Teachers TryScience

I. Introduction

Global Warming Background Information for Teachers: How can global warming affect the Earth's sea levels?

In recent years, the potential impact of global warming has been discussed widely by the scientific community. The majority of scientific reports suggest that the Earth will be soon facing climate change as the Earth increases in temperature. Global warming is the increase in the average temperature of the Earth. The increase in temperature may only be a few degrees, however, this slight change could have a profound impact on the Earth's polar ice caps. In the past 100 years, the Earth has warmed by one degree Fahrenheit. Data suggests that a change in temperature could cause polar ice caps in the North and South pole, along with land locked glaciers in other parts of the world to melt.

There are many possible causes of global warming. Climate and the temperature of the Earth is caused by many factors. In the past, the Earth's climate has changed naturally. It is possible that recent human activity may contribute to global warming. Since the Industrial Revolution, human have been using large amounts of fuel to run machines. Burning coal and gasoline releases carbon dioxide into the atmosphere. Carbon dioxide is a gas that traps energy from the sun. By trapping energy from the sun in the atmosphere, the Earth's temperature increases.

The melting of the ice in Antarctica, Greenland and other land locked glaciers is a big concern for scientists. Antarctic is covered by a layer of ice two miles thick resting on top of the continent. This ice sheet contains 70 % of the world's fresh water and makes up 90% of the world's ice. If it were divided up, every person on Earth could have a chunk of ice larger than the Great Pyramid! If this water were to melt, the ocean's sea levels could rise dramatically.

In contrast to the Antarctica ice sheet, the Arctic icebergs of the North Pole are large pieces of ice floating on top of the ocean without land underneath it. However, the melting of the Arctic icebergs would not have a large impact on the the ocean's sea levels. When water freezes to form ice, it expands in volume. As the ice floats, it displaces the same amount of water that would exist if it melted. When it melts, the water level remains the same. If all the floating icebergs in the world, such as the Arctic polar caps, were to melt, the world's sea level would not change. Because this floating ice is already displacing its own volume in water, sea level will only rise with the ice that breaks off or melts from land, i.e. the Greenland ice sheet, Antarctic ice sheet, and mountain glaciers.

A good introduction to global warming for students can be found at:
The Environmental Protection Agency Climate Change Kid's site

Student Introduction: What is Global Warming

1. In a classroom discussion ask students to discuss what they know about global warming. What have you heard recently in the news about global warming? What is it? What causes it?
2. Explain to students that global warming is the increase in the Earth's temperature. The Earth's temperature can increase and decrease naturally, such as during the Ice Ages. However, many scientists believe that humans might have contributed to global warming. When we drive a car, we are burning gasoline. This releases carbon dioxide into the air. Carbon dioxide gets trapped in the Earth's atmosphere, which makes the Earth warmer, like adding an extra blanket on the Earth. Humans have been burning lots of coal and gasoline, which puts more and more carbon dioxide in the atmosphere.
3. The Earth's increased temperature could cause several problems. If the Earth's temperature increases, the ice in Antarctica, Greenland and on other continents could melt. Antarctica contains the majority of the world's fresh water, about 70% of the world's fresh water and 90% of the world's ice. If all this ice were to melt, it would go in the ocean. All this extra water could make the sea levels rise. When sea levels rise, the extra water starts to flood parts of the coastline that have low elevations.

II. Observing Global Warming's Effect on Cities

The CyArk Hazard Map

This section can be done as a teacher demo in front of the class or in small student groups.

1. Using the CyArk Hazard map (linked above), locate the city of New Orleans, Louisiana. The city of New Orleans is a US city with a long history. One of the oldest cities in the US, New Orleans has become known as a cultural melting pot with a unique culture and cuisine. New Orleans is home to a rich culture, famous for their festivals, such as Mardi Gras, and is also known as the birthplace of jazz. In 2005, Hurricane Katrina caused considerable damage to the city of New Orleans. Many of the city's levees broke which caused water levels to rise, leaving much of the city underwater. In the events of global warming, New Orleans faces the danger of becoming submerged under the waters of the Gulf of Mexico once again.

Zoom in on the city of New Orleans to zoom level 7. Have students locate New Orleans and the Gulf of Mexico.

2. On the Hazard Map, adjust the the sea levels from 0 meters to 1 meter. How is the city affected? At 5 meters sea level rise? 10 meters sea level rise? 20 meters?

3. Explain to students that if the sea levels of the world rise, the water will first flood the parts of the city with the lowest elevation. Elevation is the height of the land above the level of the sea. Rising sea levels would first affect coastal areas with low elevation.

Extension for advanced students and high grade levels:
4. Here is a map of New Orlean's elevations

How do the areas on this map correspond to the flooded areas in the CyArk Hazard Map? How does elevation play a role in sea level rise?

III. Experiment

How will melting glacial ice from Antarctica and Greenland affect sea levels?

Find the list of materials above.

Preparation
Making Ice

Choose one of two methods below:
1. Fill ziplock bags with water.
2. Place ziplock bags flat in the freezer and let freeze.
3. When the water has completely frozen into ice, remove the ice from the ziplock bag. You should now have a small, flat sheet of ice.

1. Using ice cubes, place about 6 ice cubes in a small container or ziplock bag.
2. Wet the ice cubes slightly and then place in the freezer.
3. Remove the ice cubes after they have frozen together to form a block of several ice cubes stuck together.

Procedure
1. Fill a small plastic container with rocks or gravel. Alternatively, a small, unopened can (such as a tuna can) be be used. The container of choice should be relatively heavy to prevent the container from floating in water. This container will represent a continent or island. Place the weighted container in a large shallow pan.

2. Using sugar cubes and glue, have students construct a small city on top of the "island."

3. Place another weighed container or can in the shallow pan. Place a large block of ice on top of the the weighed container. This will represent Antarctica and its thick layer of ice.

4. Using a pitcher, slowly fill the pan with water. Fill the container until the the water level reaches the top of the small container "islands." Be careful not to splash water on the sugar cubes.

5. Measure the height of the water level in the pan with a ruler. Students should record the water level in their notebooks and record any observations about their sugar cube city. At this time students will write their predictions and hypothesis of what will happen as the ice cubes melt and what effect it will have on the sugar cube city. Optional: have students record their sugar cube city with a digital camera.

6. Direct the lamp towards the ice cubes in the container. The lamp represent solar activity and melts the ice cubes at a faster rate.

7. Once the sugar cubes have melted, students should measure the new water level with a ruler and record this number in their notebooks. Students should also record their observations on the sugar cube city. What happened to the city after the ice cubes melted? Did the level of the water rise? If so, by how much?

Optional: have students photograph the sugar cube city after the ice melted.

IV. Global Warming's Impact

• Using the CyArk Hazard map (linked above) have students explore a local coastal town. Change the rise in sea levels to see how different parts of the city would be affected.
• Have students think of a recent trip to this city. How would your trip be different if the sea levels rose? What parts of the city would be different? What would be the same?
• Ask the class to think of some famous cities and ancient monuments. Some examples include the Pyramids of Egypt, Big Ben in London, the Eiffel Tower and Chichen Izta.
• Locate one of these monuments on the CyArk Hazard Map. The CyArk Hazard map has markers for World Heritage Sites and sites documented by CyArk. How would these ancient monuments be affected by rising sea levels? If these sites are affected by rising sea levels, how do you think you would feel? How do you think this would affect the way we think about the past?
• Using the CyArk archive, select a documented site. Examine the 3-D laser scan videos or data. These records are very precise records of the monuments. Archaeologists hope to us 3-D laser scan data to learn more about sites. The images and data can also be used to study the site if something happens to the site, such as being affected by rising sea levels. How do you remember a place? What other monuments to you think are important to you and the people of the future?

Conclusion and Wrap Up
Have students write down 3 ways that they can help the environment and reduce the amount of carbon dioxide gases released in the Earth's atmosphere.