WASHINGTON – Total U.S. greenhouse gas emissions, led by the decrease in carbon dioxide, fell by 1.2 percent in 2001, from 1,907 million metric tons of carbon equivalent in 2000 to 1,883 million metric tons of carbon equivalent in 2001, according to the Emissions of Greenhouse Gases in the United States 2001 report.
The 2001 decline of 1.2 percent is in contrast to the average annual growth rate of 1.3 percent observed from 1990 to 2000, and was enough to reduce the growth from 1990 to 2001 to an average of 1 percent per year.
The 1.2-percent decline in total greenhouse emissions in 2001 is the largest decrease for the 1990 to 2001 period, and twice the level of the only other decrease in total emissions for the time period, which was the 0.6 percent decline in 1991.
Estimates. Estimated emissions of carbon dioxide in the United States and its territories, which account for more than 80 percent of total U.S. greenhouse gas emissions, decreased by 1.1 percent in 2001.
The decline in carbon dioxide emissions of 1.1 percent was the largest annual decline of the 1990 to 2001 period.
The decline in carbon dioxide emissions can be attributed to a combination of the following factors: a reduction in economic growth from 3.8 percent in 2000 to 0.3 percent in 2001; a 4.4-percent reduction in manufacturing output that lowered industrial emissions; warmer winter weather that decreased the demand for heating fuels; and a drop in electricity demand that reduced the growth in emissions from electricity generation.
The drop in electricity demand can be attributed primarily to the slowing economy and the downturn in manufacturing. These economic factors were enough to more than compensate for the warmer summer that increased air-conditioning demand and related electricity consumption.
Greenhouse gas. Detailed information by greenhouse gas includes the following:
* Estimated methane emissions, the second largest contributor after carbon dioxide to total greenhouse emissions, declined by 1.1 percent.
Since 1990, U.S. methane emissions have declined by 11.6 percent.
* Estimated nitrous oxide emissions in 2001 fell by 1.0 percent. Nitrous oxide emissions have grown by 3.2 percent since 1990.
* Emissions of human-made gases such as hydrofluorocarbons, perfluorocarbons, and sulfur hexaflouride experienced a 7.7 percent decrease between 2000 and 2001.
However, these gases as a group have grown by 24.0 percent since 1990.
Energy consumption. The report also contains estimates of carbon dioxide emissions from energy consumption, including emissions from purchased electric power, on a sectoral level:
* Transportation-related carbon dioxide emissions, which account for about a third of the total carbon dioxide emissions from energy consumption, increased by 0.8 percent in 2001 as year-end travel disruptions and a slowing economy dampened growth.
* Carbon dioxide emissions in the residential sector decreased by 1.0 percent while emissions in the commercial sector rose by 1.9 percent.
A warm winter dampened heating demand in both sectors, but the economic growth that did occur was focused primarily in the service sector of the economy and was therefore reflected in commercial sector activity.
* In large part due to slowing GDP growth (0.3 percent), energy related industrial carbon dioxide emissions in 2001 declined by 5.4 percent. Particularly hard hit was the manufacturing sector which declined by 4.4 percent in total output, and specific industries such as Primary Metals, where output declined by 11.4 percent.
* Carbon dioxide emissions from the U.S. electric power sector in 2001, which are included in the sectoral totals above, are estimated at 612 million metric tons carbon equivalent, 1.5 percent below the 2000 level.
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