Are climate models fair or just efficient? 

A new International Institute for Applied Systems Analysis-led (IIASA) study examined growing critiques of how global climate mitigation scenarios address equity and justice and identified key conditions for fair, feasible, and politically credible climate action.


Image by The Yuri Arcurs Collection | Freepik

Global climate mitigation scenarios shape real-world policy choices of who cuts emissions, who pays, and who benefits from climate action. An IIASA-led essay published in PLOS Climate identified how these influential tools address equity and justice, with implications for perceptions of fairness and public trust in climate policy. Drawing on a broad grassroots community process, the study identified practical ways to advance equity and justice in climate mitigation pathways, supporting fair, feasible, and politically credible climate action.

The research synthesised growing evidence that current scenarios fall short in reflecting unequal responsibilities, capacities, and development needs across regions and proposes a roadmap for integrating fairness into future climate pathways. According to lead author Shonali Pachauri, Transformative Institutional and Social Solutions Research Group Leader at IIASA, the study was motivated by the need to bring together fragmented critiques of climate mitigation modelling and modellers and to move the discussion forward on how to integrate fairness into future scenarios.

“We wanted to bring together existing critiques, assess where current approaches fall short and where current scenarios already go further than some critiques suggest, and set out a clear agenda for embedding equity and justice into climate mitigation futures,” she explained.

Instead of asking whether models should address equity, the authors focused on how to do so in practice. “We focus on what needs to change in scenario design, modelling practices, and research processes,” noted co-author Caroline Zimm, a senior research scholar in the same research group at IIASA.

The paper identified three broad types of limitations in current climate mitigation scenarios: Structural limitations relate to who builds models and whose perspectives count, methodological issues arise from a strong emphasis on cost efficiency, which often sidelines fairness and distributional effects, and epistemological limitations refer to challenges in representing justice at policy-relevant scales.

Building on this diagnosis, the authors proposed practical next steps, including embedding effort sharing, and climate finance directly into scenarios, safeguarding decent living standards for all, expanding demand-side solutions, and involving under-represented regions and communities in scenario design.

“We highlight a research agenda that combines incremental improvements, deeper structural reforms, and participatory approaches that is designed to be practical as well as ambitious,” stated co-author Joeri Roglj, a senior researcher in the IIASA Energy, Climate, and Environment Program; director of research at the Grantham Institute; and professor of climate science and policy at the Centre for Environmental Policy at Imperial College London, UK.

Importantly, the authors emphasised that many of the advances can be pursued within existing modelling efforts, while others point toward longer-term structural changes in the field.

Rather than offering a single technical fix, the study reframed climate mitigation modelling and scenario development itself. The authors clearly distinguished between incremental improvements and fundamentally new approaches, while recognising the limits of models in resolving political questions of justice.

“Models are indispensable tools, but they cannot replace deliberative negotiation or moral judgement. Transparency, pluralism, and co-production are just as important as technical sophistication,” said Pachauri.

The implications of this work are significant for both policymakers and the public. For policymakers, the findings underscored that climate scenarios are not value-neutral and should be interpreted with a clear understanding of the normative assumptions embedded within them. Embedding equity directly into scenarios could help governments design fairer climate targets, estimate climate finance needs more accurately, and build stronger international co-operation grounded in shared responsibility. 

The work also highlighted that climate pathways are not just technical exercises but also inform choices about how the burdens and benefits of climate action are shared, shaping livelihoods, development opportunities, and intergenerational justice.

“Climate mitigation scenarios shape what policymakers believe is possible and acceptable. They are visions of who gets what future. Greater attention to equity can help ensure these pathways are robust, transparent, and socially grounded,” concluded study co-author and IIASA Energy, Climate, and Environment Program Director Keywan Riahi.

DOI: 10.1371/journal.pclm.0000763