* Many scientists believe the world's climate is being altered and temperatures are rising because of greenhouse gas emissions, particularly carbon dioxide from burning fossil fuels like coal in power plants and petrol in cars and say these emissions need to be cut by 50 percent to limit global warming.

* Greenhouse gases are gases that trap heat in the earth's atmosphere. The main one is carbon dioxide (CO2), most of which comes from burning fuel. Others include methane (CH4), much of which comes from agriculture and waste dumps, and nitrous oxide (N2O), mostly a result of fertiliser use. Three industrial gases used in various applications, such as refrigerants, heat conductors and insulators, are also included: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6).

* The Kyoto Protocol, a pact reached by governments at a 1997 U.N. conference in Kyoto, Japan, aims to cut emissions in developed countries by 5.2 percent below 1990 levels by 2008-12. It came into force on Feb. 16, 2005.

* Opponents say the treaty is an expensive insurance policy that will damage the international economy, which is heavily dependent on coal and crude oil, and that renewable energy technology is not advanced enough to support global needs.

* The United States and Australia have refused to sign the Kyoto pact, saying it unfairly excludes developing nations such as India and China.

* The United States tops the list of polluters with 6,934 million tonnes of emissions in 2002 followed by Russia with 1,876 million tonnes, Japan with 1,330.8 million tonnes, Germany with 1,014.6 million tonnes and Britain with 634.9 million tonnes.

* A 2001 report by the United Nations Intergovernmental Panel on Climate Change (IPCC) said the 1990s were the hottest years in history since reliable records began in 1861 though some critics dispute that, saying surface temperatures do not provide the best gauge of climate change.

* Scientists have also forecast a rise in sea levels by 2100 due to global warming, leaving small island states and coastal areas at greatest risk. Climate change could also hit agricultural production near the equator as water supplies come under increased strain.