BACKGROUND: Climate summits: From Rio to Cancun

Nov 23, 2010, 11:10 GMT

Washington - Global warming was first declared a problem to be solved at a world climate conference in 1979 in Geneva. Summit milestones from the last three decades:

RIO DE JANEIRO, 1992: The world for the first time committed to reducing greenhouse-gas emissions to a level that was manageable for the global climate and would not harm food production. Scientists believe global temperatures must not be allowed to rise more than 2 degrees Celsius above pre-industrial levels. Some 190 countries including the United States ratified Rio's United Nations Framework Convention on Climate Change (UNFCC).

KYOTO, 1997: The Kyoto Protocol marked the first concrete step to achieve the goals of Rio. Industrial nations committed to reduce their greenhouse-gas emissions at least 5 per cent below 1990 levels by 2012. Developing countries were not given a target, and the US never ratified the treaty.

BALI, 2007: Governments lay out a 'road-map' toward a new global climate treaty to replace Kyoto, which expires in 2012. The new treaty would include the United States and some commitments from developing countries.

COPENHAGEN, 2009: Organizers had high hopes the summit would agree at least to the outline of a new global treaty, but talks collapsed. The 'Copenhagen Accord' instead saw leaders pledge to keep temperatures from rising more than 2 degrees, while countries released only voluntary targets for reducing their emissions in the coming decades.

CANCUN, 2010: There is no longer an expectation that governments will agree to a legally binding treaty. It is hoped that deals to tackle deforestation and set up a green fund to help developing countries could lead to a more comprehensive future deal.