Emissions of Greenhouse Gases in the United States 2003
Carbon Dioxide
The preliminary estimate of U.S. carbon dioxide emissions from both energy consumption and industrial processes in 2003 is 5,870.2 million metric tons, which is 0.8 percent higher than in 2002 (5,824.8 million metric tons) and accounts for 84.6 percent of total U.S. greenhouse gas emissions. U.S. carbon dioxide emissions have grown by an average of 1.3 percent annually since 1990. Although short-term changes in carbon dioxide emissions can result from temporary variations in weather, power generation fuel mixes, and the economy, growth in carbon dioxide emissions in the longer term results largely from population- and income-driven increases in energy use, as well as consumer choices of energy-using equipment. The “carbon intensity” of energy use (carbon dioxide emissions per unit of energy consumed) can also influence trend growth in energy-related carbon dioxide emissions.
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Figure ES2 shows recent trends in some common indexes used to measure the carbon intensity of the U.S. economy. Carbon dioxide emissions per unit of gross domestic product (GDP) have continued to fall relative to 1990; by 2003, this measure was 19.4 percent lower than in 1990. Carbon dioxide emissions per capita, however, were 0.6 percent above 1990 levels in 2003. Population growth and other factors resulted in increased aggregate carbon dioxide emissions per year from 1990 through 2003 (a total increase of 17.6 percent). Carbon dioxide emissions per unit of net electricity generation in 2003 were 0.4 percent higher than in 2002.
EIA divides energy consumption into four general end-use categories: residential, commercial, industrial, and transportation. Emissions from electricity generators, which provide electricity to the end-use sectors, are allocated in proportion to the electricity consumed in, and losses allocated to, each sector. Figure ES3 illustrates trends in carbon dioxide emissions by energy consumption sector. Average annual growth rates in carbon dioxide emissions by sector during the 1990-2003 period were 2.2 percent for the commercial sector, 1.9 percent for the residential sector, and 1.4 percent for the transportation sector. Industrial sector carbon dioxide emissions, after peaking in 1997, are now below their 1990 level.
In the residential sector, total carbon dioxide emissions were up by 1.7 percent, from 1,193.9 million metric tons in 2002 to 1,214.8 million metric tons in 2003. The increase is attributed mainly to a 4.1-percent increase in residential natural gas consumption due largely to colder winter weather that increased heating degree-days by 4.0 percent. Residential sector emissions attributable to purchased electricity also rose by 1.0 percent, and emissions from petroleum products increased by 1.9 percent.
Carbon dioxide emissions in the commercial sector increased by 0.6 percent, from 1,019.8 million metric tons in 2002 to 1,025.7 million metric tons in 2003. Emissions attributable to purchased electricity increased by 0.4 percent, from 793.9 million metric tons in 2002 to 796.7 million metric tons in 2003. Carbon dioxide emissions from the direct combustion of fossil fuels, primarily natural gas, in the commercial sector rose from 225.9 million metric tons in 2002 to 229.0 million metric tons in 2003, a 1.3-percent increase.
Energy-related carbon dioxide emissions in the industrial sector in 2003 are estimated at 1,666.2 million metric tons, which is slightly less than the level of emissions in 1990. After peaking in 1997 at 1,800.1 million metric tons, industrial emissions have generally fallen, with the exception of a slight upturn in 2000.
Industrial energy consumption and carbon dioxide emissions are concentrated in a few energy-intensive industries, and the output of the energy-intensive industries tends to be closely correlated with the industrial sector’s total carbon dioxide emissions. Among the six energy-intensive industry groups, which traditionally account for about 65 to 70 percent of total industrial carbon dioxide emissions and 80 percent of carbon dioxide emissions from manufacturing, changes in output were mixed in 2003, with production increases in three and decreases in the other three. Declines in output were seen in 2003 for primary metals (-2.3 percent), chemicals (-1.5 percent), and food (-3.6 percent), while increases in output were seen for paper (5.1 percent), nonmetallic minerals (0.9 percent), and petroleum refining (1.5 percent). Although the paper industry showed robust growth in 2003, the manufacture of paper produces relatively small amounts of carbon per energy consumed, because much of the energy used is supplied by wood waste, and the resulting emissions are part of the natural carbon cycle. By fuel type, industrial sector carbon dioxide emissions rose for purchased electricity (1.9 percent), coal (1.2 percent), and petroleum (2.2 percent), while emissions from natural gas fell by 6.3 percent. Because of the large decrease in emissions from natural gas use, total industrial emissions fell despite increases in emissions from the other three energy sources.
Carbon dioxide emissions in the transportation sector, at 1,874.7 million metric tons, were 0.5 percent higher in 2003 than in 2002 (1,866.0 million metric tons). Emissions of carbon dioxide from gasoline consumption (61.0 percent of transportation sector emissions) grew by 0.4 percent, while emissions from jet fuel use for air travel fell by 2.5 percent. Carbon dioxide emissions from distillate fuel use grew by 3.6 percent in 2003. Transportation sector carbon dioxide emissions have grown by an average of 1.4 percent annually since 1990.
Carbon dioxide emissions from the U.S. electric power sector increased by 1.0 percent (22.9 million metric tons), from 2,256.4 million metric tons in 2002 to 2,279.3 million metric tons in 2003. Carbon dioxide emissions from the electric power sector have grown by 27.5 percent since 1990, while total carbon dioxide emissions from all energy-related sources have grown by 16.0 percent. Carbon dioxide emissions from the electric power sector represented 39.4 percent of total U.S. energy-related carbon dioxide emissions in 2003; however, as noted above, in calculating emissions from the end-use sectors EIA distributes electric power sector emissions to the four sectors in proportion to their respective shares of total electricity purchases. Therefore, electric power emissions are already included in the sectoral totals.
By fuel, emissions from natural gas use for electricity generation in 2003 were down by 10.1 percent from 2002, emissions from coal use were up by 1.8 percent, and emissions from petroleum use were up by 25.8 percent. The increases in coal- and petroleum-fired generation, at the expense of natural-gas-fired generation, reflect the rapid rise in natural gas prices in 2003 (52.2 percent), while coal and petroleum prices increased by 1.6 and 29.0 percent, respectively. Petroleum-fired generation is a small component of total electricity generation in the United States.