Topic 31: Global warming (Phần 2)

Scientists believe that something very serious is happening to the Earth. It is becoming warmer. Scientists predict that there will be major changes in the climate during the 21st century. Coastal waters will have higher temperatures. This will have a serious effect on agriculture. Farmers will have trouble producing good crops. In warm regions, the weather will be too dry. The amount of water could decrease by 50 per cent. This would cause a large decrease in agricultural production.

World temperatures could increase from 1.5 to 5.6 degrees Celsius by the middle of the 21st century. And the increase in temperature could be even greater in the Arctic and Antarctic regions. A rise in temperature could cause the great ice sheets to melt, which, in turn would raise the level of oceans by one to two meters. Many coastal cities would be underwater. Why is all this happening?

The Earth and its atmosphere are kept warm by the Sun. The atmosphere lets most of the light from the Sun pass through to warm the Earth. The Earth is warmer by the sunlight and sends heat energy back into the atmosphere. Much of this energy escapes from the Earth’s atmosphere. However, some of it remains. Gases such as carbon dioxide, ozone and water vapor absorb this energy and create more heat. Then, this heat is sent back down to Earth, and the Earth becomes warmer.

Recently, however, an increase of carbon dioxide in the atmosphere is causing serious problems. Too much carbon dioxide in the atmosphere prevents heat energy from escaping. Too much heat is sent back down to the Earth, and the amount of carbon dioxide in the atmosphere continues to increase. When oil, gas, and coal burn, they create large amounts of carbon dioxide. The destruction of rain forests that absorb carbon dioxide also helps to increase the amount of carbon dioxide in our atmosphere. Some scientists believe that the amount of carbon dioxide in the air will double by the late 2000s.

Scientists call this warming of the Earth and its atmosphere “the greenhouse effect”. A greenhouse, made of glass and plastic, is a special place where plants are grown. The sunlight passes through the glass or plastic and warms the air inside. The heat inside escapes very slowly, so the greenhouse remains very warm. This is exactly what is happening on the Earth.

Another reason why the Earth is growing warmer is because of the amount of ozone in our atmosphere. Ozone is a form of oxygen. In the upper atmosphere, very far from the Earth, a layer of ozone helps to protect the Earth from 95 percent of the harmful light that comes from the sun. If your skin receives too much of this light, you would develop skin cancer. We need the ozone layer to protect ourselves. But the ozone layer is in trouble. Scientists have observed that the ozone layer is becoming thin, and above Antarctica there is a hole. This allows too much of the sun’s dangerous light into our atmosphere and makes the Earth warmer.

Scientists say we must start making changes and planning now. We need to continue to do research, so we can predict what will happen in the future. We must burn less coal, oil, and gas. Other scientists believe that the problem is not so serious. They think that the Earth is growing warmer naturally, that we don’t need to worry about it now, and that we should just get ready for life in the warmer climate. Most scientists agree that the causes of the world’s climate are very complicated. They say that we must continue to measure the amount of carbon dioxide and ozone in the atmosphere. Scientists also encourage people to learn about the changes that are occurring in the world and how we can all help protect our atmosphere.

(https://climate.nasa.gov/effects/)