Justice Dimensions in Climate Mitigation Scenarios: Insights from Marine Carbon Dioxide Removal

Marine carbon dioxide removal (mCDR) is increasingly included in integrated assessment model (IAM) scenarios, particularly in pathways that allow for temperature overshoot or delayed emissions reductions. While these scenarios explore the technical contribution of mCDR to long-term climate targets, they often leave implicit key assumptions about where deployment occurs, over what time horizons climate benefits are realized, and who bears responsibility for long-term oversight and risk.

This contribution presents ongoing research that applies a justice-informed framework to the interpretation of mitigation scenarios including mCDR, using justice as an internal evaluative dimension rather than an external critique of models. Drawing on recent work in justice-oriented scenario analysis, the framework specifies justice concerns along three axes: spatial scale, temporal scale, and the scope of affected entities.

Spatially, the analysis examines how scenario representations obscure the geographic distribution of mCDR deployment and governance responsibility, with particular attention to transboundary impacts and implications for regions with limited regulatory capacity, many of which are located in the Global South. Temporally, the framework assesses whether assumed climate benefits are aligned with the durability of storage and the long-term monitoring and liability obligations imposed on future generations, highlighting intergenerational justice concerns. Finally, where scenarios imply large-scale or irreversible impacts on marine ecosystems, justice-based assessment is complemented by environmental ethical considerations that extend beyond an exclusively anthropocentric focus.

Using selected overshoot and net-zero pathways as illustrative cases, the paper shows how mitigation scenarios may appear technically coherent while relying on ethically fragile assumptions about governance capacity, permanence, and long-term responsibility. By making these assumptions explicit and comparable across scenarios, the contribution aims to support closer integration of social science and normative insights into climate modeling, improving the transparency and policy relevance of scenario-based assessments of emerging mitigation options such as marine CDR.