Greenhouse gas emissions have increased markedly since the pre-industrial era and are increasing at such a rate that their concentration in the atmosphere is producing a warming influence on the global climate. In order to make well-informed decisions on ways to reduce greenhouse gas emissions, it is important to understand how the different economic sectors contribute to the production of greenhouse gases, which sectors are relatively carbon dioxide (CO2) intensive, and how these patterns have evolved over time. This report from the US Department of Commerce analyzes energy-related CO2 emissions and intensities for 349 industries, Government (Federal, state and local), and Households from 1998 to 2006.
The primary findings of the report are as follows:
A large number of industries in the US have seen declines in emissions intensity over the past decade. These improvements at the industry level have contributed significantly to the overall pattern of greater emissions efficiency in the economy.
Energy-related CO2 emissions in the US increased more slowly than overall output growth during 1997 to 2007, indicating that the CO2 intensity of the economy declined. If not for these improvements in emissions efficiency, we estimate that CO2 emissions in the US would have been about 25% higher than actual emissions in 2007.
The Manufacturing sector was responsible for about one-quarter of total CO2 emissions in 2006, reducing its CO2 intensity between 1998 and 2006. The level of CO2 output as well as the gain in efficiency varies significantly within the Manufacturing sector. For example, between 1998 and 2006, Chemicals had a significant emissions efficiency gain, while Nonmetallic Mineral Products had an efficiency loss.
The Transportation Services sector, which accounts for about 15 percent of total emissions in the U.S., increased its emissions and showed only slight gains in emissions efficiency.
The Household sector, accounting for almost a third of total emissions, was the largest emitter of energy-related CO2 by 2006. Household emissions levels and intensities both increased between 1998 and 2006. While emissions per household are low, the large number of households makes the cumulative effect of the Household sector a significant factor in total emissions.
In addition to direct emissions, this report provides the total carbon footprint of industries by estimating indirect emissions (emissions associated with inputs that are purchased from other industries). Indirect emissions occur both domestically and abroad since many inputs to production are imported from foreign trading partners. According to the report, emissions associated with total imports are a small fraction of total US emissions.
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