CHAPTER 9: ENDANGERED ECOSYSTEM 9.2THE GREENHOUSE EFFECT AND THINNING OF THE OZONE LAYER
THE GREENHOUSE EFFECT
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
Open burning of rubbish
Coal-fueled power stations
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 The rise in sea level Caused by the melting of polar ice caps Low-lying areas around the sea are further lowered resulting in floods Climatic change The high atmospheric temperature speeds up the rate of evaporation, causing drought and sudden floods Changes in wind direction and sea current cause natural disasters such as typhoons and hurricanes to occur more frequently.
Agricultural productivity Productivity of crops and livestock is reduced due to drought (lack of water) and the extremely high temperature. 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
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 Increases the temperature of the environment (which causes the greenhouse effect). Changes in the climate and weather patterns. Changes in wind direction. On plants The rate of photosynthesis decreases due to the destruction of the stomata and chlorophyll in the leaves. Disturbs the ecological balance by destroying aquatic organisms such as planktons.
On human health Causes skin cancer (melanoma). Damages eyesight and causes cataract. 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.
THANK YOU ShamshulNurFatinah Nadia Shakira NurAtiqah NurFatinAmirah 4 Science 2 / 2011