U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
U.S. Energy-Related Carbon Dioxide Emissions, 2012
Release Date: October 21, 2013 | Next Release Date: October 2014 | full report
U.S. Energy-related carbon dioxide emissions declined 3.8 percent in 2012
Note: All data in this analysis refers to the Monthly Energy Review of September, 2013 unless otherwise indicated. Because of slightly differing coverage and data vintage, absolute values and percent changes may differ slightly with other Energy Information Administration (EIA) publications.
The decline in energy-related carbon dioxide emissions occurred while the U.S. economy grew in 2012
A large drop in energy intensity (energy measured in Btu per dollar of gross domestic product [GDP]) assisted the 2012 decline in energy-related carbon dioxide emissions despite economic growth.
A mild heating season helped dampen energy demand and related emissions in 2012
Half of the overall energy decline was from the residential sector (1,213 trillion Btu or 5.7 percent), where a very warm first quarter of the year lowered energy demand and emissions.
Lower residential demand for electricity also helped emissions decline
Residential sector electricity consumption was lower in 2012 as compared to 2011 and this also helped to lower emissions as electricity-related emissions have been the principle source of residential sector emissions since 1965.
The transportation sector also contributed to lower energy-related carbon dioxide emissions in 2012
After the residential sector, the next biggest decline in energy consumption was in the transportation sector (513 trillion Btu) or 22 percent of the total energy decline.
The overall carbon intensity of the U.S. economy declined in 2012
The combined reduction in energy use per dollar of GDP and the carbon intensity of the energy supply meant that the overall carbon intensity of the economy (carbon dioxide per GDP) declined 6.5 percent in 2012
Substitution of natural gas for coal in power generation helped lower emissions in 2012
Because the generation of electricity, which is widely used in all sectors except transportation, is an important source of emissions, declines in the carbon intensity of electricity generation lowers emissions throughout the economy.
Since 2007 several key drivers that influence emissions growth have changed1
Cumulative changes in key drivers have reduced energy-related carbon dioxide emissions 12.2 percent from 2007 to 2012
U.S. energy-related carbon dioxide emissions have declined in all but one year since 2007. However, if the trends in drivers from the previous decade remained the same, emissions would have been over 900 MMTCO2 higher.
Causes for the drop in energy intensity since 2007
The factors behind the almost 10-percent drop in energy intensity include:
Causes for the drop in carbon intensity of energy since 2007
As indicated below, energy intensity has been consistently decreasing since 2000; however the carbon intensity of the total energy supply was relatively flat between 2000 and 2007, but fell 6 percent from 2007 to 2012.
Implications of the carbon dioxide emissions decrease in 2012 for future emissions
It is difficult to draw conclusions from one year of data. Specific circumstances such as the very warm first quarter of 2012 and the large increase in natural gas-fired generation relative to coal contributed to the significant decline in emissions in 2012. Other factors, such as improvements in vehicle fuel efficiency and increased use of renewable generation, however, could play a continuing role in subsequent years.
For EIA projections on emissions and their key drivers see either the Short-Term Energy Outlook, updated monthly with projections through 2014 (2015 beginning in January of 2014) or the Annual Energy Outlook with annual projections through 2040. EIA's International Energy Outlook contains current projections of international energy consumption and emissions through 2040.
The analysis of energy-related carbon dioxide emissions presented here is based on the data in the Monthly Energy Review (MER). The MER reports monthly U.S. energy-related carbon dioxide emissions in Chapter 12 derived from our monthly energy data. For the full range of EIA's emissions products see the Environment page.
Terms used in this analysis:
British thermal unit (Btu): The quantity of heat required to raise the temperature of 1 pound of liquid water by 1 degree Fahrenheit at the temperature at which water has its greatest density (approximately 39 degrees Fahrenheit).
Carbon intensity (economy): The amount of carbon by weight emitted per unit of economic activity. It is most commonly applied to the economy as a whole, where output is measured as the gross domestic product (GDP). The carbon intensity of the economy is the product of the energy intensity of the economy and the carbon intensity of the energy supply. Note: this value is currently measured in the full weight of the carbon dioxide emitted (CO2/GDP).
Carbon intensity (energy supply): The amount of carbon by weight emitted per unit of energy consumed. A common measure of carbon intensity is weight of carbon per Btu of energy. When there is only one fossil fuel under consideration, the carbon intensity and the emissions coefficient are identical. When there are several fuels, carbon intensity is based on their combined emissions coefficients weighted by their energy consumption levels. Note: this value is currently measured in the full weight of the carbon dioxide emitted (CO2/energy or CO2/Btu).
Cooling degree-days (CDD): A measure of how warm a location is over a period of time relative to a base temperature, most commonly specified as 65 degrees Fahrenheit. The measure is computed for each day by subtracting the base temperature (65 degrees) from the average of the day's high and low temperatures, with negative values set equal to zero. Each day's cooling degree days are summed to create a cooling degree day measure for a specified reference period. Cooling degree days are used in energy analysis as an indicator of air conditioning energy requirements or use.
Energy intensity: A measure relating the output of an activity to the energy input to that activity. It is most commonly applied to the economy as a whole, where output is measured as the gross domestic product (GDP) and energy is measured in Btu that allow for the summing of all energy forms (energy/GDP or Btu/GDP). On an economy-wide level, it is reflective of both energy efficiency as well as the structure of the economy. Economies in the process of industrializing tend to have higher energy intensities than economies that are in their post-industrial phase. The term energy intensity can also be used on a smaller scale to relate, for example, the amount of energy consumed in buildings to the amount of residential or commercial floor space.
Gross domestic product (GDP): The total value of goods and services produced by labor and property located in the United States. As long as the labor and property are located in the United States, the supplier (that is, the workers and, for property, the owners) may be either U.S. residents or residents of foreign countries.
Heating degree-days (HDD): A measure of how cold a location is over a period of time relative to a base temperature, most commonly specified as 65 degrees Fahrenheit. The measure is computed for each day by subtracting the average of the day's high and low temperatures from the base temperature (65 degrees), with negative values set equal to zero. Each day's heating degree days are summed to create a heating degree day measure for a specified reference period. Heating degree days are used in energy analysis as an indicator of space heating energy requirements or use.
Kaya Identity: An equation stating that total energy-related carbon dioxide emissions can be expressed as the product of four inputs: 1) population, 2) GDP (output) per capita, 3) energy use per unit of GDP, and 4) carbon emissions per unit of energy consumed. The change in the four inputs can approximate the change in energy-related carbon dioxide emissions.
Primary energy: Energy in the form that it is first accounted for in a statistical energy balance, before any transformation to secondary or tertiary forms of energy. For example, coal can be converted to synthetic gas, which can be converted to electricity; in this example, coal is primary energy, synthetic gas is secondary energy, and electricity is tertiary energy. In the context of this analysis it would mean energy consumed directly by a home, business or industrial operation as opposed to electricity generated elsewhere and supplied to the end-user.For other definitions see the EIA glossary.