Climate change

Climate is the average pattern of weather over the long term. The earth's climate has warmed and cooled for millions of years, however we know that the earth has become warmer over the last century.

The Intergovernmental Panel on Climate Change (IPCC), reports that the average surface temperature of the earth has increased during the twentieth century by about 0.6° ± 0.2°C. (The ± 0.2°C means that the increase might be as small as 0.4°C or as great as 0.8°C). This may seem like a small shift, but although regional and short-term temperatures do fluctuate over a wide range, global temperatures are generally quite stable.

		The World Meteorological Organisation (WMO) and United Nations Environment Programme (UNEP) established the Intergovernmental Panel on Climate Change (IPCC) to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation.

The difference between today's average global temperature and the average global temperature during the last Ice Age is about 5ºC. It is warmer today around the world than at any time during the past 1000 years, and the warmest years of the previous century have occurred within the past decade.

Sea ice in the Arctic has failed to re-form for the second consecutive winter, raising fears that global warming may have tipped the polar regions into irreversible climate change far sooner than predicted. Scientists are now convinced that Arctic Sea ice is showing signs of both a winter and a summer decline that could indicate a major acceleration in its long-term rate of disappearance.

The images below show the reduction in Arctic ice cover over a 24 year period. The image on the left shows the ice cover in January 1979. The image to the right shows the ice cover in January 2003. Source: NASA.

We now know that human activities, primarily the burning of fossil fuels, have increased the greenhouse gas content of the earth's atmosphere significantly over the past century.

The 'greenhouse effect' is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapour, carbon dioxide, nitrous oxide , and methane, for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth's average temperature would be about 60ºC colder. Because of how they warm our world these gases are referred to as greenhouse gases.

The greenhouse effect is important and without the greenhouse effect the Earth would not be warm enough for humans to live. However if the greenhouse effect becomes stronger, which can be caused by the increase in the amount of carbon dioxide emissions from power generation, it could make the Earth warmer than usual. The vast majority of climate researchers agree with these overall findings.

		Carbon dioxide (CO2) is responsible for two thirds of human-induced global warming - and around 97% of the CO2 emitted by western industrialised countries comes from burning coal, oil and gas for energy. Source WWF

For more information on Climate Change and Global Warming download the following: Climate Change report : Download Adobe reader.