U.S. Greenhouse Gas Emissions - In 2011, U.S. greenhouse gas emissions totaled 6,702 million metric tons of carbon dioxide equivalents, an 8 percent increase from 1990. Emissions of carbon dioxide, the primary greenhouse gas emitted by human activities, increased by 10 percent.
Global Greenhouse Gas Emissions - Between 1990 and 2005, global emissions of all major greenhouse gases increased. Emissions of carbon dioxide increased by 31 percent, which is particularly important because carbon dioxide accounts for nearly three-fourths of total global emissions. Methane emissions increased the least—10 percent—while emissions of nitrous oxide increased by 14 percent. Emissions of fluorinated gases more than doubled. In 2005, estimated worldwide emissions totaled nearly 39 billion metric tons of greenhouse gases, expressed as carbon dioxide equivalents. This represents a 26 percent increase from 1990.