U. S. EPA Office of Atmospheric Programs. (2006). Click on Executive Summary (PDF) (26 pp, 310K).
Provides a broad overview of all U.S. greenhouse gas emission sources and sinks, introduces key concepts and discusses the primary drivers for changes in emissions, which has resulted in global warming.
See: Global Warming Frequently Asked Questions
Greenhouse gases Carbon Dioxide (CO2) and Methane (CH4) taken together account for 93% of all emissions, with 85% for (CO2) and 8% for (CH4). Enteric fermentation (flatulence and belching), taking place as a digestive by-product of cows and other ruminant animals accounts for less than half of the Methane emissions. Coal mining and natural gas systems, in addition to the (CO2) emissions of vehicles used to transport water add significantly to the total of all greenhouse gas emissions.
For pie charts graphically showing these percentages, see pages 20-22.