Breathing Prehistoric Air II
Vocabulary: fossil fuels- carbon dioxide- natural gas- petroleum coal- oxygengreenhouse gases- greenhouse effect- global warming- deforestation
What do we mean when we talk about fossil fuels? You know that fossils are the
imprint in rocks of prehistoric plants and animals. But what are fossil fuels? Petroleum,
natural gas and coal are fossil fuels. We call them fuel because for over 200 years we
have been burning these substances—first to cook our food and keep us warm, then to
power our factories and vehicles and now our video games hairdryers and microwave
ovens.
Fossil fuels come from deep within the earth. Like fossils in rocks, they are whats
left of plants that lived millions of years ago. When these plants died they fell into wet,
swampy places where there was little oxygen in the soil. Dead plants need oxygen to
decay, so the plants just stack up in these places—layer after layer. Some of these places
were in what is now Oklahoma. After millions of year, this mass of stuff became what we
call fossil fuels.
Plants breathe in carbon dioxide, much like we breathe in oxygen. Since the
ancient plants that became fossil fuels never decayed, their carbon dioxide was never
released. So when we burn these fuels we are releasing the carbon dioxide of that ancient
atmosphere into our air. Every time you breathe out you release carbon dioxide. Bubbles
of carbon dioxide are what put the fizz in pop. Carbon dioxide is an important part of our
atmosphere. With a few other gasses it helps form what is called the greenhouse effect.
In a greenhouse sunshine passes through the walls and roof and falls on the plants,
flower pots, and tables inside. These objects absorb the sun’s energy and become warmer.
Then the objects give off energy in the form of heat. Some of the heat escapes through
the glass, but most of it is trapped inside the glass of the greenhouse walls and roof.
Carbon dioxide and water vapor—the main greenhouse gases—work the same
way the glass does in a greenhouse. As energy from the sun pours down on the earth it
passes through the atmosphere that surrounds our planet. When the sunshine reaches the
earth it is absorbed by the land and all the things on it. The waters of the ocean absorb
some of it too. Then the earth’s surface gives off the energy as heat. Some of the heat
passes back into space, but some is trapped by the greenhouse gases in the earth’s
atmosphere. This is what keeps us comfortably warm. Without the greenhouse effect, the
earth would be like the moon, with temperatures going from 221 degrees Fahrenheit
during the day to 13 degrees below zero at night.
For the past 150 years we humans have been putting huge amounts of carbon
dioxide into the atmosphere by burning fossil fuels. As the carbon dioxide enters the
atmosphere, some of it is taken up by forests and other plants, and some is absorbed by
the oceans.
But since we are burning so much fossil fuel, we are putting carbon dioxide into
the atmosphere faster than the trees and oceans can take it out. Scientists have started to
worry that all that carbon dioxide is trapping too much heat and making the earth warmer.
This is called global warming. Some scientists are worried about global warming
because it could change the weather systems that have made life comfortable for us here
all these years. Some even think the polar ice caps could melt and put many of the land
masses where people live under water.
Besides burning more and more fossil fuels in the past 150 year, we have also cut
down many of our forests. Sometimes the forests were cut to make way for our houses or
towns. Sometimes they were cut to provide timber for building houses or pulp to make
paper. Sometimes they were cut to make way for farms and ranches. Cutting down the
forests is called deforestation. Forests remove large amounts of carbon dioxide from the
air. One full-grown tree consumes about 13 pounds of carbon dioxide per year. One acre
of trees can absorb over two and half tons of carbon dioxide a year.
Some people think scientists are too worried about global warming and that they
don’t have enough proof that it is really happening. Whether we believe it is or not, there
are things we can do to make sure our planet is a good place for us to live for a long time.
Most people agree that conserving energy would help. Planting trees and other plants will
help absorb some of the extra carbon dioxide in the air. And finding something besides
fossil fuels to provide the power we need could keep us from making the problem worse
than it already is.
Questions
1. What are fossil fuels?
2. Carbon dioxide comes from ________________________.
3. How is the earth’s atmosphere like a greenhouse?
4. What two things have happened in the past 150 years to put more carbon dioxide
in the air?
5. What are the three things we can do to help slow down global warming?