Optimization of Carbon Emission Reduction Task Allocation in China (2020–2030): A Cost-Based Inter-Provincial Cooperation Mechanism

Driven by the global mandates of the United Nations Sustainable Development Goals (particularly SDG 13 and SDG 17) and the climate targets established at COP summits, China strives to achieve its carbon peaking target by 2030 but faces significant challenges due to substantial regional disparities in abatement capacities. This paper proposes a cost-based inter-provincial cooperation mechanism to optimize carbon emission reduction (CER) task allocation. Using a marginal abatement cost curve model, we simulate provincial CER tasks from 2020 to 2030 under various cooperation scenarios. The results indicate that: (1) Cooperation significantly reduces the national total abatement cost compared to independent implementation. Specifically, the cost-saving ratio can reach approximately 60–70% when the cooperation proportion is high (80%). (2) There is a trade-off between economic efficiency and regional peaking targets. While an 80% cooperation proportion is economically optimal for 2020–2028, and a 60% proportion for 2029–2030, a 40% cooperation proportion is ultimately recommended as the balanced optimal ratio to ensure that most provinces achieve their carbon peaks before 2030. (3) The mechanism effectively narrows the disparity in abatement costs across regions. By offering a scalable paradigm for inter-regional climate collaboration, this study provides a theoretical basis for designing differentiated cooperation strategies to fulfill COP commitments and advance the global SDGs.