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Carbon Dioxide The preliminary estimate of U.S. carbon dioxide emissions from both energy consumption and industrial processes in 2002 is 5,795.6 million metric tons, which is 0.8 percent higher than in 2001 and accounts for 84.5 percent of total U.S. greenhouse gas emissions. U.S. carbon dioxide emissions have grown by an average of 1.2 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, in the longer term their growth is driven by population, income, and consumer choices of energy-using equipment, as well as the “carbon intensity” of energy use (carbon dioxide emissions per unit of energy consumed).
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 GDP have continued to fall relative to 1990; by 2002, this measure was 17.7 percent lower than in 1990. Carbon dioxide emissions per capita were 0.1 percent above the 1990 level in 2001 and 0.1 percent below the 1990 level in 2002. Population growth and other factors resulted in increased aggregate carbon dioxide emissions per year from 1990 through 2002 (a total increase of 15.8 percent). Carbon dioxide emissions per unit of net electricity generation in 2002 were 1.6 percent lower than in 2001. Carbon dioxide emissions from the U.S. electric power sector (which includes utilities, independent power producers, and combined heat and power facilities whose primary business is the production and sale of electricity) in 2002 are estimated at 2,249.0 million metric tons, 1.0 percent higher than the 2001 level of 2,226.6 million metric tons. The 1-percent increase is less than the 2.7-percent increase in electricity generation during 2002 because of an increase in the average efficiency of natural-gas-fired power plants. Although total electricity generation from natural gas increased by 8.2 percent from 2001 to 2002, emissions from natural-gas-fired generators increased by only 3.4 percent, due to the improved efficiency of new natural-gas-fired combined-cycle generating units. Figure ES3 illustrates trends in carbon dioxide emissions by energy consumption sector. In general, emissions have increased steadily at the sectoral level since 1990. Average annual growth rates in carbon dioxide emissions by sector during the 1990-2002 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, have continued to fall and are now below 1990 levels. In the residential sector, total carbon dioxide emissions were up by 2.8 percent, from 1,160.8 million metric tons in 2001 to 1,193.0 million metric tons in 2002. The increase is attributed mainly to a 1.2-percent rise in natural gas use due to colder winter weather that increased heating degree-days by 1.4 percent. Emissions attributable to purchased electricity also rose by 3.3 percent, which also contributed to the overall increase in residential carbon dioxide emissions. Since 1990, residential carbon dioxide emissions have grown by an average of 1.9 percent annually. Carbon dioxide emissions in the commercial sector fell by 0.5 percent, from 1,018.3 million metric tons in 2001 to 1,012.9 million metric tons in 2002. Emissions attributable to purchased electricity decreased by 1.2 percent, from 791.1 million metric tons in 2001 to 781.8 million metric tons in 2002. Carbon dioxide emissions from the direct combustion of fossil fuels in the commercial sector, primarily natural gas, rose from 227.1 million metric tons in 2001 to 231.1 million metric tons in 2002, a 1.7-percent increase. Despite the slight decrease in 2002, commercial sector emissions of carbon dioxide have increased at an average annual rate of 2.2 percent since 1990. Energy-related carbon dioxide emissions in the industrial sector in 2002 are estimated at 1,673.7 million metric tons, which is approximately equal to the level of emissions in 1990. After peaking in 1997, industrial emissions have generally fallen with the exception of a slight upturn in 2000. Historically, industrial energy consumption and carbon dioxide emissions have been more sensitive to economic growth than to the weather. The most recent decline, in 2002, is a case in point: industrial emissions fell by 0.7 percent in 2002, coinciding with a 1.1-percent decrease in manufacturing output. Industrial energy consumption and emissions are concentrated in a few energy-intensive industries, and their performance is more closely correlated with carbon dioxide emissions than is the performance of the industrial sector as a whole. 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 2002 (see the text box in the full report, Chapter 2, page 20). Declines in output relative to 2001 were seen in 2002 for the primary metals and pulp and paper industries (-3.0 percent and -2.3 percent, respectively), while increases in output were seen for the chemicals industry (3.9 percent) and stone, clay and glass products (1.0 percent). Smaller increases in output were seen for the other energy-intensive industries: food (0.5 percent) and petroleum refining (0.5 percent). By fuel type, industrial sector carbon dioxide emissions from purchased electricity rose by 0.9 percent, while emissions from natural gas and coal fell by 2.0 percent and 6.9 percent, respectively. Carbon dioxide emissions from petroleum use in the industrial sector increased by 0.7 percent in 2002. Carbon dioxide emissions in the transportation sector, at 1,849.7 million metric tons, were 1.2 percent higher in 2002 than in 2001. Emissions of carbon dioxide from gasoline consumption (61.6 percent of transportation sector emissions) grew by 2.5 percent, while emissions from jet fuel use for air travel fell by 2.5 percent. Transportation sector carbon dioxide emissions have grown by an average of 1.4 percent annually since 1990. Released: October 2003 |
