The principal reason for the mounting thermometer is a century and a half of industrialization: the burning of ever-greater quantities of oil, gasoline, and coal, the cutting of forests, and certain farming methods.
These activities have increased the amount of "greenhouse gases" in the atmosphere, especially carbon dioxide, methane and nitrous oxide. Such gases occur naturally and are critical for life on earth; they keep some of the sun's warmth from reflecting back into space, and without them the world would be a cold and barren place.
Carbon dioxide is responsible for over 60 per cent of the "enhanced greenhouse effect." Humans are burning coal, oil, and natural gas at a rate that is much, much faster than the speed at which these fossil fuels were created.
According to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPPC) that brings together the world's leading experts in this field, the globally averaged surface temperature is projected to increase by between 1.4 and 5.8°C from 1990 to 2100 under business-as-usual, and sea levels are expected to rise by between 9 and 88 centimetres over the same period. If nothing is done to reduce these changes, they will have major consequences for the ecosystem and our economies.
Climate change is one of the greatest environmental, social and economic threats facing the planet.