The Problem: The Greenhouse Effect. Carbon dioxide and water vapor in the Earth's atmosphere act like a greenhouse, trapping some of the heat the Earth emits and reflecting it back toward the planet. Natural levels of greenhouse warming benefit the Earth, but the degree of warming is increasing. Scientists predict that greenhouse warming could heat up the Earth's climate between 2 and 8 degrees F over the next century. This would likely result in higher sea levels and inundation of low-lying coastal areas, as well as changes in local climate and growing conditions for crops and natural vegetation.
The Cause: Human activity has caused an increase in the levels of carbon dioxide and other heat-trapping gases -- including chlorofluocarbons, methane, ground-level ozone and nitrous oxides -- which has magnified the greenhouse effect. Global levels of carbon dioxide alone have increased by 25% since the start of the Industrial Revolution. The United States contributes over one billion tons of carbon to the atmosphere each year. Most of this comes from burning fossil fuels -- coal, oil and gas -- in our electric utilities, transportation, industries and buildings. Nearly half of residential energy consumption is used to heat and cool our homes. At one-sixth of residential energy use, water heating is the second-largest source of home energy demand. Refrigerators and freezers account for over one-eighth of our residential energy demand, and about one-fourth is used in lighting, cooking and other appliances combined.
The Problem: Acid Rain. Increasing acidity of rain water, snow and fog is killing forest trees, polluting streams and lakes, and destroying historic landmarks.
The Cause: The acidity is caused by sulfur and nitrogen oxides that combine with water in the atmosphere to form acids which fall to Earth as precipitation. Sulfur oxides are released by power plants and metal smelters fueled by coal and oil. Nitrogen oxides are released from motor vehicles and industrial processes. A typical rainfall in the eastern United States is 10 times more acidic than unpolluted, natural rainfall. In the United States and most other industrial countries, motor vehicles account for roughly half of all nitrogen oxide emissions.
The Problem: Smog. Ground-level ozone is the principal component of smog, which causes health problems and damages crops and natural vegetation.
The Cause: Ground-level ozone is formed by reactions between nitrogen oxides and hydrocarbons in sunlight. Exhaust from motor vehicles is the major source of smog.
You Can Help: Conserving fossil fuels not only reduces our contribution to the greenhouse effect, acid rain and air pollution, but saves energy costs and reduces the United States' dependence on foreign sources of oil. Proper insulation, conservative use of heaters and air conditioners, and good maintenance of appliances can help the environment and result in lower energy bills. While no single action will eliminate environmental problems, energy efficiency is the most important and cost-effective step we can take.
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