Fossil Fuel Emissions Estimates for North America

Anthropogenic carbon dioxide (CO₂) emissions from fossil fuel sources, while dominated by direct combustion for heating and energy production, can be defined to include a diverse set of industrial and agricultural processes. These include CO₂ production from cement manufacturing, gas and oil flaring, fugitive emissions, nonfuel oxidation of hydrocarbons, solid waste combustion, soil emissions, and geothermal power production. There are two general classes of global inventories: 1) those defined geographically at the nation-state scale and 2) those that generate estimates at the regular grid-cell scale (e.g., 10 km, 1 degree). The latter often are derived from the former via downscaling techniques but also may use “bottom-up” data such as emissions estimates and coordinates for power plants or airports. The available (nation-state or gridded) inventories, detailed in this appendix, cover these sectors in differing ways that cannot be reconciled directly to a common basis. In addition to their varying sectoral coverage, methodological differences among the inventories can lead to additional sources of difference (Macknick 2014). Some of the inventories are based on fuel sales, and others on activities such as number of road miles driven. The First State of the Carbon Cycle Report (SOCCR1) “Part II Overview” chapter (Marland et al., 2007) provides a relevant discussion of different products and methodologies.

The varying sectoral definitions, resolutions, and methodological differences make direct comparisons challenging. For example, it is sometimes unclear whether country totals from different products include fuel usage for international marine and air transport (bunker fuels). However, the difficulties reconciling the definitions used by different products can be informative of practical uncertainty when used within atmospheric inversions or budget studies.