環(huán)球英語—881：Geoengineering: Sun Block

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Welcome to Spotlight. I'm Ryan Geertsma.
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And I'm Robin Basselin. Spotlight uses a special English method of broadcasting. It is easier for people to understand, no matter where in the world they live.
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The greenhouse effect. It is a basic process that supports the global environment. Humans and other living things naturally release "greenhouse" gases into the air. These particular gases trap heat in the Earth's air. Without these gases, the Earth would be very cold and many plants and animals could not survive.
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However, in the last 150 years, humans have released more and more of these greenhouse gases into the air. And this is slowly causing the Earth's temperature to rise. Many scientists think that this global warming will soon cause serious problems - problems like extreme lack of water, floods, and other natural disasters. These extreme problems could cause many people to die.
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However, some scientists think there is hope for the Earth's future. They believe there are scientific ways to avoid these serious problems. Today's Spotlight program is one of two programs about geoengineering. This kind of science studies ways to engineer the environment. The hope is that geoengineering will stop and even repair the effects of global warming.
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Humans produce greenhouse gases by burning fossil fuels, such as oil and coal. Fighting global warming requires people to use less fossil fuels. And this is not an easy change. Right now, fossil fuels are the world's major producer of energy.
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But reducing our use of these fuels is necessary. So governments are encouraging people to think about ways they can reduce greenhouse gases - like driving and travelling less, buying more local products and using less coal. Scientists are also helping by researching new forms of energy - energy that does not release harmful emissions.
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Until recently, most scientists and environmentalists have not supported geoengineering. Instead, they have supported a simple message to fight global warming. The message is "people need to reduce their emissions and reduce them now."
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However, to keep global warming at the level it is today, people all over the world would need to reduce their emissions by about seventy percent [70%]. This is a big change to make in a short time. This is a good goal. But people are beginning to ask the question, "What if we do not reach this goal?" This is the question geoengineering is trying to answer.
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There are many different geoengineering ideas. But there are two basic kinds of ideas. This program will look at the first kind - limiting the amount of the sun's radiation that reaches the Earth.
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Many scientists believe that blocking some sunlight can help cool the Earth. In fact, they believe that blocking only one or two percent of the sun's radiation will cool the Earth enough to fight global warming.
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However, blocking sunlight is not easy. Some scientists have very complex plans about how this can be done. Roger Angel is one such scientist. His idea is to make a huge glass cover or screen for the Earth. This glass screen would be very thin. It would be made from millions of individual pieces - and it would orbit the Earth in space. The screen would only cover a small part of the Earth. But this would be enough to block the necessary sunlight.
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The sun screen would cost a lot of money. It would also take a lot of research and testing. Today, it is only an idea, but could it provide a possible answer?
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Another sun blocking idea involves clouds. For over fifty years, scientists have been trying to control clouds. They fire substances into a cloud to increase rainfall. The process is called ‘seeding'. Cloud seeding is not always successful at making rain. However, many scientists believe that seeding may help clouds to block enough sunlight to reduce global warming.
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Scientists have different ideas about how to make these sun blocking clouds. Some scientists believe that creating bright or shiny clouds can help block sunlight best. These clouds could be made by shooting seawater into the atmosphere. The salt in the seawater would seed the clouds. The seeded clouds would become thicker, and block more sun than normal clouds.
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This idea would not cost as much as the sun screen idea. Scientists could use the salt water from the Earth's oceans. And special wind powered boats have already been designed. However, for this idea to work, the boats would always have to be shooting salt water into the air.
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Another cloud making idea is based on a natural event - the erupting of volcanoes. Volcanoes are large mountains that sometimes erupt or explode. Many people think of volcano eruptions as bad events. They shoot smoke and hot, fiery liquid out of their tops. Often these eruptions kill many people or ruin towns and land.
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However, volcano eruptions also cool the Earth. This may seem surprising, since the explosions are very hot. But scientists have found that the smoke from the volcanoes spreads throughout the atmosphere. And the smoke particles block sunlight.
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In 1991, Mount Pinatubo erupted in the Philippines. Over two years, the smoke particles in the atmosphere caused the Earth's average temperature to drop more than half a degree Celsius. And scientists think this same idea can be used to fight global warming.
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To do this, scientists would launch smoke or sulfate particles into the atmosphere with rockets. These particles would act like volcano smoke, and lower the Earth's temperature. Scientists could then continue to do this whenever it was necessary.
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These sun blocking ideas all provide possible ways to stop global warming. However, they also have many possible problems. No one knows how blocking sunlight will affect the rest of the environment. Could it cause too much rain? Could it keep crops from growing well? There are many questions.
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Another problem with cloud making is pollution. The smoke particles that these scientists want to release will pollute the air. They will also damage the ozone layer of the atmosphere. But some leading scientists believe that in an emergency, lowering the Earth's temperature may be more important than protecting the ozone layer.
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Paul Crutzen won a Nobel Prize in chemistry for discovering why and how the ozone layer was being damaged. But even Dr. Crutzen supports the release of smoke particles into the atmosphere to stop global warming. In the filming of a BBC television program called "Five Ways to Save the World," Dr. Cruzten said,
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"You cannot have an ideal world... I am prepared to lose some, a bit, of ozone if we can prevent major increases in temperature in the future."
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So, what do you think about geoengineering? Do you think blocking the sun is a good way to stop global warming? Do you think it is time to explore these kinds of ideas? You can tell us what you think by emailing us at radio @ english . net.
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Also, look for another Spotlight program on geongineering. This program discusses the other major geoengineering idea - removing greenhouse gases from the air.