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date: 25 September 2022

The Two Degrees Celsius Limitfree

The Two Degrees Celsius Limitfree

  • Christopher ShawChristopher ShawEnvironmental Change Institute, University of Oxford


International climate negotiations seek to limit warming to an average of two degrees Celsius (2°C). This objective is justified by the claim that scientists have identified two degrees of warming as the point at which climate change becomes dangerous. Climate scientists themselves maintain that while science can provide projections of possible impacts at different levels of warming, determining what constitutes an acceptable level of risk is not a matter to be decided by science alone, but is a value choice to be deliberated upon by societies as a whole. Hence, while climate science can inform debates about how much warming is too much, it cannot provide a definitive answer to that question. In order to fully understand how climate change came to be defined as a phenomenon with a single global dangerous limit of 2°C, it is necessary to incorporate insights from the social sciences.

Political economy, culture, economics, sociology, geography, and social psychology have all played a role in defining what constitutes an acceptable level of climate risk. These perspectives can be applied through the framework of institutional analysis to examine reports from the Intergovernmental Panel on Climate Change and other international organizations. This interdisciplinary approach offers the potential to provide a comprehensive history of how climate science has been interpreted in policy making. An interdisciplinary analysis is also essential in order to move beyond historical description to provide a narrative of considerable explanatory power. Such insights offer a valuable framework for considering current debates about whether or not it will be possible to limit warming to 2°C.


  • History of Climate Science
  • Policy, Politics, and Governance
  • Management of Technology and Mitigation


Science has been used to support two claims that define our understanding of, and responses to, climate change. The first claim is that climate change is a phenomenon with a knowable single dangerous limit. The second claim is that this dangerous limit is represented by 2 degrees Celsius (2°C) of warming above the preindustrial average global temperature. News stories, policy announcements, and many environmental NGO campaign messages characteristically describe 2°C of warming as the point at which scientists agree climate change will become dangerous (Shaw, 2013, 2015). Meanwhile, literature from the physical and social sciences makes clear that although climate science can offer projections about possible future climate change impacts, deciding what constitutes an acceptable level of climate risk is a value choice that cannot be resolved through scientific calculation alone (Dessai et al., 2007; Guivarch & Hallegatte, 2013; Jaeger & Jaeger, 2010; Oppenheimer, 2005; Oppenheimer & Petsonk, 2005; Pidgeon & Fischoff, 2011; Risbey, 2006; Whitmarsh et al., 2011). As the Intergovernmental Panel on Climate Change (IPCC) has noted, “Defining what is dangerous anthropogenic interference with the climate system and, consequently, the limits to be set for policy purposes are complex tasks that can only be partially based on science, as such definitions inherently involve normative judgements” (Bernstein, 2008, pp. 97–99).

Signatories to the United Nations Framework Convention on Climate Change (UNFCCC) have agreed upon commitments to enhance public access to information about climate change. The goal is to improve public understanding of, and participation in, the political choices that need to be made in order to meet targets for climate change mitigation and adaptation (UNFCCC, 2012, 2015a).

Improving public participation will require increased public understanding of the political choices that have led to the definition of 2°C (or 1.5°C) as a dangerous limit to climate change. Further, given that current policies are unlikely to limit warming to 2°C (Geden, 2015; Geden & Beck, 2014; Hulme, 2016; Jordan et al., 2013; UNFCCC, 2015b; Victor & Kennel, 2014), public participation could also extend to discussions about what, if anything, should replace the 2°C concept. The development of a more inclusive public dialogue will require a very different relationship between the public and the knowledge-production process, a relationship predicated on a shared understanding of the normative nature of the 2°C limit.

Greater public involvement in discussions of what constitutes an acceptable level of climate risk is needed because currently, there is little public awareness or understanding of the targets and the risks they represent. Recently voiced aspirations “to limit global warming to well below 2 degrees Celsius, and to pursue efforts to limit the temperature increase to 1.5 degrees” (UNFCCC, 2015a do not address this democratic deficit.1 In addition, influential institutions like the European Union (EU) and G8 have already been responding to the idea of a 2°C dangerous limit with calls to limit warming to below 2°C for a number of years (Shaw, 2011, p. 167). In summary, the issues discussed here in relation to the 2°C limit apply equally to suggestions of a 1.5°C limit.

The Institutionalization of the 2°C Limit

Legally Binding Deals and 2°C

There have been two legally binding climate change agreements—the Kyoto Protocol and the deal reached in Paris in 2015. The Kyoto Protocol was first agreed in 1997 (UNFCCC, 1998) and came into force in 2005 (UNFCCC, 2005). It was the world’s first legally binding climate change deal. At the Paris climate conference (COP21) in December 2015, 195 countries adopted the first-ever universal, legally binding global climate deal (European Commission, 2016). The distinction is an important one, because the Kyoto Protocol did not cover emissions from the world’s two largest emitters, China and the United States. China was not part of the Kyoto Protocol because developing countries—including India, South Africa, and Brazil, as well as China—were excluded from the need to reduce emissions (UNFCCC, 2005). The United States withdrew from the Protocol in 2002. The Kyoto Protocol was not an agreement that sought to limit warming to an average of 2°C. Instead, the goal was for industrialized countries to cut their greenhouse gas emissions by 5% from 1990 levels by 2008–2012 (UNFCCC, 2005), cuts in emissions described by one scientist as so small as to be “irrelevant” (Flannery, 2006, p. 224).

While the Paris agreement articulates a long-term goal of keeping the increase in global average temperature to 1.5°C, the current commitments to emission reductions made by the signatories are not even sufficient to limit warming to 2°C (Hulme, 2016; UNFCCC, 2015c). Individual countries’ commitments to the overall reductions needed for the 2°C limit are spelled out in their Intended Nationally Determined Contributions (INDCs). China, the world’s largest emitter of greenhouse gases, in its INDC announced its goal to peak its emissions around 2030 and to increase its share of non-fossil fuels in primary energy consumption to around 20% by the same year (World Resources Institute, 2016). The United States intends to reduce its greenhouse gas emissions by 26% to 28% below its 2005 level in 2025, while the EU has agreed to cut domestic greenhouse gas emissions by at least 40% by 2030 (Ibid.). The combined INDCs from across all signatories mean a forecast temperature rise of around 2.7°C by 2100 (UNFCCC, 2015c).

Defining Dangerous Climate Change Under Conditions of Uncertainty—The Role of Institutions

The credibility of the single global dangerous limit idea is brought into question by the uncertainties that characterize projections of future climate change scenarios. The uncertainty surrounding projections of climate change is so profound as to make it difficult to even know the extent of the uncertainty (Arnell et al., 2005, p. 1421), hence rendering climate projections virtually worthless (Allen et al., 2009; Oppenheimer, 2005; Pearce, 2007a; Weart, 2003; Wohlforth, 2004).

However, decision-making power under modernity has taken institutional form (Rayner & Thompson, 1998) and the institutions involved in climate policy decisions tend to assume (or require) that all uncertainty be quantifiable (Schneider & Kuntz-Duriseti, 2002, p. 55; Tickner, 2003, p. 6).

The quantification of global climate risks has emerged out of an institutional process stretching back to the 1970s (for detailed histories, see, for example, Hare, 2009; Jaeger & Jaeger, 2010; Oppenheimer, 2005; Oppenheimer & Petsonk, 2005; Randalls, 2010; Shaw, 2013; Tol, 2007).

The concept of institutions is very broad, ranging from formal deliberating bodies engaged in treaty making to the informal liaisons among a range of different decision-making and non-decision-making communities and actors (O’Riordan & Jordan, 1999). What defines all these interactions as institutional is the “presence of some sort of order and guiding principles of social solidarity”—rules and norms—focused around a “locus of regularized or crystallized principle of conduct that governs a crucial area of social life and that endures over time.” (O’Riordan & Jordan, 1999, p. 346).

The UNFCCC is an institution governing a multilateral legal instrument specifying a system of norms and rules for avoiding dangerous climate change (Porter & Brown, 1991, p. 20). Under the conditions of empirical uncertainty surrounding the defining of dangerous climate change, these norms and rules come to play a determining role in defining what is true (Johnson & Covello, 1987, p. 357). In the case of complex problems requiring global coordination of responses knowledge production can be universalized only through a complex and fragile social production infrastructure. Therefore, the “global reproduction of knowledge is more dependent on the institutions involved than the facts themselves” (Wynne & Jasanoff, 1998, p. 20). Eden (2004, p. 59) draws on ideas from organization theory to show how institutions absorb uncertainty and turn it into fact—a point repeated by Cooke (1991) and Hind (2007). The greater the level of uncertainty, the more important group uniformity becomes as a determinant of decision making. Under conditions of scientific uncertainty, this consensual validation plays an important role in reaching decisions about what counts as a problem, how problems are represented, and, consequently, the best strategies to be used to solve those problems (Eden, 2004, p. 50).

Institutional Construction of Climate Risk

Bronstein, writing about government and industry responses to lung disease in Appalachian coal-mining communities, identifies three stages in the social construction of danger (Bronstein, 1984, p. 223). Stage one is the definition of danger, which in Bronstein’s account is a process initiated by the workers and local communities themselves, in the face of official opposition. Stage two involves the authorities’ legitimating the claims of danger, and stage three occurs when the same authorities co-opt the issue in order to gain control over discussions about what responses are appropriate. The obvious difference with climate change is that the initial definitions of danger did not primarily come from the public, or even norm entrepreneurs, such as NGOs and the media, but instead from scientists. While the stages are not as distinct as in Bronstein’s model, the model provides a valid heuristic for interpreting the development of the 2°C policy framework.

Identifying the Danger

The first scientific conference on climate change, held in 1979, was titled the “World Climate Conference.” The meeting issued a declaration calling on the world’s governments “to foresee and prevent potential man-made changes in climate that might be adverse to the well-being of humanity” (UNFCCC, 2014). During the 1980s, a number of conferences and events were key in furthering the idea that tackling climate change would require globally coordinated responses and agreed targets. Perhaps the most significant of these was the Villach Conference, held in October 1985, from which emerged a new set of political and policy conclusions emphasizing the urgency of action (Franz, 1997). The Advisory Group on Greenhouse Gases (AGGG) was jointly established in 1986 by the WMO, UNEP, and the International Council for Scientific Unions (ICSU) “to ensure adequate follow-up of the recommendations” emerging out of the Villach Conference (Potter, 1986, p. 365). A report commissioned for the AGGG and published in 1990 argued for an overall maximum warming of between 1 and 2°C, depending on the agreed level of risk, with 1°C of warming considered a low- risk strategy and 2°C a high-risk strategy (Rijsberman & Swart, 1990, p. viii).

The AGGG was made up almost entirely of scientists (Ambrus et al., 2014). In 1988 it was replaced by the IPCC, which was characterized by a process that brought in governments from across the world, giving them the chance to define the questions to be assessed by the climate scientists and the chance to approve the final report (Ambrus et al., 2014, p. 133). This meant the IPCC was a much more political institution than the AGGG (Ibid.). Boehmer-Christiansen (1994) has argued that the AGGG was disbanded for being too partisan and policy prescriptive. In other words, authorities were unhappy that decisions about limits to warming were being made without their oversight.

Defining Danger

In 1990, negotiations for the UNFCCC began and were agreed in 1992 at the Earth Summit. Article 2 of the UNFCCC formalized the idea of a knowable, single global dangerous limit for climate change. In contrast to the AAAG paper, neither the first IPCC report nor Article 2 of the UNFCCC made any recommendations about targets for emissions, nor did they mention either a 1 or 2°C dangerous limit (Houghton et al., 2001). The Organisation for Economic Co-operation and Development (OECD), a prominent institution in global governance, wrote, “given that many uncertainties remain about the prediction of climate change, rigid targets are deliberately avoided” (OECD, 1995, p. 11).

As Oppenheimer (2005) noted, the UNFCCC was in effect a call to climate scientists and policy makers to constrain these uncertainties. To climate scientists, the convention said, “Climate change is a phenomenon with a dangerous limit, and we have defined the effects that should be considered dangerous. Your job is to find out what levels of carbon dioxide and warming will cause these dangerous effects.” As the definition of dangerous impacts provided by the UNFCCC was only “skeletal” (Oppenheimer, 2005, p. 1399), this left a lot of work to be done on trying to reduce the uncertainties raised by the UNFCCC.

No IPCC reports have ever sought to recommend a dangerous limit for climate change. The IPCC Third Assessment Report of 2001 confirmed that attempts to define dangerous climate change were beyond the IPCC’s legal remit (Dokken et al., 2001). However Chapter 19 of the Working Group II report (2001) identified five “reasons for concern” that could be used to “aid readers in making their own determination about what is ‘dangerous’ climate change” (Smith et al., 2009, p. 915). The “Reasons for Concern” diagram (more colloquially known as the “burning embers” diagram) lists different forms of physical impacts—risk to unique and threatened systems, risk of extreme weather events, distribution of impacts, aggregate impacts, and risk of large-scale discontinuities (Ibid).

Co-opting the Issue

The German Advisory Council on Global Environmental Change (WBGU) reports of 1995, 1997, and 2003 are seen as important milestones in the effort to turn the dangerous limit concept into a number that policy makers could use (Jaeger & Jaeger, 2010; Oppenheimer & Petsonk, 2005; Tol, 2007). The WBGU papers were commissioned by the German government, and they fed directly into the UNFCCC process and the first Conference of the Parties (WBGU, 1995), the creation of the Kyoto Protocol (WBGU, 1997) and, later, EU climate policy (WBGU, 2003). Jaeger and Jaeger argue that it was these reports, and the efforts of the WBGU’s chairman, John Schellnhuber, that convinced Angela Merkel (who became Germany’s Environment Minister in 1994) to push for the 2 ºC target at international conferences. For these authors, the WBGU reports “did indeed trigger the political process that fifteen years later led to the global visibility conferred to the 2°C target by the G8, the Major Economies Forum, and the Conference of the Parties held in 2010 in Copenhagen” (Jaeger & Jaeger, 2010, p. 7). “We can acknowledge that the limit was—sometimes inadvertently, sometimes consciously—introduced into the policy debate not by policy makers but by some of us,” wrote the economist Carlo Jaeger (ibid, p. 25).

The 2003 WBGU report called on the EU to take the lead by committing to limiting warming to 2°C. The 2610th EU Council Meeting of 2004 confirmed “the maximum global temperature increase of 2°C over preindustrial levels should be considered as an overall long-term objective to guide global efforts to reduce climate change risks in accordance with the precautionary approach” (European Commission, 2004). From this point, official policy announcements increasingly sought agreement on the 2°C limit using science to legitimate those calls. For example, in the lead up to the Copenhagen conference, the G8 announced “We recognize the scientific view that the increase in global average temperature above preindustrial levels ought not to exceed 2 degrees C” (G8, leader’s declaration, 2009). In claiming a scientific consensus on the 2°C dangerous limit, the declaration mirrored the wording of the Copenhagen accord, which stated, “to stabilize greenhouse gas concentration in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system we shall, recognizing the scientific view that the increase in global temperature should be below 2 degrees Celsius, on the basis of equity and in the context of sustainable development, enhance our long-term cooperative action to combat climate change” (UNFCCC 1992). The 2°C limit was formally agreed as a target for mitigation policy in Cancun in 2010 (UNFCCC, 2011).

2°C in the Public Sphere

The Role of NGOs and the Media as Norm Entrepreneurs

An in-depth analysis of the language used to communicate the 2°C idea in the public sphere is beyond the scope of this article (for a fuller account of the public communication of the dangerous limit idea, see Shaw, 2013). It is, however, important to recognize that this language, whether used by decision makers, the media, or environmental NGOs, works as a purposeful and directed “linguistic action” (Wodak, 2008, p. 5) that seeks to act upon the social world in significant ways. The invisibility of the interests and power relationships inherent in linguistic performances (Roberts, 2004) makes language a powerful device for building consent to policy decisions (Newell, 2000, p. 77). In the case of climate change, language has been used to make a value choice appear to be an objective fact, by substituting discussion of what counts as an acceptable level of climate risk with the uncontestable claim of a scientifically derived dangerous limit (Machin, 2013).

This article now examines the role of two sets of norm entrepreneurs involved in the “social amplification” (Kasperson et al., 1988) of those risk messages—the media and environmental NGOs. For norms to emerge, societal actors need to act as “norm entrepreneurs,” mobilizing support for particular ways of talking about and responding to social issues (Ingebritsen, 2002, p. 12). First, the role of the media and environmental NGOs is addressed at a theoretical level. Then the theoretical case is supported with a few actual examples drawn from the United Kingdom. The United Kingdom is an appropriate case study because it is the country with the most ambitious legally binding climate targets in the world. Therefore, the way these targets are legitimated through the invocation of science in the United Kingdom has implications for the global discourse on dangerous limits to climate change.

The News Media as Norm Entrepreneur

It has been argued in this article that the contest for control of how to interpret climate science occurs primarily in institutional settings, The mass media constitutes an important institutional setting with regard to public attitudes to climate change (Carvalho & Burgess, 2005; Doulton & Brown, 2009; Koopmans, 2004; Oluasson, 2009).

Modern societies are characterized by a much closer relationship among science, politics, and the media than has hitherto been the case. Consequently, science is increasingly called on “to make pronouncements on issues that potentially concern the safety and well-being of the population at large, and are thus of immediate political relevance and have a high news value for the media” (Weingart, Engels, & Pasengrau, 2000, p. 261).

Most research in mass communication has found journalism to be profoundly conservative in support of existing power structures and the status quo (Stocking & Holstein, 2009). This extends to a widespread respect among journalists for expert and scientific knowledge (Weigold, 2001). Pollack attributes this respect to the fact that journalists and scientists share the same intellectual foundations (2003, p. 23). Yet the media reporting of science is widely held to be far less nuanced than the science itself (Doulton & Brown, 2009; Stocking & Holstein, 2009, and is deemed unable to accommodate the possibility of irreducible uncertainties in climate science (Smith, 2005, p. 1475; Ziman, 1991, p. 189).

A clear example of the ubiquity of the 2°C as scientific fact in media discourses is demonstrated by a Guardian editorial from December 2009. This editorial was published on the same day by 56 newspapers around the world in 20 languages (Guardian, 2009). In support of the 2 °C limit, the editorial announced “The science is complex but the facts are clear. The world needs to take steps to limit temperature rises to 2C” (Ibid.). Thus, in presenting the 2°C limit as fact derived from the science, the editorial makes clear there is nothing to debate about acceptable risk.

NGOs as Norm Entrepreneurs

Pluralist theories stress that policy options are dictated by public opinion and that environmental campaigners have a key role in shaping public opinion on environmental issues (Carter & Ockwell, 2007; Dunleavy & O’Leary, 1987). It has also been argued that environmental campaigners are heavily reliant on ideas of danger as a driving plot device in their media campaigns (Smith, 2005, p. 1473).

However the ability of campaigners to shape public opinion and environmental policy has been treated more critically elsewhere (Dryzek et al., 2003; Newell, 2000; Roberts, 2004). Crenson explains how power relations create or enforce social, political, and institutional practices and values that limit political processes to issues deemed comparatively innocuous by the holder of power (Crenson, 1971, p. 21). Lukes (1974) describes a second dimension of power to explain the way certain issues are kept off the political and institutional agenda. Newell, in his analysis of the influence of NGOs on international climate change policy, cites Kripp’s identification of “non active forms of power” (2000, p. 176). Thus, rather than look for evidence of conflict to see whether or not power is being exercised, one needs to illuminate the ways in which, and reasons why, actors adjust behavior to actual or anticipated preferences of others (Ibid.). In this case, it means aligning with dominant narratives around the scientific justification for 2°C. In research carried out in the lead up to Copenhagen (Shaw, 2011), the need for pragmatism was stressed more than once. As one interviewee said, “I think when you are trying to have some sort of policy impact you have to be fairly pragmatic about the targets you are using and to have some point at which you can begin to engage.” Such responses help explain why 2°C was a target campaigners were willing to use. When asked why use any single target at all in campaigning, respondents from environmental NGOs reasoned that it allowed communicators to provide a simple message that side-stepped the uncertainty in climate science:

“We can start to hang things on it, use it as a peg you know?”

“Uncertainty is really not a big help in the political domain and public communication. If there is some kind of certainty that going past 2º would be dangerous, catastrophic, then the politicians who are resistant to change and the public in general who are resistant to change in general I think will hang on to that.”

“We are asking people to do big things to change their lifestyles, to change the way they use energy and we need to make a cogent argument to people why we’re trying to do it and the reason were trying to do it is much clearer now.”

The case for a more participatory approach to defining acceptable climate risk

The Benefits of a More Participatory Process

Research into public understanding of the 2°C limit demonstrates it has not succeeded as an aid to public communication of climate risks (Carbon Brief, 2013). In an online poll, 2002 U.K. adults where asked “at what level of temperature rise do you think climate change will become dangerous?” The average mean temperature suggested was 8°C, and, ignoring the “don’t knows,” the three most popular choices were 5, 2, and 10°C (ibid.).

So what should happen now? Given the failings of the 2°C policy framework, could a more participatory process, as called for by the UNFCCC, be implemented?

A participatory process for deliberating on how much warming is too much has the potential to improve public understanding because the coproduction of knowledge about climate risk is itself thought to be pedagogic (Carvalho & Peterson 2012, p. 317; Stevenson & Dryzek, 2012, p. 192). The coproduction of knowledge has long been identified as essential to the building of successful environmental policies (Rayner, 1987, p. 8). Cash et al. argue that some form of extended peer-review process is essential not only in order to find a solution to environmental problems, but also to legitimate current institutions and social relations in the face of these issues, thus ensuring environmental science and policy continue to be seen as “credible, salient and legitimate” (2003, p. 8086). This is a view shared by Lövbrand, who calls for an explicit recognition of the social limits to climate science “to ensure rather than undermine continued scientific authority in the international climate regime” (2004, p. 449). These arguments suggest there are substantive benefits to be gained from a participatory dialogue that begins with the recognition that we are not discussing a scientifically defined dangerous limit, but are engaging in a subjective debate about acceptable levels of climate risk.

This approach is in line with Weinberg’s idea of “transcience” (1972), which maintains that currently scientific questions are being asked of nonscientific problems. In terms of climate change, this means science is providing quantitative answers to essentially qualitative questions (Baer, 2005, p. 4; Rayner, 1987, p. 19; Shrader-Frechette, 1991, p. 57). Therefore, the answer to the question “How safe is safe enough?” must be “Totally systemic, possessing no definitive answer. Also, defying any attempt at quantification, it belies the numerological reductionism that characterizes our scientistic world view” (Ravetz, 2006, p. 14).

In arguing that many environmental issues resist simplification through the reductive frames of normal science, Ravetz urges his readers to view the idea of certainty in science as an impossible goal (2006, p. 78). Instead, it is necessary to recognize that scientific activity is creating fresh uncertainty and instability, and should no longer be considered a terminus (Nowotny et al., 2001). Rather than being the singular means of responding to environmental problems, science should instead become one of several inputs into the decision-making process, a process wherein the ideal of rigorous scientific demonstration is replaced by that of open public dialogue that seeks to accommodate the plurality of legitimate perspectives (Ravetz, 2006). Scholz et al. call for transdisciplinary processes as a key element in developing socially inclusive, representational knowledge. This requires the inclusion of knowledge and values from agents from the scientific and the nonscientific world (2000, p. 477). So, while science has a role in describing the landscape of uncertainties and facts, the discussion about how to respond to these situations should be a societal one, not the preserve of scientific experts (Evans & Plows, 2007, p. 828). These perspectives are a reflection of the unique status of environmental science as the most socialized, and thus most complex, of all scientific activity (Nowotny et al., 2001; Ravetz, 2006).

What Might a Participatory Debate on Climate Change Science Look Like?

There has been a global proliferation of exercises of public engagement in science and technology over the past two decades (Philips, 2012). Many of these exercises have employed a model that sees the public as in need of education about what the problem is and the correct way to engage in discussions about it (Pestre, 2008; Thorpe & Gregory, 2010). This “deficit model” approach assumes that low public awareness of issues like climate risks is linked to a deficit of knowledge that could be addressed by public engagement (Hagendijk & Irwin, 2006; Wynne & Irwin, 1996).

Climate change is inescapably complex and often technical, so it is probably not possible or desirable to avoid entirely the notion of public engagement on climate change being partly about members of the public “learning” about the issue and its implications (Corner & Clarke, 2016). Nonetheless, the past decade has seen a concerted shift away from the deficit model of public engagement, partly because it embodies the old-fashioned idea that public engagement is a one-way process, rather than a dialogue with the public (Rowe & Frewer, 2005). It has been argued that successful public engagement means finding new ways of listening to and valuing diverse forms of public knowledge and social intelligence, and involving the public in fundamental questions about “why” certain developments are taking place, rather than just “what and when” (Corner & Pidgeon, 2010; Wilsdon, Wynne, & Stilgoe, 2005).

There have been few attempts in English-speaking countries to apply these principles in order to engage the public in debate about what counts as acceptable climate risk. There have, however, been two exercises that have at least in part touched on the 2°C issue.

Department of Energy and Climate Change—My2050

The Department of Energy and Climate Change (DECC) has developed an online interface to encourage engagement with the question of what energy sources the U.K. government should adopt in order to reduce CO2 emissions by 80% by 2050 (DECC, My2050). The My2050 simulation was developed to enable DECC to “engage in an open and transparent debate around the choices and trade-offs the UK faces to reach the 2050 emissions reduction target” (Allen & Chatterton, 2013). My2050 is based on three scenarios emerging from the U.K. government’s emission-reduction strategy HM Government (2010). Scenario 1 postulates a future of higher renewables and more energy efficiency, scenario 2 assumes higher carbon capture and storage and more bioenergy, and the third scenario anticipates greater nuclear energy use and less energy efficiency (Allen & Chatterton, 2013, p. 17). Three scales of social activity are represented—home, city, and country—and fourteen variables, seven on the supply side and seven on the demand side. Each variable has a slider that the user employs to select the extent to which any particular activity contributes to the overall target. The results of all the sessions where a user achieves a reduction of 80% or more are recorded, to provide a database of user preferences for energy pathways to 2050.

The link on the home page of the My2050 website poses the question, “Can you reduce our CO2 emissions to 20% of 1990 levels and help avoid dangerous climate change?” In line with the majority of existing discourses, the relationship between emission targets and dangerous climate change is left unexamined and beyond debate. A user of the My2050 interface would not be aware of any problems with the 2°C limit, the existence of a debate about whether that framing is fit for purpose, or the question marks over warming of less than 2°C being safe. Hence, the interface reproduces and extends the reach of the 2°C hegemonic discourse into more democratic forms of interaction, and signals that participation in the debate will not include involvement in decisions about what counts as an acceptable level of climate risk.

WWViews on Global Warming

WWViews, in its own words, “establishes a model for the future inclusion of the world’s citizens in global policymaking” (WWViews, 2015, p. 6). WWViews on Global Warming is a global citizen consultation organized by the Danish Board of Technology. Consultations have taken place in the lead up to both the Copenhagen summit and the Paris summit. In advance of the Paris summit, WWViews implemented 97 debates involving around 10,000 citizens in 76 countries (WWViews, 2015). The consultations happened on the same date, June 6, 2015. All meetings followed the same schedule: the citizens, divided into tables of 5 to 8 people, were led through a program, divided into five thematic sessions, by a head facilitator and a number of group facilitators. Each thematic session was introduced by the head facilitator and an information video. The participants then engaged in moderated discussions at their tables. Each thematic session concluded with citizens’ casting their votes anonymously on alternative answers to a total of 34 questions. The scheduling of the consultation is designed to allow time for analysis of the results and for release of the report in advance of the summit and to send a clear message to negotiators about the desire for ambitious agreements to be met in the summit (ibid.).

The question related to acceptable climate risks is “The world should decide in Paris to do whatever it takes to limit temperatures exceeding two degrees Celsius” (WWViews, 2015, p. 21). Thus, what it was possible to ask and imagine had already been defined in advance by the institutional norms governing the process designed to deliver the outcomes required by those very same norms. There was no sense of a debate or a question about how we should go about defining acceptable levels of climate risk and who should be involved in the debates.

Participatory Debates on Climate Risk—From Closing Down to Opening Up

The engagements outlined above were exercises in closing down the debate, in as much as the process was directed toward focusing on answering narrowly defined questions. To explore the role of science in the knowledge-production process would actually require taking the debate in the completely opposite direction, from consensus on one figure to an opening up of diverse perspectives on the various criteria for defining acceptable climate risk, without any effort at reaching consensus on a predefined answer. It would be the process of holding a democratic and inclusive dialogue, and the learning and engagement generated by the process would be the outcomes. The initial goal would be simply to build understanding that the question of how much warming is too much actually exists, and remains unanswerable by science alone.

Roberts has identified the need for deliberation on climate futures to draw on the storytelling all humans use to make sense of the world (2010). Allowing people to tell their own stories about climate futures offers an accessible means to democratize the building of bottom-up climate policy scenarios to compete with those that are used to communicate elite constructions of acceptable climate risk. The emission scenarios that are most likely to work are those that “take people with them” (Roberts, 2010, p. 145). It is therefore apparent that scenarios based on the stories people tell about the world they want and are unashamedly value based, are much more likely to engage public interest than the constrained technical exercises that currently constitute the limit of participation. For these stories to emerge, it is necessary to break with the formal and constrained deliberation methodologies employed to date (Roberts, 2010, p. 151).

A methodology for opening up the knowledge-production process should, first, permit participants to engage in a two-way dialogue. Second, the primary focus of engagement should be on the “why” questions first, and the “what and when” questions second. Third, the public should be engaged as early as possible in the process of policy decision making. This will help ensure that there is a possibility that the public’s view can be meaningfully incorporated and reflected in policy decisions over the coming decades.

What is required for such debates is a storytelling or narrative methodology that recognizes that sustained public engagement with the policy debates surrounding responses to the threat of climate change will require overcoming the disconnect between the technical and abstract language of the dangerous limits discourse and “the public's grounded set of storied experience” (Roberts, 2010, p. 152). The goal of participatory exercises then becomes about finding ways of closing the gap between policy and public narratives, so that the public can engage in conversations about climate change in their own terms, with reference to the things that matter to them.

Research into this form of participatory dialogue has shown people are more likely to react positively to climate change messages when they are presented within narratives that validate their values and identity—what motivates people to engage with climate change stories and low carbon behaviors is not necessarily worries about the ecosystem but the desire for a fairer and more compassionate world.

Hence what is now needed throughout the world is a national series of conversations about climate change, initiated by representatives of different communities to unearth the values and principles on which different people base their views about the world, and to build a bridge—a meaningful storyline—between people’s values and those of a more sustainable society. The challenge for anyone invested in building broad-based engagement with questions of acceptable climate risk is to catalyze a chorus of public debate and discussion (Corner, 2012).

Whilst the costs involved in such a process may be high, this methodology offers the most robust way of achieving the goals outlined by the UNFCCC in Paris. With the 2 ºC limit under review, now is the time to begin the conversations.


Defining a dangerous limit for climate change has been essentially an institutional process, not a scientific one. Climate science has never defined a dangerous limit. In fact, the vast majority of scientists have long made clear that choosing to define climate change as a phenomenon with a single dangerous limit is a value judgment that should be made through the appropriate democratic processes. The analysis provided in this article shows how institutional processes have acted as a barrier to the development of the democratic processes, falsely invoking climate science to construct a dangerous limit for climate change that can be codified and removed from contestation.

The fact that the UNFCCC is now considering a 1.5°C dangerous limit was interpreted as evidence that the 2°C concept is not a representation of dangerous climate change. This interpretation was used to argue that the important issue is for this moment, when the 2°C limit is under review, to be opened up to participatory processes that bring in a broader set of values, perspectives, and knowledge than have currently been used to frame the debate about what counts as an acceptable level of climate risk. The role for science remains central—it is the bedrock of the decision-making process. However, that scientific knowledge, and the uncertainties surrounding it, can best be used to help humanity respond to climate change if it is mediated through deliberative processes that bring in the diverse perspectives of humanity, not just a narrow set of institutional norms. Narrative methodologies provide a tried and trusted way of bringing other voices into the debate, and hence allowing the longstanding potential of participatory politics finally to be brought to bear on this increasingly urgent crisis.

Public involvement in the dangerous limit debate has the potential to generate new ideas about productive framings of climate risk, strengthen public support for the responses that emerge from the process, and help rebuild trust in the institutions tasked with delivering mitigation and adaptation policies.


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  • 1. Readers are directed to Fuss (2016) and Geden (2016) for in-depth analysis of options for limiting warming to 1.5°C.