Earth Science: Geology, the Environment, and the Universe

Unit 7: Resources and the Environment

WebQuest Projects 1

Is Global Warming Beyond Our Control?

Introduction

In this WebQuest, students use specific Web sites to investigate climate change on Earth. They conduct research to answer questions related to the topic, and analyze graphs showing atmospheric data from Earth's recent and distant past. Students examine the nature of the relationship between atmospheric greenhouse gas concentration and global warming.

While students conduct internet research, they will answer questions related to the greenhouse effect, the current global warming trend, and cycles of warming and cooling that have occurred throughout Earth's history. Students should be able to compile information to answer the questions as they read through each Web site. They will analyze data from six different graphs showing changes in surface temperature and concentration of greenhouse gases that have taken place over varying lengths of time.

As students evaluate information from each Web site, they will focus on the extent of the role humans play in global climate change. Citing specific evidence to support their opinions, students will formulate a written response to the question "Is human activity responsible for the current global warming trend affecting the Earth?"

• Describe the atmospheric process known as the greenhouse effect.
• Identify the major greenhouse gases in Earth's atmosphere.
• Explain the importance of the greenhouse effect to life on Earth.
• Compare the level of atmospheric carbon dioxide in 1750 to the level of atmospheric carbon dioxide in 2004.
• Identify natural factors that can cause changes in Earth's surface temperature.
• Describe the relationship between the level of atmospheric carbon dioxide and global warming.
• Explain how a history of climate change can be reconstructed from an ice core.
• Recognize that weather data has been directly measured and systematically recorded in the United States for less than 200 years.
• Describe weather conditions during the Younger Dryas period.
• Analyze graphs to identify trends or patterns in specific atmospheric conditions throughout Earth's recent and extended history.
• Form an opinion about the extent of the impact of burning fossil fuels on global climate change.

Students will use the internet links provided to learn about global climate change. The Web sites highlight specific topics related to the broader theme. For example, students learn about the greenhouse effect and its importance to life on Earth, as well as about the specific gases that cause the process to occur. They learn how the level of atmospheric carbon dioxide changed between 1750 and 2004, as well as how scientists estimate it has changed over the last 420,000 years. Students examine how Earth's temperature changed between the late 1800s and the present, as well as how scientists estimate it has changed over the last 800,000 years of Earth's history. They investigate natural phenomenon that can cause both individual periods and continuous cycles of climate change. Students also study how scientists make direct and indirect measurements of past atmospheric conditions. While students examine these factors individually, they will begin to make connections between them as their research evolves.

As students examine the relationships between various atmospheric factors, they will begin to form an opinion about the extent of the role played by human activity, particularly the burning of fossil fuels, in climate change. The Web sites chosen for student review are neutral, offering data and clear, factual explanations about climate change rather than opinion. Students are asked to make their own judgements about the relationship between human activity and the current global warming trend, rather than having the beliefs of specific organizations or individuals with various agendas put before them.

1 week to answer the questions, analyze the graphs, and write an opinion

As students conduct internet research, be available to discuss any of the eight questions they may have difficulty answering. These questions are designed to help students gain sufficient understanding to write an opinion about whether or not human activity is responsible for the current global warming trend. It is important, therefore, that students have a solid understanding of factors affecting global climate change before attempting to draft a written statement.

Students will gain additional knowledge by writing brief analyses of six different graphs that show how various atmospheric factors have changed over Earth's recent and extended history. Encourage students to print the graphs and make notes on a hard copy. Be available to discuss their analyses and answer any questions students might have about the graphs. Remind students that most historical data prior to at least the early 1800s comes from indirect measurements, which are based on accepted, validated scientific methods of data collection. Because these are indirect measurements, however, a certain degree of uncertainty exists.

Talk with students about the structure and style of the written opinion. The written document does not need to be lengthy, but should be supported by data from the research. Student opinions may vary from those who believe that human activities are solely responsible for the current warming trend, to those who feel the trend is part of a natural cycle unaffected by the burning of fossil fuels, to those who believe the burning of fossil fuels plays some role, but not a deciding one, in global climate change. Remind students that opinions within the classroom represent a microcosm of beliefs within the scientific community about the topic, and that debate continues as additional research occurs.

Have students review the rubric to understand how the final product will be evaluated. Provide the opportunity for students to share their opinions with classmates. Consider devoting time to a class-wide debate. For optimum effectiveness, act as a firm and objective moderator. Establish, model, and enforce rules of the debate prior to and throughout the discussion.

You may assign ten points to each of the eight questions for a total of 80 possible points. The answers to the questions are given below. Rate the answer to each question using the following scale: Excellent – 9-10 points; Very Good – 7-8 points; Good – 5-6 points; Satisfactory – 3-4 points; Poor – 1-2 points; and Unsatisfactory – 0 points.

1. Earth is surrounded by a blanket of gases, which comprise the atmosphere. Some gases, known as greenhouse gases, allow high-energy, short-wave radiation from the Sun to pass through the atmosphere unabsorbed. However, some long-wave radiation is absorbed by these gases as it is reflected from Earth's surface back toward space. This process is influenced by the amount of solar radiation that enters Earth's atmosphere, as well as the type and concentration of greenhouse gases present in the atmosphere. The net result of the greenhouse effect is that more heat is received from the Sun than is reflected back to space, which keeps the surface of the planet warmer than it would be otherwise.
2. Major greenhouse gases found in Earth's atmosphere include water vapor, carbon dioxide, methane, tropospheric ozone, nitrous oxide, and carbon monoxide.
3. The greenhouse effect is crucial to life on Earth. Without a natural greenhouse effect, Earth's average surface temperature would be about 0o Fahrenheit rather than 57o Fahrenheit.
4. In the mid-1700s the carbon dioxide concentration in Earth's atmosphere was roughly 280 parts per million. Carbon dioxide concentration has risen steadily since that time, reaching a level of 379 parts per million in 2004.
5. Large volcanic eruptions, changes in the Sun's energy output, and periods of El Nino can cause climate changes. Changes in Earth's position and orientation relative to the Sun also can result in global climate change.
6. Some weather diaries were kept in the United States by various individuals beginning in the mid-1600s. Consistent collection and recording of weather data did not take place in the United States until the mid-1800s. The National Weather Service was created in 1870.
7. Scientists find evidence of past climate conditions, including precipitation, temperature, and atmospheric composition, in tree rings, ocean and lake sediments, coral, and ice cores from polar regions. Ice cores can provide an extended record of Earth's climatic history. As snow falls to the surface, it carries with it compounds that are in the air at the time. In world locations where snow rarely melts, layers accumulate each year. By drilling from the surface through successively deeper layers, scientists can analyze how various compounds in the atmosphere changed over time. Ice cores also include air samples from various periods in history. Deeper layers of snow turn into ice due to the weight of snow on top of them. As this occurs, small bubbles of air are trapped in the ice. These air samples can be analyzed for atmospheric composition.
8. The Younger Dryas period began about 12,000 years ago. Scientists believe that within a time span of about 50 years, the climate from the eastern United States and Canada to much of Europe went from being like it is today to frigid conditions that were more like the last Ice Age. The average temperature cooled by as much as 10o Fahrenheit. The Younger Dryas period lasted roughly 1000 years. Scientists believe that within a span of 20 years, the climate changed back to conditions that existed before the cooling began. Some scientists believe the cooling period actually was related to a previous global warming trend. As Earth was emerging from the end of the last Ice Age and the surface temperature was increasing, glaciers worldwide began to retreat. Cold meltwater from these glaciers entered oceans around the world. Some researchers believe this process disrupted the flow of specific ocean currents, which regulate temperatures in the eastern United States, Canada, and Europe, leading to a cooling period.

Use the evaluation rubric or other means to assess written opinions. Evaluation of the written opinion should include self-assessment and teacher assessment. Students may want to add a third column to the rubric to be completed after debating their opinions with class members.

The factors affecting global climate change are numerous, and are related in complicated ways. After students complete this WebQuest, they will have an understanding of the complexity of the issue of global warming, and will realize that the simplified descriptions sometimes given in the media do not reflect the total range of issues and factors involved. The written opinions students produce should reflect a knowledge of the greenhouse effect and how fossil fuel combustion enhances the process. The opinions also should demonstrate an understanding of the natural cycles of change Earth's atmosphere has experienced for hundreds of thousands of years. Finally, students should understand that while scientists agree that the surface temperature on Earth is currently rising, there is debate about how much of this warming is due to human activity.