Modeling Just Transitions Upstream: A Diagnostic Framework for Integrating Justice and Equity into Energy and Climate Assessment Models

Energy justice and equity shape the legitimacy, feasibility, and societal acceptance of decarbonization pathways, yet are often treated as ex-post modeling outputs rather than design principles. This paper argues that equity enters models upstream, through choices on system boundaries, aggregation, objectives, constraints, policy instruments, and scenario design. We develop a diagnostic mapping that translates justice concerns into modeling entry points and distinguishes representational choices from pathway-selecting levers. Illustrated through MEDEAS-W and CLEWs-OSeMOSYS, the approach shows how different model architectures condition equity-oriented choices and offers a transferable procedure for making these choices more transparent, auditable, and open to stakeholder scrutiny.