Lecture # 7: Global Warming

Objectives1.To Define Global Warming2.To Discuss the Causes of Global Warming3.To Discuss the Consequences of Global Warming4.To Detect the Remedies for global Warming

Presented by Abul Kalam Azad

Senior Lecturer, GEDNorthern University Bangladesh

E-mail: kalamadd@gmail.com

Introduction Since few centuries, we have been

observing the increase in the average temperature of the Earth's near-surface air and oceans. The predicted countries vulnerable to such global warming are much more concerned about its devastating aftermath for many environ-mental scientists consider global warming as the greatest environmental threat of the 21st Century. Bangladesh will be one of the most serious victim countries of global warming due to its geographical location. Let’s, first of all, define the concept ‘global warming’ and then discuss the causes, consequences and remedies of global warming.

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans, and its projected continuation.

Global warming is potential increase in average global atmospheric temperatures resulting from the greenhouse effect. [Encyclopedia Britannica]

Broadly speaking, sunlight/ solar energy reaches to the earth atmosphere in three forms: i) Ultra Violet Radiation; ii) Visible light; and iii) Infra-red & radio waves. During the day time, visible light and infra-red &

Definition of Global Warming:

radio waves come to the earth and some of its hit is absorbed by the earth and the rest goes back into the atmosphere. After entering the atmosphere, part of this hit is absorbed by Carbon dioxide and water vapor present in the atmosphere and the rest is absorbed into the universe. During the night, when there is no sunlight, Carbon dioxide and water vapor release this hit to the earth. Otherwise the earth would be cooled and the survival of life would be impossible.

Carbon dioxide and water vapor, thus, balances the temperature. However, due to relatively recent increase of the concentration of CO2, CFCs, methane (CH4), nitrous oxide (N2O), the temperature is rising gradually and hitting ozone layer. As a result, ozone hole that is noted cause Ultra violet rays to reach directly to the earth, and global warming. Thus, global warming is the result of green house effect (see the next slides concerning green house effect & global warming).

1. Visible light and infra-red rays pass through the CO2 into the lower region of the atmosphere.

2. Incoming energy is converted to heat3. Longer, infra-red wavelengths hit green-house

gas molecules in the atmosphere 4. Greenhouse gas molecules in the atmosphere

emit Infrared radiation back towards earth. [N.B. Infra-red is a type of light that feels warm but cannot be seen]

5. Greenhouse gases being more concentrated into the atmosphere hit the ozone layer and cause ozone hole.

6. Ultra violet rays hit the earth directly and cause global warming.

Steps of Global Warming

Carbon Dioxide (CO2)

- Source: Fossil fuel burning, deforestation Methane (CH4)

-Source: Rice cultivation, cattle & sheep ranching, decay from mining.

Nitrous oxide (N2O)

- Source: Industry and agriculture (fertilizers)

CFCs-Source: fridge, refrigerator, air conditioner,

aerosol etc. These Greenhouse gases absorb infrared radiation and prevent it from escaping to space.

Greenhouse Gases

The “greenhouse effect” & global warming are not the same thing.

– Global warming refers to a rise in the temperature of the surface of the earth

An increase in the concentration of greenhouse gases leads to an increase in the magnitude of the greenhouse effect. (Called enhanced greenhouse effect)

– This results in global warming (See increasing rate of global warming in the next slide)

Greenhouse Gases Vs. Global Warming

Causes of global warming There are many causes of global warming.

Most important causes are:1. Deforestation.2. Industrialization. 3. Burning of fossil fuels.4. Decay of dead organisms. 5. Respiration/ breathing of living organisms. 6. pollution of Automobile 7. Thermal power plant8. Cultivation of land.9. Eruption of volcanoes (a mountain with a

large circular hole at the top through which lava, gases, steam and dust are forced out)

10. Domestic cooking

Concern of Bangladesh for Global warming Though Bangladesh is less responsible for

global warming, she will be one of the most victim countries for her geographical location (see next slide). Bangladesh is concerned for the following impacts of global warming –

The coastal area of Bangladesh will go under the Bay of Bengal.

Bangladesh will have to face critical food crises.

Bangladesh will have to face the refugee problems.

The largest mangrove forest in the world will be destroyed.

Total environmental balance will be destroyed.

Effects of global warming

Environmental scientists inform that if only 3 % global temperature on an average is increased, 40 crore tones of crop-production will be obstructed and 40 crore of population will be hunger of food. However, global warming has the following impacts-

1. Melting ice2. Flooding of low lying costal areas3. Sea level change4. Increase in the flow of rivers and

change in the rainfall pattern.

Impacts of Global Warming

5. Submersion of Islands.6. Occurrence of more

cyclones and hurricanes.7. Damage of agricultural

crops.8. Water pollution9. Refugee problems10. Deforestation11. Ozone layer depletion

The broad agreement among climate scientists that global temperature will continue to increase has led some nations, states, corporations and individuals to take proper actions to limit global warming or adjust to it. Some encourages action against global warming individually, communally and by regional organizational effort. Others suggest a quota on worldwide CO2 emissions. However, we can take the following initiatives:

Remedial Policies

1. Decreasing emission of green house gases e.g., carbon dioxide, methane (CH4), Nitrous oxide (N2O), CFC etc.

2. Forestation3. Use of eco-friendly goods4. Well environmental management5. Implementation of different inter-

national agreement and treaty favorable for sustainable environ-ment. For example- Kyoto protocol agreement.