An Integrated Evaluation of Climate Change and Environmental Sustainability in G20 Countries Using Advanced MCDM Methods

This study analytically assesses the climate change and environmental sustainability performance of G20 countries using data from the 2024 Climate Change Performance Index (CCPI) and Environmental Performance Index (EPI) reports. The analysis employs Sum-Weighted Information (SWI) and Ranking Alternatives with Weights of Criterion (RAWEC), which are Logarithmic Decomposition of Criteria Importance (LODECI)-based multi-criteria decision-making (MCDM) methods. The study created three separate decision matrices, taking into account the CCPI and EPI criteria individually, as well as their combination. The criterion weights were determined using the LODECI method; greenhouse gas emissions, climate policy, and air quality were the most significant criteria. The results show that China and Saudi Arabia demonstrate strong environmental performance in CCPI-based rankings, while Germany, the United Kingdom and France demonstrate strong performance in EPI-based evaluations. In the integrated analysis, Germany ranked first using both methods. The consistency of the rankings obtained using the SWI and RAWEC methods was high, which supports the reliability of the analyses. However, some differences in ranking were observed depending on the method used, the distribution of criteria and the country sample. Overall, the study emphasizes the pivotal role of methodological diversity and data-driven approaches in multidimensional environmental assessments for policy-making, while demonstrating the robustness of the findings through sensitivity and comparative analyses.