ENVIRONMENTAL SCIENCE PUBLISHED FOR EVERYBODY ROUND THE EARTH
1. Answer individually or in groups
In great forest fires, an enormous number of trees burn, and such fires lead to great amounts of CO2 being released into the air. Despite this, forest fires are not thought to increase the greenhouse effect.
Fossil fuels, just like trees, are also natural substances. When fossil fuels such as coal and gas are burnt they also release CO2 into the air. Explain why burning fossil fuels affects our climate but burning forests doesn't.
1. Forest fire on Bitterroot National Forest, Montana. Photo courtesy of John McCougan, Alaska Fire Service, 2000
Melting sea ice
a) Put an ice cube in a water bath and mark the level of the water. What do you think will happen when the ice cube melts? Will the water level be higher, lower or stay the same.
Observe the water level after the ice has melted. Were you correct?
Do you know a physical principle that explains what you saw?
2. Idea and illustration: Pål Kirkeby Hansen, Oslo University College, Norway
b) Repeat the experiment, but this time put a stone in the water bath. Make sure the stone sticks out of the water a bit. Put an ice cube on top of the stone. Mark the level of the water. What will happen to the water level when the ice cube melts? Will it be higher, lower or the same?
Observe the water level after the ice melted. Were you correct?
c) One of these experiments is a model of what happens around the North Pole and one models what happens around the South Pole. Which one is which and why?
Use these experiments to deduce what will happen to the sea level if the ice around the North Pole melts and if the ice around the South Pole melts.
Fill a test tube with coloured water. Put in a rubber bung with a glass tube through it. Mark the level of water in the tube. Place the test tube in a hot water bath. What do you think will happen to the water level?
Observe your system for a few minutes. What do you see? Were you correct? What is likely to happen to the sea level as the Earth gets warmer?
3. Idea and illustration: Pål Kirkeby Hansen, Oslo University College, Norway
About this page:
Authors: Ellen K. Henriksen and Camilla Schreiner - University of Oslo - Norway.
Scientific reviewer: Andreas Tjernshaugen - CICERO (Center for International Climate and Environmental Research - Oslo) - Norway - 2004-01-20
Educational reviewer: Nina Arnesen - Marienlyst school in Oslo - Norway - 2004-03-10.
Last update: 2004-03-27.