author(s)
Feyisayo Michael Ogunyemi

abstract
Global climate governance increasingly depends on transparent, consistent, and verifiable carbon accounting systems capable of supporting international mitigation efforts and corporate decarbonization strategies. As multinational corporations expand their operations across jurisdictions with differing regulatory expectations, the need for harmonized carbon accounting frameworks has become more urgent. Existing methodologies including the Greenhouse Gas (GHG) Protocol, ISO 14064 standards, and newer mandatory disclosure regimes provide structured approaches for quantifying and reporting emissions, yet diverge in their scopes, boundaries, verification requirements, and treatment of value chain emissions. These variations create reporting inconsistencies, hinder comparability, and increase compliance burdens for global enterprises managing multi-regional carbon footprints. This paper provides a detailed comparative analysis of the GHG Protocol, ISO 14064, and emerging regulatory frameworks such as the EU Corporate Sustainability Reporting Directive (CSRD), the U.S. SEC climate disclosure rules, and anticipated frameworks under the International Sustainability Standards Board (ISSB). The discussion highlights methodological alignment and divergence across emissions categorization, data quality thresholds, assurance expectations, and treatment of Scope 3 value chain emissions areas where multinational corporations face the greatest technical and governance challenges. The study further examines how the lack of global harmonization affects enterprise-level carbon strategy, including risk management, investment planning, and supply chain decarbonization. Finally, the paper proposes a harmonization pathway grounded in common definitional baselines, interoperable reporting structures, and cross-standard verification protocols. These recommendations aim to support multinational corporations seeking consistent, scalable, and regulatory-compliant carbon accounting systems while enhancing global comparability and market transparency in emissions reporting.