Global Changes in the Atmosphere Chapter 14 Section 4 Essential Questions C14 S4 1. What events can cause short-term climate change? 2. How might human activities be affecting the temperature of Earth’s atmosphere? 3. How have human activities affected the ozone layer? Short-Term Climate Change El Niño and La Niña are short-term changes in the tropical Pacific Ocean caused by changes in ocean surface currents and prevailing winds Short Term Climate Change Changes in ocean currents and winds can greatly affect climate. Short Term Climate Change El Niño is a period of warm water that occurs every few years in the Pacific Ocean. The warm waters of El Niño change the normal ocean currents along the Pacific coast of South America. When ocean currents change, it causes weather patterns to change. El Niño can bring heavy rains or droughts to other parts of the world. Short Term Climate Change La Niña is a period of colder than normal surface waters in the Pacific Ocean. La Niña is the opposite of El Niño. La Niña brings cold winters and greater precipitation to the Pacific Northwest of the United States. Global Warming Many scientists have hypothesized that human activities that add greenhouse gases to the atmosphere may be warming Earth’s atmosphere. Global Warming Over the last 120 years, the average temperature of the troposphere has increased. The gradual increase in the temperature of the atmosphere is called global warming. Global Warming Earth’s surface is heated by energy from the sun. Some of the heat is radiated back into space. Certain gases in the atmosphere hold heat that is radiated from Earth. The process by which the gases trap heat energy is called the greenhouse effect Global Warming The gases in the atmosphere that trap heat energy are called greenhouse gases. Greenhouse gases include carbon dioxide, water vapor, and methane. Global Warming Human activities add carbon dioxide to the atmosphere. For example, burning wood, coal, and oil adds carbon dioxide to the air. Global Warming Adding carbon dioxide to the air increases the greenhouse effect. Increasing the greenhouse effect may be the cause of global warming. Ozone Depletion Chemicals produced by humans have been damaging the ozone layer. Ozone Depletion Ozone in the atmosphere blocks ultraviolet radiation from the sun. The loss of ozone means more ultraviolet radiation reaches Earth’s surface. Ultraviolet radiation can cause eye damage and skin cancer. Ozone Depletion In the 1970s, scientists noticed a hole in the ozone layer of the atmosphere. Holes in the Ozone from 1980 2001 Ozone Depletion A major cause of the ozone hole is a group of chemicals that were used in air conditioners, refrigerators, and spray cans. The chemicals are called chlorofluorocarbons, or CFCs. In the atmosphere, CFCs break down ozone into oxygen atoms. Ozone Depletion The United States and other countries have cut down use of CFCs. People will stop using CFCs completely by about 2010. Essential Questions C14 S4 1. What events can cause short-term climate change? • El Nino & La Nina can cause short-term climate changes. 2. How might human activities be affecting the temperature of Earth’s atmosphere? • We may be adding greenhouse gases such as carbon dioxide to the atmosphere. EQ Answers Continued 3. How have human activities affected the ozone layer? • We have released CFCs into the atmosphere that break ozone down into oxygen. This has thinned the ozone layer and reduced our protection from harmful ultraviolet radiation.