Climatologists are studying ways to limit global warming. Two key methods would be (1) limiting CO2 emissions and (2) carbon sequestration-either preventing carbon dioxide from entering the atmosphere or removing CO2 already there.

Limiting CO2 emissions.
Two effective techniques for limiting CO2 emissions would be (1) to replace fossil fuels with energy sources that do not emit CO2, and (2) to use fossil fuels more efficiently.

Alternative energy sources that do not emit CO2 include the wind, sunlight, nuclear energy, and underground steam. Devices known as wind turbines can convert wind energy to electric energy. Solar cells can convert sunlight to electric energy, and various devices can convert solar energy to useful heat. Geothermal power plants convert energy in underground steam to electric energy.

Alternative sources of energy are more expensive to use than fossil fuels. However, increased research into their use would almost certainly reduce their cost.

Increased fuel efficiency.
CO2 emissions could be greatly reduced if automobiles and trucks utilized fuel more efficiently. Some scientists and engineers are working on engines with improved fuel efficiency. Other inventors are developing devices to replace fuel-burning engines or to use with smaller engines. Cars known as hybrids have already entered the market. A hybrid has all the components of a battery-driven electric car plus another power source, usually a small gasoline engine. Fuel cells, devices that convert chemical energy to electric energy, may be used in future automobiles.

Carbon sequestration could take two forms: (1) underground or underwater storage and (2) storage in living plants.

Underground or underwater storage would involve injecting industrial emissions of CO2 into underground geologic formations or the ocean. Suitable underground formations include natural reservoirs of oil and gas from which most of the oil or gas has been removed. Pumping CO2 into a reservoir would have the added benefit of making it easier to remove the remaining oil or gas. The value of that product could offset the cost of sequestration. Deep deposits of salt or coal could also be suitable.

The oceans could store much CO2. However, scientists have not yet determined the environmental impacts of using the ocean for carbon sequestration.

Storage in living plants.
Green plants absorb CO2 from the atmosphere as they grow. They combine carbon from CO2 with hydrogen to make simple sugars, which they store in their tissues. After plants die, their bodies decay and release CO2. Ecosystems with abundant plant life, such as forests and even cropland, could tie up much carbon. However, future generations of people would have to keep the ecosystems intact. Otherwise, the sequestered carbon would re-enter the atmosphere as CO2.

Contributors:
Michael D. Mastrandrea, B.S., Graduate Fellow, School of Earth Sciences, Geological and Environmental Sciences, Stanford University. Stephen H. Schneider, Ph.D., Professor of Biological Sciences, Stanford University.

Additional resources

Christianson, Gale E.Greenhouse: The 200-Year Story of Global Warming. Walker, 1999. Godrej, Dinyar.The No-Nonsense Guide to Climate Change. Verso, 2001. Johansen, Bruce E.The Global Warming Desk Reference. Greenwood, 2002. Stein, Paul.Global Warming. Rosen Pub. Group, 2001. Younger readers. -

Source : World Book 2005.