The Greenhouse Gas Effect

Greenhouse gases (GHGs) are gas phase components of the atmosphere that contribute to the greenhouse gas effect, the trapping of radiant heat from the sun within the Earth's atmosphere by various GHGs. One GHG of particular interest is carbon dioxide (CO₂) because it accounts for over 80 percent of total United States GHG emissions. CO₂ is a colorless, odorless, nonflammable gas. Atmospheric CO₂ originates from both natural and man-made sources. There are multiple natural sources including volcanic out-gassing, the combustion of organic matter, and the respiration processes of living aerobic organisms: man-made, or anthropogenic, sources of CO₂ are primarily the burning of various fossil fuels for power generation and transportation.

The GHG effect is a natural and important phenomenon of the Earth's ecosystem. However, GHG levels in the atmosphere have significantly increased above the pre-industrial level. Emissions of CO₂ from human activity have increased from an insignificant level two centuries ago to over 30 billion metric tons (33 billion tons) worldwide today. This increase of GHGs is considered by many scientists to contribute to the phenomenon of global warming and could cause unwelcome shifts in regional climates.

The U.S. is one of 189 countries which are signatories to the United Nations Framework Convention on Climate Change (UNFCC), a treaty which calls for stabilization of atmospheric GHGs at a level that would prevent anthropogenic interference with the world's climate. Conservation, renewable energy, and improvements in the efficiency of power plants, automobiles, and other energy consumption devices are important first steps in any GHG emissions mitigation effort. But those approaches cannot deliver the level of emissions reduction needed to stabilize the concentrations of GHGs in the atmosphere--especially against a growing global demand for energy. Technological approaches are needed that are effective in reducing atmospheric GHG concentrations yet, at the same time, have little or no negative impacts on energy use and economic growth and prosperity. Carbon capture and storage (CCS) efforts hold great promise as such GHG reduction technologies.

For more information, please refer to the DOE/NETL Carbon Sequestration Technology Roadmap, available online.