Activity 3.

Index

• What are the causes of Global Warming? 
• Worksheet A -Gases that Contributed Most to the Greenhouse Efect in the 1980s
• Worksheet B - Activities Contributing to Greenhouse Gas Emissions
• Worksheet C- Carbon Emissions From Selected Countries

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Graph A

Some greenhouse gases are stronger "heat-trappers" than others. The pie chart above illustrates that carbon dioxide is responsible for roughly half of the greenhouse effect. Although chlorofluorocarbon (CFC) molecules are relatively scarce in the atmosphere, they have strong heat trapping properties and are responsible for 14 percent of the greenhouse effect.

Note: This pie chart does not show how much of each greenhouse gas is in Earth's atmosphere -- only its estimated contribution to the greenhouse effect in the 1980s.

The sources of these gases:

Carbon dioxide (CO2) is released into the atmosphere when:

• Fossil fuels - such as coal, oil, and natural gas - are burned in electric power plants, cars, heating furnaces, machinery, etc.
• Trees decay or are burned (deforestation).
• Soils disturbed by erosion, plowing, and other activities lose their carbon-holding organic matter.

• 'Anaerobic" (no oxygen) decay takes place in landfills, manure piles and lagoons, rice paddies, swamps, and arctic tundra.
• It leaks from natural gas wells, pipelines, and coal mines.
• It is naturally produced in the digestive tracts of termites and ruminants (cattle and sheep).
• Fossil fuels, wood, and garbage are burned.

• Refrigerators and air conditioners, which use CFCs as coolant.
• Plastic foams, which can use CFCs as a "blowing agent."
• Aerosol sprays, which can use CFCs as a propellant.
• Cleaning solvents used in manufacturing electronics.

• Fossil fuels (especially coal) and wood are burned.
• Nitrogen fertilizers are used in agriculture.
• Soils are disturbed by erosion, plowing, and other activities.

• Low-level ozone - "smog" (03). Produced by burning fossil fuels.
• Methyl chloroform, carbon tetrachloride, halons, and other chemicals primarily used in industrial processes.

Source: Abrahamson, Karas & Kelly

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Graph B

Many causes contributed to greenhouse gas emissions in the 1980s. They included:

• the use of current industrial technologies, including internal combustion engines and CFC-filled refrigerators and air conditioners;
• energy production technologies, such as coal-fired electricity generating plants;
• agricultural practices, such as deep-plowing of fields; and
• poverty, which forces people to use natural resources in ways that contribute to greenhouse gas emissions (deforestation, erosion).

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Graph C

Carbon emissions - a major contributor to global warming - vary greatly from country to country. In general, however, most greenhouse gas emissions are produced by industrialized countries. Annual contributions to the greenhouse effect in the 1980s due to C02 and CFC emissions have been calculated as:

• 46% - the industrial market economies (including the U.S., Japan, and Great Britain);
• 19% the Soviet Union and Eastern Europe; and
• 35 % - the developing nations.

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