The earth has warmed by 0.74 celsius degree over the last hundred years. Around 0.4 celsius degree of this warming has occurred since the 1970s.

The recent Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change leaves us in no doubt that human activity is the primary driver of the observed changes in climate.

The main human influence on global climate is emissions of the key greenhouse gases -- carbon dioxide, methane and nitrous oxide. The accumulation of these gases in the atmosphere strengthens the greenhouse effect. At present, just over 7 billion tons of carbon dioxide is emitted globally each year through fossil fuel use, and an additional 1.6 billion tons are emitted by land use change, largely by deforestation. The concentrations of these gases in the atmosphere have now reached levels unprecedented for tens of thousands of years.

According to AR4, mean global temperatures are likely to rise between 1.1 and 6.4 celsius degrees (with a best estimate of 1.8 to 4 celsius degrees) above 1990 levels by the end of this century, depending on our emissions. This will result in a further rise in global sea levels of between 20 and 60 centimeters by the end of this century, continued melting of ice caps, glaciers and sea ice, changes in rainfall patterns and intensification of tropical cyclones.