U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
U.S. Energy-Related Carbon Dioxide Emissions, 2014
Release Date: November 23, 2015 | Next Release Date: February 2017 | full report
U.S. Energy-related carbon dioxide emissions increased 0.9% in 2014
Note:Unless otherwise indicated, all data in this analysis refer to the U.S. Energy Information Administration's (EIA) October 2015 Monthly Energy Review. Because of slightly differing coverage and data vintage, percent changes may differ slightly with other EIA publications.
Carbon dioxide emissions by fuel exhibit differing patterns over time
Industrial and transportation sectors' energy-related carbon dioxide emissions further diverged in 2014
The largest absolute increase in 2014 energy-related carbon dioxide emissions was from the transportation sector
Price decreases in gasoline and other fuels from 2013 to 2014, along with the continued economic recovery, has induced higher fuel consumption. Transportation-related CO2 emissions increased by 24 MMmt (1.3%) in 2014, or 47% of the total emissions increase from 2013.
Energy-related carbon dioxide emissions in the commercial sector increased by over 2% in 2014
The increase in commercial sector CO2 emissions in 2014 was 19 MMmt (2.0%), accounting for 38% of the total increase in emissions.
Residential energy-related carbon dioxide emissions increased in the first quarter of 2014
Residential CO2 emissions increased in the first quarter of 2014 by about 12% compared with the first quarter of 2013, due largely to colder weather; heating degree days (HDD) increased 10% over the first quarter of 2013. For the year, residential CO2 emissions increased 18 MMmt (1.6%), accounting for 36% of the total increase in energy-related CO2 emissions in 2014.
Industrial sector energy-related carbon dioxide emissions declined in 2014
The industrial sector's CO2 emissions, which fell by 11 MMmt (0.7%) in 2014, have remained largely flat in recent years despite increasing output. Continuing growth in less energy-intensive output (such as computers) has helped to stabilize emissions.
The increasing share of electricity from natural gas-fired generation and wind and solar power has helped to lower the carbon intensity of electricity supply
The natural gas share of electricity generation grew from approximately 11% in 1990 to 29% in 2012, dipping to 26% in 2014.
Growth in wind and solar electricity generation has been a key component in the decreasing carbon intensity of the electricity supply
While nuclear power remains the dominant source of non-fossil electricity generation, growth in wind and solar generation since 2008 has also contributed to a decline in the carbon intensity of electricity generation.
About half of the increase over trend in energy-related carbon dioxide in 2014 was due to growth in per capita economic output
In 2014, per capita output (GDP divided by population) grew by 1.7% compared with the average growth of just 0.5% from 2004 to 2013. This contributed about 62 MMmt to the increase in CO2 emissions when compared with the average shown over the previous ten years.
Declining carbon intensity of the energy mix since 2008 has contributed to a general decoupling of carbon dioxide emissions from economic growth
The carbon intensity of energy supply began declining in 2008, in step with the recession that resulted in a two-year drop in per capita economic output.
Increased use of natural gas and the growth in non-carbon generation have contributed to the decline in power sector carbon dioxide emissions since 2005
Implications of the 2014 carbon dioxide emissions increase
It is difficult to draw conclusions from one year of data. Specific circumstances such as the very cold first quarter of 2014 and the increase in coal generation relative to 2013 (while natural gas generation remained flat) affected the year-to-year change, as did the growth in transportation emissions influenced by lower fuel prices. In the longer term, other factors (such as improvements in vehicle fuel efficiency and increased use of natural gas and renewable generation) could help mitigate future emissions growth.
For EIA's projections on emissions and their key drivers, see the Short-Term Energy Outlook (STEO), updated monthly with projections through 2016 (2017 beginning in January of 2016) and the Annual Energy Outlook (AEO) with annual projections through 2040.
The analysis of energy-related carbon dioxide emissions presented here is based on data in the Monthly Energy Review (MER). Chapter 12 of the MER reports monthly U.S. energy-related carbon dioxide emissions derived from EIA’s monthly energy data. For the full range of EIA's emissions products, see the Environment webpage.
Terms used in this analysis:
British thermal unit(s) (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. 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.
For other definitions see the EIA glossary.
Methodology used in this analysis
Most of the data presented in the slides require no explanation. However, slides 10 and 12 involve some underlying complex calculations. The methodology for those slides is as follows:
Slide 10 entitled: About half of the increase over trend in energy-related carbon dioxide in 2014 was due to growth in per capita economic output – This slide gives context to the most recent year-to-year change by comparing it to the average change for key parameters over the previous decade. The key parameters are: population, per capita output (GDP/population), energy intensity of the economy (Btu/GDP), and carbon intensity of the energy supply (CO2/Btu). The changes in these key parameters determine changes in energy-related carbon dioxide. By comparing the rate of change for each parameter for the 2013 to 2014 time period to the average rate of change for that parameter for the previous decade, the contribution of each towards the overall deviation from trend can be calculated. The table below summarizes the rates of change that drive the results. The larger the positive value the greater the increase in emissions and the larger the negative value the lesser the increase in emissions.
Slide 12 entitled: Increased use of natural gas and the growth in non-carbon generation have contributed to the decline in power sector carbon intensity since 2005 – This slide shows graphically the emissions savings from two factors in the generation of electricity that have allowed emissions to decrease in recent years while generation has risen slightly. The first factor is the shift within fossil fuel generation from coal to natural gas. To capture this shift the fossil fuel carbon factor (fossil fuel CO2/fossil fuel generation) is calculated for 2005. This factor is then multiplied times the actual fossil generation for subsequent years. The difference between that value and the actual value for fossil fuel generation CO2 emissions is the reduction in CO2 generation emissions. For example the carbon factor in 2005 for fossil fuel generation was .865 metric tons per megawatthour. By 2014 the carbon intensity had declined to .778 metric tons per megawatthour. Using the 2005 value times the 2014 level of generation would yield 2,275 MMmt, versus the actual value of 2,046 MMmt. Therefore the savings was 229 MMmt. Because non-carbon generation (the second factor) has a zero carbon factor for direct emissions, the overall reduction in total carbon intensity was applied to total generation. The savings in fossil fuel generation was subtracted from the total and the difference was credited to non-carbon generation. For example, the total savings in 2014 was 398, so the amount allocated to non-carbon generation is 398 – 229 = 169.