The Kyoto Protocol was an international summit held in Kyoto, Japan, in December 1997. Its goal was for governments around the world to reach an agreement regarding emissions of carbon dioxide and other greenhouse gases. The Kyoto Protocol called for the industrialized nations to reduce national emissions over the period 2008–2012 to five percent below the 1990 levels. The protocol covers these greenhouse gases: carbon dioxide, methane, and nitrous oxide. Other chemicals such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride were to be added in subsequent years.