Wednesday, March 18, 2015
WHAT CAUSES GLOBAL WARMING
The earth’s atmosphere is warming up, just as if it was trapped inside a greenhouse. This warming process is often called the greenhouse effect.
The panes of glass in a greenhouse let in light from the sun but trap it when it is released as heat. This makes the climate inside the greenhouse hot.
In a similar way, the earth’s atmosphere lets in sunlight and then traps the heat near the earth’s surface. This is the “greenhouse effect.
Why is the earth warming up?
More of the sun’s energy is reaching the earth’s atmosphere because the ozone layer is becoming thinner.But there is another reason why the earth is warming up.
When we burn fuels like coal, oil, gas, or wood, carbon dioxide is released into the atmosphere. Plants use carbon dioxide to help make their food. So tropical rain forests take in large amounts of carbon dioxide from the atmosphere, but at the same time people are cutting down vast areas of these forests.
The earth is warmed by the sun.
Most of the heat is sent back, or radiated, into the atmosphere. Carbon dioxide in the atmosphere traps some of this heat, preventing it from escaping into space. This keeps the earth warm. But if there is too much carbon dioxide in the atmosphere, it will trap too much heat, and the earth’s atmosphere will become too hot.
As the earth’s atmosphere becomes much warmer, the ice in the Arctic and in Antarctica constantly melts. This raises the level of the seas all over the world. A rise of only a few inches could flood many coastlines. Low-lying coastal towns and cities would be endangered by floods, and so would large areas of farmland.
If the seas became warmer, the sea animals and plants would be affected. And many might not be able to survive at all. In other parts of the world, a lack of rain may mean that farmland would become too dry and dusty.
Too much carbon dioxide in the atmosphere prevents more heat than usual from escaping into space. But we still need some heat to keep us warm.
