Climatic modeling studies generally estimate that global temperatures will rise a few degrees Celsius in the next century. Such a warming is likely to raise sea levels by expanding ocean water and melting glaciers and the polar ice cap. Recent studies have predicted that changes in global temperatures will introduce new infectious diseases, cause species of animals to become extinct, intensify storms, and increase the likelihood of droughts and floods.
Greenhouse Effect
The Earth stays warm the same way a greenhouse does. Gases in the atmosphere, such as carbon dioxide, methane, and nitrogen, act like the glass of a greenhouse: they let in the Sun’s light and warmth, but they keep the Earth’s heat from escaping. This is known as the greenhouse effect. Scientists think that if too many of these greenhouse gases are released into the atmosphere, from pollution, for example, the gases can trap too much heat, causing temperatures to rise.
Acid Rain
Acid rain occurs when rainwater is contaminated with pollutants like nitrogen oxide and sulfur dioxide. These gases come from fuels being burned at high temperatures, as in car exhausts. When acid rain falls, it can damage wildlife and erode buildings.
Depletion of the Ozone Layer
The ozone layer, a thin sheet of an invisible gas called ozone, surrounds Earth about 15 miles above its surface. Ozone protects us from the Sun’s harmful rays. In recent years, the amount of ozone in the atmosphere has decreased, probably due to human-made gases called chlorofluorocarbons (CFCs). As the ozone level decreases, the Sun’s rays become more dangerous to humans.
Pollution
Pollution is the contamination of air or water by harmful substances. One source of pollution is hazardous waste—anything thrown away that could be dangerous to the environment, such as paint and pesticides. These materials can seep into water supplies and contaminate them.
