Subskill: Reading Comprehension
Concept: Cause and Effect
Grade Level: Upper Elementary
Have you ever been inside a greenhouse? A greenhouse is a glass building that is used for growing plants. Light and energy from the sun enter a greenhouse through the glass, which traps the heat inside. As a result, plants stay warm enough to live even in very cold weather.
So what does a greenhouse have to do with global warming? Well, pretend that the Earth is inside a giant greenhouse. Light from the sun warms the land, water and air. The warmed-up Earth gives off heat, which rises into the sky. Gases in the Earth’s atmosphere, such as carbon dioxide and methane, act like the glass walls and roof of a greenhouse. They prevent some of the heat from escaping into space, which keeps the Earth warm enough for plants, animals and humans to live here. Without these gases, all of the heat would escape back into space, and the Earth would become about 60 degrees colder. This is known as the greenhouse effect. The gases that warm the Earth are called greenhouse gases.
But scientists today say greenhouse gases are now causing the Earth’s atmosphere to get hotter. This is known as global warming. Over the last 100 years, the Earth has warmed up 1 degree Fahrenheit, and the four warmest years in the 20th century happened in the 1990’s. The amount of carbon dioxide, one of the greenhouse gases, in the Earth’s atmosphere is 30% greater than it was 150 years ago, and it is expected to rise another 30% in the next 50 years. Scientists say this could increase the average temperature of the Earth from 2 to 9 degrees in the next 50 to 100 years.
So what is causing global warming? Scientists believe the major cause is the burning of fossil fuels for energy, like coal and oil. Fossil fuels cause greenhouse gases to escape into the air. Power plants use coal and oil to make electricity. Another cause of global warming is deforestation, which is the cutting down of trees. We need trees because they soak up the greenhouse gas, carbon dioxide, from the air. The more energy we use and the more trees we cut down, the more the Earth heats up.
No one knows exactly what will happen in the future if global warming continues, but scientists have many theories. They say as the Earth becomes warmer, weather will become more unpredictable. Hurricanes will be more powerful, and rain will become heavier, causing more floods. Glaciers and ice caps in the North and South Poles are already beginning to melt. The sea level has already risen six to eight inches in the last 100 years. If the sea level continues to rise, ocean waters will overflow onto the land. People who live along the coastlines will have to move inland. Animals that require colder climates will be forced to move to other areas or will become extinct. Mosquito-borne diseases like malaria will spread because mosquitoes thrive in warm weather.
What can we do now to stop global warming? Global warming cannot be stopped completely, but there are things we can do. For example, use less energy by turning off lights, TV’s, computers and other appliances when they are not being used. Use the air conditioner less in the summer and your heating system less in the winter. Walk whenever possible instead of riding in the car. Plant trees wherever possible to absorb carbon dioxide and provide shade for buildings. Become informed about solar energy to heat your home. Recycle and reuse whatever you can to lessen the amount of trash in the landfills, as trash in landfills gives off methane, a greenhouse gas. Together, we can work to save the Earth for future generations.
Here are some questions to ask after listening to the passage:
According to this passage:
- what keeps plants warm inside a greenhouse on cold days?
- how do greenhouse gases affect the Earth?
- what are some causes of global warming?
- how do trees affect the air we breathe?
- what might be some long-term effects of global warming?
- what can be done to help stop global warming?