Français

Script 27.10

Notes to broadcasters

Contents:  The Earth’s atmosphere is changing for the worse because of ozone depletion and global warming.

Script

Is the weather getting worse where you live? Does the sun seem to burn hotter? Do the rains fail to fall?

Some scientists believe what is happening is different from the year‑in, year‑out changes in the weather that farmers have always had to put up with. And they think pollution from such sources as big factories, burning fuel for heat and cooking, and machines, cars, and trucks is to blame.

To understand what these scientists are worried about, it helps to know a bit about the Earth as a planet and the effect of the gases that surround it – what we call the atmosphere.

Earth’s atmosphere:
The atmosphere is like a cloak covering the Earth, protecting it and keeping it warm, the way a cloak protects a person. And even though the Earth’s cloak is made out of gases that you can’t see, it works very well.

That is because the gases that make up the atmosphere have special characteristics that have helped the Earth develop into the beautiful, fertile place it is. Getting back to the cloak idea, it is as if a person’s cloak were woven from many different threads, and each of the threads served a useful purpose.

The gases that make the atmosphere such a successful cloak help keep out harmful rays of the sun. At the same time, the gases keep in warmth.

The trouble is, most scientists think, that we are causing changes in the mix of gases that make up the atmosphere, and changing the way the atmosphere works.

The thinning ozone layer The scientists who study the atmosphere say several dangerous changes are happening. We will talk about two of them right now.

One is that more ultra‑violet light from the sun is reaching the earth. Ultra‑violet light is just one of the kinds of light that the sun provides. Unfortunately, it is harmful. Ultra‑violet rays from the sun burn the skin, damage our eyes, and affect the growth of plants. There is a special kind of gas in the atmosphere which protects the earth from ultra‑violet rays. But that gas is now thinner and lets more ultra‑violet rays through.

The gas that is too thin is called ozone. So this problem is called the thinning of the ozone layer. Sometimes the gas is so thin that people say there is a hole in the ozone layer.

Global warming:
Other gases in the atmosphere, particularly a gas called carbon dioxide, can act like a blanket, keeping heat in. Carbon dioxide keeps heat from escaping in the same way that a pane of glass traps heat in a greenhouse, so this is called the greenhouse effect. The earth never would have been a good place to live if there had not been carbon dioxide in the atmosphere to trap the sun’s warmth so plants could grow.

But now there is too much carbon dioxide. Scientists think that the air all over the Earth is getting hotter because there is too much carbon dioxide building up in the atmosphere and so heat cannot escape. It floats up in the atmosphere and sits there, forming a barrier. When the sun warms the earth, the heat from the earth is reflected back up into the sky. Before there was so much carbon dioxide, enough heat escaped into space so the earth did not get too hot. But now, too much of the heat is trapped and the air just gets hotter and hotter. This gradual increase in temperature is known as global warming.

It is hard to prove that the ozone is thinning or that there is global warming because, of course, weather is always changing. Maybe the hotter sun and lack of rain would have happened anyway. But many scientists think our climate is changing for the worse because people use so many machines and chemicals.

For instance, the ozone layer is thinning because of certain chemicals which escape into the atmosphere. So the way to stop the ozone from thinning is to stop these chemicals from escaping. The trouble is, they are useful, and when they are used, some are bound to escape. The chemicals are called chlorofluorocarbons and furons and they are vital in air conditioning and refrigerators. They also were used in making products such as plastic foam, or to make liquids spray out of aerosol cans. Different ways have been found to do some of these things, and scientists are working on finding others. But chlorofluorocarbons last a long time in the atmosphere. That means that even if we stopped using them completely right now, the chlorofluorocarbons that have already escaped into the atmosphere will continue to make the ozone thinner for another hundered years.

Global warming is blamed mainly on burning. For example, burning coal, oil, gas, or wood give off carbon dioxide, which stops heat from escaping from the atmosphere. So machines like cars, trucks, or generators that burn fuel contribute to global warming. Using efficient, well‑tuned machines, and turning machines off when they are not in use cuts down on the amount of carbon dioxide they emit. Another way to fight global warming is to plant and conserve trees, because trees help remove carbon dioxide from the atmosphere.

Methane is another gas that behaves like carbon dioxide and traps heat in the atmosphere. Methane comes from many sources. For instance, it is produced by rice paddies and by ruminants, such as cows.

What does all this mean for you and your family? It may mean in the years to come that land will not be farmed in the traditional way. Because of global warming, sub‑tropical regions may become even drier, and tropical regions even wetter. Sea levels may rise and flood lowlying coastal areas. But these changes will not happen in any predictable way.

Meanwhile, the thinner ozone layer means you and your family should protect yourselves from the sun. Cover your skin and shield your eyes. It may also affect the health of your crops and livestock.

The scientists who are worried about the ozone layer and global warming say that, if we keep using more and more chemicals and burning more and more fuel, we risk destroying the world. We can all help solve this problem by making wise use of machines and chemicals.

Information Sources

The following OUTREACH Information Packs are available free from:

Dr. James Connor, OUTREACH Director, Teaching & Learning Center, 200 East Building, 239 Greene Street, New York University, New York, New York 10003, USA OR Mr. Richard Lumbe, OUTREACH Co‑ ordinator, Information & Public Affairs, UNEP, P.O. Box 30552, Nairobi, KENYA.

#55  Weather

#56  The changing atmosphere (1) the “Greenhouse effect”

#57  The changing atmosphere (2) the “Greenhouse effect”

#58  The changing atmosphere (3) the Ozone layer

#59  The changing atmosphere (4) acid rain and pollution