Key Points

• In 2014, U.S. greenhouse gas emissions totaled 6,870 million metric tons (15.1 trillion pounds) of carbon dioxide equivalents. This total represents a 7 percent increase since 1990 but a 7 percent decrease since 2005 (see Figure 1).
• For the United States, during the period from 1990 to 2014 (see Figure 1):
  • Emissions of carbon dioxide, the primary greenhouse gas emitted by human activities, increased by 9 percent.
  • Methane emissions decreased by 6 percent, as reduced emissions from landfills, coal mines, and natural gas systems more than offset increases in emissions from activities such as livestock production.2
  • Nitrous oxide emissions, predominantly from agricultural soil management practices such as the use of nitrogen as a fertilizer, decreased by 1 percent.
  • Emissions of fluorinated gases (hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride), released as a result of commercial, industrial, and household uses, increased by 77 percent.
• Among the various sectors of the U.S. economy, electricity generation (power plants) accounts for the largest share of emissions—31 percent of total greenhouse gas emissions since 1990. Transportation is the second-largest sector, accounting for 26 percent of emissions since 1990 (see Figure 2).
• Emissions sinks, the opposite of emissions sources, absorb carbon dioxide from the atmosphere. In 2014, 11 percent of U.S. greenhouse gas emissions were offset by net sinks resulting from land use and forestry practices (see Figure 2). One major sink is the net growth of forests, which remove carbon from the atmosphere. Other carbon sinks are associated with how people use the land, including the practice of depositing yard trimmings and food scraps in landfills. While the land use, land-use change, and forestry category represents an overall net sink of carbon dioxide in the United States, this category also includes emission sources resulting from activities such as wildfires, converting land to cropland, and biomass burning.
• Emissions increased at about the same rate as the population from 1990 to 2007, which caused emissions per capita to remain fairly level (see Figure 3). Total emissions and emissions per capita declined from 2007 to 2009, due in part to a drop in U.S. economic production during this time. Emissions decreased again from 2010 to 2012, largely due to the growing use of natural gas to generate electricity in place of more carbon-intensive fuels.3
• From 1990 to 2014, greenhouse gas emissions per dollar of goods and services produced by the U.S. economy (the gross domestic product or GDP) declined by 40 percent (see Figure 3). This change may reflect a combination of increased energy efficiency and structural changes in the economy.