Divergence in International Shipping CO ₂ Emissions across Economies from an Export Perspective

International shipping plays a vital role in global trade but remains a significant source of CO₂ emissions, posing challenges for global climate goals. This study systematically investigates the evolution of shipping CO₂ emissions associated with countries' maritime export trade from 1995 to 2021 using a trade-driven approach and evaluates disparities in national emission patterns. Results show a shift from a high-income dominance toward a more balanced distribution, with growing contributions from upper-middle-income and emerging economies. While the global average GDP-normalized shipping emission intensity declined by 33.6% during the study period, substantial variations exist across economies. Middle-income countries once exhibited nearly twice the GDP-based emission intensity of high-income economies, but this gap has narrowed with economic diversification. Per capita shipping emissions saw only modest growth globally, yet differences across countries remain pronounced. High-income countries account for over half of global emissions despite representing only 15% of the world's population, maintaining persistently above-average per capita levels. Major emitters─including the United States, Australia, Brazil, and China─show striking contrasts: Australia records both GDP- and population-normalized intensities well above the global average, whereas China's values fall below it, underscoring structural inequities in the distribution of the shipping-related carbon burden. These findings highlight persistent disparities in maritime emissions and underscore the need for a differentiated, multimetric framework to guide equitable responsibility allocation.