Optimal Decarbonization Pathways for South Africa’s 2030 Nationally Determined Contribution Targets

Abstract

South Africa’s updated Nationally Determined Contribution sets a 2030 emissions ceiling of 420 MtCO2. Using historical data from 2000 to 2023 and projections to 2050, this study identifies optimal decarbonization pathways by integrating logistic decay model, linear programming, genetic algorithm optimization (Decay–LP–GA), and Pareto analysis. A prior study notes that 2023 emissions lie substantially below the NDC ceiling, leaving 239.1 MtCO2 of unused carbon space. However, the present study finds that optimized pathways transcend rather than utilize this space, achieving 67–85% emissions below 2023 levels. Notably, aggressive near-term coal phase-out increases 2050 emissions by disrupting efficiency investment, indicating that timing governs long-term outcomes. The optimal strategy therefore prioritizes slow near-term coal reduction (0.69% annually) to allow front-loaded efficiency gains (4.46% annually) through 2035, followed by accelerated phase-out to achieve 96% reduction by 2050. This sequencing reduces cumulative emissions by 8.0% (300 MtCO2) relative to the LP minimum. The Pareto frontier spans 51.5–92.6 MtCO2 in 2030 and 52.8–64.2 MtCO2 in 2050, with all Pareto-optimal solutions requiring coal shares below 40% by 2030, conflicting with Integrated Resource Plan constraints. Consequently, maintaining a ≥40% coal floor raises minimum feasible emissions to 101.5 MtCO2, generating a 22.8–49.4 MtCO2 feasibility gap. The findings show that optimal strategy is not to use its remaining carbon space, but to render the 420 MtCO2 target redundant through front-loaded efficiency gains and strategically timed coal phase-out, providing clear direction for sustainable climate finance.