A synthesis of carbon in international trade

[摘要] In a globalised world, the transfer of carbon between regions, eitherphysically or embodied in production, represents a substantial fraction ofglobal carbon emissions. The resulting emission transfers are important forbalancing regional carbon budgets and for understanding the drivers ofemissions. In this paper we synthesise current understanding in two parts:(1) CO₂ emissions embodied in goods and services that are produced inone country but consumed in others, and (2) carbon physically present infossil fuels, petroleum-derived products, harvested wood products, crops, and livestock products. We describe the key differences between studies and provide aconsistent set of estimates using the same definitions, modelling framework,and consistent data. We find the largest trade flows of carbon ininternational trade in 2004 were fossil fuels (2673 MtC, 37 % of globalemissions), CO₂ embodied in traded goods and services (1661 MtC, 22 %of global emissions), crops (522 MtC, 31 % of total harvested cropcarbon), petroleum-based products (183 MtC, 50 % of their totalproduction), harvested wood products (149 MtC, 40 % of total roundwoodextraction), and livestock products (28 MtC, 22 % of total livestockcarbon). We find that for embodied CO₂ emissions, estimates fromindependent studies are robust, and that differences between individualstudies are not a reflection of the uncertainty in consumption-basedestimates, but rather these differences result from the use of differentproduction-based emissions input data and different definitions forallocating emissions to international trade. After adjusting for theseissues, results across independent studies converge to give less uncertaintythan previously assumed. For physical carbon flows there are relatively fewstudies to be synthesised, but differences between existing studies are dueto the method of allocating to international trade, with some studies using"apparent consumption" as opposed to "final consumption". While resultsacross studies are sufficiently robust to be used in further applications,more research is needed to understand differences and to harmonisedefinitions for particular applications.

[学科分类] 地球化学与岩石