Estimates of Monthly CO2 Emissions from Fossil-Fuel Consumption in the U.S.A. The data from which these carbon-emissions estimates were derived are values of fuel consumed: in billions of cubic feet, for natural gas; in millions of barrels, for petroleum products; and in thousands of short tons, for coal. The resulting emissions estimates are expressed as teragrams of carbon. A teragram is 10^12 grams, or 10^6 metric tons. The fuel-consumption values were multiplied by their respective thermal conversion factors, which are in units of heat energy per unit of fuel (i.e., per cubic foot, barrel, or ton). In keeping with conventional usage in the United States, values are for the gross (higher) heating values of the respective fuels. The results are expressed in units of heat energy derived from the fuel. These energy values were then multiplied by their respective carbon dioxide emission factors, in units of the mass of carbon emitted per unit of energy liberated by the oxidation of the carbon in the fuel.