Embodied Environmental Emissions in U.S. International Trade, 1997−2004

Significant recent attention has been given to quantifying the environmental impacts of international trade. However, the United States, despite being the world's largest emitter of greenhouse gases and having large recent growth in international trade, has seen little analysis. This work uses a multi-country input−output model of the U.S. and its seven largest trading partners (Canada, China, Mexico, Japan, Germany, the UK, and Korea) to analyze the environmental effects of changes to U.S. trade structure and volume from 1997 to 2004. It is shown that increased import volume and shifting trade patterns during this time period led to a large increase in the U.S.' embodied emissions in trade (EET) for CO₂, SO₂, and NO_x. Methodological uncertainties, especially related to uncertainties of international currency conversion, lead to large differences in estimation of the total EET, but we estimate that the overall embodied CO₂ in U.S. imports has grown from between 0.5 and 0.8 Gt of CO₂ in 1997 to between 0.8 and 1.8 Gt of CO₂ in 2004, representing between 9−14% and 13−30% of U.S. (2−4% to 3−7% of global) CO₂ emissions in 1997 and 2004, respectively.