The Earth has a natural temperature control system. Certain atmospheric gases are critical to this system and are known as greenhouse gases.

Approximately one third of solar radiation that hits the earth is reflected back into space. The remaining solar radiation is absorbed partly by the atmosphere, and mostly by land and the ocean. The Earth's surface becomes warm and as a result it emits infrared radiation. The greenhouse gases trap the infrared radiation, thus warming the atmosphere.

1. The greenhouse effect

Naturally occurring greenhouse gases include water vapour, carbon dioxide, ozone, methane and nitrous oxide. Together they create a natural greenhouse effect. Human activities are causing greenhouse gas levels in the atmosphere to increase.

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