Unit 4 Lesson 7 Climate Change Copyright © Houghton Mifflin Harcourt Publishing Company

The Temps are a-Changin’ Copyright © Houghton Mifflin Harcourt Publishing Company 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. 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? Intensity of 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? Copyright © Houghton Mifflin Harcourt Publishing Company 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 greenhouse gases, Earth would be colder. Greenhouse gases include carbon dioxide (CO 2 ), water vapor, methane, and nitrous oxide. 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 CO 2 levels. Since the 1950s, scientists have observed a rise in both CO 2 levels and the average global surface temperature. To explain this correlation, scientists note that CO 2 is a greenhouse gas, and increasing levels of CO 2 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 CO 2 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 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 Copyright © Houghton Mifflin Harcourt Publishing Company 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 CO 2 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. 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 Unit 4 Lesson 7 Climate Change