Biology Form 4

BIOLOGY FORM 4

CHAPTER 9.2THE GREENHOUSE

EFFECT

GREENHOUSE EFFECT

When the sun's radiation enters the earth's atmosphere, some of the radiation is reflected back to space by the atmosphere layer.

The sun's energy that penetrates the atmosphere is absorbed by the earth.

A part of the energy is reflected back into space as infrared radiation (heat).

Most of the infrared radiation in the atmosphere is absorbed by greenhouse gases such as carbon dioxide, methane, nitrous oxide, water vapour as well as chlorofluorocarbon.

As a result, the earth's temperature increases.

At the same time, the greenhouse gases also radiate infrared radiation towards the surface of the earth.

The absorption and reradiation of infrared radiation by greenhouse gases that trap the heat and warms up the earth's atmosphere is known as the greenhouse affect.

This greenhouse effect is important because without it, the earth would be too cold to sustain life.

Over the last 40 years, the earth's temperature has increased.

As a result of human activities such as combustion of fossil fuels (coal, petroleum and natural gas) increased deforestation and industrial production, the concentration of carbon dioxide has increased.

Hence, the greenhouse effect becomes more pronounced as the concentation of greenhouse gases increase, trapping more heat in the atmosphere. This causes the earth's temperature to increase. This effect is called global warming.

Effect of GLOBAL WARMING

1.The polar ice caps and glaciers melt. This raises the sea level. Flooding occurs especially at low-lying areas around the sea.

2.Evaporation of water increases.Quantity of water vapour in the

atmosphere is higher.Atmospheric heat retention increases as

water vapour is a greenhouse gas.The greenhouse effect become more

pronounced.

3.Precipitation (rainfall and snowfall) and climatic conditions change.The higher the rate

of evaporation causes drought or greater rainfall.

Storms are stronger and more destructive.

The crop yields, forests and water supplies are reduced

This affects marine life, human health and biodiversity.

4.Tropical pests and vectors can spread to new areas.More outbreaks of

diseases such as malaria and dengue fever can occur.

THANK YOUNURUL AHYA AHMAD