12th Zoology

Global warming – Green house effect

Global warming – Green house effect

Global warming refers to an average increase in the earth’s
temperature, which in turn causes changes in climate. During the past 4.65
billion years of its history, earth has warmed many times. But at present it is
facing a rapid warming mainly due to human activities. The average
temperature of earth is about 590F (150C). During the last century this
average has risen by about 10F. By the year 2100, it is believed that the rise
would be between 2.5 and 10.40F. This will cause dramatic changes such as
rise in sea level, changes in rainfall patterns, wide range of impacts on plants,
wildlife and humans.

Green house gases and Green house effect

The trapping of energy from the sun by certain gases in the
atmosphere leading to the rise in earth’s temperature is known as Green
house effect. Hence these gases are known as green house gases. Some
gases such as water vapour, carbon dioxide, nitrous oxide and methane act
as the trap. These gases absorb and reflect infra-red waves radiated by earth.
By doing so, these gases conserve heat as the glass in a green house does.

Normally all life on earth depends on this green house effect. If it
does not exist, earth would be cooled, and ice would cover earth from pole
to pole. But if the greenhouse effect becomes strong it could make the earth
warmer than usual. Even a little extra warming may cause problems for
humans, plants and animals.

Types of Greenhouse Gases

In the environment, greenhouse gases occur (i) naturally or (ii) from
human activities.
The most abundant greenhouse gas is carbon dioxide. It reaches
the atmosphere due to volcanic eruptions, respiration of animals, burning
and decay of organic matter such as plants. Normally carbon-dioxide is
removed by the plants by photosynthesis. Carbon-dioxide is also absorbed
into ocean water. But humans by their activities increase the release of
carbon dioxide into the atmosphere . Such activities include burning of fossil
fuels, solid wastes, wood and wood products to drive vehicles, generate
electricity etc. At the same time due to deforestation, the number of trees
available to absorb carbon-dioxide through photosynthesis has been greatly

Human activities have caused carbon-dioxide to be
released to the atmosphere at rates much faster than that at which earth’s
natural processes can recycle this gas. There were about 281 molecules of
carbon-dioxide per million molecules of air (i.e., parts per million or ppm) in
1750. Today atmospheric carbon-dioxide concentrations are 368 ppm, a
31% increase.

Methane traps 20 times more heat than carbon-dioxide. It is
emitted during the production and transport of coal, natural gas and oil. It is
also emitted from rotting organic waste in sand fills, by the cows as a by
product of digestion. Since 1750, the amount of methane in the atmosphere
has more than doubled.

Nitrous Oxide traps 300 times more heat than carbon-dioxide.
burning fossil fuels and ploughing farm soils releases nitrous oxide. Since
1750 its level increased by 17%. Hydrocarbons formed from the manufacture
of foams, coolants such as chlorofluorocarbons used in refrigerators
are the other gases responsible for global warming.

In 2000, scientists discovered an alarming increase in the level of a
new gas called trifluoromethyl sulphur penta fluoride. Eventhough the
gas is rare, it traps more effectively than all other greenhouse gases. The
saddest part of it is that the industrial source of the gas is not yet

Effects of Global warming

1. Due to the warming of oceans, sea level will rise. Glacier ice will also melt,
causing further rise in sea level. As a result in the 21st century sea level will
rise from 9 to 88 cm. Such a rise will submerge many parts of countries.
2. Seasons will be longer in some areas.
3. The warmed world will be generally more humid and greater humidity will
increases the rainfall.
4. Storms are expected to be more frequent and intense.
5. Some regions of the world would become dry.
6. Wind blows will be harder and in different patterns. Hurricane would be
more severer.
7. Weather patterns would be less prediclable and more extreme.
8. Crops and forests may be affected by more insects and plant
9. Animals and plants will find it difficult to adjust to the changed
environment. Animals will tend to migrate toward the poles and toward higher
10. Some types of forests may disappear.
11. More people will get sick or die from heat stress.
12. Tropical diseases such as malaria, dengue fever, yellow fever and
encephalitis will spread to other parts of the world.

Efforts to control Global warming

Two major ways are there to control global warming: 1. to keep the
carbon-dioxide out of the atmosphere by storing the gas or its carbon
component somewhere else, a strategy called carbon sequestration.
2. to reduce the production of green house gases.

Carbon sequestration

The simple technique is to preserve trees and plants more. Trees,
take up carbon-dioxide, break it down in photosynthesis, and store carbon
in new wood. It need massive reforestation. Carbon-dioxide can also be
sequestrated directly into deep ocean water or into oil wells or some aquifer
form which it cannot escape.
Usage of alternate fuels such as nuclear energy, solar power, wind
power and hydrogen fuel cells which emit no greenhouse gases are being

Related Topics in Zoology:

Bio Zoology All Important Topics

  1. Human population and explosion

  2. Population Explosion

  3. Growing Population and Environmental impacts

  4. Global warming – Green house effect

  5. Ozone layer depletion

  6. Prevention and Effect of Ozone depletions

  7. Waste management – Classification

  8. Management of hazardous wastes

  9. Management of non hazardous wastes

  10. Waste water treatment and management

  11. Biodiversity

  12. Conservation of Biodiversity

  13. Characteristics of a Bioreserve

  14. Energy crisis and its environmental impact

  15. Steps to be taken to resolve energy crisis

  16. Environmental impacts of Power Sources

  17. Poverty and environment

  18. Fresh water crisis and management

Unit 6. APPLIED BIOLOGY Topic List Zoology

  1. Livestock and Management

  2. Important cattle breeds and their characteristics

  3. Milch breeds (or) Dairy breeds

  4. Dual purpose breeds & Draught breeds

  5. Exotic breeds of cattle

  6. Common diseases and control in Cattle – Contagious diseases

  7. Non-contagious diseases – Cattle

  8. Techniques adopted in cattle breeding

  9. Poultry Breeds

  10. Farming methods

  11. Poultry byproducts

  12. Fish Pond

  13. Edible Fishes Of Tamilnadu

  14. Medical Lab Techniques – Stethoscope

  15. Sphygmomanometer

  16. Haemocytometer

  17. Urine Sugar analysis

  18. ECG Electrocardiogram

  19. Computed Tomography CT

  20. Endoscopy (Laproscopy) techniques , Artificial Pacemaker

  21. Autoanalyser

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