The report looks at four main categories of greenhouse gases pumped out by human activities in the United States. It lists all emissions in 'carbon dioxide equivalents', which reflect the amount of a gas that would cause the same amount of warming in the atmosphere as carbon dioxide. Methane and nitrous oxide emissions have declined, but carbon dioxide is up so much it completely swamps these gains (see 'Changes in US annual emissions between 1990 and 2004').
Total emissions topped 7 billion tonnes CO2 equivalent in 2004.
...The United States is the biggest national emitter of greenhouse gases worldwide, and these figures reinforce that position.
Many other countries have committed to reducing their emissions to below 1990 levels, although it is questionable how well they are doing (see 'European greenhouse emissions climb again').
UK emissions, for example, came to about 656 million tonnes CO2 equivalent in 2004 (less than a tenth of US emissions), which is 14% below its 1990 levels. The British government says it is on track to hit targets set by the Kyoto Protocol, an international agreement to reduce emissions of greenhouse gases.