18.4 Global changes in the atmosphere Page 641 Key concepts: What events can cause short-term climate changes? How might human activities be affecting the temperature of Earth’s atmosphere? How have human activities affected the ozone layer? Key terms: El Nino, La Nina, global warming, greenhouse gas, chlorofluorocarbon

Short-term climate changes El Nino and La Nina are short-term climate changes in the tropical Pacific ocean caused by changes in ocean surface currents and prevailing winds. El Nino – warm-water event begins when an unusual pattern of winds forms over the western Pacific. It cases the surface to be unusually warm. La Nina – when the water is colder than usual. The opposite of El Nino. Brings colder weather.

Global warming Gradual increase in the temperature of Earth’s atmosphere. Greenhouse hypothesis – human activities add greenhouse gases and warm the atmosphere

Changing levels of Carbon dioxide Increase in carbon dioxide in the atmosphere Checked against air bubbles caught in Antarctic ice

Climate variation hypothesis Some scientists think the rising temperatures are due to natural variations in climate

Possible effects Global warming could have some positive effects Maybe. Not really. I can’t imagine that and your book is a little vague on it.

Ozone depletion Ozone filters out UV rays. Chemicals produced by humans have been damaging it for years Chlorofluorocarbons – compounds (CFCs) that were used in air conditioners and aerosol sprays

Result of ozone depletion Increase in UV rays – eye damage, cancer