Emission intensity of trade

Understanding the emission intensity of trade between countries is crucial for assessing the carbon footprint of international shipping within specific geopolitical or economic contexts. This has been explored before in the work of Wang et a. (2021), “Trade-linked shipping CO₂ emissions” that has pointed to a potential unfairness if allocating shipping emissions responsibility to bilateral traders due to external beneficiaries.

By quantifying how much CO₂ is emitted per unit of trade exchanged between nations, we can identify trade routes or country-pairs that contribute disproportionately to shipping emissions. In particular, country-level analysis helps reveal how trade dependencies and supply chains shape emission patterns.

We present emission intensity for country pairs agreggated in different ship types and different units, each providing a distinct lens on the environmental performance of maritime transport. One metric is emissions per unit of cargo (i.e. kg CO₂ per tonne), which reflects the emissions of transporting a given mass of goods and is useful for understanding the emissions embodied in specific product flows. The other metric is emissions per unit of transport work (i.e. grams CO₂ per tonne-nautical mile), which accounts not just for cargo mass but also for distance traveled. This latter unit provides a more precise assessment of shipping efficiency and allows comparison across routes and vessel types, making it especially relevant in lifecycle assessments and international benchmarking.