Emissions of CO2 - from Gas Fuel Consumption (CDIAC): Annual estimations of CO2 emissions from gas Gas Fuel Consumption, primarily derived from U.N. data. Thereafter supplemented with data from the U.S. Department of Energy's Energy Information Administration, Rotty (1974), and with a few national estimates provided by G. Marland. For information about the data collection methodology used by Rotty (1974) and G. Marland see http://cdiac.esd.ornl.gov. The sum of emissions estimates for all countries is not equal to the estimate of global total emissions because : 1. The global total includes emissions from bunker fuels (i.e., fuels used by ships and aircraft during international trade) whereas these are not included in any national totals. 2. The global total includes estimates for the oxidation of non-fuel hydrocarbon products (e.g., asphalt) whereas national totals do not. 3. National totals include annual changes in fuel stocks whereas the global total does not. 4. Due to statistical differences in the international statistics, the sum of exports from all exporters is not identical to the sum of imports by all importers.