Imbalance of carbon emissions embodied in the US-Japan trade: temporal change and driving factors

In US-Japan trade, Japan ran both economic export surplus and export CO2 emission surplus with the US. Positive net monetary exports for Japan were actually a kind of economic losses of the US, while positive net export CO2 emissions, or net CO2 emissions embodied in US-Japan trade, were regarded as pollution transfer from U.S. to Japan. However, due to lack of unified measurement units and standards between the two research fields, it is difficult to directly assess whether positive effects of U.S. via carbon transfer outweigh negative effects caused by economic losses. The study transforms absolute values of net monetary exports and net export CO2 emissions from 2000 to 2011 in US-Japan trade into two ratios: the ratio of net monetary exports to GDP of U.S. and the ratio of net embodied CO2 emissions to total CO2 emissions of the US. By comparison, the result shows that on average, net monetary exports between U.S. and Japan accounted for 0.45% of American GDP, while ratio of net export emissions to aggregate consumption-based CO2 emissions of U.S. kept about 0.20% during the research period concerned, which indicated that negative effects of economic losses in U.S. outweighed positive effects via carbon transfer in US-Japan trade. Furthermore, a structural analysis of CO2 emissions embodied in US-Japan trade during the 11 years is given. The most significant driver was emission coefficients, defined as CO2 emissions per unit of energy consumption. The driving force of emission coefficients led to dramatic reduction in CO2 flows from Japan to the US and thus caused decrease of net export emissions, which also explained the major reason for the low ratio of export emissions to total CO2 emissions of the US. Finally, according to sectoral distributions of CO2 flows between Japan and the US, emission sources of two countries presented different characteristics. •Aimed to uncover economic and environmental loss and gains in US-Japan trade.•Economic losses of U.S. outweighed its environmental benefits via carbon transfer with Japan.•Emission coefficients contribute most to CO2 emissions embodied in US-Japan trade.•Manufacturing in Japan exports more than half of whole embodied CO2 emissions to the US.•Sectoral distributions of export CO2 emissions in U.S. are more balanced than that of Japan.