Smog hanging over cities is the most familiar and obvious form of air pollution. Carbon dioxide, a greenhouse gas, is the main pollutant that is warming Earth associated with cars, planes, power plants, and other human activities that involve the burning of fossil fuels such as gasoline and natural gas. Other greenhouse gases include methane which comes from such sources as swamps and gas emitted by livestock and chlorofluorocarbons. Sulfur dioxide and closely related chemicals are known primarily as a cause of acid rain Most people agree that to curb global warming, a variety of measures need to be taken. On a personal level, driving and flying less, recycling, and conservation reduces a person’s
"carbon footprint" the amount of carbon dioxide a person is responsible for putting into the atmosphere