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Download Lesson 7 - Climate Change - Hitchcock
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Unit 4 Lesson 7 Climate Change Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change The Temps are a-Changin’ What are some natural causes of climate change? • The weather conditions in an area over a long period of time are called climate. • Natural factors have changed Earth’s climate many times during our planet’s history. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some natural causes of climate change? • Tectonic plate motion has contributed to long-term climate change over billions of years. • The present continents once fit together as a single landmass called Pangaea. • As Pangaea broke up, some continents moved closer to the equator and grew warmer. Other continents moved to higher latitudes and became colder. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some natural causes of climate change? • How was the climate on various continents affected by the breakup of Pangaea? Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some natural causes of climate change? • Short-term changes in climate can be due to natural events that send tiny, solid particles called particulates into the atmosphere. • Particulates absorb some of the sun’s energy and reflect some of it back into space. This process temporarily lowers temperatures on Earth. • Particulates can come from asteroid impacts and volcanic eruptions. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some causes of repeating patterns of climate change? • The output of energy from the sun is slightly higher during times of higher sunspot activity. • Sunspot activity tends to increase and decrease in a cycle that lasts approximately 11 years. • The effect of this cycle on global temperatures is not dramatic, but there appears to be a link between sunspot activity and global rain patterns. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some causes of repeating patterns of climate change? • Climate is also affected by changes in ocean temperature, such as happen during El Niño and La Niña conditions, which usually alternate. • During El Niño years, ocean temperatures are above normal in the tropical Pacific Ocean. The opposite effect occurs during La Niña years. • Both conditions affect temperatures and rainfall in different areas, leading to droughts and flooding. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some causes of repeating patterns of climate change? • The geological record shows that at different times, Earth’s climate has been both cooler and warmer than it is today. • Earth’s history contains extremely cold periods called ice ages. An ice age is a long period of cooling during which ice sheets spread beyond the polar regions. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some causes of repeating patterns of climate change? • Geologic evidence indicates that ice ages occur every 200 million years or so, and each ice age lasts for millions of years. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some causes of repeating patterns of climate change? • Ice sheets have alternately advanced (glacial periods) and retreated (interglacial periods). Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change Is It Getting Hotter? How may humans affect climate change? • Certain gases, called greenhouse gases, warm the Earth’s surface and lower atmosphere by a process called the greenhouse effect. • In this process, greenhouse gases absorb and radiate energy as heat back to Earth. Without these gases, Earth would be colder. • Greenhouse gases include carbon dioxide (CO2), water vapor, methane, and nitrous oxide. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change How may humans affect climate change? • There is evidence to support the idea that by burning fossil fuels such as gasoline and coal, humans are causing a rise in global CO2 levels. • Since the 1950s, scientists have observed a rise in both CO2 levels and the average global surface temperature. • To explain this correlation, scientists note that CO2 is a greenhouse gas, and increasing levels of CO2 will warm Earth’s surface and lower atmosphere. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change How may humans affect climate change? • Processes such as the burning of fossil fuels emit carbon into the atmosphere and are called carbon sources. • Processes such as the growth of plants remove carbon from the atmosphere and are called carbon sinks. • Scientists note that deforestation converts a carbon sink into a carbon source, thereby playing a large role in greenhouse gas emissions. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change How may humans affect climate change? • What is the relationship between atmospheric CO2 concentration and average global temperature? Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some predicted effects of climate change? • Studies show that the average global surface temperature has risen by about 0.3 °C to 0.8 °C over the last 100 years. • Global warming is a gradual increase in average global temperature. It will affect global sea level, global weather patterns, and life on Earth. • Scientists predict that storms will increase in power and frequency, and as much as half of Earth’s surface may be affected by drought. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some predicted effects of climate change? • Rising temperatures will lead to an increase in the melting of glaciers, arctic sea ice, and ice sheets that cover Greenland and Antarctica. • A 2010 report observed record-setting high temperatures, resulting in record melting of the Greenland ice sheet. • Global sea level rose by 10 to 20 cm during the 1900s. Scientists project that sea level may rise by 60 cm by 2100. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What are some predicted effects of climate change? • Scientists predict that global warming will change ecosystems, threatening the survival of many species. Some species may benefit, however. • If Earth warms more than a few degrees Celsius, many of the world’s farms could suffer, though less severe warming would help agriculture. • Warmer temperatures could increase the number of deaths related to heat and certain diseases, but deaths associated with extreme cold could drop. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change How are climate predictions made? • Climate data are being collected by instruments placed in the atmosphere, in the oceans, on land, and in space. • These data, along with historical climate data, are used to create climate models, which describe how different variables affect Earth’s climate. • Scientists use climate models to predict the effects of an increase in greenhouse gases on future global climate. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change Think Clean and Green How can people reduce their impact on climate change? • The Kyoto Protocol, adopted in 1997, is the only existing international treaty in which nations have agreed to reduce CO2 emissions. • Individuals can reduce greenhouse gas emissions by conserving energy, increasing energy efficiency, and reducing their use of fossil fuels. • One can take steps such as driving less, using nonpolluting energy sources, turning off lights, and recycling products. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change How can people reduce their impact on climate change? • Deforestation contributes up to 20 percent of carbon emissions globally. • Planting trees and supporting reforestation programs are ways to balance carbon sources with carbon sinks. • Another solution is to educate people about the importance of the carbon that is stored in forests for stabilizing climate. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change How can people reduce their impact on climate change? • Clean-energy technologies are being researched and used in different parts of the world. • New biofuels, solar power, wind power, and water power reduce the need to burn fossil fuels. • However, many new technologies are currently more expensive than fossil fuels. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What factors make climate change a global issue? • Greenhouse gases enter Earth’s atmosphere wherever they are produced. • Consequently, the economic, political, and social factors related to climate change make it a global issue. • However, the need to reduce greenhouse gas emissions is more often seen as a problem that affects people locally. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What factors make climate change a global issue? • The cost of climate change includes the costs of crop failure, storm damage, and human disease. • However, developing countries may not be able to afford technologies needed to reduce human impact on climate. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 4 Lesson 7 Climate Change What factors make climate change a global issue? • Political action can lead to regulations that reduce greenhouse gas emissions. • However, these laws may be challenged by groups who disagree with the need for change or object to the proposed solutions. • No matter what choices are made to handle the challenges of climate change, it will take groups of people working together to make a difference. Copyright © Houghton Mifflin Harcourt Publishing Company