5. Place the appropriate word from the list in each of the blanks below:

rays, ozone layer, latitude, greenhouse gases, greenhouse effect, contributing, trend

1. The … is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface.

2. The major … are water vapor, which causes about 36–70 percent of the greenhouse effect; carbon dioxide (CO2), which causes 9–26 percent; methane (CH4), which causes 4–9 percent; and ozone (O3), which causes 3–7 percent.

3. The main positive … in global warming is the tendency to increase the amount of water vapor in the atmosphere, a significant greenhouse gas.

4. Most scientists accept that humans are … to observed climate change.

5. The … of the Earth's atmosphere plays an important role in depleting the amount of ultraviolet (UV) radiation that reaches the surface.

6. The climate of a region depends on a number of factors, especially …

7. The sun's … hit the equator at a direct angle between 23 ° N and 23 ° S latitude.

Reading for Speaking and Discussing

Read the text and choose the title to each part:

1. Causes of climate change

2. Impacts of climate change

3. Human causes

4. Definition of climate change

5. Natural causes

Climate Change

1. Ever since the earth came into being there has been a climate system. The climate of a place is the average weather that it experiences over a period of time. The factors that determine the climate at a location are the rainfall, sunshine, wind, humidity, and temperature.

Climate change is a change in the statistical distribution of weather over periods of time that range from decades to millions of years. It can be a change in the average weather or a change in the distribution of weather events around an average (for example, greater or fewer extreme weather events). Climate change may be limited to a specific region, or may occur across the whole Earth.

While changes in the weather may occur suddenly and noticeably, changes in the climate take a long time to settle in and are therefore less obvious. Throughout the earth's history there have been changes in the climate. There have been well-marked cold and hot periods and all life forms adapted naturally to this change.

Over the last 150-200 years climate change has been taking place too rapidly and certain plant and animal species have found it hard to adapt. Human activities are said to be responsible for the speed at which this change has occurred and it is now a cause of worry to scientists.

The atmosphere surrounding the earth is made up of nitrogen (78%), oxygen (21%) and the remainder, 1%, is made up of the greenhouse gases: carbon dioxide, methane, ozone, water vapour, and nitrous oxide. These greenhouse gases act as a blanket and protect it from the harmful ultra violet rays of the sun. They can also be regarded as natural controllers of the earth's temperature system.

2. The earth's climate is dynamic and always changing through a natural cycle. What the world is more worried about is that the changes that are occurring today have been speeded up because of man's activities. These changes are being studied by scientists all over the world who are finding evidence from tree rings, pollen samples, and sea sediments. The causes of climate change can be divided into two categories - those that are due to natural causes and those that are created by man.

3. There are a number of natural factors responsible for climate change. Some of the more prominent ones are continental drift, volcanoes, ocean currents, the earth's tilt, and comets and meteorites. Any or all of these phenomena can have an impact on the climate.

4. The Industrial Revolution in the 19th century saw the large-scale use of fossil fuels for industrial activities. These industries created jobs and over the years, people moved from rural areas to the cities. This trend is continuing even today. More and more land that was covered with vegetation has been cleared to make way for houses. Natural resources are being used extensively for construction, industries, transport, and consumption. Consumerism (our increasing want for material things) has increased by leaps and bounds, creating mountains of waste. Also, our population has increased to an incredible extent.

All this has contributed to a rise in greenhouse gases in the atmosphere. Fossil fuels such as oil, coal and natural gas supply most of the energy needed to run vehicles, generate electricity for industries, households, etc. The energy sector is responsible for about ¾ of the carbon dioxide emissions, 1/5 of the methane emissions and a large quantity of nitrous oxide. It also produces nitrogen oxides (NOx) and carbon monoxide (CO) which are not greenhouse gases but do have an influence on the chemical cycles in the atmosphere that produce or destroy greenhouse gases.

5. Climate change is a threat to mankind! Since the end of the 19th century the earth's average surface temperature has increased by 0.3-0.6 °C. Over the last 40 years, the rise has been 0.2-0.3 °C. Recent years have been the warmest since 1860, the year when regular instrumental records became available.

Some important aspects of our lives can be affected through changes in weather patterns.

They are:

Agriculture

Extreme weather conditions such as high temperature, heavy rainfall, floods, droughts, etc. will also affect crop production.

Weather

A warmer climate will change rainfall and snowfall patterns, lead to increased droughts and floods, cause melting of glaciers and polar ice sheets, and result in accelerated sea- level rise. Coastal areas and small islands are among the most densely populated parts of the world. They are also the most threatened because of rises in sea level that global warming may cause

Health

Global warming will directly affect human health by increasing cases of heat stress.

Forests and wildlife

Ecosystems sustain the earth's entire storehouse of species and genetic diversity. Plants and animals in the natural environment are very sensitive to changes in climate. The ecosystems that are most likely to be affected by this change are the ones in the higher latitudes, the tundra forests. Polar regions will feel the impact of warming more than others. Interiors of continents will experience more warming than the coastal regions.

Marine life

Corals are known as the tropical forests of the oceans and sustain diverse life forms.

As ocean waters in the tropics become warmer, the damage to coral reefs seems to be increasing. These corals are very sensitive to changes in water temperature, which causes bleaching.

There is still a great deal that we do not understand about our climate, and about how our activities will change it. But one thing can be said loud and clear: if we wait to get answers to these questions, it will probably be too late!