The Paris Agreement, adopted 10 years ago at COP21, marks a major focal shift in the multilateral climate change agenda. Like its predecessor, the Kyoto Protocol, it is a legally binding treaty aimed at reducing greenhouse gas emissions. However, it goes further by setting a global goal to limit temperature rise to well below 2°C above pre-industrial levels and by also establishing targets related to adaptation to climate change and climate finance. While both agreements share an overarching climate change mitigation goal, they embody fundamentally different approaches. The Kyoto Protocol imposed top-down, binding targets primarily on developed countries, reflecting historical responsibility. In contrast, the Paris Agreement adopts a bottom-up model based on voluntary, nationally determined commitments from all countries, supported by mechanisms to raise ambition over time and to periodically assess progress.
Evaluating the impact of this major shift is of high importance, especially at the current critical juncture. Ten years after its adoption, the Paris Agreement is at a turning point, with its credibility being tested in a difficult geopolitical situation. Crucially, the ultimate success of the Paris Agreement hinges on sustained confidence that it can deliver results more effectively and rapidly than any potential alternative. This confidence is essential to fuel a virtuous cycle of increased ambition and action. In this context, an evidence-based estimate of the impact that the Paris Agreement had over its first decade (2015–2025), along with the expectations it created for the near future, may help safeguard the momentum against backsliding.
This report assesses the added value of the Paris Agreement, reviews the current situation and identifies avenues for its successful implementation. To assess the Agreement’s added value, it compares what has been achieved with it to what might have happened without it. To that end, it uses both retrospective and forward-looking analysis. The retrospective part contrasts actual progress between 2015 and 2025 with a scenario in which the Agreement has not been adopted. The prospective part examines expectations for 2025-2040, with and without the Paris Agreement.
Since these comparisons rely on hypothetical scenarios that cannot be observed directly, the analysis draws on an expert survey. Policymakers and other climate change experts were asked to assess a world in which the Paris Agreement was absent. The survey captures the perceived contribution of the Agreement to climate progress over the past decade. At the national level, this includes questions on how high climate ranks in policy priorities; the stringency of targets and mitigation policies; the actual emission levels; the extent to which climate action is mainstreamed in politics and society; and the involvement of private actors, local governments, and civil society. Similar metrics are used to assess the Agreement’s impact at the international level.
The survey findings indicate a strong perception that the Paris Agreement accelerated climate action domestically and internationally, and that it will continue to do so. Among experts, the agreement levels on whether climate change mitigation currently constitutes a domestic policy priority are considerable. Agreement levels that climate change mitigation was a domestic policy priority in 2024 exceed 83% for government respondents and 64% for other climate change experts. Similarly, agreement levels on whether climate change mitigation policies are stringent approach 70% for the former group and 52% for the latter. At the same time, perceptions are considerably weaker in the counterfactual scenarios, where the Paris Agreement is absent. For example, the agreement level on whether climate change mitigation policies would be stringent in 2024 without the Paris Agreement ranges between 32% and 41%. These striking differences persist in forward-looking questions. Overall agreement on whether climate change mitigation policies would be stringent in 2040 without the Paris Agreement is 45-51%, but rises to 70-83% in scenarios where the Paris Agreement is present.
Respondents believe that the Paris Agreement strengthened GHG mitigation targets but are less confident in the effect it had on actual GHG emissions. Agreement levels on whether national GHG emissions targets are stronger than what they would be without the Paris Agreement lie between 76% and 79%. The respective agreement levels that current GHG emissions are lower than they would be without the Agreement are 68-76%.
The analysis highlights strong beliefs about the role of the Paris Agreement beyond climate. Respondents agree that it set a precedent for future international agreements dealing with cross-border environmental issues. Importantly, policymakers are equally confident that the architecture and mechanisms of the Paris Agreement could be used to effectively address global challenges calling for multilateral cooperation.
Several challenges emerge as the main barriers to achieving the goals of the Paris Agreement. Respondents identified four key challenges to climate policy implementation. These primarily include the provision of necessary infrastructure for the transition to net zero, but also the public acceptability of mitigation measures. The affordability of clean alternatives and the effective adoption of cleaner technologies by firms are also among the top policy challenges. On the economic front, limited public funding stands out as the most important constraint. Other barriers, including the mobilisation of private finance and concerns about the distributional fairness of climate policies, are seen as significant but less important hurdles. Worries about the competitiveness of the export sector and concerns about the overall economic performance are considered less critical. Both climate experts and policymakers consistently point to vested interests and the lack of policy continuity across electoral cycles as significant institutional barriers.
The findings show strong confidence in the core channels of change as the means to achieve the 1.5 °C goal of the Agreement. Experts and policymakers highlight market-based instruments, regulatory measures, and policies that support green innovation as the main levers to deliver 61-67% of the necessary progress. Technological advancement without accompanying policy support is considered beneficial but secondary, accounting for 11-12% of expected progress. Voluntary action (13-16%) and behavioural change (8-11%) are also seen as relevant contributors, though they are seldom ranked as top priorities.
Policies linked to the decarbonisation of the energy sector and the management of carbon sinks are believed to have the greatest potential to deliver deep emission cuts. These include scaling up renewable energy, phasing out fossil fuels in power generation, protecting and expanding carbon sinks, and investing in green infrastructure. Policies related to nuclear energy, carbon capture and alternative fuels received the lowest average scores in terms of transformative potential.
Overall, the study highlights that experts value the transformative effect of the Paris Agreement. Barriers to implementation persist, but the Paris Agreement appears to have contributed to scaling up climate action.
