subtopic 9.2 .. slide show

CHAPTER 9: ENDANGERED ECOSYSTEM

9.2 THE GREENHOUSE EFFECT AND

THINNING OF THE OZONE LAYER

THE GREENHOUSE EFFECT

What is Greenhouse Effect?

Phenomenon of an increase in the

temperature of the Earth’s atmosphere.

How this happened?

This is due to the heat that is absorbed and

trapped in the Earth’s atmosphere by certain

gases (greenhouse gases); ex: CO2 ,

methane, chlorofluorocarbon, nitrogen oxide.

These greenhouse gases, especially CO, trap

and absorb heat in the atmosphere, causing a

rise in the temperature of the atmosphere.

The layer of gas act as an insulator to prevent

the heat energy from being transmitted to space.

As a result, the Earth’s temperature increases

causing global warming.

The main cause of the greenhouse effect is due

to the high levels of greenhouse gases in the

atmosphere.

Emission of carbon dioxide from human activities

have increased tremendously, causing the

greenhouse effect to occur worldwide

The greenhouse effect causes the atmospheric

temperature throughout the world to increase.

Hence, the whole Earth’s temperature is

increased and the effect is called global

warming.

Human activities that increase the concentration

of CO2 in the atmosphere

Burning of fuels in factories

Forest fires

Deforestation

Open burning of rubbish

Coal-fueled power stations

Motor vehicles

Use of chlorofluorocarbon (CFC)

The sun’s radiation to the Earth penetrates through

the atmosphere as solar radiation and ultraviolet

radiation.

About 30% of the sun’s radiation is reflected back as

high energy into space by the atmospheric layer while

70% will penetrate through the atmosphere.

About half of the 70% of the sun’s radiation that

penetrates the atmosphere, is changed to heat

energy.

Most of the energy that reaches the Earth’s surface is

absorbed into the Earth.

Part of the heat energy that reaches the Earth’s

surface is absorbed into the Earth.

Most of the infrared radiation are absorbed by carbon

dioxide and other greenhouse gases.

The heat energy in the atmosphere is also absorbed

by carbon dioxide and other greenhouse gases.

As a result, the heat energy is trapped in the lower

atmospheric level, causing the Earth’s temperature to

increase.

The effect is similar to that occurring in a greenhouse

where the sun’s similar to that occurring in a

greenhouse where the sun’s radiation and ultraviolet

radiation that penetrate the glass panels of the

greenhouse are not totally reflected back to the

atmosphere.

Some of these radiations are trapped in the

greenhouse as heat energy.

The overall effect is that the average temperature of

the Earth and its atmosphere is increased resulting in

the greenhouse effect.

Consequences of the greenhouse

effect

1. The rise in sea levela) Caused by the melting of polar ice caps

b) Low-lying areas around the sea are further lowered

resulting in floods

2. Climatic changea) The high atmospheric temperature speeds up the rate of

evaporation, causing drought and sudden floods

b) Changes in wind direction and sea current cause natural

disasters such as typhoons and hurricanes to occur more

frequently.

3. Agricultural productivitya) Productivity of crops and livestock is reduced due to

drought (lack of water) and the extremely high temperature.

b) In temperate countries, productivity of crops will increase during winter because of the moderately higher temperature enable the crops to photosynthesise efficiently.

Today, as level of CO2 and greenhouse gases in the atmosphere continue to rise, the temperature of the Earth and its atmosphere is expected to increase by 1.5 ̊ C to 4.5 ̊ C in the year 2030.

Thinning of Ozone Layer, O3

Ozone is actually a gas that

contains three oxygen atoms.

The ozone layer is located at the

atmospheric layer called the

stratosphere which is 20-50 km away from the

Earth’s surface.

The ozone Layer acts an absorbance to the harmful

ultraviolet rays (UV rays) and prevents them from

reaching the surface of the Earth.

Today, the ozone layer is becoming thinner

because of the destruction of the ozone gas.

It was found that the depletion of the ozone layer

occurred over both Artic and Antartic, creating

ozone holes. The ozone hole in the Antartic is

found to be as big as the continent of U.S.A.

The depletion of ozone is caused by the

increasing use of chlorofluorocarbons which can

break down and destroy ozone molecules into

other elements.

Other pollutants such as halons, chlorine gas and

nitrogen oxides can also destroy the ozone.

The main cause of ozone depletion is the use of

chlorofluorocarbons (CFC).

CFC are widely used as a cooling agent in

refrigerators and air-conditioners, in aerosol

sprays, polystyrene food container, and rubber

foams for making cushions, pillows and

mattresses.

The Process of Ozone Depletion by

CFC

Ultraviolet radiation reacts with CFCs by breaking

the chlorine atom bond in the CFCs.

A chlorine atom is released. The highly reactive

chlorine atom destroys the ozone by reacting with

the ozone to produce chlorine monoxide and

oxygen molecules.

Free oxygen atoms in the atmosphere will break

the chlorine monoxide bond. As a result, a

chlorine atom is released and this chlorine atom

can destroy more ozone molecules.

Effects of the Thinning of the Ozone

Layer

On the environment

1. Increases the temperature of the environment

(which causes the greenhouse effect).

2. Changes in the climate and weather patterns.

3. Changes in wind direction.

On plants

1. The rate of photosynthesis decreases due to the

destruction of the stomata and chlorophyll in the

leaves.

2. Disturbs the ecological balance by destroying

aquatic organisms such as planktons.

On human health

1. Causes skin cancer (melanoma).

2. Damages eyesight and causes cataract.

3. Weakens the human immune system.

Skin cancer (melanoma)

Impact of the Thinning of the Ozone Layer

and Global Warming on the Ecosystem

The thinning of the ozone layer allows ultraviolet

radiation to reach the Earth’s surface and destroy the

planktons in the food chain. This upsets the balance

in the ecosystem and consequently threatens the

other ecosystems in the water.

Ultraviolet radiation also reduces the number of

stomata and amount of chlorophyll in the leaves.

Hence, green plants which are the producers in a

food chain cannot carry out photosynthesis efficiently.

The plants will die and the biotic components in the

ecosystem are threatened.

Global warming causes the atmosphere to be very

hot, resulting in drought and changes in the climate.

This affects the a biotic components in the ecosystem

which consequently affects the distribution and

population of the biotic components. As a result, the

balance of various ecosystems on Earth in not

equilibrium.

Shamshul Nur Fatinah

Nadia Shakira

Nur Atiqah

Nur Fatin Amirah

4 Science 2 / 2011