This chapter provides an overview of the report. It sets out the context in which the study was conducted and explains the methodology applied. It details the rationale for using an expert survey to quantify the added value of the Paris Agreement and outlines the key questions explored. The chapter also presents the main takeaways and an extended summary of the findings. Finally, it discusses the study’s contribution and the relevance of its results in the current landscape of global climate action.
The Paris Agreement at Ten Years
Expert Views on Progress and Challenges for Climate Change Mitigation
Abstract
1.1.1. The novelty of the Paris Agreement
The year 2025 represents an important milestone in the international climate process, as it marks the 10-year anniversary of the Paris Agreement. Adopted at the 21st Conference of Parties (COP21), the Paris Agreement established a legally binding international treaty on climate change with extensive, nearly global membership. The Agreement includes, for the first time, a clear goal to limit the increase in the global average temperature well below 2°C above pre-industrial temperature levels, while pursuing efforts to limit the increase to 1.5°C (UNFCCC, 2015[1]).
The Paris Agreement is not the first legally binding treaty to tackle climate change. It replaced another international agreement, namely the Kyoto Protocol, which constituted the status quo approach until 2015. The Kyoto Protocol imposed legally binding targets for emissions reduction, which applied primarily to developed countries. It created a structured policy framework that combined market-based mechanisms, such as emissions trading and the Clean Development Mechanism, with formal enforcement provisions. The compliance system required countries that failed to meet their first commitment period targets (2008-2012) to make up the shortfall in the second period (2013-2020), with an added penalty of 30%. Non-compliant countries also faced temporary suspension from emissions trading schemes until the shortfall was rectified. These elements contrast sharply with the architecture of the Paris Agreement.1
The Paris Agreement adopts a novel framework, which differs widely from the top-down setting of the Kyoto Protocol. Countries are expected to set their own climate commitments, via their Nationally Determined Contributions (NDCs). The successful implementation of the Agreement relies on transparency, regular monitoring and reporting. Central to the architecture of the Paris Agreement is a commitment that ambition to mitigate future greenhouse gas (GHG) emissions cannot be reduced over time. The latter commitment, which came to be known as the “ratchet-up mechanism”, is not enforced but instead induced via peer-pressure. The Paris Agreement also brought adaptation and finance to the forefront, embedding them in its core architecture and reporting logic.
1.1.2. Why assessing the impact and the future possibilities of the Paris Agreement is timelier than ever before?
In 2025, climate action appears to be slowing in several sectors and regions, as geopolitical tensions and economic pressures put international cooperation under strain (OECD, 2025[2]). As a result, the long-term resilience of the Paris Agreement framework may be increasingly uncertain. Understanding whether the Paris Agreement makes a tangible difference, and to what extent, is critical. Clear evidence of its impact can help reinforce the credibility of the Agreement at a time when maintaining confidence in the multilateral climate efforts is more important than ever.
Source: Graph generated by the authors.
Beyond safeguarding the Agreement itself, understanding the barriers it faces and the strategies to overcome them has direct practical value. In 2025, countries need to revise their NDCs, as well as to review and possibly strengthen their climate pledges. This revision succeeds the first Global Stocktake (GST1), i.e. a collective assessment of the progress toward the goals of the Paris Agreement and the remaining gap to meet them. GST1 emphasised that current efforts fall short of what is needed, urging countries to act faster and more decisively. As such, 2025 is a pivotal moment to identify barriers to implementing current pledges, outline strategies to eliminate them and explore which policy directions can raise ambition in cost-effective ways.
1.1.3. What does this report examine?
The report explores four sets of questions related to the Paris Agreement and climate change mitigation action.
The first set of questions deals with the added value of the Paris Agreement. It considers a counterfactual world, in which the Paris Agreement has not been achieved in 2015 or in any subsequent year:
Would climate change mitigation today be lower or higher in the hierarchy of policy priorities?
Would climate change mitigation policies today be stronger or weaker?
Would these differences widen or shrink in the future (e.g. 2030, 2040)?
The second series of questions pertain to the shift from the Kyoto Protocol to the Paris Agreement. Examples of questions explored include:
Has it strengthened the emissions reduction targets and mitigation policies?
Would GHG emission targets and GHG emissions be higher today without this shift?
Would climate action be equally mainstreamed without the shift that occurred in 2015?
Has the shift increased or decreased policy action to tackle other environmental challenges, such as plastic pollution?
The third series of questions deal with the current constraints in the implementation of the Agreement. Key questions here include:
To what extent are current mitigation policies in line with each other?
Is current progress in line with ambition?
What are the economic, institutional and other domestic barriers to overcome to put economies on the 1.5 °C path?
The fourth series of questions deal with how drastic emissions cuts can be achieved in an efficient way. Examples include:
What part of the necessary change can be achieved with conventional policy instruments, such as taxes, subsidies and regulations?
How much can we rely on technological innovation to bring emissions to a net-zero path?
What policy directions are the most promising in cutting down GHG emissions?
1.2.1. Why relying on an expert survey using “what-if” scenarios?
Understanding the impact of the Paris Agreement goes beyond tracking emissions or climate pledges. Several of the potential effects of the Paris Agreement play out through complex political processes, negotiation dynamics and institutional change. Examples of such impacts that the report explores include raising climate ambition, changing policy priorities and increasing awareness of other transboundary environmental problems. Most often, such developments are hard to quantify or are not visible in short-term data. Public opinion, which can often offer useful insights via the “wisdom of the crowd”, can help measure the acceptability of climate policies. However, it is not suitable for making an informed guess of the full value of the Paris Agreement. To circumvent this problem, the study draws on the views of policymakers and other climate experts with direct experience in the design and delivery of climate policy. Their responses reflect institutional knowledge, technical expertise and a deep understanding of domestic and international climate governance.
At the same time, assessing the Agreement’s added value means asking a counterfactual question: what would have happened without it? Progress since 2015 may have occurred regardless of the Paris Agreement. Furthermore, the observable progress in climate action that took place before 2015 may have continued, stalled, or reversed without the Agreement. To disentangle these possibilities, the study uses a structured “what-if” approach. Experts are asked to consider a scenario where the Paris Agreement had not been adopted, and to compare this scenario with the actual trajectory of climate action. This way, the beneficial effects of the Paris Agreement are not only evaluated in terms of achievements that occurred since 2015, but also relative to the respective achievements that could have occurred even without the Paris Agreement. This relative evaluation stretches to the future: the study compares the achievements that experts do anticipate between 2025 and 2050 with the Paris Agreement, vis-à-vis the achievements that they would anticipate between 2025 and 2050 without it.
1.2.2. An overview of the survey
To evaluate the effect of the Paris Agreement, a global survey was used to gather the views of policymakers and other climate experts. The novelty of this survey lies in the employment of quantitative methods that help measure the added value of the Paris Agreement, as it is perceived by the survey participants.
The survey uses a structured questionnaire to collect the views of government experts and non-government experts from institutions including academia and international organisations, as well as from the private sector. The former group responds to questions with a focus on national climate action and progress, while the latter group responds with a reference to international climate action in part of the questionnaire. Participation from government experts includes 70 responses from 64 countries. Among these, most OECD countries (33 out of 38 countries) are represented, alongside 31 non-OECD countries. Experts from non-governmental institutions include a total of 178 responses from 46 countries, with 26 OECD countries represented.
The survey was based on a detailed questionnaire covering the following areas:
Imagining a world without the Paris Agreement: Respondents were asked whether climate change would be seen as less of a priority and whether climate policies would be weaker without the Agreement.
Comparing the Paris Agreement to its predecessor: The survey explored how the move from the Kyoto Protocol to the Paris Agreement has influenced climate targets, policy strength, public awareness, and international cooperation.
Examining today’s challenges: Respondents assessed how well current policies align with emissions targets, other national priorities, and what obstacles still stand in the way of full implementation.
Looking to the future: Experts shared views on which strategies and policy approaches are most likely to drive deep cuts in greenhouse gas emissions and how far along those policies are in being implemented.
A detailed description of the survey is provided in Chapter 2 of the report.
1.2.3. What is the contribution of this work?
Vis-à-vis the existing literature, the study offers complementary perspectives and unique new insights. The existing literature includes several public opinion surveys gauging support for climate action and specific climate policies, and some of them focus particularly on the Paris Agreement (Carson et al., 2025[3]; Dechezleprêtre et al., 2025[4]; Andre et al., 2024[5]; OECD, 2024[6]; UNDP, University of Oxford and Browning Environmental Communications, 2024[7]). However, public opinion surveys are not well suited to gauge the extent of progress that the Paris Agreement has helped countries to achieve since 2015. Nor can they reliably identify which climate policies are the most efficient, or quantify the challenges in raising climate ambition and implementing current commitments. Several analytical studies address these questions (IDDRI, 2025[8]; Dogan and Li, 2025[9]; Guérin and Tubiana, 2025[10]; Kustova et al., 2025[11]), yet their insights are predominantly qualitative. The survey presented in this report uses exclusively quantitative methods to measure how experts perceive the added value of the Paris Agreement, the progress made since 2015 and the challenges that persist in 2025. Through the views of the participating policymakers, government officials and other climate change experts, the survey encapsulates counterfactual reasoning, knowledge of international negotiations, and institutional memory of policy evolution since 2000. Its findings also reflect expert understanding of the economic trade-offs involved in the path to net zero, and informed judgment on climate policy that goes beyond that of public opinion. Most importantly, the focus of the present survey widely differs from that of the few available expert surveys on the Paris Agreement (e.g. Victor, Lumkowsky and Dannenberg (2022[12])) and from the broader set of expert surveys on climate policies without a focus on the Paris Agreement (e.g. Drupp, Nesje and Schmidt (2024[13]) and Drews, Savin and van den Bergh (2024[14])). Its contribution should therefore be seen as strictly complementary to that of these contributions.
The survey not only informs current climate policy debates but also helps chart a path forward for global cooperation under the Paris Agreement. The findings of the survey can contribute to the ongoing climate discussions in several ways. First, highlighting the positive effect of the Paris Agreement and its design can help maintain the momentum to scale up climate action in an era of interlocking crises. Second, it can encourage countries to continue relying on the Agreement to collectively work towards its goals, especially in the context of the new round of NDCs. Finally, the survey results can encourage future additional work to evaluate the effect of the Paris Agreement on other factors, most notably emissions, sectoral policy efforts and enabling factors.
Comparing the Paris Agreement to a hypothetical world without it, responses from policymakers and other climate experts highlight its added value.
The Paris Agreement helped make climate change mitigation a national priority and will help keep it as such. Policymakers believe climate change mitigation is taken much more seriously today than in 2015 and expect it to remain a top priority through 2040 under the Paris Agreement.
The Agreement helped keep climate change high on the international agenda during 2015-2025. Without it, experts believe global attention to climate action would have declined after 2015.
Without the Paris Agreement, progress made before its signature would have stalled. Experts believe that the momentum gained during 2000-2015 would not have been maintained after 2015.
The Paris Agreement is a source of confidence in long-term action. Experts who expect strong policies in place by 2040 are much more likely to hold this view when considering a world with the Paris Agreement than one without it.
There is room to strengthen political commitment. While survey respondents agree that progress has been made, they are less confident that policies are sufficiently strong today, and far from fully convinced that this will be the case in 2040.
Respondents point to four domestic barriers to the implementation of the Paris Agreement: green infrastructure gaps, public acceptance of climate policy, affordability of clean alternatives, and firm-level adoption of clean technologies.
Economic and institutional challenges hinder progress, in particular limited public funding, distributional concerns, vested interests opposing the green transition, and lack of policy continuity between electoral cycles.
Technological progress is key but alone would be insufficient to achieve substantial emission reductions. Respondents expect only a small part of the solution (12%) to emerge without policy intervention.
Policy is considered the most important way to reach the goals of the Paris Agreement. Respondents expect market-based instruments, regulations, and innovation policies to generate nearly two thirds of the solution.
The most transformative net-zero policies pertain to the energy sector. Improving energy efficiency, decarbonising energy supply, and electrifying end-use sectors are viewed as the most transformative strategies for emission reductions.
Ten years after its adoption, the Paris Agreement is widely seen as having reshaped both national and international climate agendas. Policymakers report that climate change mitigation has steadily moved up the list of domestic policy priorities since 2015. The average agreement level that mitigation was a national policy priority rose from about 66% in 2015 to 84% in 2024, with projections reaching close to 90% by 2040. This trajectory shows that the Paris Agreement has helped embed climate action more firmly in national policy frameworks. Without it, this trend would have been far weaker, hovering between 50% and 60% through 2040.
At the international level, experts outside government share this view. They credit the Paris Agreement with keeping climate change high on the international agenda at a time of growing geopolitical and economic challenges. Their overall agreement that mitigation is an international policy priority increases from 63% in 2015 to more than 80% by 2040 under the Paris framework. In contrast, in a world without the Agreement it remains below 60%. Experts stress that the key contribution of the Agreement between 2015 and 2025 was not to raise ambition but to safeguard climate action from declining political attention.
The Paris Agreement is also viewed as a catalyst for stronger mitigation policies. Agreement that mitigation policies are stringent starts from a relatively low level, i.e. around 45% for policymakers and 35% for non-government experts in 2015. However, under the Paris Agreement by 2040 they rise steadily to over 80% and 70%, respectively. Without the Agreement, these figures linger around 50% or less. Therefore, this mirrors the pattern of perceptions on whether climate change is a policy priority. This result suggests that both groups perceive policy ambition and policy strength evolving together under the Paris framework.
The survey highlights the positive momentum in climate action that preceded the Paris Agreement. Looking back, experts recall that in 2000 climate change mitigation was not widely regarded as a major policy concern. Agreement that mitigation was an international priority in 2000 lies near 35%, and agreement that policies were stringent at only 20%. By 2015, both indicators rise significantly, to roughly 60% and 36%, respectively. This clear trend indicates progress before the Paris Agreement. This justifies the methodological choice to carefully account for the degree to which such progress could be sustained after 2015 without the Paris Agreement. Here, the experts highlight that the answer is negative: in its absence, confidence in mitigation priorities declines sharply after 2015 and recovers only slowly thereafter.
The Paris Agreement strengthens conviction in long-term action. The share of respondents who strongly agree that mitigation policies will be stringent by 2040 is more than three times higher in a world with the Agreement (30-35%) than without it (below 10%). Similarly, strong agreement that mitigation will remain a policy priority is about 2.5 times higher under the Agreement.
Experts caution that current policy strength remains insufficient. Around one in five policymakers actively disagree with the statement that mitigation policies are stringent in their country, while fewer than 10% of non-government experts express strong agreement that global mitigation policies are sufficiently strong. These results indicate that, although the Paris Agreement has clearly boosted ambition, implementation gaps persist, underscoring the need to translate ambition into measurable outcomes.
The added value of the Paris Agreement becomes clearer when comparing it to its predecessor. Experts believe the Paris Agreement is more effective than the Kyoto Protocol in raising ambition, strengthening policies and securing public support for climate action. They also credit it with helping to bring climate action into the mainstream of national and international agendas. Most of the respondents also believe that the Paris Agreement is more suitable to induce efforts to tackle other environmental challenges, such as plastic pollution.
In summary, the findings from the counterfactual analyses reveal a consistent narrative. The Paris Agreement has played a decisive role in elevating climate change mitigation as both a national and international priority, in sustaining policy momentum after 2015, and in driving stronger climate policy design. It has also fostered greater confidence in the long-term trajectory of global mitigation efforts. Yet this progress remains incomplete: experts and policymakers alike recognise that achieving the Paris goals will depend on further strengthening the political will and institutional commitment that the Agreement has helped to build.
Policymakers and non-government experts present complementary but sometimes diverging views on the current state of global climate action. Policymakers tend to see national progress in a relatively positive light: on average, they express a weak agreement, i.e. they “somewhat agree”, that domestic mitigation policies are well-aligned. They also “somewhat agree” that progress is broadly consistent with stated ambition, as the latter is inscribed in the nationally determined contributions. The average level of agreement for this statement hovers around 60%, suggesting moderate confidence in domestic delivery. In contrast, climate change experts who assess the situation globally rather than nationally, are more sceptical. Their agreement that policies internationally are on track or well-aligned with each other ranges only between 25% and 37%, reflecting persistent doubts about coordination between countries and ambition across them.
Both groups of respondents converge to a view that climate mitigation policies could be compatible with economic growth. In the question of whether climate action can go hand-in-hand with objectives such as employment and GDP growth, policymakers register a cautiously optimistic agreement of about 64%. Internationally, this confidence drops to 53%, pointing to higher uncertainty about the balance between climate progress and economic performance when viewed at global scale.
When identifying what holds back faster progress, both policymakers and other climate experts highlight a common set of barriers. Four domestic challenges dominate, accounting for over 80% of total voting scores: developing adequate infrastructure for the net-zero transition, promoting wider adoption of clean technologies by businesses, ensuring public acceptance of mitigation measures, and improving the affordability of clean products for households. Within this group of interrelated challenges, the expansion of green infrastructure and the technology uptake by firms attract the strongest consensus among respondents.
Limited public funding emerges as the single most important economic barrier, capturing roughly 22% of policymakers’ voting points and being ranked first by 45% of them. This is followed by concerns about the distributional fairness of mitigation costs and the employment impacts in affected sectors. Difficulties in mobilising private finance also rank high. While impacts on overall economic performance and export-competitiveness receive attention, these concerns rank lower. Each accounts for around 10% of total points, suggesting that most respondents see them as secondary hurdles rather than binding constraints.
Vested interests and the lack of policy continuity across electoral cycles are viewed as major institutional obstacles by both groups. Together with resource shortages in government agencies, these factors account for about 45% of the institutional challenges. Policymakers, drawing on direct administrative experience, tend to emphasise limited capacity and coordination issues, while external experts focus more on systemic political resistance and the need for stable long-term governance.
Respondents identify policy intervention as the main lever for closing the gap between current ambition and implementation. Three policy families, i.e. market-based instruments, regulations and innovation-support measures, collectively account for roughly two-thirds of the expected contribution to achieving the goals of the Paris Agreement. Market mechanisms such as taxes, subsidies and carbon cap-and-trade schemes receive 23-26% of voting points, regulatory measures 21-24%, and policies supporting green innovation 17-19%. All remaining channels of progress remain relevant, but their role is seen as secondary. Together, voluntary and behavioural approaches are expected to deliver about a quarter of total emission reductions, with individual actions, corporate initiatives and behavioural interventions each contributing 6-11%. Autonomous, market-driven technological progress alone without policy support is believed to account for just 11-12% of the required change, underscoring that innovation needs supportive policy frameworks to translate into deep emission cuts.
When asked about strategies with the greatest transformative potential, respondents emphatically point to the energy sector. Electrification, decarbonisation of energy supply, and improvements in energy efficiency account for roughly half of all voting points allocated, and about two-thirds of respondents rank one of them as their top priority.
Respondents identify a series of energy-related policy directions as the most transformative: scaling up renewable energy and phasing out fossil fuels in power generation are seen as the most transformative policy directions, each scoring above 3.8 out of 5 in perceived impact. Investing in green infrastructure and protecting carbon sinks are also seen as highly transformative policy directions. In contrast, options such as nuclear expansion, carbon capture and storage, and alternative fuels receive the lowest scores, generally between 2.9 and 3.1 out of 5. The limited enthusiasm for these may reflect costs, technological maturity, political constraints and safety concerns, rather than an outright dismissal of their role. Importantly, policymakers and other experts report that the policies seen as most transformative are also those that have advanced the furthest since 2015. This holds true particularly for renewables and energy-efficiency measures, suggesting that attention and resources tend to concentrate where confidence in impact is highest.
Taken together, the findings from the analyses on the current situation and future possibilities of the Paris Agreement present a mixed but encouraging picture. Policymakers see national actions as broadly aligned with climate goals, while experts remain cautious about global coordination and delivery. Both groups agree that climate policy and economic growth can advance together. However, fiscal constraints, institutional capacity and political continuity continue to hinder faster progress. Despite these obstacles, there is strong consensus that effective policy remains the key driver of change. Market instruments, regulation, and innovation support are viewed as the main tools. Across both groups, energy transformation, through electrification, decarbonisation, and efficiency, emerges as the cornerstone of future mitigation.
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← 1. The degree to which these mechanisms affected the proliferation and stability of the Kyoto Protocol remains a topic of debate. Kallbekken and Hovi (2007[15]) warned that this mechanism allowed a non-compliant country to entail considerable costs to complying countries via affecting permit prices, likely posing a legitimacy problem. Peer-reviewed articles that provide a technical overview of the Kyoto Protocol and its support mechanisms include, but are not limited to Bohringer (2003[16]) and Grubb (2004[17]).