Global warming refers to the overall rise in the average temperature of the Earth’s atmosphere. The main source of global warming is the increase of greenhouse gases such as carbon dioxide, oxides of nitrogen, methane and chlorofluorocarbon in the atmosphere.

The Concentration of greenhouses gases

The above table shows the concentration of gases in the atmosphere.

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When the sun’s rays shine on the Earth, part of the light energy is absorbed as heat by the Earth’s surface while the rest is reflected back into the atmosphere. Greenhouse gases act like the glass surface of a greenhouse and reflect the heat back to the earth, resulting in an increase in temperature.

The Greenhouse Effect

When sunlight enters the atmosphere, some of the solar radiation is reflected back into space but most of it is absorbed by the Earth’s surface to heat up land and sea surfaces. As the Earth is heated up, heat in the form of infrared radiation is reflected back into space. However, most of the heat does not escape as it is trapped in the atmosphere by greenhouse gases which in turn radiate infrared rays back to Earth.

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This heats up the Earth which would otherwise to be too cold for living organisms. This phenomenon is called the greenhouse effect. The greenhouse effects is linked to global warming because when more greenhouse gases are produced, more heat is trapped, resulting in an increase of Earth’s temperature. Ways to reduce greenhouse gases and global warming: a) reducing the burning of fossil fuels b) using alternative sources of energy such as hydro, wind and solar energy c) reducing deforestation d) replanting forest trees.

The importance of the Ozone Layer

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The ozone molecule (03) is made up of three atoms of oxygen. The ozone layer is a natural layer of ozone gas in the stratosphere about 15 to 30 kilometers from Earth’s surface. The ozone layer absorbs about 95% to 99% of ultraviolet (UV) radiation and protects all living organisms on Earth from the harmful effects of this radiation. Sunburn is due to UV rays that penetrate through the ozone layer. These rays are absorbed by plant and animal tissues which damage protein and DNA molecules.

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Chemicals that Damage the Ozone Layer

The Thinning of the ozone layer is due to the increasing levels of chlorofluorocarbons in the atmosphere. In the stratosphere, CFCs are broken down by UV rays, thus releasing active chlorine radicals. These free chlorine radicals break down ozone molecules of ozone molecules.

It is the chlorine atom which is produced by the splitting of CFC molecules by ultraviolet rays. This leads to a series of chemical reactions and the breakdown of ozone molecules.

Effects of the Thinning of the Ozone Layer on Living Thing

On humans: a) mutation b) cataracts c) skin cancer d) sunburn e) affects the human immune system thus reducing the ability of the body to resist infections diseases. On plants and animals: a) reduces crop yields and reduces their nutrient content b) destroys cell membranes of leaves and reduces the amount of chlorophyll, thus affecting the rate of photosynthesis c) kills aquatic organisms, phytoplankton (which supply proteins) and aquatic plants (producers in food chains).

Effects of Environmental Pollution

Human activities associated with rapid development seriously upset the balance of nature, for example an increase or decrease in the population of animals and the loss of their habitats. Such activities cause harmful effects on several aspects such as: a0 human health b) habitats and nature c) the extinction of species d) the loss of economics resources.

a) Harmful effects on human health

i) A clean and unpolluted environment ensures good health for human.

ii) Air pollution causes diseases such as bronchitis and asthma, the inflammation of the respiratory tract and weakens the immune system, thus resulting in the body being easily attacked by bacteria and viruses.

iii) Effluent from heavy industries is the main source of heavy metal (lead and mercury) pollution which can cause damage and death. The heavy metal cadmium causes damage to the kidneys, lungs and the heart.

iv) Radioactive wastes can cause cancer and leukemia.

b) Destruction of Habitats and Nature

i) Water containing toxic substances and chemical fertilizers kill aquatic organisms. Acidic water from mines contain large amounts of sulphide and iron which react with oxygen in the air. This pollutes the water thus destroying the habitat of aquatic organisms. Eutrophication also causes the death of aquatic organisms.

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ii) Gases (sulphur dioxide and oxides of nitrogen) released from factories result in the formation of acid rain. Acid rain corrodes the stems and leaves of plants. Rainwater causes the leaching of minerals in the soil which affects the absorption of nutrients by plant roots.

iii) Acid rain causes the death of trees and indirectly the loss of habitats for organisms which depend on trees for food and shelter.

iv) Disturbances to living organisms on land and in water affect the food webs in the respective ecosystems.

c) The extinction of species

i) The population of living organisms that cannot adapt to changes in the environment decreases and finally becomes extinct. For example, a decrease in frog and crocodile population is due to spraying of chemicals made from plastics and pesticides. These chemicals affect the secretion of hormones and the reproduction processes in these animals.

ii) Deforestation carried out by humans destroys the habitats and affects the lives of many wildlife species.

iii) Coral reefs are breeding grounds for many aquatic species. Destruction of corals reef due to oil spills, sewage disposal and effluent from factories may result in the extinction of many aquatic species.

iv) Noise pollution caused by ships in the oceans, oil drills and fishing activities which involve the use of explosives disturb the communication of whales and other aquatic organisms. It also affects the whales’ habitat, their health and reduces their ability to reproduce which leads to a decrease in the whale population.

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d) Loss of economic resources

i) Air pollution causes the formation of acid rain which destroys forest trees. This results in a loss of economic resources from forests which include timber, rattan as well and minerals.

ii) Water pollution causes a decrease in aquatic plants and organisms which lead to lost revenues.

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Info Gallery

Over the past 40 years, the Earth’s average temperature has risen by 0.2 to 0.3°C. In Malaysia, the temperature is rising by about 0.18°C every decade.

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A greenhouse is built from glass to grow plants in cold countries during winter. Sunlight enters through the glass roof and heats up the soil, plants and floor of the greenhouse. The heat generated cannot escape but is trapped inside the greenhouse to keep the plants warm. Earth is like a big greenhouse where greenhouse gasses behave like glass panes which trap heat and heat up the surroundings.

Nitrogen oxide decomposes into nitric oxide and free oxygen radicals in the presence of sunlight. The free oxygen radicals combine with oxygen molecules, producing low level ozone which acts as a greenhouse gas. Ozone gas causes smog and imitation to the eyes, throat and lungs.