Greenhouse Gases

U.S. Greenhouse Gas Emissions in 2016

Gases that trap heat in the atmosphere by absorbing infrared radiation are called greenhouse gases.
The major greenhouse gases that are the result of human activity are:

2016 U.S. Carbon Dioxide Emissions
(By Source)

Carbon dioxide (CO2): Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas, and oil), solid waste, trees and wood products, and also as a result of certain chemical reactions.
Carbon dioxide is removed from the atmosphere as part of the biological carbon cycle.
Lifetime in atmosphere: CO2 is part of the global carbon cycle, and its lifecycle is a complex function of geochemical and biological processes. Some carbon dioxide will be absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years.

2016 U.S. Methane Emissions
(By Source)

Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.
Lifetime in atmosphere: 12 years

2016 U.S. Nitrous Oxide Emissions
(By Source)

Nitrous oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
Lifetime in atmosphere: 114 years

2016 U.S. Flourinated Gas Emissions
(By Source)

Fluorinated gases: Unlike many other greenhouse gases, fluorinated gases have no natural sources and only come from human-related activities. There are four main categories of fluorinated gases — Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3).
Lifetime in atmosphere:
   HFC: up to 270 years
   PFC: 2,600–50,000 years
   NF3: 740 years
   SF6: 3,200 years

Did you know?

Water vapor is the most abundant greenhouse gas, but most scientists believe that water vapor produced directly by human activity contributes very little to the amount of water vapor in the atmosphere.

Source: U.S. Environmental Protection Agency (2018). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2016. EPA.gov.