Report on international cooperation and support to increase fairness across regions

Achieving the goals of the Paris Agreement requires more than emissions reductions—it demands a balance between ambition, feasibility, and fairness. This report explores the international cooperation and support necessary to advance fairness across regions, structured around three interrelated dimensions: governance 
capacity, interregional equity, and intergenerational equity.

Drawing on scenarios from the ENGAGE project, we show that incorporating feasibility reshapes the timing and distribution of regional mitigation efforts. OECD90+ and China+ regions are projected to reach net-zero emissions earlier, aligned with current pledges and stronger institutional capacity, compared to default scenarios without any feasibility considerations. In contrast, the Rest of the World (RoW) will require substantial international support to enhance ambition and action. This includes deeper near-term mitigation in high-capacity regions, as well as expanded mechanisms for technology transfer, institutional capacity-building, and climate finance.

We find that scenarios with more ambitious mitigation in regions with high institutional capacity still fall short of equity benchmarks such as historical responsibility. To address this, we introduce the concept of net-zero carbon debt—a transparent metric for quantifying excess emissions and drawdown obligations, offering additional guidance for climate finance and fair-share assessments.

Achieving ambitious climate targets in a way that balances feasibility and fairness will require coordinated global action. This includes deep domestic emissions reductions in high-capacity regions, alongside significantly scaled-up support for lower-income countries—particularly in areas such as clean energy, infrastructure, and governance. Equally critical is the large-scale mobilization of climate finance, ensuring it is more closely aligned with principles of equity. The newly launched Justice Model Intercomparison Project (JustMIP) will further explore how various dimensions of justice influence global mitigation pathways and the resulting demands for international cooperation.