• Included are anthropogenic emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), hydrochlorofluorocarbons (HCFCs), chlorofluorocarbons (CFCs), the aerosol precursor and the chemically active gases sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxides (NOx), and non-methane volatile organic compounds (NMVOCs).

• In addition, carbon monoxide (CO) emissions have recently been identified as a cause of increasing CH4 concentration.

• However, during the past century or so it has also been produced in increasing quantities near the Earth 's surface through chemical processes involving nitrogen oxides, carbon monoxide, other air pollutants, and sunlight.