3.2.3.1 Mitigation

The Paris Agreement adopted in 2015 provides the foundation for current global climate mitigation efforts. Three components of the agreement are central for mitigation efforts and should be re-evaluated in light of the growing knowledge of tipping points: global goals related to global temperature and corresponding discussions about suitable mitigation pathways, Nationally Determined Commitments (NDCs), and the system of transparency and review mechanisms that are supposed to ensure accountability and drive ambition (see 3.1.3.2 for more detail).

The Paris Agreement established a two-pronged global long-term temperature goal – limiting warming to well below 2°C, and aiming for 1.5°C, above pre-industrial levels (Art. 2 (1) PA), combined with an objective of global peaking of GHG emissions (as soon as possible), and balancing emissions and removals of GHG (in the second half of this century) (Art. 4 (1) PA). These objectives need to be read in the context of the overarching aim of the Agreement to “significantly reduce the risks and impacts of climate change” (Art. 2), which requires the consideration of the most recent climate science. The newest scientific evidence regarding ESTPs creates an imperative to revisit the meaning of the global long-term temperature goal, its adequacy and its implications for the types of emission pathways that can achieve it (Pouille et al., 2023).

Adopting the prevention of climate tipping processes as an explicit objective of global climate governance has important implications for the selection of global and national emission pathways towards the temperature goals established in the Paris Agreement. Only a subset of the emission scenarios included in IPCC AR6 are suitable if decision makers take into account the need to prevent the passing of tipping points.

A recent OECD working paper (Pouille et al., 2023) identified a set of criteria for the selection of emission pathways that are consistent with the temperature and mitigation objectives of the Paris Agreement (see above), and specifically considering the risk of crossing ESTPs. These criteria include, among others, the likelihood of keeping global warming below 1.5°C by 2100, avoiding or limiting temperature overshoot to 1.6°C, and early peaking of global emissions (2025/2030). Applying these criteria at two levels of stringency to the emission scenario database for IPCC AR6, the analysis demonstrated that only a subset of all ‘likely below 2°C’ emissions scenarios used by the IPCC can be considered in line with the long-term goals of the Paris Agreement, especially when also considering the objective of minimising tipping risks.

More specifically, emission pathways that are consistent with the objective to prevent climate tipping points have three important common features. First, they minimise ‘temperature overshoot’. While accepting that warming of more than 1.5ºC warming above pre-industrial levels can likely no longer be avoided, emission pathways that minimise temperature overshoot beyond this level have a higher chance of avoiding the crossing of tipping points (Palter et al., 2018; Drouet et al., 2021; Wunderling et al., 2023). In other words, considering only long-term (end of century in most analyses) temperatures is not sufficient; global peak temperature is an equally important measure for achieving global objectives, Second, emission pathways that are more likely to avoid tipping points keep the duration of the overshoot period as short as possible (Wunderling et al., 2023). These two features lead to a third characteristic of emission pathways that effectively prevent tipping points: rapid, early emission reductions (this decade) coupled with rapid scaling of carbon removal capacities.

The UNFCCC Periodic Review and the Global Stocktake provide opportunities to discuss and adjust the shared understanding of the long-term global temperature goal within the current institutional framework of the Paris Agreement. These processes should be used to consider the risk of ESTPs and the need to prevent their transgression. Further, in 2021, the UNFCCC established a Mitigation Work Programme with the objective to scale up mitigation ambition and implementation. This negotiation stream offers opportunities to discuss the question of ‘tipping safe’ emission and mitigation pathways, for example as a topic of a future global dialogue. Specific criteria for acceptable emission pathways that comply with the temperature and mitigation objectives of the Paris Agreement should also inform short- and medium-term national policymaking – e.g. mitigation strategies to achieve net-zero goals.

The Paris Agreement’s pledge and review system requires all participating countries to iteratively submit Nationally Determined Contributions (NDCs), which include national pledges of future emissions reductions, sink management measures, and the development of carbon-removal capacity. Future NDC revisions should include specific considerations of ESTPs, and to what extent national mitigation plans, policies and decarbonisation strategies contribute to their prevention. This should include an effort to identify the country’s historic and current contributions to creating tipping point risks. In addition to affecting most ESTPs with domestic GHG emissions, multiple national processes can contribute to secondary drivers of tipping processes – e.g. deforestation, pollution or other extractive activities, and globally sourced consumption via international trade. Based on an understanding of its responsibility and capacity to engage in tipping point prevention, countries could describe how national measures and cooperative initiatives with other countries and non-state actors contribute to the prevention of specific tipping points. For example, Norway, Canada, the US and Russia could detail efforts to reduce pressures on boreal forests to prevent dieback at their Southern boundary, including logging policies and other extractive activities, fire and pest management (see 3.2.2).

Countries are also required to develop longer-term (mid-century) strategies for national decarbonisation. Many countries have adopted ‘net-zero’ commitments when developing their mid-century strategies, setting specific dates for reaching the point where remaining emissions are balanced by removal. These mid-century strategies have important implications for mitigation pathways and the governance of tipping point risks. Future revisions of these strategies should include an analysis of ESTPs, and to what extent long-term national decarbonisation strategies contribute to their prevention. For example, many net-zero strategies today imply high reliance on carbon-removal methods, which are needed but could impose additional pressure on other drivers of Earth system tipping (e.g. from afforestation in unsuitable locations that add pressure to biosphere tipping systems like grasslands or lakes). Further, countries should consider shortening net-zero timelines to accelerate decarbonisation and reduce tipping point risks.

The architecture of the Paris Agreement encourages increasingly ambitious NDCs and national action over time through transparency and review mechanisms like the Global Stocktake. The reporting requirements of the transparency mechanism provides another opportunity for countries to describe national mitigation measures and their impacts, not just with a view to the global temperature goals, but to the prevention of tipping points. The Global Stocktake serves to review collective progress towards the goals of the Paris Agreement – i.e. illuminating whether the international community is on track towards achieving the temperature goals, allowing countries to adjust their levels of ambition if needed. Starting in 2028, the Global Stocktake could explicitly address to what extent national and collective prevention efforts have limited the risk of passing ESTPs. This would require collecting tipping point-specific materials (e.g. this report, a potential IPCC special report on tipping points, a report by IANAS on the state of the Amazon rainforest, reports by AMAP on the state of Arctic tipping points) in the technical phase and providing a technical assessment of collective progress on reducing tipping risks. Building on our discussion of criteria for acceptable mitigation pathways above, this assessment would consider whether actual mitigation pathways fall within the envelope of modelled pathways that limit tipping risks. The political component of the GST could include deliberations on tipping point prevention and to what extent tipping point risks warrant increased global mitigation ambition. Including tipping points in the GST could stimulate the formation of multi- and minilateral initiatives for tipping point governance.

While the Paris Agreement provides an international framework for climate mitigation efforts, the actual work of reducing emissions takes place at the national scale. Countries pursue the aim of decarbonising economies and societies using a vast range of national policies, especially in the domains of energy production (transitions towards renewable energy sources) and use (energy efficiency), mobility (e.g. electrification of road transport), housing and agriculture. There are vast differences among the approaches and successes of different countries so far. While decarbonisation measures often create resistance and face political challenges (Egli, Schmid, and Schmidt, 2022; Martin and Islar, 2021), they need to accelerate and expand in scope to address the growing risk of transgressing tipping points. This includes the removal of fossil fuel subsidies (Skovgaard and van Asselt, 2019; Coady et al., 2019) and other forms of government support for the fossil fuel industry, cancellation of government licences for new extraction projects, and ultimately publicly guided deliberate phase-out strategies for fossil fuel industries that proactively and carefully consider justice implications (Pellegrini et al., 2021; Whitfield et al., 2021; Heffron, 2021; Newell and Mulvaney, 2013). Civil society actors also play a crucial role in advancing mitigation and societal decarbonisation efforts, including by pressuring national governments to acknowledge that effective climate change mitigation requires phasing out all fossil fuels.