The climate of the Earth is always changing. In the past it has altered as a result of natural causes. Nowadays, however, the term climate change is generally used when referring to changes in our climate which have been identified since the early part of the 1900's. The changes we've seen over recent years and those which are predicted over the next 80 years are thought to be mainly as a result of human behaviour rather than due to natural changes in the atmosphere.
The Earth retains its temperature thanks to "greenhouse" gases in the atmosphere, which trap energy from the sun. Without this greenhouse effect, the average global temperature would be more than 30oC colder than it is now.
However, every time we switch on a light, use a computer, watch television or travel by any form of motorised transport, we are creating carbon dioxide (CO2), the principal contributor to global warming. And as human activity increases, the concentrations of greenhouse gases - particularly CO2 but also methane and nitrous oxide - in the atmosphere build up. This causes the world to heat up unnaturally, and the weather to become more extreme. The heating process is often referred to as global warming, and the overall effect is known as climate change.
About two-thirds of greenhouse gas pollution comes from the CO2 emitted when we burn fossil fuels such as coal, gas and oil. We are also depleting the Earth's biggest natural absorbers of carbon dioxide - the world's forests. In combination, these factors are seriously disrupting the natural balance of the world's climate.
