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Ex. 4. Answer the following questions and give your comments on the problem:
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1. What is the acid rain?
2. What will be the consequences of acid rain?
3. Where does the carbon dioxide come from?
4. What are the causes of the ozone hole?
5. In what way could the pollutants coming from the automobile industry be reduced?
6. Will the greenhouse effect make the world hotter?
7. What could be done to improve the quality of air we breathe?
Active Vocabulary
amount n
burn (burnt) v ,
by-product
carbohydrate n
carbon n
~ dioxide n ,
~ monoxide n
charge v
combine v 1. (); 2. (), ()
compound n ; ,
constituent n
content n ()
derive v 1. , ; 2.
emit v 1., ; 2.
evaporation n ;
evolve v ;
exert v ,
grain n ; , ;
harmful a ,
interaction n
layer n ,
manufacture n
nitrogen n
nitrous a
nutrient n
odorless a
oxide n .
oxygen n
particle n ,
penetrate v ,
require v
respiration n
scatter v
vapour n ;
Additional Texts
Greenhouse gases
An increase in the greenhouse effect (caused by an increase in the concentration of greenhouse gases in the atmosphere) may lead to global warming, with disastrous consequences.
The higher average temperatures produced by global warming could cause dramatic changes in the weather. Less rain might fall over large land masses. Central Africa, south Asia and some of the United States could risk severe drought and famine. More rain might fall in coastal areas and over the oceans; there might be more storms and hurricanes in the Pacific. A rise in the earths average temperature of only one or two degrees would probably melt large expanses of ice in the Arctic and the Antarctic (the polar ice caps) and raise sea levels. Sea levels throughout the world are already rising by about two millimeters a year. If the polar ice caps melt, sea levels could rise by more than a meter over a few decades. Many heavily populated regions, such as Bangladesh, the Nile delta, the Netherlands and Indonesia, would be permanently flooded. Cities are often found on the coast where a river meets the sea, so many of the worlds major population centers could become uninhabitable. About one billion people would lose their homes and become environmental refugees. Some islands, such as the Maldives in the Pacific, might disappear completely.
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Carbon dioxide accounts for 55 percent of the greenhouse effect; CFCs account for 17 percent; methane for 15 percent and nitrous oxide for 5 percent. Carbon dioxide occurs naturally in the atmosphere. It is produced when animals and plants respire. But natural carbon dioxide forms only 0.03 percent of the atmosphere. Higher concentrations of carbon dioxide are not natural at all. Carbon dioxides are produced when living things burn, so it is a by-product of industrial processes which use fossil fuels (coal, gas or oil), and motor vehicles which burn gasoline or diesel fuel. It is also produced when volcanoes erupt and when tropical rainforests are cleared by burning. Methane is also a natural gas, produced when living things decompose in the absence of oxygen. Methane in the atmosphere comes from rotting vegetation, particularly rice fields, and from cattle (because bacteria in their intestines produce methane). It also comes from leaks in the extraction of natural gas. Methane in the atmosphere breaks down relatively quickly (in about 10 years, compared to over 100 years for carbon dioxide and CFCs), so it is a relatively minor environmental problem. However, some scientists believe that huge quantities of methane are trapped within the polar ice caps and will be released suddenly if the polar ice caps melt. This phenomenon would accelerate global warming. Nitrous oxide in the atmosphere comes from bacteria beneath the earths surface, which convert nitrates in the soil to the gases nitrogen and nitrous oxide. The increased use of artificial fertilizers in recent years has increased the production of nitrous oxide. Levels of nitrous oxide in the air will continue to increase for many years, because there is already a large reservoir of artificial nitrates within the soil.
The air we breathe
Air pollution comes in many forms, but four pollutants are particularly important: the sulphur oxides, emitted mainly by power stations and industry; nitrogen oxides, emitted by power stations, industry and vehicles; carbon monoxide, emitted mainly by vehicles; and soot and dust, known technically as suspended particulate matter (SPM), found everywhere where fuels are burnt.
The industrial countries have begun to clean up their air and have invested heavily in the technology to do so. As a result, emissions of sulphur oxides in OECD countries fell from 65 to 40 million tonnes a year over the past two decades. But they increased in the rest of the world, now slowly industrializing from 48 to 59 million tonnes.
GEMS monitors air pollution at 175 sites in 75 countries. In a recent assessment of sulphur dioxide pollution in 54 cities, GEMS reports that air quality was acceptable in 27 cities, marginal in 11 (including London, New York and Hong Kong) and unacceptable in 16 (including Madrid, Paris and Rio de Janeiro). Dust and soot levels were acceptable in 8 cities, marginal in 10 and unacceptable in 23 (including Bangkok, Rio de Janeiro and Tehran).
The effects of acid rain, which prompted Sweden to help set up the UN Conference on the Human Environment 20 years ago, have not diminished over the past two decades. In fact, measurements over large areas of North America and Europe have shown that rain is often 10 times more acid than normal. Thousands of lakes have been affected in Canada, Scandinavia, Scotland and the United States and in many of them all fish has been killed. While acid rain used to be a problem only in developed countries, the issue is emerging, or will probably soon do so, in countries such as Brazil, China, India, Jamaica, Venezuela and Zambia.
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Many countries have introduced tougher laws, cleaner fuels and installed pollution control equipment. In this way Bulgaria, for example, managed to reduce emissions of SPM by 1.6 million tonnes a year during 1976 80. A witness to all this effort is the sale of pollution control equipment which stood at US 12.7 billion in 1991 more than double the expenditure of 10 years previously.
During the 1980s, two new international protocols were signed on limiting emissions of sulphur and nitrogen oxides. Several countries have already gone further than these conventions required. Nine countries had pledged themselves to reduce sulphur dioxide emissions to less than half of 1980 levels by 1995; and Austria, Germany and Sweden had committed themselves to a two-thirds reduction. Twelve west European countries had agreed to reduce nitrogen oxide emissions by 30 percent by 1998.
UNIT VI
| CLIMATE AND WEATHER |
Reading Material
Text A
Task
