Equity assessment of global mitigation pathways in the IPCC Sixth Assessment Report

This paper analyses 556 model scenarios assessed by IPCC's Working Group-III for the 6th Assessment Report, which have an underlying 10-region classification and correspond to restricting warming levels to 1.5 ℃ and 2 ℃. We show that across all scenarios, the current global inequalities in incomes, energy use, and emissions, are projected to continue even in 2050. Scenarios also project higher per capita fossil fuel use and lower carbon dioxide removal in developed countries in 2050 compared to developing countries. Our results demonstrate the scale and scope of unequal outcomes in these scenarios, that have been anticipated by theoretical critiques of the underlying models. The paper explores the potential reasons for the unequal outcomes of the scenarios focusing on the two key issues of scenario design and modelling framework. Our analysis also suggests that instead of summary assessments focusing on singular median values or percentile ranges, as undertaken in the IPCC report, more could be learned from focusing on differences between models or considering outliers that could present new and innovative solutions to the determination of equitable and efficient future mitigation pathways. Our analysis underlines the need for new frameworks for emissions modelling and scenario building, for constructing possible futures that can also foreground equity and climate justice.