The Earth's climate is predicted to change because human activities are altering the chemical composition of the atmosphere through the buildup of greenhouse gases—primarily carbon dioxide (CO2), methane (CH4), and nitrous oxide (NOx). The heat-trapping property of these gases is undisputed. Although uncertainty exists about exactly how Earth's climate responds to these gases, global temperatures are rising. For more information about climate change, visit EPA's Climate Change Web site.In addition, EPA prepares a national inventory of U.S. greenhouse gas (GHG) emissions each year for submission under the United Nations Framework Convention on Climate Change. EPA’s Clean Air Markets Division coordinates the development of this inventory and leads an inter-agency GHG inventory team. For more information, visit EPA's National Greenhouse Gas Inventory Web site.