China's commitment to the UN's 2030 Agenda and the SDGs, coupled with its ambitious pledge to achieve carbon neutrality by 2060, necessitates the exploration of effective climate mitigation pathways (CMPs). Existing research has examined the relationship between climate change mitigation and specific SDGs or a limited set of indicators. However, a comprehensive analysis assessing the impact of CMPs on all 17 SDGs is lacking. This study addresses this gap by investigating the broad socioeconomic and environmental consequences of various CMPs on all SDGs, aiming to identify a cost-effective pathway that maximizes sustainability co-benefits. The importance of this study lies in providing crucial insights for policymakers in China to design effective strategies that align carbon neutrality with long-term sustainable development, given China's current gaps in achieving the SDGs, particularly in the environmental dimension. The research uses the iSDG-Climate-China model, an integrated system dynamics model built upon the core iSDG model, but enriched with new climate mitigation interactions and calibrated with Chinese historical data to accurately reflect the country's unique context.

Existing literature highlights the linkages between climate change mitigation and the SDGs. Many studies focus on the nexus between climate action and specific sustainability aspects, such as poverty, inequality, food security, health, water resources, economic costs, and biodiversity. While some studies utilize quantitative methods (integrated assessment models) to assess linkages between climate mitigation and multiple SDGs at global and regional levels, most studies only consider a limited set of indicators and interlinkages. This research addresses the limitations of previous studies by examining the impacts of CMPs on all 17 UN SDGs and by designing a cost-effective pathway to maximize sustainability co-benefits associated with emissions reduction.

The study utilizes the iSDG-Climate-China model, an integrated system dynamics model developed from the core iSDG model. This model was enhanced by incorporating new climate mitigation interactions, such as the effects of carbon capture and storage (CCS) on CO2 emissions and PM2.5 atmospheric concentration on PM2.5-related premature mortality. The model was calibrated using China's historical data and encompasses 30 sectors across the economy, society, and environment. Nine commonly used CMPs with diverse assumptions were selected, covering energy efficiency, energy mix, and negative emissions (LULUCF and CCS). To explore additional policy options, 180 bundled CMPs were created by combining policies from the nine original CMPs. The Reference pathway represents a business-as-usual scenario. The model assesses the performance of each pathway against all SDG indicators, quantified by a normalized score from 0 to 100. Socioeconomic assumptions were based on a tailored version of SSP2. The SDG-emissions-cost index was developed to assess the overall performance considering sustainability, CO2 emissions, and mitigation costs.

The results show that implementing mitigation policies significantly promotes SDG achievement. Synergistic impacts outweighed trade-offs, leading to an overall improvement in SDG scores across all scenarios compared to the Reference pathway. The magnitude of improvement varied among CMPs, with the Updated NDC to Carbon Neutrality CMP performing best in the long term (2060), while the NET-led CMP performed best in the short term (2030). The Below 2°C CMP performed worst in both timeframes. Analysis of individual SDGs revealed improvements in environmental goals (SDGs 6, 7, 12, 13, 15) and socioeconomic goals (SDGs 1, 2, 9, 11), primarily driven by improved energy access, reduced pollution, increased energy efficiency, and sustainable agriculture. However, some trade-offs were observed, particularly in SDGs 10, 14, and 17 (inequality, life below water, and partnerships), mainly due to economic costs. Bundled CMPs demonstrated greater synergies, with the EEmature, EMRE-led, LULUCF1.65, and CCS2 CMP achieving the most remarkable progress. The cost-effective CMP (EEmature, EMRE-led, LULUCF1.65, and CCS2) balanced sustainability, CO2 emissions, and economic costs, achieving the highest SDG-emissions-cost index (76.15 by 2060), with substantial improvements in overall SDG scores, CO2 reduction, and a relatively low mitigation cost. Uncertainty analysis considering various energy efficiency levels and five tSSPs confirmed the robustness of the findings, with the cost-effective CMP consistently outperforming others.

The study's findings underscore the significant potential of climate mitigation policies to advance sustainable development in China. The synergies between climate action and various SDGs outweigh the trade-offs, highlighting the potential for integrated policy design. The identification of a cost-effective CMP provides policymakers with a valuable tool for balancing sustainability goals with economic realities. The results emphasize the importance of comprehensive policy approaches that consider the interconnectedness of economic, social, and environmental factors. The cost-effective CMP, while achieving substantial progress, also highlights potential conflicts regarding water and land resource use, necessitating careful management to prevent unintended consequences. The study's implications extend beyond China, providing a framework for other countries to assess their climate mitigation pathways and their effects on SDG achievement.

This research provides a comprehensive assessment of the impact of various CMPs on SDG achievement in China. The identification of a cost-effective CMP that maximizes sustainability co-benefits offers valuable guidance for policymakers. Future research should focus on incorporating aspects like carbon trading schemes, carbon pricing, and transnational climate financing into the model to enhance its scope and accuracy. Furthermore, a more detailed cost analysis of mitigation technologies and a broader assessment of carbon sinks would further refine the model’s capabilities. The iSDG-Climate-China model itself offers a valuable framework for other countries to analyze their unique circumstances.

The study's limitations include the partial coverage of future uncertainties in the CMP scenarios (e.g., exclusion of carbon trade schemes and transnational climate financing), a potentially incomplete estimation of mitigation costs, and the focus on forests as the primary carbon sink. The iSDG-Climate-China model, while comprehensive, is a simulation model and therefore, results should not be interpreted as precise predictions. The model's reliance on specific assumptions and data also limits the generalizability of some findings.