The Paris Agreement aims to limit global warming, but its implementation must consider the UN Sustainable Development Goals (SDGs). Achieving climate targets without compromising other sustainability dimensions is crucial. Previous studies have assessed national and regional SDG progress, but these often lack a climate change perspective and fail to project long-term indicator progress. This study addresses this gap by employing integrated assessment models (IAMs), which have evolved to incorporate broader sustainability considerations beyond climate action. While many studies focus on specific SDG aspects, a holistic, multi-model assessment across numerous SDGs remains limited. The European Union (EU), being a leader in climate action but facing SDG challenges, provides a suitable case study to understand the interplay between climate policies and broader sustainability. The EU's internal heterogeneity and policy harmonization framework offer a unique opportunity for a detailed analysis of national-level SDG progress. This research uses a diverse ensemble of nine IAMs to offer a robust, multi-faceted analysis of the impact of decarbonization pathways on SDG progress in the EU and its member states, achieving greater geographic granularity than prior studies.

Several studies have quantitatively assessed national and regional progress toward the SDGs using available data and indicator gaps. However, these lack a climate target orientation and ignore policy gaps. IAMs, initially designed for GHG emission reduction pathway projections, have expanded to incorporate sustainability aspects, with some focusing on poverty and inequality, land use, water access, health impacts of pollution, and biodiversity risks. Yet, most IAM studies have focused on energy, industry, and infrastructure, neglecting broader social and environmental dimensions. Soergel et al. provided a global assessment of climate change mitigation across a wide range of SDGs, but regional assessments, particularly focusing on the EU, were limited. This paper fills this gap.

This study employs a multi-model assessment framework comprised of nine IAMs: GCAM (partial equilibrium), GEMINI-E3 and ICES-XPS (computable general equilibrium), NEMESIS (macroeconometric), EU-TIMES (energy system), FORECAST and ALADIN (sectoral). GCAM is coupled with TM5-FASST (atmospheric model) and HECTOR (global climate carbon-cycle model) to assess health and environmental impacts. The models cover various socioeconomic, climate, and resource dimensions of the SDGs. A harmonized scenario design process minimizes outcome gaps due to differing model structures, using socioeconomic parameters from the 2018 Ageing Report, and historical emissions and climate policy data from the literature. The study focuses on three scenarios: Current Policies, NZE Benchmark (most cost-efficient net-zero pathway), and NZE Policy Standard ('Fit for 55' policy package). 32 indicators across 15 SDGs (excluding SDGs 5 and 16 due to model limitations) are analyzed, normalized to a 0-100 scale using benchmarks from SDG targets, previous studies, or model value distributions. Indicator outcomes are averaged across models. National SDG indices are computed by averaging normalized indicators within each SDG and then across all SDGs for each country.

Under the Current Policies scenario, the EU+ would see improvements in several SDGs by 2050, including increased wealth, reduced poverty and inequality, improved education, higher life expectancy, increased renewable electricity shares, and reduced carbon footprints. However, there may be some negative effects from mitigation strategies, such as increased natural resource depletion. NZE scenarios show further improvements in health and agricultural productivity due to decreased air pollution and reduced crop losses from ozone. However, there are negative impacts, such as a reduction in GDP (around 0.4–0.9%), increased poverty, hunger, and higher food prices. The NZE Benchmark scenario, prioritizing cost efficiency, performs slightly better than the NZE Policy Standard, although the latter exhibits more ambitious sectoral decarbonization and stronger air pollution reductions. Model variance was most apparent in water prices, renewable electricity shares, GDP growth, and transport CO2 intensities, reflecting different model structures and technology assumptions. Analyses on the Member State level reveal that while countries like Poland, Sweden, and Finland may experience declines in specific indicators due to increased mitigation costs, overall, ambitious climate policies significantly reduce SDG achievement gaps, especially for current laggards. This highlights the potential for mitigation policies to not only improve environmental sustainability but also bridge SDG performance disparities between EU member states. There is a clear trade-off between socioeconomic and environmental goals, particularly evident in economic indicators such as GDP and poverty/hunger, even in the cost-efficient NZE scenario. This emphasizes the need for complementary policies to mitigate negative impacts.

The findings demonstrate that while ambitious climate policies yield significant co-benefits for the environment and some socioeconomic indicators, particularly for countries currently lagging in SDG achievement, they also bring potential trade-offs requiring attention. The study highlights the need for complementary policies to address these trade-offs, such as using carbon tax revenues for social support and investing in low-carbon technologies. These corrective measures can help achieve both climate and broader SDG goals. The results suggest that the Paris Agreement goals are achievable with targeted policies based on ex-ante analyses. While the study focuses on mitigation co-benefits, it does not quantify the cost of climate damages avoided, which could substantially alter the cost-benefit balance. The use of a multi-model ensemble enhances the robustness of the results by accounting for model-specific uncertainties. However, there is a possibility of underestimating SDG outcomes in NZE scenarios and overestimating those in Current Policies due to the lack of climate damage costs.

This study provides a comprehensive, multi-model assessment of the impacts of EU decarbonization pathways on SDGs. It highlights the co-benefits of ambitious climate action but also underscores the need for complementary policies to mitigate negative socioeconomic impacts. Future research should refine the models, broaden SDG coverage, and integrate assessments of climate change impacts to provide more realistic scenarios for policymaking. Further scenarios should incorporate SDG-related policies.

The study acknowledges several limitations: the exclusion of SDGs 5 and 16 due to model limitations, the potential underestimation of SDG outcomes in NZE scenarios and overestimation in Current Policies due to the exclusion of climate change damages, and the reliance on a specific set of models and scenarios which could influence the results. While a multi-model ensemble was used to reduce uncertainty, further enhancement could involve the use of sensitivity analysis or portfolio theory to strengthen the robustness of the findings.