US%20GHG%20Emissions%20Trends

US%20GHG%20Emissions%20Trends - 2. Trends in Greenhouse Gas...

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Trends in Greenhouse Gas Emissions 2-1 2. Trends in Greenhouse Gas Emissions 2.1. Recent Trends in U.S. Greenhouse Gas Emissions I n 2006, total U.S. greenhouse gas emissions were 7,054.2 teragrams of carbon dioxide equivalents (Tg CO 2 Eq.). 1 Overall, total U.S. emissions have risen by 14.7 percent from 1990 to 2006, while the U.S. gross domestic product has increased by 59 percent over the same period (BEA 2007). Emissions decreased from 2005 to 2006 by 1.1 percent (75.7 Tg CO 2 Eq.). The following factors were primary contributors to this decrease: (1) compared to 2005, 2006 had warmer winter conditions, which decreased consumption of heating fuels, as well as cooler summer conditions, which reduced demand for electricity, (2) restraint on fuel consumption caused by rising fuel prices, primarily in the transportation sector and (3) increased use of natural gas and renewables in the electric power sector. Figure 2-1 through Figure 2-3 illustrate the overall trends in total U.S. emissions by gas, 2 annual changes, and absolute changes since 1990. As the largest source of U.S. greenhouse gas emissions, carbon dioxide (CO 2 ) from fossil fuel combustion has accounted for approximately 79 percent of global warming potential (GWP) weighted emissions since 1990, growing slowly from 77 percent of total GWP-weighted emissions in 1990 to 80 percent in 2006. Emissions from this source category grew by 19.3 percent (913.8 Tg CO 2 Eq.) from 1990 to 2006 and were responsible for most of the increase in national emissions during this period. From 2005 to 2006, these emissions decreased by 1.6 percent (93.1 Tg CO 2 Eq.). Historically, changes in emissions from fossil fuel combustion have been the dominant factor affecting U.S. emission trends. Changes in CO 2 emissions from fossil fuel combustion are infuenced by many long-term and short-term Factors, including population and economic growth, energy price fluctuations, technological changes, and seasonal temperatures. On an annual basis, the overall consumption oF Fossil Fuels in the United States generally fuctuates in response to changes in general economic conditions, energy prices, weather, and the availability of non-fossil alternatives. 1 Estimates are presented in units of teragrams of carbon dioxide equivalents (Tg CO 2 Eq.), which weight each gas by its global warming potential, or GWP, value. (See section on global warming potentials, Executive Summary.) 2 See the following section for an analysis of emission trends by general U.S. economic sector. Figure 2-1 U.S. Greenhouse Gas Emissions by Gas 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Tg CO 2 Eq. 6,148 1990 6,106 1991 6,192 1992 6,343 1993 6,435 1994 6,494 1995 6,731 1996 6,760 1997 6,801 1998 6,839 1999 7,033 2000 6,921 2001 6,981 2002 6,998 2003 7,078 2004 7,130 2005 7,054 2006 HFCs, PFCs, & SF 6 Nitrous Oxide Methane Carbon Dioxide
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2-2 Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 –2006 Figure 2-2 Annual Percent Change in U.S. Greenhouse Gas Emissions -2% -1% 0% 1% 2% 3% 4% -0.7% 1991 1.4% 1992 2.4% 1993 1.5% 1994 0.9% 1995 3.6% 1996 0.4% 1997 0.6% 1998 0.6% 1999 2.8% 2000 -1.6% 2001 0.9% 2002 0.2% 2003 1.1% 2004 0.7% 2005 -1.1% 2006 For example, in a year with increased consumption of goods and services, low fuel prices, severe summer and winter weather conditions, nuclear plant closures, and lower
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This note was uploaded on 09/17/2009 for the course CE 108 taught by Professor Harley during the Fall '09 term at University of California, Berkeley.

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US%20GHG%20Emissions%20Trends - 2. Trends in Greenhouse Gas...

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