisoning some of the latter.