環(huán)球英語(yǔ)—895: Geoengineering: Carbon Dioxide

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Welcome to Spotlight. I'm Robin Basselin.
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And I'm Ryan Geertsma. 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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Can we use science to end the danger of global warming? Many people do not think it is possible. However, there are many scientists attempting to do just this.
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Today's Spotlight program will be on one kind of geoengineering. Geoengineering is using science to engineer the environment to fight global warming. This particular kind of geoengineering tries to remove greenhouse gases, like carbon dioxide, from the air.
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You may have heard another Spotlight program on Geoengineering. That program was about a kind of geoengineering called sunblocking. Sunblocking tries to reduce global warming by blocking some of the sun's radiation.
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However, the major issue with sunblock geoengineering is that it does not address the basic cause of global warming. Blocking some of the sun's radiation might cool the Earth's temperature. But it does not decrease the greenhouse gases in the air - and these are the gases that cause the warming. This is the problem that led many scientists to concentrate on another kind of geoengineering - removing carbon dioxide from the air. Scientists have concentrated on carbon dioxide because it is one of the most harmful greenhouse gases.
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One way of removing carbon dioxide is based on increasing a natural process. You see, every day, trees and plants all over the world take in carbon dioxide from the air and break it down, releasing oxygen. This process is called photosynthesis. Scientists believe that if they can increase this process, the amount of carbon dioxide in the air will reduce. People have been planting more trees to help this process.
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However, we humans are cutting down and using trees faster than we are planting them. The trees that we plant take time to grow and reproduce. And all the trees in the world simply cannot take in the amount of carbon dioxide that we humans release.
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So, scientists have thought of a new way to greatly increase the earth's amount of plant life quickly. However, the plants they want to increase are not trees and they do not live on land. Instead, these plants live in the world's oceans. They are very small pieces of plant life called phytoplankton.
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Each phytoplankton is so small that it cannot be seen by the human eye. Together, millions of phytoplankton can make an area of the ocean appear green. And together, they take in a lot of carbon dioxide.
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So, scientists want to increase the ocean's phytoplankton by fertilizing them. They want to feed the phytoplankton minerals, like iron or nitrogen, to help them grow quickly. Experiments have shown that fertilizing phytoplankton does make them grow very quickly. In fact, scientists can even grow phytoplankton in "dead" areas of the ocean - areas where phytoplankton could not live before.
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By increasing phytoplankton, scientists would increase the amount of carbon dioxide removed from the air. And when a phytoplankton takes in carbon dioxide, it releases good oxygen into the air. The carbon stays in the phytoplankton. And when the phytoplankton dies, it sinks to the bottom of the ocean floor.
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Could phytoplankton be the answer to global warming? Many people are not so sure. Scientists cannot solve global warming just by releasing fertilizers into the ocean one time. Instead, they would have to manage this process forever.
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Another issue is that scientists would have to carefully control the amount of phytoplankton in the ocean. Scientists know that too much phytoplankton can kill fish. However, the bigger problem is what scientists do not know. No one knows what other effects fertilizing phytoplankton could have on the world's oceans.
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One leading scientist in the area of ocean fertilizing is Ian Jones. He wants to fertilize parts of the world's oceans that do not have a lot of phytoplankton. He spoke to filmmakers of the BBC television program "Five Ways to Save the World" about the possible problems. He told them,
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"If you do not like the result of ocean fertilizing, you can just turn off the supply... When you turn off the food supply for the phytoplankton, they will just die and fall to the deep ocean."
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Another idea for removing carbon dioxide from the air tries to copy the work of trees. However, this idea does not involve real trees or plants. Instead, it involves an artificial tree - one made by humans.
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Klaus Lackner is the scientist that invented the artificial tree. He told the television science program NOVA,
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"We are trying to copy what the leaves of a tree can do... Some people would say this cannot be done, and yet every tree can do it."
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However, Lackner's tree does not look like a natural tree. Instead, it is a large metal and glass structure. Inside the structure are many long, flat pieces of material. These hanging pieces of material are the artificial tree's "leaves." And these leaves are the secret to removing carbon dioxide from the air.
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Lackner began his work on the artificial tree based on a simple chemical process. He knew that when carbon dioxide was mixed with sodium hydroxide, it would become sodium carbonate. He recognized that if air passed through a structure with sodium hydroxide, it would remove much of the carbon dioxide. He believed this carbon dioxide could be stored in rocks deep below the ocean floor.
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Lackner and other scientists have spent a long time developing the artificial tree. Today, the tree is designed to use very little energy, and it uses a different material to take in the greenhouse gas - not sodium hydroxide. Wind blows the air through the tree. Then the long, flat pieces of material or "leaves" take in the carbon dioxide from the air. Next the captured carbon dioxide is removed from the pieces of material and made into liquid.
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The artificial tree does not produce oxygen, as a real tree does. One of the greatest problems with the artificial tree is finding storage for the carbon dioxide that it catches. Lackner wants to store the trapped carbon product deep underground. Lackner and other scientists continue to experiment and think about how this problem can be solved.
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Lackner believes that science must and will find an answer to global warming. In fact, he told NOVA,
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"I believe that it is not possible to stop people from using fossil fuels, so we need to develop technologies that let us use them without creating environmental damage to the planet."