Chapter 4 Section 4Chapter 4 Section 4Global Changes in the AtmosphereGlobal Changes in the Atmosphere

OBJECTIVE: Investigate current issues concerning climate change

1. El Nino & La Nina are short-term changes in the tropical Pacific Ocean caused by changes in ocean surface currents andprevailing winds. Both influence weather patterns world-wide.

*El Nino causes the surface of the ocean in the eastern Pacificto be unusually warm.

*La Nina causes the surface of the ocean in the easternPacific to be colder than normal.

2. Global Warming: The gradual increase in the temperature ofEarth’s atmosphere.

*Greenhouse Gases Hypothesis: Human activities that addgreenhouse gases to the atmosphere may be warming Earth’satmosphere.

*Changing Levels of Carbon Dioxide: An increase in CarbonDioxide may be a major factor in global warming.*Climate Variations Hypothesis: The amount of energy the sun produces increases and decreases from year to year.

*Possible Effects:

Farmers in some areas that are now cool could plant two cropsper year instead of one.Higher temps could cause dust bowls like in the 1930’s.

Warmer ocean temps could increase the strength of Hurricanes.

As water warms, it would expand, raising sea levels.

Melting glaciers and polar ice caps could increase sea levels.

This would cause flooding of low-lying coastal areas.

3. Ozone Depletion: Chemicals produced by humans have beendamaging the ozone layer.

*Chlorofluorocarbons: (CFC’s) Used in air conditioners, Refrigerators, cleaners, and aerosol sprays.

*Results of Ozone Depletion:An increase in UV radiation that reaches Earth’s surface.Worldwide production of CFC’s has greatly decreased.

The ozone hole is expected to gradually shrink over time.