Generally, any substance that people bring into the atmosphere that has damaging effects on living things and the environment is considered air pollution. Other greenhouse gases include methane”which comes from such sources as swamps and gas emitted by livestock”and chlorofluorocarbons (CFCs), which were used in refrigerants and aerosol propellants such as hairspray, until they were banned because of their deteriorating effect on Earths ozone layer. Another pollutant associated with climate change is sulfur dioxide, a component of smog. Sulfur dioxide and closely related chemicals are known primarily as a cause of acid rain. But they also reflect light when released in the atmosphere, which keeps sunlight out and causes Earth to cool. Volcanic eruptions can spew massive amounts of sulfur dioxide into the atmosphere, sometimes causing cooling that lasts for years. In fact, volcanoes used to be the main source of atmospheric sulfur dioxide; today people are. Industrialized countries have worked to reduce levels of sulfur dioxide, smog, and smoke in order to improve peoples health.
But a result, not predicted until recently, is that the lower sulfur dioxide levels may actually make global warming worse. Just as sulfur dioxide from volcanoes can cool the planet by blocking sunlight, cutting the amount of the compound in the atmosphere lets more sunlight through, warming the Earth. This effect is exaggerated when elevated levels of other greenhouse gases in the atmosphere trap the additional heat. Most people agree that to put a harness around global warming, a variety of measures will need to be taken.
On a personal level, driving less, (carpooling when you can, using mass transit systems as much as possible) recycling, and conservation reduces a persons carbon footprint: the amount of carbon dioxide a person is responsible for putting into the atmosphere. On a larger scale, governments are taking measures to limit emissions of carbon dioxide and other greenhouse gases. One way is through the Kyoto Protocol, an agreement between countries that they will cut back on carbon dioxide emissions. Another method is to put taxes on carbon emissions or higher taxes on gasoline, so that people and companies will have greater incentives to conserve energy and pollute less.