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.

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

1. Before reading the text discuss these points with a partner.

• What is climate?

• What climatic belts do you know?

• What is the typical climate of Belarus?

2. Now read the text, translate it and get ready to do the exercises after the text. Climate

Climate is the aggregate of day-to-day weather conditions over a period of many years. It is the result of the interaction of many different elements, the most important of which are temperature and precipitation.

Climatic patterns are a result of the interaction of three geographic controls.¹ The first is latitude. The earth is tilted on its axis² with reference to³ the plane of its orbit around the sun. As it makes its annual revolution around the sun, first the Northern Hemisphere and then the Southern are exposed to the more direct rays of the sun. During the Northern Hemisphere’s summer, higher latitude locations have longer days, with far northern points experiencing a period of continuous daylight. Daylight periods during the winter months are shorter at higher latitudes, whereas more southerly locations have both longer days and exposure to more direct rays of the sun.

The second control is based on the relationship between land and water. Land tends to heat⁴ and cool more rapidly than water. In a tendency called continentality, places far from large bodies of water experience greater seasonal extremes of temperature than do coastal communities⁵. Parts of the northern Great Plains experience annual temperature ranges close to 65⁰C; annual differences of as much as 100⁰ C (from 50⁰C to – 50⁰C) have been recorded in some locations.

The converse effect occurs at maritime locations, especially on the western coast of continents in the mid-latitudes. These locations have smaller temperature ranges as a result of what is called a maritime influence. Summer and winter extremes are moderated by the movement onshore of prevailing westerly wind systems⁶ from the ocean. Horizontal and vertical ocean currents minimize seasonal variations in the surface temperature of the water. The moderated water temperature serves to curb⁷ temperature extremes in the air mass above the surface.

Proximity to large water bodies also tends to have a positive influence⁸ on precipitation levels, with coastal locations receiving generally higher amounts. The reason for this should be obvious; large water bodies provide greater levels of evaporation and thus increase the amount of moisture in the atmosphere.

The third prime geographic influence on climate is topography. Most obvious is the relationship between elevation and temperature, with higher elevations cooler than lower elevations. The influence of topography can be broader, however, because of its effect on wind flow. If a major mountain chain lies astride a normal wind direction, the mountains force the air to rise and cool. As the air mass cools, the amount of moisture that it can hold is reduced. Precipitation results if the cooling causes the relative humidity to reach 100 percent. Moisture falls on the windward side, and the lee is dry.

Notes:

1. geographic control – географический фактор, воздействие

2. earth is tilted on its axis – ось Земли наклонена

3. with reference to – относительно

4. land tends to heat… – земля имеет тенденцию нагреваться

5. community – местность, территория

6. westerly wind system (westerlies) – западные ветры, западный перенос

7. curb – сдерживать

8. … tends to have a positive influence… – оказывать положительное влияние