Fact Sheet 2

GLOBAL WARMING

Some scientists believe an enhanced greenhouse effect has been created by large increases of greenhouse gases in the atmosphere. This increase may have been caused by human activities, especially the burning of fossil fuels. Every year billions of tonnes of greenhouse gases are released into the air. These include carbon dioxide (CO₂), and methane (CH₄). Besides gases that may cause global warming, other hazardous pollutants created by human activity include sulphur dioxide (SO_x), nitrogen dioxide (NO_x) and particulates.

About a quarter of greenhouse gas emissions come from transport. Other sources include coal-fired power stations, factories and increased agriculture, especially methane from livestock. The increased concentrations of these greenhouse gases, like an invisible blanket trapping heat around the earth, are contributing to an enhanced greenhouse effect and causing global warming.

This increase in global temperature is expected to affect the water cycle. The water cycle has been an endless cycle of evaporation-condensation-precipitation since the world began. Evaporation occurs when the sun heats water in lakes, oceans, rivers and streams. The liquid water evaporates into a gas called water vapour.

Condensation occurs when the water vapour comes together to make clouds. Precipitation occurs when water from the clouds falls to earth as rain, hail or snow. Collection occurs when the rain, hail and snow goes back into oceans, lakes, rivers and streams.

However the natural rhythm of the water cycle may be being disturbed by global warming because:

• It has increased the amount of water vapour in the atmosphere.
• It has increased the extent of cloud formation.
• It has produced higher rainfall in many areas.

This could lead to even greater warming because water vapour is itself a greenhouse gas, and it is more efficient at absorbing heat energy than carbon dioxide. This increased warming could result in even more water vapour being taken up by the atmosphere, leading to still greater warming. This cycle has been described as a runaway greenhouse effect.

Predictions based on computer simulations suggest that an increase in average global temperatures may cause major changes in world climatic patterns and local weather patterns. Some of the possible effects of changing climatic patterns that are caused by global warming include:

• Some areas receiving much higher rainfall than at present, resulting in greater flooding.
• Other areas receiving much less rainfall than at present, resulting in drought.
• Changes in the distribution of plants and animals around the world, with changing habitats.
• Changes to patterns of agriculture around the world.
• More severe storms.
• More violent cyclones resulting from increasing sea surface temperatures, with the cyclone belt extending much further south, perhaps as far as Sydney and Perth.
• The increasing of sea levels, due to thermal expansion of the oceans. This could result in the flooding of low-lying coastal areas.
• The melting of glaciers and polar icecaps.
• Reduction, or even disappearance of Australia’s snow fields.

Available as:

PDF – Fact Sheet 2

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