What is Climate Change?

What is the greenhouse effect?

A car parked in the sun feels warmer inside than the outside air. The car windows allow the sun's light energy to enter the car, where it is converted to heat energy. Glass windows do not allow heat energy to pass through as easily as light, so some heat is trapped in the car, raising its temperature. This is an example of a greenhouse effect.

In Europe greenhouses are used to capture the sun's heat, especially in the northern latitudes, where not enough sunlight and warmth occurs to grow some plants. Greenhouses are mostly made of glass, and they get that name because of the lush greenery that can be produced inside them at the right time of year – and which would not normally appear in that part of the world.

The Earth is covered by a blanket of gases which, like the car window, allows light energy from the sun to pass through to the Earth's surface, where it is converted to heat energy. Some of this heat energy is trapped by gases in the atmosphere as it tries to escape back into space. This keeps the Earth, and us, warm. The gases which trap heat are called greenhouse gases.

The Earth's atmosphere is made up of 78 per cent nitrogen and 21 per cent oxygen. Less than 1 per cent of the atmosphere is greenhouse gases, however this small amount can make a big difference.

Human activity is generating more greenhouse gases (mainly carbon dioxide, methane, nitrous oxide and halocarbons), which are trapping more heat. It is widely accepted that increasing the concentrations of these greenhouse gases is leading to an increase in the world's average temperature, and climate scientists have now concluded that the rising temperatures will affect the environment, and hence humans, plants and animals, in a number of ways. These impacts are predicted to include the melting of polar ice caps, rising sea levels, increasing intensity and frequency of storms, and changes to weather patterns that will alter agricultural productivity as well as affecting snowfall and associated recreational and tourism activities.

Further information about the greenhouse effect is available from the Victorian Government's greenhouse website – http://www.greenhouse.vic.gov.au .

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