A、It is the result of decreasing the amount of carbon dioxide. B、It could melt the polar ice caps, which would cause disastrous

W: Good morning, Dr. Morgan. Welcome to "The Future World".
M: Thank you.
W: Well, what are your predictions about the world? What is it going to be like in the year 2020?
M: Hum, if present trends continue, I’m afraid the world in 2020 will be more crowded and more polluted than the world we live in now.
W: Yes, however, food production is constantly increasing. Don’t you think we will be able to cope with the increase in world population?
M: I don’t think so. Even though production is constantly increasing, the people of the world will be poorer than they are today. For hundreds of millions of the desperately poor, the supply of food and other necessities of life will not be any better. And for many they will be worse, unless the nations of the world do something to change the current trends.
W: What about energy? Will there be enough oil to satisfy our needs in the year 2020?
M: World oil production will reach the maximum and the price of oil will begin to increase. The available supplies will not be sufficient for our needs. So at least part of these needs will have to be met by alternative sources of energy.
W: Yes, water is becoming a problem, too.
M: Yes, unfortunately. Water shortage will become more severe in the future, and due to the increase of births there will be enough water only for half of the population.
W: Which of the present trends do you think will continue over the next decade?
M: Well, significant loss of the world’s forests will continue over the next 10 years as the demand for wood for fuel and manufacturers increases. Also atmospheric concentration of carbon dioxide and other chemicals is expected to increase at rates that could alter the world’s climate due to the "green-house effect".
W: The "green-house effect"? Could you explain what it is?
M: Sure. The amount of carbon dioxide in the air is progressively increasing and it traps more of the heat of the sun in the lower atmosphere. This has a warming effect which could change the climate and even melt the polar ice caps, which would cause disastrous flooding.
19. According to the conversation, what is Dr. Morgan?
20. According to what Dr. Morgan says, what will happen to the world in 2020?
21. What are human beings now faced with?
22. What is "green-house effect"?