1 Introduction

In 1990, scholars suggested that “socially acceptable” climate risks were low under 1 ℃ and high beyond 2 ℃ above preindustrial levels (Rijsberman & Swart, 1990). However, subsequent research and discussions on the 1 ℃ threshold were minimal (Jehn et al., 2022; Kemp et al., 2022; Knutti et al., 2016), and the 2015 Paris Agreement aimed for “well below 2 ℃.” The adoption of climate targets is central to international climate action. Nonetheless, they are not inherently efficient or just, as they have been adopted within a political context that protects the interests of the fossil fuels industry, largely ignoring justice concerns. An unclear temperature target muddies the carbon budget, its allocation, and the urgency of fossil fuel phase-out. An unjust target escalates climate risks and perpetuates inequalities. Almost a decade from the Paris Agreement, government plans for fossil fuel production are 110% and 69% more for 2030 than would be consistent with limiting warming to 1.5 °C and 2 °C degrees, respectively (SEI et al., 2023). Thirty-five years since the climate negotiations began, it is long overdue to review how ‘dangerous’ anthropogenic interference with the climate system has been quantified in science and how this has influenced the negotiations, including delaying discussions on phasing out fossil fuels.

In 2023, the Earth Commission calculated 1 ℃ to be a just target (Rockström et al., 2023). Through our Earth System Justice (ESJ) framework, we shed light on the injustices that have been overlooked throughout the history of target setting, making a normative contribution to what constitutes dangerous climate change. Firstly, we show how the protection of fossil fuels’ vested interests has contributed to rendering the 1 ℃ target unachievable. We then highlight supply-side policies as a more just alternative to the contemporary focus on the demand-side in climate negotiating processes (Lazarus & van Asselt, 2018; Pellegrini & Arsel, 2022), while acknowledging the unjust context that underpins these processes. Thus, we aim to provoke a reflection on the past failures of the climate regime in target setting to promote better-informed decision-making, centered on principles of historical responsibility and justice. The paper concludes by proposing supply-side policies rooted in the ESJ framework to ensure accountability of the fossil fuel industry and the Global North, as well as adequate compensation to the Global South.

2 Climate target setting and fossil fuel influence

2.1 A context of vested interests

Understanding the history of target setting requires awareness of the context in which it evolved. The development of the Global North was founded—and still depends—on fossil fuels, and the Global South is following the same path. In fact, the fossil fuel industry, worth up to $295 trillion USD (Linquiti & Cogswell, 2016), has further deepened the fossil fuel dependence by continuously influencing climate policy and hindering the energy transition (Franta, 2022; Supran & Oreskes, 2021). This carbon entanglement causes the urgency of action imposed by the climate crisis to be undermined by vested interests in maintaining the fossil-fueled status quo (Piggot et al., 2020).

Despite pledges like the temperature targets, fossil fuels subsidies are colossal, at $5.9 trillion—or 6.8 percent of global GDP—in 2020 alone (Parry, Black & Vernon, 2021), and estimated to be up to €21 billion per year in the European Union (Gençsü et al., 2020). These numbers are probably underestimates as in the Netherlands alone, the annual fossil fuel subsidy is as high as €45 billion.Footnote 1 Such enormous subsidies deter climate action, inevitably leading to the protection of fossil fuels interests even within climate policy (Piggot et al., 2020). An example of this is the Paris Agreement, which fails to mention fossil fuels, avoiding placing accountability and rendering pledges to mitigate emissions vague and unclear.

2.2 Fossil fuel-influenced decision-making

The continued support for fossil fuels is largely due to this industry’s political influence, specifically its lobbying activity (Bang & Lahn, 2020; Graham et al., 2019; Stokes, 2020; Strambo & González Espinosa, 2020). Fossil fuel lobbyists are most active when threatened by impending climate policy, and the setting of the temperature targets during the Paris Agreement has been accompanied by a continuous dialogue between government and fossil fuel representatives (Lantushenko & Schellhorn, 2023; Tansey, 2019; Laville, 2019a; Laville, 2019b; Corporate Accountability, 2017). Clémençon (2023) connects the relative failure of globally coordinated efforts to address climate change to the US decision to withdraw from the Kyoto Protocol. This decision is also linked to the fossil fuel industry’s influence on Congress (Oreskes & Conway, 2011; Pooley, 2010; Supran & Oreskes, 2021), such as the bankrolling of political campaigns for sympathetic lawmakers in the USA (Mayer, 2017).

Fossil fuel interests exercise an outsized influence in international climate negotiations. Industry groups representing fossil interests such as BusinessEurope and the US Chamber of Commerce participate as ‘observers’ or hosts at UNFCCC talks (Corporate Accountability, 2017). Big polluters have also sponsored COP talks or provided services to delegates, and business interests lobbied for specific targets at COP15 in Copenhagen (Beder, 2014). The sponsors of COP21 in Paris included fossil fuel companies (Corporate Accountability, 2017), while 35 side events at COP26 in Scotland either featured or were organized by big polluters or by related financial groups (Dobson, 2021). At COP27 in Egypt, an estimated 636 fossil fuel lobbyists (Harvey & Michaelson, 2022) outnumbered any single national delegation besides the UAE (Dietzel, 2022). The influence of fossil fuel interests on the international stage is encapsulated in the International Emissions Trading Association (IETA), which counts among its members BP, Rio Tinto, Chevron, and BHP. Not only does the IETA predictably advocate for demand-side, market-based solutions to climate change, one of its board members and former presidents is part of Panama’s climate delegation. In short, fossil fuel interests are inextricably involved in the UNFCCC climate negotiation process, with a long history of resisting any supply-side regulation (Meckling, 2015; Piggot et al., 2018). This hinders effective and just climate action. If the principle of leaving no one behind in Agenda 2030 is taken seriously, the deaths, displacements, income loss, and loss of health and well-being for millions of people worldwide should be deemed unacceptable by decision makers within target-setting processes.

2.3 The earth system justice approach

These injustices arise from prioritizing fossil fuel-based economic growth over the harm caused to others. The Earth Commission (set up by Future Earth and the Global Commons Alliance) developed an Earth System Justice (ESJ) approach to Earth system challenges, drawing from extensive literature on climate, environmental, biodiversity, energy, and water justice (e.g., Hartwig et al., 2022) after several years of discussion between natural and social scientists from the global North and South. This ESJ approach (Gupta et al., 2023a; Rockström et al., 2023) builds on existing but not fully operationalized calls for justice in diverse international scientific assessments (Gupta et al., 2023b). ESJ straddles local to global scales and opts for transformative over reformative justice. It is in the self-interest of rich countries to promote equity as it may be “a necessary, and perhaps even sufficient, condition for achieving global sustainability” (Steffen & Smith, 2013: 403). An analysis by Rammelt et al. (2023) shows that meeting the minimum needs stipulated by the Sustainable Development Goals in 2018 would have surpassed climate targets unless drastic global transformations occurred.

ESJ encompasses both recognition (prioritizing the views of the disadvantaged) and epistemic (acknowledging diverse knowledge systems) justice. This entails a precautionary approach, minimizing harm to humans and other species. It requires that science goes beyond being policy-relevant to being explicit about who is harmed, when, where, how, and why; and what each temperature level implies in terms of damage. ESJ involves balancing the ‘Three I’s’ of justice: Interspecies and Earth system (I1), Intergenerational (I2), and Intragenerational (I3). It requires both procedural and substantive justice, with clear targets and equitable resource allocation (Gupta et al., 2021; see Fig. 1). We apply this framework in Sect. 4.

Fig. 1
figure 1

Source: Adapting from Fig. 1 in Gupta et al. (2021), and Fig. 2 in Gupta et al. (2023)

The Earth System Justice approach.

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Based on the ESJ approach, breaking free from the continued delay in climate action necessitates adequate allocation of responsibility. The fossil fuel industry has avoided accountability through the focus of climate policy on consumers rather than suppliers (Piggot et al., 2020; Supran & Oreskes, 2021). Additionally, the influence of this industry in decision-making processes has deepened the countries’ dependence on fossil fuels, enabling the development of the Global North and locking the Global South into the same path. While radical demand-side mitigation through transformative shifts in infrastructure and services provision is critical (IPCC, 2018a Ch5), demand-side measures alone are insufficient to leave fossil fuels underground (Costa, 2020). Supply-side policies stand out for mobilizing more public support as they directly target the fossil fuel industry (Green & Denniss, 2018). Such measures must be accompanied by political clarity, transparency, and equity to avoid the perpetuation of injustice and climate delay; thus ensuring accountability of the Global North for its historical emissions, and the Right to Development of the Global South (Newell & Simms, 2020).

2.4 Limitations and advantages of climate targets

Against the background of continued fossil fuel dependence, climate targets are set up for failure. The problem might not be the targets themselves, but the vested interests of governments deeply entrenched in fossil fuels. This paradigm has led to an unjust and inefficient climate target (1.5°–2 °C) (see Sect. 4), that is set to be exceeded (Climate Action Tracker, 2022). That is why the aim of this paper is not to corroborate nor criticize target setting a priori, but rather encourage reflection on the current international negotiation praxis in order to promote more just and transformative climate action.

From an epistemic justice standpoint, we consider criticisms of a singular, quantitative climate objective. Such targets can overlook local realities and alternative global south framings (Morseletto et al., 2017), often due to the power imbalances within climate negotiations, meaning that the input of Global South countries lapses into “compromise and accommodation to the desires of the powerful states” (Nanda et al., 2021: 170). This is due to unjust veto mechanisms, lack of access to technical knowledge, and lack of leverage in cooperative arrangements (Nanda et al., 2021). Additionally, targets create a ‘scarcity mindset’ where “we are forced to see climate change merely as the managerial problem of staying within a given physical limit. (…) There is no future imagined beyond these numbers” (Asayama, 2021: 33).

While ESJ acknowledges these perspectives, we believe that the temperature objective is necessary to address the climate crisis (Ngwadla, 2014), and organize long-term climate action (Achuta, 2023). Since technology and innovation have their own limits (Pan, 2022), the need for a just solution can unleash human creativity. We disagree with Asayama’s (2021) rejection of targets since it would likely multiply intertemporal injustices (see 4.3), but agree with his call to care for all species (4.2), generations (4.3), and communities (4.4). Hence, the application of the ESJ framework addresses the justice concerns that have so far been overlooked. While the application of the ESJ framework favors supply-side measures, we acknowledge that such measures must rely on temperature targets. Hence, they will not be immune to their limitations. It is therefore important to learn from the failures of target setting processes to promote more transparency and equity in climate negotiations, ultimately ensuring that supply-side policies are implemented in a procedurally just manner.

3 The evolution of temperature targets in the international climate regime

3.1 Introduction

Drawing on the existing literature, this section offers historical context, links science and politics, and analyzes the IPCC’s evolving views, underscored by the fossil fuel industry’s influence on decision-making. This aims to explain the shift away from the 1 ℃ target and its implications for supply-side targets.

In the 1970s, scientists assessed the changes in the climate system correlated to temperature increases above pre-industrial levels. Nordhaus (1975) noted that irreversible changes could occur beyond 2 ℃. Krause et al. (1989) argued that between 1 and 1.5 ℃, the global average warming would be greater than in the Holocene and called for limiting CO2 equivalent concentrations to 430–450 ppm followed by a decline. Vellinga and Gleick (1990) highlighted the utility of climate targets for limiting societal and ecological impacts. Rijsberman et al. (1990) used a traffic-light reference to show a temperature rise of less than 0.1 °C and a sea level rise of less than 0.02 m per decade and a 1 °C rise as ‘green’; and 0.2 °C and sea level rises above 0.05 m per decade and a 2 °C rise as ‘red’. The range in between was ‘amber’, although “rapid, unpredictable, and non-linear responses that could lead to extensive ecosystem damage” were possible above 1 ℃ (Vellinga & Gleick, 1990: viii), while “it is recognized that temperature changes greater than the lower limit (1 °C) may be unavoidable due to greenhouse gases already emitted […] [a]n absolute temperature limit of 2 °C can be viewed as an upper limit beyond which the risks of grave damage to ecosystems, and of non-linear responses, are expected to increase rapidly” (Rijsberman & Swart, 1990). Vellinga and Swart (1991) argued that only the IPCC’s ‘accelerated policy’ scenario would enable living in the green area, but was economically challenging. Their conclusions were interpreted as a dismissal of the 1 °C target as unrealistic (Randalls, 2010), favoring a more politically palatable 2 °C target. See Fig. 2 for a timeline.

Fig. 2
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The timeline of the long-term objective

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Fig. 3
figure 3

Evolution of the burning ember figures in IPCC reports. Note: Risks increased with every single IPCC report; see lower part of Fig. 3. This figure compiles the RFCs published for AR4 in Smith et al. (2009), for TAR in IPCC (2001a), and for AR6 in IPCC (2022)

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3.2 Defining ‘dangerous anthropogenic interference’

The Climate Convention (UNFCCC, 1992: 4) aims at stabilizing GHG concentrations that would “prevent dangerous anthropogenic interference with the climate system” as opposed to dangerous impacts on humans and ecosystems. It omits the responsibility of major GHG emitters, including the fossil fuel sector, for the harm that is caused to people and species, and thereby depoliticizes the objective. Although “[t]he duty of prevention, or ‘no harm’ rule, … has become an omnipresent feature of multilateral environmental agreements” (McIntyre, 2020: 602), this principle was excluded from the Climate Convention (Gupta, 1997).

In the early 2000s, three schools of thought debated on the role of science in defining “dangerous.” The first argued that given uncertainties and divergent national interests, attempts to define dangerous would fail (Tol & Yohe, 2006: 2), be guesswork (Barrett, 2010), and politically naïve (Victor, 2006: 94). President G.W. Bush claimed that: “no one can say with any certainty what constitutes a dangerous level of warming.”Footnote 2 This discouraged scholarly work on target setting (Gupta & van Asselt, 2006).

The second school claimed that science can outline temperature impacts, leaving choices to politicians (e.g., Oppenheimer & Petsonk, 2005; Steffen et al., 2005). Pachauri (2006: 3) stated: “[w]hat is dangerous is essentially a matter of what society decides. … But science certainly can provide the inputs for facilitating that decision.” This school has since proposed planetary boundaries for all biophysical domains (Rockström et al., 2009; Steffen et al., 2015). Unfortunately, such research sparks debate rather than action (Hermansen et al., 2021).

The third school advocated for post-normal science in urgent, high-stakes, uncertain scenarios (Funtowicz & Ravetz, 1993). This requires science-based societal debates to quantify “dangerous anthropogenic interference” (Dessai et al., 2004; Gupta & van Asselt, 2006) possibly based on the precautionary principle (e.g., Oppenheimer & Petsonk, 2005; UNFCCC, 1992). However, if those vulnerable cannot influence the societal debate, their voices are lost. Since then, scholars have worked on the co-production of knowledge and boundary institutions that see science and policy as one world (Sundqvist et al., 2018). Although there was some post-normal research into targets, this did not take off.

These perspectives influenced the debate and funding in the subsequent decade. The IPCC and many climate scientists adhered to the second school, avoiding policy prescriptions and thus not recommending what target could prevent dangerous climate change. Where dangerous anthropogenic interference was seen as a political issue, less public money funded such research (Lövbrand, 2011). Skepticism around socio-political feasibility and fossil fuel industry lobbying helped delay discussions on the temperature target beyond a point where it may no longer be achievable, exacerbating injustices.

This section has shown that the UNFCCC’s long-term objective was vague to avoid focusing on the responsibilities of states not to cause significant harm to others and that the subsequent debate on defining “dangerous” delayed clarity on target setting. We can expect similar politicking around production targets despite attempts by UNEP and SEI to define them in the Production Gap Report (see Sect. 1).

3.3 The 2 °C target

Despite existing knowledge of risks beyond 1 °C, focus remained on the 2 °C target. Although Nordhaus deemed the 2 °C target financially prohibitive (Oreskes & Conway, 2011: 182), the 1987 Bellagio climate conference (Jaeger, 1988) proposed it. However, the IPCC’s, 1990 Report side-stepped long-term objectives, presenting emissions-focused scenarios instead (Randalls, 2010: 600). IPCC (1990: 52) stated that: “immediate reductions in emissions from human activities of over 60% [are needed] to stabilize concentrations at today’s levels…” but Barrett (1992) argued that this would be too costly, as did a report (Montgomery, 1992) commissioned by the American Petroleum Institute (API) in 1991. This report was publicized in the New York Times as independent research, despite the API’s funding (Franta, 2022).

EU adoption of the 2 ℃ target was influenced by the IPCC’s 1995 emission scenarios (EU Council of Ministers, 1996), which was reiterated in 2005 (Commission of the European Communities, 2005) and in the G8 (2005) decision. In parallel, the fossil fuel industry’s lobbyist group “Global Climate Coalition” led by former API executives, challenged IPCC’s credibility and promoted alternative mitigation cost projections. In 1997, one of their associates, David Montgomery, testified before the US Senate Committee on Foreign Relations, which later introduced a resolution to block any mitigation policy that could have followed the Kyoto Protocol (Franta, 2022). API subsequently proposed that the US government could replace the targets in the Kyoto Protocol with voluntary actions (Lorenzetti, 1998), which the Bush administration accepted before withdrawing from the Kyoto Protocol. This unwillingness to accept short-term targets underlies the reluctance to adopt longer-term objectives.

The 2009 Copenhagen climate negotiations concluded that “deep cuts in global emissions are required … to hold the increase in global temperature below 2 degrees Celsius”. In June 2015, oil and gas multinationals campaigned to promote carbon pricing and markets, promoting gas, thus continuing to shape climate action (Nasiritousi, 2017). Ultimately, the 2015 Paris Agreement called for: “Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels.” Although US President Obama ratified the agreement, Trump withdrew from the Paris Agreement for economic reasons based on Montgomery et al.’s report (Bernstein et al., 2017). Biden has once more ratified the Agreement.

3.4 The 1.5 °C target

Although the 1 °C target disappeared from the agenda, poorer countries doubted whether the 2 °C target would protect them (Ourbak & Magnan, 2018). In 2009, they demanded a 1.5 °C target (ICCAD, 2016). A Structured Expert Dialogue (SED) between negotiators and scientists between 2013 and 2015 concluded that while limited research existed on the different impacts of 1.5 °C and 2 °C (UNFCCC, 2015a, para. 27, para. 53), the 2 °C target was inadequate (Tschakert, 2015: 8). This influenced the Paris objective.

Negotiators tasked the IPCC with closing the research gap. Some scholars argued that this created “false hopes for … the most vulnerable countries” (Boucher et al., 2016: 7288) not least because reducing emissions equitably was a “lost battle” (Guillemot, 2017). Nevertheless, subsequent research highlighted the serious impacts of 1.5 °C (Cointe et al., 2019) and showed that a 50–50 chance of limiting warming to 1.5 °C requires achieving “net zero” CO2 emissions by mid-century (IPCC, 2018a). This target is now politically daunting as only ~ 380 GtCO2 of the carbon budget remained in 2022 and will be depleted in nine years at current rates (Friedlingstein et al., 2022). Why did the IPCC not explicitly discuss 1.5 °C or lower targets before?

3.5 Evolution of the ‘reasons for concern’ (RFC) figures in IPCC

Implicitly, the IPCC reports have discussed the impacts of each degree increase in temperature through its burning embers figures on “Reasons for Concern” (RFCs) since the Third Assessment Report. IPCC (2001b: 68) stressed that developing countries face higher climate risks. The RFCs (IPCC, 2001b: 103) showed risks to unique and threatened systems, risks from extreme climate events, unequal distribution of impacts, global aggregate impacts, and risks from future large-scale discontinuities such as tipping points. If the impacts were negative for some regions, this was shown in yellow (moderate risk). Only if this was negative for all, was it shown in red (high risk). Ironically, the idea of “moderate risk” could then be used to justify causing significant harm to some! The fourth assessment (IPCC, 2007) concluded that the RFCs were much stronger than in the AR3 but excluded the burning embers figure. An updated figure was later published in Smith et al., (2009: 4133) arguing that “many of the noted vulnerabilities begin or continue to grow with increases in [global mean temperatures] GMT of less than 1 °C” (p. 4136). Although clear visual information helps in communication (O’Neill, 2017), IPCC Working Group II removed the figure (Mahony, 2014). Steve Schneider, stated that:

The main opposition comprised officials representing the United States, China, Russia, and Saudi Arabia. … Because words are less powerful than a colorful, iconic chart, many from Europe, Canada, New Zealand, and small island states demanded to include it ... the four big fossil-fuel dependent and producing nations opposed it (Mahony, 2015: 161).

The fifth IPCC (2014: 99) report used different wording for the burning embers figure and included specific risks such as for specific species. The Special 1.5 °C Report (IPCC, 2018a: 181) stated:

The risk transitions by degrees of global warming are now: … from moderate to high risk between 1°C and 1.5°C for RFC2 (Extreme weather events) (medium confidence); … and from moderate to high risk between 1°C and 2.5°C for RFC5 (Large-scale singular events) (medium confidence).


The Sixth Report (2022: 13) asserts that all RFCs pose high to very high risks at lower global warming levels than in AR5. “Between 1.2 °C and 4.5 °C global warming level very high risks emerge in all five RFCs compared to just two RFCs in AR5 (high confidence).” The Technical Summary states (2022: 69) that “RFC1, RFC2 and RFC5 include risks that are irreversible, such as species extinction, coral reef degradation, loss of cultural heritage or loss of a small island due to sea level rise.” Risks associated with current warming rates (then 1.1 ℃) for unique and threatened systems are moderate to high, while “Present-day risks associated with large-scale singular events … are already moderate (high confidence), with a transition to high risk between 1.5 and 2.5 (medium confidence).”

Although RFCs show “dangerous” interference in the climate system, the IPCC does not “conclude what level of impact … would constitute [dangerous anthropogenic interference], a value judgment that would be policy-prescriptive” (Smith et al., 2009: 4133). As “no single metric could adequately describe the diversity of impacts and associated risks for any one RFC, let alone aggregate across all of them into a single “dangerous” global temperature threshold… no aggregation was attempted across the RFCs” (p. 4135). This demonstrates that while the IPCC did collate evidence on climate risks below 2 °C, it did not define “dangerous.” (Fig. 3).

3.6 Inferences

History shows that despite early warnings about the risks beyond 1 °C and intolerable global risks beyond 2 °C, the focus remained on higher temperature targets. High mitigation costs, a theme promoted by the fossil fuel industry, have delayed discussion on the long-term climate objective (Franta, 2022). While the IPCC addressed “dangerous” climate change through its RFCs and burning embers figure (see Sect. 3.4), it avoided defining “dangerous.” Analysis of the risk difference between 1.5 and 2 °C was not undertaken until after the Paris Agreement. Had the USA and other members of the Umbrella Group agreed to it earlier, this analysis might have been included in the 1997 Kyoto Protocol. Similarly, the 1.5 °C goal in the Paris Agreement likely owes its inclusion to demands from poorer countries.

4 Applying the ESJ approach to avoid repeating past failures

4.1 Introduction

We now apply our ESJ approach to the long-term climate objective in order to shed light on the injustices that have so far been overlooked. While assessing what is “dangerous” from a research institute in a wealthy country is a theoretical exercise, for the most vulnerable countries it is a matter of life, death, disease, and displacement. The RFCs’ yellow indicators, could spell severe harm for some countries, yet have been accepted as tolerable. From a recognition and epistemic justice perspective, we argue for redefining “dangerous” anthropogenic interference from the standpoint of those most at risk (e.g., Small Island States, Least Developed Communities, Arctic Communities). Recent research by Breyer et al. (2023) proved that 1 °C is a safer target. We build on this perspective incorporating the ESJ approach by going beyond assessing what constitutes dangerous climate change (see Sect. 3.2), to question what has so far constituted acceptable dangerous climate change. At 2.7 °C a third of the global population faces less favorable climate conditions due to unprecedented heat, and while at 1.5 °C, this number would be 5 times smaller, already today at 1.2 °C, 9% of people are exposed (Lenton et al., 2023).

4.2 I1: Interspecies justice and earth system stability

From an interspecies justice and Earth system stability perspective, we argue that 1 °C warming has “transformed our planet” (Hoegh-Guldberg et al., 2019) and affected ecosystems. We crossed 1 °C in 2015–2017 (IPCC, 2018b, FAQ 1.2), and climate change is already an independent driver exacerbating the pressures on our resources and ecosystems (UNEP, 2019).

All the IPCC’s “Terrestrial & Freshwater Ecosystems Key Risks” to biodiversity, wildfires, tree mortality, carbon loss, and biome shifts transition to moderate risk by 0.8 °C and tree mortality and structure change reach high risk by 1.5 °C (Parmesan et al., 2022). Around 9% (and a maximum of 14%) of species reach a high risk of extinction at 1.5 °C, which is 1000 times the estimated natural background rate (Parmesan et al., 2022). At 1 °C warming, 4% of global terrestrial ecosystems have been transformed, while marine heatwaves have damaged coral reefs (IPCC, 2022: 2500). The Great Barrier Reef lost 50% of the shallow-water corals in four years. Some marine organisms and ecosystems have moved to higher latitudes at about 40 km/year and phenological patterns have shifted by almost three days every decade (Hoegh-Guldberg et al., 2014). Ocean ecosystem impacts including localized tipping points are evident beyond 1 °C warming (Heinze et al., 2021).

The Amazon rainforest carbon sink peaked in the 1990s (at ~ 0.6 °C) while its resilience has declined since the early 2000s (~ 0.7 °C) (Boulton et al., 2022). South-eastern Amazonia is already a net carbon source (Gatti et al., 2021), and the aboveground carbon sequestration potential of the entire Amazon may reach zero by 2035 (Hubau et al., 2020). The global leaf area index indicates a slowdown in the land carbon sink since ~ 2000 and a net decline since ~ 2015 (~ 1 °C), suggesting the tropical and potentially the global land carbon sink may be declining earlier than model projections (Winkler et al., 2021) and is mirrored by evidence of declining global vegetation resilience since the early 2000s (Smith et al., 2022). The number and intensity of heatwaves, droughts, floods, and storms has increased, damaging species and ecosystems (Allen, 2018). Under current warming, the probability of 1-in-1,000-day heat extremes on land has increased fivefold since pre-industrial times (Fischer & Knutti, 2015: 562). Huang et al., (2022: 9) found that a 1 °C increase in the annual mean surface air temperature is associated with an almost 10-day decline in lake ice duration. Between 1992 and 2017 annual ice loss rose from 52 to 159 and 7 to 33 billion tonnes in West Antarctica and the Antarctic Peninsula, respectively (IMBIE team, 2018). From an Earth system stability perspective, beyond 1.5 °C four climate tipping points become likely, several key carbon sinks like the Amazon or tundra are projected to transition to carbon sources, and the Earth’s climate will leave the interglacial range of natural climate variability (Rockström et al., 2023).

4.3 I2: Intergenerational impacts

From an intergenerational justice perspective, the above debate raises four justice issues. First, delays in target setting imply steeper, costlier future reductions because of inertia in socio-technical systems. “[B]y “overspending” the budget in the earlier years (until around 2020) both steeper emission reductions in later decades and a deeper absolute reduction level by 2050 is required” (Schaeffer et al., 2011: 6) creating more injustices for current generations. Second, these delays implicitly allow harm to continue, thus absolving those responsible from accountability. Third, such delays “shifts the cost burden from developed countries to developing countries, which have to face additional adaptation needs and higher levels of ‘residual damage’, i.e., damage beyond adaptation potential, even with unlimited funding. Limiting warming to below 1.5 °C … will reduce, but not eliminate major risks and damages to LDCs, and will still require substantial support from the international community for adaptation” (Schaeffer et al., 2011: 8). Fourth, such delays have empowered fossil fuel producers and users, enabling the Global North to use their fossil fuels while now calling on the South to phase out theirs.

In terms of intergenerational impacts, we look at the present impacts of past behavior (see Sects. 4.2 and 4.4) and the future impacts of current behavior. At 1 °C we see significant long-term consequences or committed impacts such as continued and irreversible ocean heating and sea level rise for centuries (IPCC, 2021), with at least 27 cm of sea level rise already committed from the Greenland ice sheet melt alone (Box et al., 2022). Committed sea level rise associated with 1 °C will adversely impact 40 UNESCO sites over the next two millennia (Marzeion & Levermann, 2014). Several climate tipping points including the collapse of the Greenland and West Antarctic ice sheets or widespread abrupt permafrost thaw are still possible at 1 °C or lower (Armstrong McKay et al., 2022). These would lock in substantial impacts for centuries, with up to 7 m of sea level rise equivalent from Greenland and ~ 3 m from West Antarctica.

4.4 I3: Intragenerational justice

Turning to intragenerational justice, at 1 °C warming, damages to countries, communities, and humans are massive. Climate-related extreme events have doubled since 1980 (GEO-6: 48). Relative to the yearly average between 1986 and 2005, 2020 had “3.1 billion more person-days of heatwave exposure among people older than 65 years and 626 million more person-days affecting children younger than 1 year” (Romanello et al., 2021: 1619). Climate change accounts for almost 40% of warm-season heat-related deaths, and increased mortality globally (Vicedo-Cabrera et al., 2021) as the number of hot days has increased sixfold (Knutti et al., 2016). At 1 °C, over 70 million people have already been exposed to wet bulb temperature extremes, while at 1.5 °C, over 100 million people could be exposed to wet bulb extremes, over 200 million to unprecedented mean annual temperatures, and more than 500 million to future sea level rise (Rockström et al., 2023). Less resilient populations are more affected, reporting 300,000 deaths because of extreme heat in 2018. These populations were “exposed to an additional 475 million heatwave events globally in 2019” (Watts et al., 2021: 129). Global warming also aggravates food insecurity: compared to the baseline 1981–2010, in 2020, yields of maize, winter wheat, soybean, and rice decreased by roughly 6%, 3%, 5%, and 2%, respectively, and 51 countries experienced an overall decline in agricultural production (Romanello et al., 2021: 1619; FAO, 2022). In terms of health, “in Asia and Africa, 1 °C warming can cause a 7% increase in diarrhea, an 8% increase in E. coli and a 3% to 11% increase in deaths (medium confidence)” (IPCC, 2022: 64), increasing undernutrition, stunting, and related childhood mortality (IPCC, 2022: 70) and the spread of malaria and other tropical viruses (Romanello et al., 2021: 1620). Predictably, 1 ℃ has heavier costs for poorer countries: agricultural workers in low human development index countries bore half the 295 billion work hours lost because of heat. The average GDP loss in these countries was ± 4–8% (Romanello et al., 2021: 1619). Higher temperatures or heavy precipitation are increasing human conflicts (Hsiang et al., 2013), global poverty, and disadvantage (IPCC, 2018a: 39). The global economic loss related to human-induced climate change, for the period 1992–2013 ranged from US$5 trillion to $29 trillion. The impact was most severe in low-income tropical nations, where the average reduction in national income was approximately 6.7% (Callahan & Mankin, 2022). It has been estimated that for the period 1980–2017, the number of climate-related deaths was 400,000 (GEO-6: 48) or 727,403 for 1992–2022 by calculating from the Georeferenced Emergency Events Database (EM-DAT).Footnote 3

4.5 1 °C would have been more just than 1.5 °C

Knutti et al., (2016: 14) argue that: “the current 2 °C UNFCCC target is a compromise between what is deemed possible and desirable, rather than a “planetary boundary” that clearly separates a ‘safe’ from a ‘dangerous’ world.” Recent IPCC reports clearly demonstrate substantially less danger at 1.5 °C than at 2 °C (Cointe & Guillemot, 2023). We have shown that climate change above 1 ℃: (a) causes significant harm to nature and humans, (b) is already a driver of other environmental problems; and (c) even if we stop emitting, we are committed to long-term impacts. Figure 4 illustrates the differences between 1 and 1.5 ℃ and how the RFCs reveal the growing damage to nature and humans since the first RFCs in IPCC (2001b). Hence, 1 °C is more just and less dangerous than 1.5 °C (see Fig. 4) from the perspective of climate impacts on humans and nature and has been accepted as a safe and just Earth System Boundary (Rockström et al., 2023). However, such justice concerns have been largely overlooked when the current climate targets first emerged within the scientific and political arenas. As with 6 other just boundaries, the climate boundary has already been crossed, motivating the need to ensure that the global community should not miss the 1.5C target. Therefore, this section has (a) identified political influences and scientific blind spots that have and could continue to hinder research into dangerous climate thresholds, (b) highlighted that there is already widespread injustice from climate change well before 1.5 °C or 2 °C targets, and (c) added to the urgency of mitigation actions.

Fig. 4
figure 4

Justice in a half degree change: 1 °C vs 1.5 °C. Note: Fig. 4 (justice in a half degree change: 1–1.5 °C) is based on Hoegh-Guldberg et al. (2019), IPCC (2022), Huang et al. (2022), Matthews et al. (2017). Rockström et al. (2023), and Lenton et al. (2023). Note that the decline in coral reefs, the exposure to flooding, and heat stress in megacities are compared to warming at the date of the source’s publication (which is roughly 1 °C). All other boxes explicitly compare 1–1.5 °C

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5 Earth system justice to phase out fossil fuel supply

To guarantee interspecies, intergenerational, and intragenerational justice, we apply the ESJ framework on supply-side policies to phase out fossil fuels. Supply-side policies are intended to mitigate GHG emissions by decreasing the supply of fossil fuels (Pellegrini & Arsel, 2022). Starting with procedural justice, we have shown that fossil fuel corporations have, over the years, wielded significant influence on the decision-making process through their lobbying endeavors. Practices of greenwashing, coupled with a dearth of transparency in lobbying activities, have substantially compromised the integrity and quality of information that reached the negotiating room and propagated a narrative that places responsibility on the consumer rather than the producer (Piggot et al., 2020; Supran & Oreskes, 2021).

We believe that to achieve procedural justice, the over-representation of fossil fuel companies and lobbying at the political level should urgently be subjected to stringent restrictions, together with stricter regulations to tackle greenwashing practices, enhanced transparency in lobbying activities, and rigorous climate-related information disclosure and emissions accounting (Erickson, et al., 2018; Lazarus & van Asselt, 2018). Additionally, the judicial system plays a crucial role in accountability placement—both at the international and national levels—following the example of the Hague District Court landmark case which called on Royal Dutch Shell to reduce its emissions (Mayer, 2022). With regard to a substantive idea of justice, the Global North bears responsibility for a greater historical share of emissions and a more extensive use of fossil fuels, thus, being accountable for more significant climate impacts, in line with the principle of common but differentiated responsibilities (Newell & Simms, 2020). Given the already devastating effects on both humans and nature above 1 °C, there is an imperative to take action on the present production and dependence on fossil fuels. This entails suspending licenses, permits, and subsidies while enforcing non-proliferation treaties to keep fossil fuels underground (Lazarus & van Asselt, 2018; Newell & Simms, 2020). However, the target setting process demonstrates the highly political nature of assigning responsibility given the disproportionate power held by the Global North. Moving forward with this political challenge necessitates convergence and compliance to common principles of justice when it comes to measures or treaties governing fossil fuel production and supply.

Additionally, as climate impacts and risks are borne primarily by the Global South which also contributed less to climate change, mechanisms of compensation need to be set in place. These mechanisms should encompass: (a) addressing damages and losses where mitigation and adaptation measures are no longer feasible (Loss & damage) and funds for adaptation, (b) establishing compensation funds to offset revenue losses resulting from refraining from using the remaining fossil fuel reserves in the Global South. Indeed, as of 2020, non-OECD countries plus Colombia and Mexico, had nearly 85% of proved oil reserves, 53% of coal, and 89% of natural gas, these resources could serve as means to support their economic growth (Heras & Gupta, 2023). We advocate for the development of global guidelines on energy transition which take into account the 3Is approach, including aspects at the local level to ensure intersectional justice (Pellegrini & Arsel, 2022). Given that the Global North holds most of the low-carbon technology patents, as well as resources and capabilities, the role of technology transfer mechanisms and dedicated funds allocation are crucial to facilitate a just energy transition. Progress has been initiated in this direction through the creation of the ad hoc UN body, the Climate Technology Centre and Network, aimed at facilitating the transfer of low-carbon technology. Nevertheless, the committed funds for supporting its operations have not yet been operationalized (IEA, 2021; Weko & Goldthau, 2022). A possible alternative is the idea of a Global Transition Fund put forth by Newell and Simms (2020) which aims at reallocating existing fossil fuel investments toward low-carbon energy sources. Lastly, the remaining carbon budget must be allocated to the Global South according to equitable principles and based on historical accountability (Morrow, 2017; Muttitt & Kartha, 2020).

6 Conclusion

This paper has drawn together the history of the international target-setting process, the influence of the fossil fuel industry on climate negotiations, and an ESJ analysis of the justice implications of climate goals. While the science highlighted the escalating risks beyond a 1 °C increase, the 1.5 °C-2°C target was favored for its perceived feasibility and cost-effectiveness, a perception partly induced by fossil fuel vested interests that continue to side-line the potential and irreversible dangers for people and nature. We have applied the ESJ framework to argue that 1 °C is more just than 1.5 °C for humans and nature, and although this target is now unachievable, the prevalent injustices under the 1.5 ℃ threshold highlight the urgency of addressing existing damages. Lastly, we advocate for supply-side policies in line with ESJ to phase out fossil fuel as a means of avoiding past failures and achieving substantive and procedural justice. Unless confronted, political inertia and scientific blind spots within climate mitigation will impede efforts to leave no one behind. Past political and scientific failures to justly and promptly take climate action should not deter but rather incentivize new and improved mitigation efforts including rapidly phasing out fossil fuel supply aimed at limiting warming to 1.5 °C.

7 Appendix

See Table 1.

Table 1 Exact references for Fig. 4
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