Shahid Beheshti University International Journal of New Political Economy 3060-6233 Articles in Press 2026 06 09 Investigating the impact of water, energy, and greenhouse gas uncertainty on investment returns: Application of fuzzy regression (Iran case study) 107076 10.48308/jep.2026.243351.1264 EN Reza Ashraf Ganjoei Assistant Professor, Economics Department, Faculty of Economics and Management, University of Sistan and Baluchestan, Sistan and Baluchestan, Iran. 0000-0003-3854-8445 Mahboobeh Khadem Nematollahy Ph.D of Econometrics, Faculty of Economics. Allameh Tabatabai University, Tehran, Iran 0000-0002-8340-0127 Teymour Mohammadi Faculty Member of Economics, Allameh Tabataba'i University, Tehran, Iran 0000-0003-4394-774X Journal Article 2026 01 30 This study employs a fuzzy logic-based approach to estimate the impact of uncertainty in key sustainability-related sectors—namely water, energy, waste, greenhouse gas (GHG) emissions, and debt-to-capital ratio—on return on investment (ROI) over the period from 1993 to 2024. Given the inherently imprecise and dynamic nature of environmental and financial variables, fuzzy logic provides a robust framework to model vagueness and ambiguity in data. The analysis integrates longitudinal data across global markets, incorporating fuzzy sets to represent uncertain input variables and their nonlinear relationships with ROI. Results indicate that increased uncertainty in water and energy usage, as well as higher GHG emissions and waste production, negatively influence ROI, particularly when coupled with elevated debt-to-capital ratios. However, the application of sustainable practices that reduce these uncertainties can lead to more stable and higher investment returns. The findings offer strategic insights for investors and policymakers aiming to balance economic performance with environmental and financial risks. They also highlight the importance of investments needed to meet regulatory requirements, which are the main drivers for organizations at the financial level.