UNIT FOUR: Matter and its Changes Chapter 12 Atoms and the Periodic Table Chapter 13 Compounds Chapter 14 Changes in Matter Chapter 15 Chemical Cycles and Climate Change Chapter Fifteen: Chemical Cycles and Climate Change 15.1 Chemical Cycles 15.2 Global Climate Change Section 15.2 Learning Goals Define climate change and describe factors that influence global climate change. Explain the greenhouse effect. Research and discuss public policy initiatives designed to combat negative effects of global climate change. Investigation 15B Oceans and the Carbon Cycle Key Question: What role do the oceans play in the carbon cycle? 15.2 Global climate change Global climate change refers to changes in the factors used to describe a climate (such as temperature, precipitation, or wind) that last for two or more decades. Since the Sun and the oceans affect weather patterns, changes in the Sun’s intensity or in ocean circulation can cause climate change. 15.2 Global climate change Greenhouse gases “blanket” our planet by trapping heat from the Sun that Earth’s average temperature is hospitable for living things. These gases are water vapor, carbon dioxide, methane, nitrous oxide, ozone, and carbon compounds produced by industry. 15.2 The greenhouse effect The greenhouse effect is the warming of Earth that results when greenhouse gases trap heat emitted from the planet’s surface. 15.2 Upsetting the balance Excess carbon dioxide, produced by many combustion reactions since the Industrial Revolution, is one of the main causes of global warming. 15.2 Understanding climate change Two scientists, Revelle and Keeling, collected data on atmospheric levels of CO2 at Mauna Loa Observatory (MLO) in Hawaii over about a 30-year period. Other scientists have analyzed gas bubbles trapped in glacial ice. 15.2 Today and the future Currently, the amount of carbon dioxide in our atmosphere is 35 percent more than it was 200 years ago. There are several indicators of global warming: 1. 2. 3. 4. Warming temperatures Rising sea level Decreasing ice coverage Increasing water vapor in atmosphere Investigation 15C Natural Resources Key Question: How fast are we using nonrenewable resources? Harvesting the Wind There is a new kind of farm that is unlike any other—it doesn’t produce food—it produces energy from wind. As wind turbine technology has improved over the past 30 years, the cost per kilowatthour of electricity generated by wind has decreased dramatically.