The analysis is based on fossil energy resources of coal, oil, natural gas, and secondary fuels traded among 57 industrial sectors and 112 countries in 2004 (Narayanan and Walmsley, 2009). We use the term "countries" to describe the spatial disaggregation of this data, though in some cases we intend collections of related countries. CO2 emissions produced in each country (production emissions) are calculated using country-, sector- and fuel-specific data of CO2 emissions per unit of energy. Using trade data, these emissions are traced back to the point of extraction, even if the extracted fuels were processed in and re-exported from an intermediate country (extraction emissions). The forward link from production emissions to where goods are consumed (consumption emissions) are based on a global multi-regional model that ties sector-level economic data with trade data (Davis and Caldeira, 2010).
The difference between production emissions and extraction emissions represents the net difference in emissions related to traded fuels, and therefore equals emissions from imported fuels less emissions from exported fuels. Emissions from burning of traded fuels are distinct from emissions embodied in traded goods, which are the emissions produced during manufacture of the goods. The net of emissions embodied in trade represents the difference between production emissions and consumption emissions. By combining emissions related to trade in fuels and goods, it is possible to examine the difference between extraction emissions and consumption emissions and follow the supply chain of emissions from where fuels are extracted to where dependent goods or services are ultimately consumed.
Data on international trade, economic input-output by sector, GDP, population, energy use and combustion-based CO2 emissions of each region-sector are all taken from Version 7.1 of the Global Trade Analysis Project (GTAP), which compiles the primary data from voluntary contributions of each region and harmonizes them to remove conflicts and inconsistencies (Narayanan and Walmsley, 2009).
Details of the Multiregional Input-Output Model (MRIO) used to calculate consumption emissions and the accounting model we developed to assess extraction emissions are available in the PNAS paper and its Supplemental Information (Davis, Peters and Caldeira, 2011).
Definition of Regions
The following list defines the regions of aggregated countries used in our analysis and presentations of the data: