Turning out the light: criteria for determining the sequencing of countries phasing out oil extraction and the just transition implications

ABSTRACT There is a pressing need to curb the extraction of fossil fuels, alongside their use and consumption, to remain within reach of the 1.5C global warming limit. Yet, a reduction in the supply of fossil fuels does not inherently indicate a just or equitable transition. A growing number of papers are proposing approaches and criteria for determining the allocation of remaining production of fossil fuels and the sequencing of countries phasing out extraction and production. With a focus on oil, this paper identifies, and reviews 15 criteria found in the literature for determining the sequencing of phase out of fossil fuel supply. These criteria are economic efficiency, wealth, dependence, development, historical responsibility, procedural justice, and variations within these approaches. In addition, this paper reviews the extent to which these criteria have been operationalized and discusses the just transition implications of pursuing a fossil fuel supply phase out based on the criteria and indicators identified. This review suggests that the sequencing of countries that phase out oil extraction differs depending on the criteria adopted but that there are gaps in the criteria identified and in their operationalization, with implications for how to usher in just transitions. This paper calls for a more holistic view of the equity implications of a global phase out, supported by further research broadening and deepening the scope of equity considerations. Key policy insights Without policy interventions, market dynamics alone are unlikely to lead to a deliberately equitable distribution of the remaining extraction of oil in line with a 1.5C global warming goal. The sequencing of countries phasing out oil extraction differs depending on the criteria adopted and sequencing based on individual criteria can lead to ill-considered outcomes. There is a gap in the criteria and indicators needed to determine a sequencing of a global phase out that is aligned with a just transition, which hampers informed decision-making and a holistic assessment of circumstances across countries. Basing a phase out on an incomplete assessment of indicators poses a risk to just transition, particularly regarding development needs and procedural justice.


Introduction
To date, the majority of climate policy efforts have focused on reducing the demand for fossil fuels as a means of achieving the Paris Agreement's goal to limit global warming, while addressing the supply-side of the equation has been absent from international climate policy (Pellegrini et al., 2021;Piggot et al., 2020;Verkuijl & Lazarus, 2020).Reducing supply would require no further approval of new oil fields (IEA, 2021a) and means most regions would need to reach peak production within the next decade (Welsby et al., 2021).Furthermore, compared to 2019 levels, oil production would need to fall by 56% by 2040 and by 75% by 2050, leaving production at just 24 million barrels per day (IEA, 2021a).Instead, the world's governments plan to produce 57% more oil by 2030 than would be consistent with limiting global warming to 1.5°C and this production gap widens considerably by 2040 (SEI et al., 2021).
In spite of demand-side efforts, progress has not materialized at the pace needed to remain on track to meet global climate commitments (Asheim et al., 2019;Le Billon & Kristoffersen, 2020).Against this backdrop, a body of literature has emerged stressing the importance of not only reducing demand for fossil fuels, but also in tandem, reducing supply (Armstrong, 2020;Asheim et al., 2019;Green & Denniss, 2018;Pellegrini et al., 2021).In particular, scholars have established a case in favour of supply-side measures by highlighting their value, among others, as insurance against the risk of failed demand-side measures and as protection against carbon leakage, as well as their potential to galvanize public support for further climate action (Asheim et al., 2019;Caney, 2016;Green & Denniss, 2018;Lazarus & van Asselt, 2018;Pellegrini et al., 2021;Rempel & Gupta, 2022).Beyond academia, there is also a growing number of government-and civil society-led initiatives focusing on reducing the global supply of fossil fuels (Gaulin & Le Billon, 2020;Lazarus & van Asselt, 2018;Lenferna, 2018;Linde et al., 2022;Newell & Simms, 2020).
Addressing oil supply through a global phase out of extraction and production entails a major transition away from the status quo.Though the term is contested and encapsulates a range of conceptions of justice, for the purposes of this paper a 'just' transition can be broadly defined as a transition where consideration is given to the most vulnerable while addressing the uneven spread of socio-economic and environmental burdens and benefits between and within countries, arising from a global supply reduction (Atteridge & Strambo, 2020;Caney, 2016).Putting in place measures protecting workers, boosting infrastructure, and investing in skills and education can smooth out the transition and may reduce resistance to a global phase-out, though countries with greater institutional capacity will have a better chance of succeeding (Green & Gambhir, 2020;Lenferna, 2018).Meanwhile, unmanaged transitions or a phase-out for all overlook the capacities of countries and communities to curb extraction and transition, which risks perpetuating existing inequalities and creating new ones (Atteridge & Strambo, 2020;Kartha et al., 2018).It is even conceivable that the pace of the transition needed to rapidly decarbonize may warrant pursuing an unjust transition to avoid a greater injustice of prolonging the extraction of oil (Lenferna, 2018).In other words, a reduction in global supply alone does not inherently indicate a just or equitable transition.
As already mentioned, global oil production must decrease by more than half by 2040 for the world to be in line with the 1.5C target.This will affect all oil-producing countries.Yet these country producers can find multiple justifications for continued oil extraction.For instance, in higher income countries, these can include lower carbon footprint in the case of Gulf states; lower operating costs in Norway; and energy security in the UK (Ghaleigh et al., 2021;IISS, 2022;Szuleck et al., 2021).Meanwhile, in lower income countries including Nigeria, Kenya and Colombia, justifications can include, for example, extraction as a catalyst for growth; exercising the right to develop vis-a-vis historical extraction, use and emissions in developed countries; and maintaining economic stability (Bos & Gupta, 2016;Obeng-Odoom, 2021;Strambo & González Espinosa, 2020).These justifications (and others) can be reconceptualised as examples of criteria for phasing out extraction, and by adopting indicators or metrics for the criteria, it is possible to determine the sequence of countries phasing out.
At the time of writing, only a few scholars have attempted to review and catalogue criteria-based approaches for supply reduction.Most notably, Muttitt and Kartha (2020) as a means of developing a set of guidelines for equitably curbing fossil fuel extraction, and Le Billon and Kristoffersen (2020) to connect conceptions of justice to the policy instruments for delivering just supply constraints.Furthermore, Calverley and Anderson (2022) have focused on determining a sequencing for countries phasing out oil and gas production based on the explicit operationalization of criteria.To address this research gap, this paper identifies the criteria for determining the sequencing of countries phasing out and the extent to which these criteria have been operationalized, followed by the just transition implications of pursuing a phase out based on the criteria and metrics identified.
This paper does not aim to provide the building blocks for a methodology for precisely determining the sequencing of a global phase out.Instead, it aims to contribute to the growing literature on supply reduction by demonstrating how different criteria and metrics could impact the sequencing of a global phase out, thus enriching ongoing discussions on how to bring equity to the forefront of phasing out.The importance of addressing the research gap lies in showcasing the breadth of rationales for continued production and the just transition implications, to inform national debates and better decision-making and promote the inclusion of a wider range of perspectives in assessing countries circumstances.This is timely, given the high level of volatility of the global oil market in recent years.
Our paper focuses specifically on oil, as opposed to oil and gas, for several reasons.Compared to natural gas, oil has a higher carbon intensity, generates relatively higher rents for producing countries, and is traded in a generally more globalized market (Le Billon & Kristoffersen, 2020;Stevens, 2018).It is also argued that, given natural gas' lower carbon intensity, phasing out more carbon intensive fossil fuels provides more room for an equitable distribution of the remaining carbon budget (Le Billon & Kristoffersen, 2020;Lenferna, 2018).As the literature on supply-side measures for fossil fuels collectively expands, there is a greater need to consider the differences and dynamics between these fuels and investigate them separately in a bid to deepen the analysis.
This paper is structured as follows.The next section outlines the methodological approach for the review.This is followed by a presentation of the criteria identified through our literature review.Then, a discussion on the just transition implications of determining future extraction based on the criteria identified.Lastly, we conclude our paper.

Methods
As outlined in the previous section, this paper aims to shed light on the just transition implications of determining a phase out based on certain criteria.The term 'criterion' is used throughout this paper to refer to the proposed condition(s) that must be met for oil producing countries to phase out extraction and production.
To begin with, a review was conducted to identify explicitly stated criteria for determining which countries phase out soonest, as found in the literature focused directly on equitable fossil fuel phase out.This approach aims to provide a 'state of play' in this literature as a foundation for uncovering gaps.The search string 'TITLE-ABS-KEY ("supply-side" AND fossil AND climate)' was used in the Scopus database for journal articles between 2015 and 2021-12-20 (the date of the search).This rendered a total of 68 articles.Based on titles, abstracts, and introductions, the authors labelled 17 articles as covering topics of overarching ideas for determining which countries ought to decrease oil production.These 17 papers were then read in detail and relevant references from these papers were also added to the list of articles included in our review.This included, for instance, a report by Caney (2016) which is not an academic publication.This approach also loosely acted as a backstop in case relevant publications before 2015 had been missed.Shortly before this paper's submission, Calverley and Anderson (2022) published a report which was also included in our review given the relevance of their methodology for this paper.
After the criteria were identified, they were loosely grouped by the principles of market dynamics, distributive justice, and procedural justice to facilitate the flow of the paper and the discussion.The connection between extraction, use and emissions of fossil fuels means that the equity principles framing applied to burden sharing for emissions reduction can also be usefully applied to extraction since they can provide the normative underpinnings of the criteria (Calverley & Anderson, 2022;Dooley et al., 2021).Although equity principles can be applied at the individual level, it is also possible to collectively attribute intergenerational extraction, use and emissions to a geographic region, positioning states as the collective bodies and agents to which the equity principles apply (Caney, 2021).It is worth noting, however, that the grouping by principles is not definitive or conclusive since criteria are not always explicitly framed in the literature based on these principles or other principles of equity in relation to climate justice more broadly.
As part of the review, the extent to which criteria have been operationalized was also identified.For the operationalization of a given criterion, the term 'metric' is used throughout the paper.For instance, the national 'income level' criterion suggests that countries with the highest national incomes should phase out extraction soonest, and a potential metric for income level is per capita income.Table 1 presents metrics where data was publicly available (Table 2 in the following section provides the exhaustive list Described as 'per capita income levels' by Muttitt and Kartha (2020) and Newell and Simms (2020).Available at, for example, UNDP (2020).

Income level without oil and gas incomes
Calverley and Anderson (2022) Described as 'non-oil GDP per capita' by Calverley and Anderson (2022) by subtracting oil and gas contribution to GDP.Authors' own dataset.6. Economic dependence Achakulwisut and Erickson (2021); Le Billon and Kristoffersen (2020); Muttitt and Kartha (2020) Exemplified as rents in share of GDP with data from the World Bank in Achakulwisut and Erickson (2021) and as share of export and as share of government revenue in Muttitt and Kartha (2020).

Workforce dependence
Le Billon and Kristoffersen (2020); Muttitt and Kartha (2020) Exemplified as share of workforce by Muttitt and Kartha (2020).8.The availability of alternative sources of energy to replace fossil fuels Caney (2016); Kartha et al. (2018) There is an abundance of data on this topic.However, the authors did not suggest any publicly accessible data on metrics for this criterion.9. Institutional capacity Kartha et  of criteria identified and suggested metrics).Following the literature review, this data is then used to illustrate how the outcome of a simple choice of a criterion and a metric could influence the sequencing of oil production phase out by country.

Criteria and metrics
Table 2 presents the criteria and metrics identified in the literature review.To facilitate the flow of the paper, these criteria are loosely grouped under headings based on principles and the criteria are discussed from both normative and practical perspectives.The groupings should not be interpreted as an indication of the relation between criteria within and across the clusters.

Market dynamics
Following present models of oil markets, producers with the lowest cost of production and the lowest-cost reserves will produce oil the longest.This is the business-as-usual case, and is how the future of oil, to a large extent, is modelled by for example IEA (2021c; 2021a) and Welsby et al. (2021).Adding a layer of nuance to this economic efficiency perspective is possible by incorporating GHG emission efficiencies of different types of oil resources.For exmaple, the emission intensity is lower for most conventional oil resources compared to unconventional resources, such as tar sands and tight oil (Carnegie Endowment, 2021;Gordon, 2021).This could be added to energy models through a tax on greenhouse gases, which is differentiated for greenhouse gas emission intensities for different oil resources (i.e.not only treating all oil resources as the same).Least-cost of production and greenhouse gas intensities of resources are used or mentioned together as criteria by IEA (2021c; 2021a), Le Billon and Kristoffersen (2020), McGlade and Ekins (2015), and Welsby et al. (2021), pointing to the need to consider cost and emissions in tandem.Although the measurement of such criteria based on production is shared across these papers, data is not publicly accessible but is instead held by private databases.The size of reservoirs, and the extent to which they have to be left unexploited, is detailed by McGlade and Ekins (2015) and Welsby et al. (2021).The size of the reservoirs is also mentioned by Newell and Simms (2020), but from the perspective of burden-sharing of leaving fossil fuels in the ground.Newell and Simms (2020) propose countries to be compensated from the financial value of these reserves.This is also in line with the idea suggested by the Ecuadorian government to leave a vast oil resource in Yasuni in the ground (Macintosh & Constable, 2017;Sovacool & Scarpaci, 2016), and as suggested in the context of Uganda by Snyder and Ruyle (2020).However, there are no straightforward metrics to evaluate the financial value of reserves.Snyder and Ruyle (2020) adopt a technoeconomic analysis of the value from the Albertine Graben field in Uganda, but evaluating the value of oil fields also depends on the market oil price, and the maturity of fields, which can change considerably over time (Misund & Osmundsen, 2017).

Capacity to transition
The capacity to transition is one of the principles of equitable sharing and a key element of the UNFCCC's principle of 'Common but Differentiated Responsibilities and Respective Capability' (CBDR-RC), both in terms of capacity to phase out extraction and transition to low carbon pathways (Kartha et al., 2018).The general wealth of a country can be considered an important determinant of its capacity to transition away from fossil fuel production, with high levels of wealth indicating the capacity for a faster transition (Fossil Fuel Non-Proliferation Treaty, 2021;Newell & Simms, 2020;The Lofoten Declaration, 2022).Newell and Simms (2020) and Muttitt and Kartha (2020) specifically define the metric for wealth as income per capita.
For a more nuanced approach on wealth and capacity for transition, Calverley and Anderson (2022, p. 10) remove the contributions from oil and gas to GDP to determine a 'country's capacity to fund a just transition even without benefit of its production related national income'.This captures the funds available for transition and the precarious circumstances of oil dependent nations in a single metric.As noted by Calverley and Anderson (2022), Muttitt and Kartha (2020) also add a dimension of oil dependence to wealth in the form of government revenues derived from oil, as indication of the capacity to transition, but access to this data for a full list of producers is limited.While Calverley and Anderson (2022) solve this issue through the development of their own dataset, Achakulwisut and Erickson (2021) opt for the readily available oil and gas rents as a share of GDP, following Muttitt and Kartha's (2020) wealth versus capacity criteria.Muttitt and Kartha (2020) further highlight workforce dependence as another facet of the capacity to transition, which is also alluded to by Le Billon and Kristoffersen (2020) with reference to fiscal revenue dependence.
Aside from the criteria outlined so far, two additional criteria are identified in the literature related to the capacity to transition.Kartha et al. (2018) argues that the capacity to transition not only includes income and alternative energy sources but includes the ability of government to implement transition policies.This also points to the role of leadership that nations with such capacity ought to play in the global transition, which links to Le Billon and Kristoffersen's (2020) criteria of the willingness of producers to implement cuts.Le Billon and Kristoffersen (2020) note that despite only negligible producers banning further exploration, a coalition of the willing could encourage other producers to follow suit, pre-empting the objectives of initiatives such as the Beyond Oil & Gas Alliance.However, metrics are not suggested for either of these criteria.

Development needs
The development criterion touches on a second principle of equity that also aligns with CBDR-RC and international law in its regard for the right of the world's poorest to develop (IPCC, 2014).A common candidate for development's metric is the Human Development Index (HDI).The argument follows that extraction provides domestic resources for energy and export revenue that can spur development (Caney, 2016).
However, authors exploring development as a criterion question the normative assumptions of arguments unconditionally in favour of focusing on development (Caney, 2016).Firstly, the focus on domestic energy sources overlooks the availability of alternative sources, to the extent that such availability can be considered as an additional criterion to be linked to the development criterion (Caney, 2016;Kartha et al., 2018;Lenferna, 2018).Secondly, exports as a route for development neglects the role of compensation as an alternative route for development, in principle (Caney, 2016).Thirdly, to truly contribute to development, the proceeds of extraction (or compensation) would need to benefit the most vulnerable communities in developing countries rather than being misappropriated by elites, thereby hindering an equitable distribution in line with the resource curse (Bos & Gupta, 2016;Caney, 2016;Muttitt & Kartha, 2020).Le Billon and Kristoffersen (2020) even suggest prioritizing phase out among those countries with a poor record of managing oil rents as an additional criterion, as a means of preventing resource curse.This would only presumably apply to existing producers.More broadly, given the dwindling carbon budget, the time, and costs required to shift production to less developed countries and the benefits of gradually building up local capacity to avoid resource curse, the feasibility of using the development criterion alone becomes challenging (Muttitt & Kartha, 2020;Pye et al., 2020), hence the observance of this criterion alongside others in the literature.

Historical responsibility
As with the capacity to transition, historical responsibility is a key feature of CBDR-RC.Historical responsibility implies that those countries which have extracted, used, or emitted the most have an obligation to phase out first (Caney, 2016;Kartha et al., 2018).Both Caney (2016) and Kartha et al. (2018) follow a similar line of reasoning on the relevance of historical responsibility.They argue that benefits have been accrued from fossil fuels by present generations and that knowledge of the damage caused by fossil fuels has been known for long enough to discredit reasonable ignorance as an excuse for most extraction.However, treating the benefits as spread evenly across present generations overlooks that extraction in some countries may have benefited a few individuals, factions or companies, rather than improved the overall wealth or development in the country.This casts doubt on the extent to which such countries could be said to have truly accrued benefits.In this respect, Caney (2016) and Kartha et al. (2018) further argue in favour of conditional responsibility based on attaining a certain level of development before being held responsible, thereby indicating a 'fair' share of extraction.This approach does not entirely address the root of the problem since an uneven allocation of benefits within a country would be permissible below a certain development threshold.
With regards to the spread of damages, focusing on historical extraction and emission only implicitly captures the negative environmental impacts to the biodiversity and ecological resources on which communities depend (Muttitt & Kartha, 2020).Yet the protection of biodiversity and ecosystem services can be a key driver for oil exploration moratoria, as in Latin America (Tudela, 2020).Alongside the impacts of climate change and pollution, the extraction of oil can also be accompanied by violations of human rights, in particular those of Indigenous and marginalized communities (van Asselt, 2021).The burden of responsibility for such local damages could be borne by the extractor or the beneficiary but this pushes the value of a collectivist (i.e.country-level) approach to equity principles to its limits, since the damages and benefits may be borne within countries.For example, extraction for the benefit of the common good at the expense of damages at the local level.These issues may help to explain why despite the number of environmental justice violations related to fossil fuel extraction (see Temper et al., 2015), criteria linked to these aspects of environmental justice were not explicitly found in the literature.
In any case, the criteria identified in the literature split historical responsibility into benefits and emissions.With regards to measuring historical benefits, Pye et al. ( 2020) adopt a country's accrued benefit from past production using cumulative rents between 1970 and 2017 based on World Bank data, in addition to the development criterion.The Lofoten Declaration (2022), Kartha et al. (2018), and Caney (2016) also highlight past benefits and raise the need for development considerations.Le Billon and Kristoffersen (2020, p. 1077) focus instead on past production described in overall '(e.g.percentage of global historical production per capita) or relative terms (i.e. percentage of total domestic reserves already produced per capita)'.Regarding historic emissions, cumulative levels of greenhouse gas emissions provide a readily available metric, as suggested by Lenferna (2018) and The Lofoten Declaration (2022).Likewise, Newell and Simms (2020) suggest emissions with the added condition that these emissions come from the direct burning of a country's own fossil fuel reserves, thereby removing the burden of responsibility on importers.

Procedural justice
An important aspect of environmental justice highlighted in the literature is procedural justicethe participation of communities in decision-making related to extraction and respect for 'Free Prior and Informed Consent' (Lenferna, 2018;Muttitt & Kartha, 2020;The Lofoten Declaration, 2022).Although, the ability to guarantee participation and inclusivity depends on institutional capacity (Bos & Gupta, 2016).Muttitt and Kartha's (2020) call for phasing out extraction in line with environmental justice is partly a call for greater participation from local communities to provide procedural equity and secure their rights.It can also be interpreted as making the case that countries violating such rights should halt extraction (Muttitt & Kartha, 2020;van Asselt, 2021).
However, the papers reviewed do not suggest a metric for operationalizing a criterion linked to procedural justice.One approach would be to use indices akin to the now outdated Environmental Democracy Index, which ranked countries based on transparency, participation, and access to justice on environmental issues (Worker & de Silva, 2015).However, indices may deviate from the criterion depending on scope and the aggregation of data at the country level may not reflect the true impact at a local level.This may partly explain the lack of suggested metrics in the literature.

Practical considerations
Based on the identification of criteria and potential metrics, three related practical considerations are noteworthyinteractions and trade-offs between criteria; risks posed by value judgements; and incomplete metrics and missing criteria.To illustrate these practical considerations, consider first the outcome of a simple choice of a criterion and a metric based only on publicly available data, on the sequencing of country phasing out oil production as presented in Table 3.
As presented in Table 3, ranking countries by income and wealth suggests a similar need for countries such as the USA, Saudi Arabia, Canada, UAE, Qatar, Norway, and UK to phase out soonest (the red rankings).Using oil rents as metric for economic dependence, there is a shift and high-income countries such as Saudi Arabia and Kuwait, together with lower income countries such as Iraq, Libya, Azerbaijan, and Angola are the countries that should be able to produce oil the longest (the green rankings).While countries with significantly less income per capita, such as Egypt, India, Nigeria, and Algeria, should phase out sooner.
The countries that should phase-out soonest based on cumulative CO2 emissions per capita as a metric for historical responsibility correspond quite well with the level of development.Countries such as the USA, Saudi Arabia, Russia, Canada, UAE, Kuwait, and Qatar should phase-out first according to this criterion.However, this changes when looking at cumulative oil production per capita as a loose proxy for historical benefits, with Saudi Arabia, Russia, Canada, Norway, UAE, Kuwait, and Kazakhstan also joined in phasing out soonest by countries with significantly lower incomes such as Iraq, Iran, Algeria, Venezuela, and Libya.

Interactions and trade-offs
Table 3 demonstrates that some of the criteria and associated metrics identified in our review may converge or diverge on determining which countries phase out soonest.In some cases, the reason for this interaction is known.For example, national income as a component of the HDI means these metrics converge.Likewise, wealth and emissions may converge given their historic coupling (see Haberl et al., 2020).On the other hand, metrics related to economic efficiency (not included in Table 3) and development diverge due to the nature of different oil resources and the cost of their extraction (Lenferna, 2018;Muttitt & Kartha, 2020).Table 3 also illustrates that relying on criteria and associated metrics individually risks an equitable phase out.For instance, appealing to oil rents or cumulative production alone suggests some countries with a low income and development, such as Algeria, Nigeria and Venezuela, ought to be among the first to phase out.However, this may prove to be a moot point since most criteria identified during the review are proposed in combination with others rather than independently, with the aim of reconciling ethical principles.What's more, as with burden sharing on demand reduction, the case for fossil fuel supply reduction is rarely made in the global South in isolation from appeals to address ecological debt, historical responsibility, and restorative justice (Martinez-Alier, 2002;Obeng-Odoom, 2021;Roberts & Parks, 2009).Nevertheless, little or no indication is given on the relative weighting between the criteria given the normative implications of making such an assessment.Only Calverley and Anderson (2022) provide an indication of weighting by combining two criteria into a single metric (i.e.income level minus economic dependence on production).

Value judgements
As has been alluded to during the review, the criteria identified adhere to different principles of equity, conceptions of justice and market forces.Arriving at a metric may therefore require a chain of value judgements to be made on which metric operationalizes a given criterion best and which criterion best adheres to certain principles.Even for concepts such as national wealth and development, which may seem relatively simple to operationalize, variations in measurements (e.g.types of GDP) and the link between HDI and GDP complicates matters.The choices of criteria and metrics raise critical questions regarding the extent to which the narratives, values, ethical perspectives of communities affected by oil extraction are reflected (Caney, 2021;Lenferna, 2018), particularly those from the global South.This issue is compounded in circumstances where there is limited publicly accessible data for a metric (e.g. economic dependence on production) or no consensus on the measurement of a concept (e.g.accrued benefit).It may also reflect the intellectual marginalization of knowledge produced in the global South (see Obeng-Odoom, 2019).The ethical underpinnings of criteria and metrics, as well as combinations of them, need to be transparent to avoid the perception of a sequencing based on any criteria as value-free (Dooley et al., 2021).

Incomplete metrics and missing criteria
Given the criteria presented in Table 2 and the lack of accessible data for metrics, it goes without saying that the sequencing in Table 3 is based on an incomplete set of metrics.Since the criteria provide different dimensions of equity and other principles for determining which countries phase out, incomplete metrics result in suboptimal outcomes from a normative perspective.This is particularly important when considering criteria linked to equity for vulnerable communities and environmental justice issues.Limited availability of data does not reduce the need to include such considerations in the sequencing of phasing out, and sequencing based on an incomplete picture of criteria relegates such considerations to an after-thought.Furthermore, even including cases where data is not publicly available, the criteria identified in the review do not include energy security, domestic beneficiaries of extraction, geopolitics, or international sanctions.This could likely be attributed to the narrow scope of our review.They also do not take into account the pioneering efforts being made by some countries with regards to the implementation of breakthrough technologies or renewable energy, though the willingness criterion does point in this direction.Going a step further, there may be missing criteria linked to ethical principles that have not been identified in the review and would not be considered in an assessment for phasing out (Dooley et al., 2021).A more complex set of criteria with a complete array of metrics could add significant nuances to the question of phasing out and enable a better assessment of countries across criteria.

Discussion
Having identified the criteria for determining the sequencing of countries phasing out, it is evident that the sequencing varies by metric.Thus, an incomplete set of criteria and metrics provides an incomplete picture, and it is possible to reflect on the implications of not having a holistic view on just transitions.

Market dynamics
At present, cost efficiency as measured by least-cost is a key factor for production and would remain the dominant and default way for the market to determine the future extraction during a global supply phase-out (Muttitt & Kartha, 2020).As scenarios by the IEA (2021a) show, leaving the future production to market dynamics favours countries in the Middle East, North America, and to a lesser extent Africa, without due consideration for the just transition implications of such outcomes.Leaving the future production to market dynamics may even inhibit other aspects of a just transition.Firstly, unregulated environmental and social impacts are not captured by the cost of production; as such, market forces do not reflect the true social cost of production (Pellegrini et al., 2021).Secondly, market forces place the burden of transition on those countries least able to shoulder it (Kartha et al., 2018).In addition, leaving the transition solely to market forces forgoes the opportunity to apply policy levers to meet climate or sustainable development goals which can contribute towards just transitions (Muttitt & Kartha, 2020).Thirdly, past transitions, particularly those that have been left to market forces, provide cautionary tales of the negative consequences for vulnerable communities (Atteridge et al., 2020;Linde et al., 2022).Ultimately, a phase-out driven by market forces alone fails to address existing inequalities and risks creating new ones.Consideration is therefore needed for the way in which future production impacts the ability of countries to embark on just transitions.

Capacity to transition
Regarding the first set of criteria connected to the principle of equity, countries with the capacity to transition have an obligation to phase out sooner, bearing the burden of stranded assets, job and revenue losses, and wider economic impacts of doing so (Kartha et al., 2018).One of the favourable normative qualities of the capacity criteria based on the ability to pay is that it is indifferent to who is responsible for the harm which requires redress, and as a result, focuses on the future rather than the past (Caney, 2010).Yet, when considering fossil fuels, it would be difficult to refute that those countries that have the ability to pay and the capacity to transition at present, do so due to their past exploitation of climate-endangering resources and other historic injustices (Moellendorf, 2014).This strengthens the case for the ability to pay to play a primary role in comparison to the other criteria identified in the literature as part of this equity principle.
Even so, the combination of wealth and economic dependence to provide a broader understanding of capacity is apparent in the literature.As with other criteria, the scope of the criteria determines the accuracy of the outcome targeted.For instance, as argued by Calverley and Anderson (2022), using a metric based on government revenues for economic dependence partly captures the efficiency of tax regime which is not the intended focus.Meanwhile, using workforce dependence as a criterion hones the just transition implications narrowly on labour issues.In line with the literature on distributive justice, the capacity to transition may even benefit from considering minimum thresholds on national income or 'survival income' following the burden-sharing literature for emissions (Caney, 2021;Kartha et al., 2009).
Despite the normative merits, a just transition could still benefit from focusing beyond wealth and the ability to pay in the following ways.Firstly, one missing dimension of capacity is the availability of alternative energy sources, or physical capacity as defined by Kartha et al. (2018), which is not captured by metrics in the literature despite the availability of data.Despite the falling costs of renewables in recent years, access to affordable alternative energy sources and the lack of renewables infrastructure continue to be a challenge (IEA, 2021b;IRENA, 2021), locking-in emissions from fossil fuels.This also links to the need for an appreciation for the lack of institutional capacity in some countries to limit disruption during the transition (Kartha et al., 2018).Secondly, aside from the benefits of global leadership, government willingness to implement cuts plays an important role by ensuring a steady trajectory towards a targeted phase out which reduces the risk that a faster, costlier, and more disruptive transition may be required later (Muttitt & Kartha, 2020).Although, it may be challenging to reconcile economic capacity to transition with such willingness, since those with the biggest economic burden may be the least willing to implement cuts.

Development needs
The just transition implications of determining phase out based on the development criterion stems from tensions between the right to develop as it appears in international law and the narrative of extraction as the route to development.This narrative remains strong within extractive countries (Strambo & González Espinosa, 2020;Szuleck et al., 2021).However, extraction sets countries on a carbon-based path dependency at a time when the rest of the world seeks to decarbonize.In doing so, it raises the risk that such countries fall prey to technological, institutional, and behavioural lock-in to fossil-based production and infrastructure, resulting in higher costs and technological obsolescence relative to clean energy alternatives (Kartha et al., 2018;Pye et al., 2020;Seto et al., 2016).The development narrative also overlooks resource curse issues experienced by many countries with significant oil resources including misappropriation of benefits by elites, dispossession of communities, human rights violations, macroeconomic (i.e.'Dutch disease') and geopolitical instability, that ultimately hamper development outcomes (Caney, 2016;Kartha et al., 2018;Lenferna, 2018).Although Le Billon and Kristoffersen's (2020) development efficiency criterion attempts to reduce the occurrence of resource curse as part of phasing out, defining what constitutes the threshold for mismanagement of resources presents challenges from both a normative and practical perspective.
As noted in the previous section, the development criterion is not advocated for in the literature in isolation.Instead, it is combined with other criteria to bring in consideration for the right to develop in phasing out.At a fundamental level this relates to the infringement of such a right and calls for compensation, but it can also be construed more mildly as a call for assistance.With regards to compensation, this provides an alternative route for development for least developed countries foregoing the benefits of extraction.This is fraught with challenges such as determining the conditions under which compensation is due, calculating the value of losses, determining who pays and how the benefits from the compensation are shared (Armstrong, 2020;Kartha et al., 2018;Lenferna, 2018).These challenges have been compounded by a lack of willingness from the international community to compensate developing country forgoing extraction, as demonstrated by the Yasuni-ITT initiative (Macintosh & Constable, 2017;Sovacool & Scarpaci, 2016).In spite of the challenges, scholars have continued to propose solutions for compensation (Armstrong, 2020; Kartha et al., 2018;Snyder & Ruyle, 2020).
Regarding assistance, highlighting the developing needs of countries raises the importance of international cooperation and coordination between affected countries and countries that can provide assistance (Kartha et al., 2018).It is argued that the provision for assistance ought to take into account wealth and economic dependence on oil, and can inform the sequencing of phase out (Le Billon & Kristoffersen, 2020;Muttitt & Kartha, 2020).For instance, wealthy countries with low economic dependence such as Canada and Norway, ought to phase out the fastest without recourse to international assistance, while countries such as Iraq or Libya with low wealth and high dependence should phase out slowly with technical and financial assistance from the international community (Muttitt & Kartha, 2020).Furthermore, Kartha et al. (2018) argue that the focus of such assistance on shared efforts to reduce extraction and promote economic diversification, mirroring the type of support offered for global demand-side climate mitigation, could make a stronger case than a myopic focus on compensating countries for stranding resources.In sum, considerations for the needs of developing countries by including the development criterion alongside other criteria, can help to realize a just transition.

Historical responsibility
Contemplating historical responsibility in terms of benefits and emissions criteria simplifies the complexity of the notion of responsibility.Firstly, as noted by Caney (2016), historic responsibility can be conceptualized through a distinction between extraction, benefits, and use of fossil fuels.Although extracting and benefitting may seem to have a considerable overlap, extraction and reaping its benefits may occur across generations and with varying degrees of efficiency in benefitting from extracted resources (Caney, 2016).Treating them interchangeably may lead to the extractor bearing responsibility without consideration for the beneficiaries of extraction.Secondly, historical responsibility for the damages caused by extraction that is limited to emissions, narrows the interests of those affected to the impact of emissions.Yet the non-substitutable loss of cultural attachment and identity resulting from the forcible displacement of people from their homelands, associated with the local impacts of extraction, is disregarded by such a narrow conception of interests and rights (Caney, 2021;Martinez-Alier, 2002).Thirdly, ushering just transitions based on historic responsibility requires not only assigning appropriate responsibility to extractors, beneficiaries, and users, but disentangling perennial issues such as land tenure and property rights which in some cases are legacies of colonialism (Obeng-Odoom, 2021).This is further complicated by perceptions of the global North's failure to take responsibility for historic fossil fuel emissions while promoting the transition away from such fuels in the global South (Marais et al., 2021).

Procedural justice
The protection of vulnerable and frontline communities is a key tenet of just transitions and the rationale for incorporating ethical principles into climate action (Atteridge & Strambo, 2020;Dooley et al., 2021) It is also prevalent in the literature on equitable supply reduction (Kartha et al., 2018;Lenferna, 2018;Macintosh & Constable, 2017;Sovacool & Scarpaci, 2016;van Asselt, 2021).An interesting aspect of this debate is the circumstances under which the will of marginalized communities does not align with principles of equity on a global scale (Lenferna, 2018).In these cases, the pursuit of procedural justice in hand with global distributive justice poses complex questions integral to delivering a just transition, that need to be considered alongside other equity criteria.This includes second-order questions such as those regarding compensation or assistance (Kartha et al., 2018) and more fundamental questions regarding the understanding of community narratives and values (Caney, 2021;Lenferna, 2018).There is also a difference between compensation for foregoing extraction versus compensation for the loss of nature and the value placed on that nature by communities (Caney, 2021).While it may be challenging to operationalize into a metric for determining the sequencing of phase out, a lack of recognition of the needs and rights of marginalized communities from the outset makes the feasibility of truly delivering a just transition inconceivable.

Conclusion
There is a pressing need to curb the extraction of fossil fuels, alongside their use and consumption, to remain within reach of the 1.5C global warming limit.Yet, a reduction in the supply of fossil fuels does not inherently indicate a just or equitable transition.Producer countries have justifications for their own continued production appealing to principles of market dynamics and equity that suit their circumstances.However, an equitable, global phase out calls for a sequencing of countries phasing out.This paper did not seek to develop a methodology for such a sequencing but it has begun to fill a research gap by charting the spectrum of criteria explicitly found in the literature on equitable supply-side fossil fuel reduction.
By exploring the criteria in the literature and conducting a simple sequencing, it is possible to see that criteria point to different orders of sequencing.It is also clear that focusing on criteria individually can lead to imprudent conclusions on which countries ought to phase out oil extraction soonest.Instead, the interactions and trade-offs between criteria provide vital nuances to the question of phase out by appealing to different principles of equity and, thus, bring in broader considerations for determining a phase out.This paper has also shown that most of the criteria identified have not been operationalized and are missing metrics, not least because of the complexity of some criteria, but also the availability of data and the value judgements involved.By doing so, it has provided an initial view of potential phase out considerations despite the limited scope.Nevertheless, incomplete criteria and metrics limit the ability to provide the full picture needed to make informed decisions based on the relative circumstance of countries phasing out.Furthermore, a phase out sequencing based on such an incomplete assessment poses risks to ushering a global just transition, particularly with regards to development implications and the omission of the impacts on marginalized communities which brings into doubt the feasibility of achieving truly just transitions.
Further research could address limitations posed by the narrow scope of our review of criteria-based supply reduction.The breadth could be widened by casting a net beyond the literature on equitable fossil fuel supply to gather potential criteria from the broader literature on climate justice, climate policy, equitable burden sharing principles, etc., with a view to cover the types of missing criteria presented earlier in this paper.Meanwhile, greater depth could be added to a review by engaging with the philosophical and ethical aspects of climate justice literature to propose prioritisations or weightings of criteria, while ensuring that the risk posed by value judgements and concealed ethical underpinnings are reduced.Alternatively, by identifying and connecting suitable publicly available metrics to these criteria and avoiding the perpetuation of historic injustice that arises from solely valuing perspectives, research and data generated in the global North.Lastly, a further opportunity for future research is an assessment of the relevance of the criteria given the complexities of global energy transitions.This could include consideration for the need for a faster phase out given the potential widening of the gap between oil production and climate targets; the perceived or actual role that carbon capture techniques could play on oil supply reduction depending on national income; and differing speeds of energy transitions across the world, among others.

Table 1 .
Suggested metrics for criteria with publicly available data.See supplementary material A for a detailed breakdown of data.

Table 3 .
Ranking of top 30 oil producing countries and phase out sequencing based on five criteria and publicly available metrics.