Defining ‘science-based targets’

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The 2015 Paris Agreement to keep global warming well below 2°C above pre-industrial levels and aim towards limiting warming to 1.5°C marked a watershed in planetary governance, for two reasons. First, of course, it set an explicit, quantitative target for sustainability with strong support from science, in a clearer way than had ever been done before. Second, perhaps even more important, this target is structured in a way that it can be disaggregated across the sectors of society which will need to take action to achieve it. This includes not only the nations who agreed on the target in the first place, but also non-state actors, such as cities, regional governments and the private sector. We see the prospect for each component of society to ‘do their bit’ towards ameliorating climate change as a fundamentally important precedent for global governance. With the upcoming 2020 timelines for a number of the targets under the 2030 Agenda for Sustainable Development, as well as for the plans of a number of multilateral agreements, the world has a grand opportunity to replicate this concept of ‘science-based targets’. Examples of global environmental goals as overall science-based targets. The first goal of the Paris Agreement, the mission of the Strategic Plan for Biodiversity 2011–2020, and the Land Degradation Neutrality Target exhibit all three of the characteristics defined here for being considered ‘overall science-based targets’—achievability, quantification and rationale. Sustainable Development Goals 14 and 15 have the first of these, and two of the clauses of the latter also have explicit quantification and underlying rationale. Examples of global environmental goals as overall science-based targets. The first goal of the Paris Agreement, the mission of the Strategic Plan for Biodiversity 2011–2020, and the Land Degradation Neutrality Target exhibit all three of the characteristics defined here for being considered ‘overall science-based targets’—achievability, quantification and rationale. Sustainable Development Goals 14 and 15 have the first of these, and two of the clauses of the latter also have explicit quantification and underlying rationale. The term ‘science-based targets’ has burst into the discourse of the science– policy interface for sustainability over recent months. Rockström et al. [1] used the term to describe the targets under the Paris Agreement. An entire Science-based Targets Initiative has been established by the Carbon Disclosure Project, United Nations Global Compact, World Resources Institute and World Wildlife Fund to guide companies in setting science-based emissions reductions targets for climate change. The initiative has reached critical mass, illustrative of the rapid growth in application of the term by many non-governmental organizations and governments. As another example, the charity Oxfam emphasizes ‘setting and implementing science-based targets’ in their corporate engagement, while in 2016 the International Union for Conservation of Nature's Resolution 96 highlighted the term in the context of biodiversity conservation. However, it has become apparent that the term is being used in widely different ways, which is generating substantial confusion. Here, we therefore seek to define what ‘science-based’ means in relation to ‘science-based targets’, and to differentiate between overall science-based targets (for the world) and specific science-based targets (for individual entities). We do not seek to explore the experiences, challenges and impacts of the establishment of science-based targets in practice; such work is underway through a wide range of processes, and will be reported on in due course. Setting targets for addressing major planetary concerns is an essential prerequisite for concerted global action (both inside and outside multilateral environmental agreements) and is necessarily a societal and political process, requiring negotiation and convergence among often-conflicting interests [2]. There is no such thing as a ‘scientific target’ applied in policy or business—operational targets are socio-political choices. However, this is not to say that targets cannot be ‘science-based’. What, then, does it mean for a target for addressing major planetary concerns to be ‘science-based’? First, recall that ‘science’ is ‘the organised, systematic enterprise that gathers knowledge about the world and condenses the knowledge into testable laws and principles’ [3]. Building from this, we propose the following characteristics as defining ‘science-based targets’: Analytical evidence suggests that the achievement of the target is a biophysical possibility within its specified time frame. This clearly does not mean that its achievement is a foregone conclusion; addressing cultural, political, social and economic constraints to achieving targets can be hugely challenging. But for a target to be science-based, it must be theoretically achievable. It must be possible to demonstrate—and test—the degree to which a target has been achieved. The target should be quantified, such that progress towards it is measurable. Such quantification could be in the form of an absolute value (e.g. ‘2°C above pre-industrial levels’) or a relative one (e.g. ‘halt the loss’, or ‘reduction by x%’). The target should be supported by a clear, analytical rationale for why it is set at this particular level. This might often be expressed in the form of a probability of achieving an ethical imperative (such as ending hunger or preventing extinction), or of reducing the risk of a negative outcome, such as transgression of a ‘planetary boundary’, to an acceptable level. The first and second of these characteristics overlap with the characteristics of ‘SMART’ targets, i.e. targets that are specific, measurable, assignable, realistic and time-related [4]. However, while science-based targets are necessarily ‘SMART’, the converse is not necessarily the case, because SMART targets are not necessarily underpinned by a scientific rationale. Overall science-based targets are those established through intergovernmental process at the level of the entire planet. The best-known example comes from the Paris Agreement under the United Nations Framework Convention on Climate Change, which sets an overall science-based target of ‘keeping a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius’. While the 2°C target is of course a product of political negotiation, and is based on decades of climate science and requires accepting what many consider to be unacceptable risks of negative consequences [5], it meets all three of the characteristics proposed above for being considered ‘science-based’ (Table 1) as well as all five characteristics of a ‘SMART’ target. Schematic process for development of science-based targets. The establishment of overall science-based targets is informed by independent assessment and synthesis of the state of the science of a given planetary concern (1) and then negotiated through policy dialogue to reach global agreement (2). Once overall science-based targets have been established, scientific research into method development is then necessary to allow disaggregation of these across (3), allowing engagement across all sectors of society to set specific science-based targets and ensure implementation of actions to reach them (4). A number of other overall science-based targets for addressing major planetary concerns have been set through intergovernmental processes. For example, the Strategic Plan for Biodiversity 2011–2020 sets a target to ‘take effective and urgent action to halt the loss of biodiversity in order to ensure that by 2020 ecosystems are resilient and continue to provide essential services’, while the United Nations Convention to Combat Desertification maintains a ‘Land Degradation Neutrali

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.