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NOVA scienceNOW: Stronger Hurricanes

Viewing Ideas

Before Watching

1. Help students learn about hurricanes, the factors that contribute to them, and the role warmer sea surface temperatures may have on them. In class (or as homework), assign each student one of the questions below.

   • What is a hurricane?
   • How is a hurricane different from a thunderstorm or a tornado?
   • When and where do hurricanes usually form?
   • What causes them to form?
   • How are hurricanes rated?
   • What factors contribute to a hurricane's intensity?

   Provide the class with Web addresses or books (see Links and Books). Have each student first answer his or her question and then write down one additional interesting fact. Set up teams so that each team has one person with an answer to each question. Have students take turns teaching the other team members about their topic and sharing their interesting fact. Then, ask each team to write 10 questions for a class quiz game. In the game, teams ask each other their questions. Award one point for a correct answer and one point for a question that stumps another team (assuming, of course, that the team asking the question can provide the correct answer).

2. Warm oceans typically increase a hurricane's intensity. Perform the following change-of-state demonstration for the class, and have students brainstorm how it relates to hurricane intensity.

Procedure

Materials: bowl of very hot tap water (not scalding); bowl filled with ice

Place the bowl of ice above the bowl of hot water. Have students observe the changes and discuss the energy transfers occurring in the system.

The hot water vapor rises. When it rises from the water bowl and comes in contact with the ice bowl's cold surface, it cools, losing energy and condensing into liquid water. The energy from the vapor is transferred to the ice bowl, and the ice melts. The water vapor represents warm, moist ocean air. The ice-filled bowl represents the cool atmosphere. The condensing water and melting ice represent the transfer of energy from the ocean to the atmosphere. The release of energy into the atmosphere warms the air, an action that generates winds and alters the barometric pressure—changes that can increase storm intensity.

After Watching

1. There is presently a debate about the relationship between global warming and hurricane intensity. Some scientists believe global warming is contributing to hurricane intensity, and others believe global warming's impact is minimal. To help students better understand this debate, review the following concepts:

   Global warming: An increase in Earth's surface temperature.

   Greenhouse effect: Greenhouse gases let solar radiation pass through our atmosphere, but they trap some infrared radiation, preventing it from escaping into outer space.

   Possible causes and effects of global warming: An increase in greenhouse gases, which trap infrared energy, may contribute to global warming. Effects of a warmer climate include: melting of ice caps, warming of sea surface temperature, and an increase in intensity of hurricanes.

   Sources of greenhouse gases: Greenhouse gases are important for life on Earth. Without them, Earth would lose its heat quickly and be too cold for most life forms. However, if current trends continue, many scientists predict that the 21^st century will see greenhouse gas levels rise to the highest they have been in the past 200,000 years, raising Earth's average temperature considerably.

   Greenhouse Gas	Source
   Carbon dioxide	Fossil fuel combustion, land use conversion, cement production
   Methane	Fossil fuels, rice paddies, waste dumps, livestock
   Nitrous oxide	Fertilizer, industrial processes, combustion
   Chlorofluorocarbon	Liquid coolants and foams
   Fluorocarbon 22	Liquid coolants
   Perfluoromethane	Aluminum production
   Sulfur hexa-fluoride	Dielectric fluid in transformers and some kinds of electrical wires

2. Have pairs of students brainstorm some of the possible long-term impacts of global climatic changes on their own lives and on the Earth. Ask students to consider how climate has influenced life in different regions of the world. (It determines the biome, rainfall patterns, flora and fauna, and the types of food, shelter, and adaptations required for survival.) What can students do to decrease greenhouse gases and the possible threat of global warming?

3. Many people worry about how Earth's recent warming trend will affect life and ecosystems in the near future. Have students conduct a written, anonymous survey to learn what the public understands about the possible relationship between global warming and greenhouse gases. Use the results of this survey to have students generate an informative Global Warming and Greenhouse Gases pamphlet to share with those who were surveyed. Sample questions should include:

   1. Do you think global warming will have serious negative impacts on your family's daily life and lifestyle?

   2. Some people consider global warming to be an important issue, while others do not. How important an issue do you consider global warming to be?

   3. How much above pre-industrial levels do you think the concentration of carbon dioxide gas in the atmosphere is currently? (a) 20% (b) 30% (c) 40% (d) 50% (The answer is 30%, which is higher than it has been in 400,000 years.)

   4. What things do you think can be negatively affected by global warming in the next decade? (Answers include: agriculture, weather, ecosystems, the range of plants and animals, economy, polar ice caps, and climate.)

   5. Do you think that science, inventions, and new technologies will solve global warming?

Web Sites

NOAA's National Weather Service
nws.noaa.gov/organization.php
Find local weather and climate data using the main location index.

U.S. Global Change Research Information Office
www.gcrio.org/
Features general information, resources, and links to other organizations dealing with global change. Also includes an e-mail service, Ask Dr. Global Change, where you can send questions about global environmental change.

What's up with the weather?
www.pbs.org/wgbh/warming/
NOVA and Frontline examine the truth about global warming.

Books

Global Warming by Fred Pearce and John Gribben. Dorling Kindersley, 2002.
Examines the causes and effects of global warming.

Weather by Brian Cosgrove. Dorling Kindersley, 2004.
Includes information about designing a weather station.