earth The Greenhouse Effect earth


About this Lesson by Alicia Pinderhughes

Recommended Age: Middle School

Guiding Question

What is the greenhouse effect and why does it happen?


Objectives

Concepts:

Global warming is a natural process that keeps the planet warm and hospitable for living organisms. The greenhouse effect (understood to mean an enhancedgreenhouse effect) is the warming of the earth beyond this natural process of global warming.

Principles:

  • Greenhouse gases are in the earth’s atmosphere.

  • Some solar radiation is absorbed by these greenhouse gases; some reaches the earth and is absorbed by its surfaces. In both cases, light is absorbed as heat.

  • Earth’s surfaces, warmed both by solar radiation and by warmth from deep within the earth, radiate heat into the atmosphere, where some is absorbed and some passes out into deep space. The enhanced greenhouse effect occurs when more heat is absorbed by the atmosphere, due to increased greenhouse gases, than can pass by convection into space in a normal manner.
diagram

A diagram illustrating the process of the greenhouse effect. Click on it to see a full-size version that you can print out.

Facts:

Skills


Preparation

Materials:

  1. Cardboard boxes
  2. Black construction paper
  3. 3 thermometers for every box
  4. 1 classroom thermometer
  5. 3 glass panes for every box (have them cut to fit in the box at the store)
  6. 6 blocks of wood for every box
  7. Glue
  8. Scotch tape
  9. Electrical tape

Room Preparation

Have materials ready and glass pre-cut to desired size (small enough to just fit into boxes).

Safety Precautions

Caution! Danger of broken glass! Handle glass with care. Cover edges of each pane with electrical tape to prevent injury from cut edges.


Procedures and Activity

Prelab Discussion

  1. Introduce greenhouse effect concepts, principles, and vocabulary.
  2. Ask:
  3. Many scientists believe that we are experiencing an enhanced greenhouse effect. Unfortunately, accurate recordings of the earth’s temperature go back only 100 years. This is not a long enough period to be sure of what is happening. However, we can simulate the greenhouse effect with a box and panes of glass. Keep in mind that the mechanism is not the same:heat is trapped in a car or a real greenhouse by the glass interfering with natural convection. In the atmosphere, the heat is not literally trapped; rather, enhanced global warming stems from the increased ability of the atmosphere to absorb heat due to greenhouse gases.

Construction

  1. Using glue, completely line the inside of a cardboard box with black construction paper.
  2. Tape down one thermometer towards the left side of the box, at the bottom. Be sure the thermometer can still be read.
  3. Get two blocks of wood. Place one block to the far left and one to the far right so that they will support a pane of glass.
  4. Carefully place one pane of glass on top of the wood blocks.
  5. Position a second thermometer in the center, on top of the glass pane.
  6. Repeat steps 3 and 4.
  7. Position the third thermometer to the right on the topmost glass pane.
  8. Repeat steps 3 and 4.
The result should
look like this.

(Click on images to
see full-size versions
you can print out).

Top View

Side View

top view side view

Testing Procedure

  1. Have students put their boxes in direct sunlight.

  2. Have students read their thermometers and record their data once a day, at the same time. Example: At the beginning of each class period. data chart
  3. Also have students record the classroom temperature.
  4. The collected data should be placed in a chart that looks
    like this (Click on it to see a full-size version you can print out):
  5. Compute the average daily temperature for each thermometer.

Discussion

Have students examine the relationship between increase in average daily temperature and an increase in the number of panes of glass. Think about why this is happening. Relate to greenhouse effect. A pane of transparent glass allows solar radiation to pass through, but interferes with the convection that would let heat out. This is the kind of role that greenhouse gases play in the greenhouse effect: they absorb more heat than normal atmospheric gases would. Therefore, in this model, the effect of the increasing number of panes of glass is similar to the effect of increasing greenhouse gas levels.

Closing

Ask again: What is the greenhouse effect? Why does it happen?


Evaluation

Have students share reasons why we need global warming to an extent. Then have students share how we are changing the natural system of warming with greenhouse gases. Have students share what they think are the side effects of global warming.


Extension Ideas

  1. Discuss the impact of increasing temperatures on the polar regions, aquatic life, humans, and the planet in general. Some possibilities are: the effect on weather, rising sea levels, rise in ocean temperatures and how this affects sea life, effects on agriculture, etc. See other Web pages for more information on this topic: Global Change/Climate Change (a report from Hawaii on NASA’s Mission to Planet Earth studies of the greenhouse effect); the Consortium for International Earth Science Information Network’s Thematic Guide Potential Increases in Mortality Due to Global Warming; or the report Consequences: Trends in U.S. Climate from the National Climatic Data Center in North Carolina.

  2. Relate Earth to Venus and its runaway global warming and to Mars and its deep freeze in a page from the American Institute of Physics.

  3. The theory that we are experiencing unusual global warming now is somewhat controversial. Some sites that try to help you make sense of the conflicting information available include a chemistry professor’s article Debunking Rush Limbaugh on the Environment, and another professor’s Bad Greenhouse page, debunking myths and common misperceptions about the greenhouse effect (including the idea that the atmosphere "traps" heat or reflects it back to earth). NASA has a great Web page on this called Earth’s Fidgeting Climate, and see the Environmental Protection Agency’s Climate Change page.

Vocabulary

Atmosphere
The air that surrounds the earth.
Carbon Dioxide
A heavy colorless gas that does not support combustion. It is formed naturallyby the combustion and decomposition of organic substances and is absorbed by photosynthesis of plants.
Fossil Fuels
Fuels that are formed in the earth from plant or animal remains. Examples are coal, oil, and natural gas.
Global Warming
The result of the greenhouse effect. It is the warming of the planet’s atmosphere. Natural global warming is a result of the natural greenhouse effect and is what makes the planet hospitable to life. Sometimes, "global warming" is used to mean "the greenhouse effect." That is, sometimes it is used to refer to the warming that is a result of the enhanced greenhouse effect.
Greenhouse Effect
The cause of global warming. It is the actual process of greenhouse gases absorbing heat in the atmosphere. There is a natural greenhouse effect which the planet needs to support life. We amplify or enhance the natural greenhouse effect when we load the atmosphere with an excess of greenhouse gases. Usually, the term "greenhouse effect" is used to refer only to the amplified greenhouse effect and not to the natural greenhouse effect.
Greenhouse Gases
Gases, such as carbon dioxide, methane, and chlorofluorocarbons, which are released into the atmosphere by burning fossil fuels and by manufacturing. These gases trap additional heat in the earth’s atmosphere.
Solar Radiation
Sunlight

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This lesson amended 15 Dec 97, 10 July 00, 23 Oct 00, 16 Mar 01, 25 May 02, 2 Apr 10