A UN conference exploring ways of avoiding disaster from global warming has opened faced with faltering efforts to cut deadly greenhouse gases.

The summit in the Kenyan capital will also discuss what steps to take after the UN Kyoto treaty on greenhouse gas emissions expires in 2012, and will seek to convince top polluters outside the treaty to do more to stop climate change.

Around 6,000 delegates over two weeks will press for political decisions and review scientific findings during the 12th session of the Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC).

"Climate change is rapidly emerging as one of the most serious threats that humanity has ever faced," Kenyan Vice President Moody Awori told experts and government officials at the opening session on Saturday.

"There is a great task ahead of us."

At the first such summit in sub-Saharan Africa -- one of the regions hit hardest by global warming -- countries whose leaders signed the Kyoto Protocol but whose parliaments failed to ratify it will be put under the spotlight.

These include the United States, the world's biggest single polluter, and Australia, the biggest polluter on a per capita basis and a major supplier of fossil fuels such as coal which cause global warming.

The protocol is an annex of the 1992 treaty on climate change, which has been humstrung by the uncontrolled release of ozone-depleting gases, especially from developing economies such as India and China.

Experts have warned that the treaty in its present form will not even dent the greenhouse gas problem.

The summit will also address ways in which rapidly industrialising nations such as India, China and Brazil can minimise the environmental damage of their economic progress.

Despite being the second world polluter, China is still exempt from targeted emmission slashes owing to its developing country states.

Kyoto took life in February 2005 and was supposed to commit industrialised countries to a cut of about five percent in annual emissions by 2012 compared with their 1990 level.

President George W. Bush abandoned the protocol in 2001, citing its cost to the US economy.

But a recent report by British economist Sir Nicholas Stern stressed that the costs of unrestrained climate change could be far worse than the measures needed to slow it down.

The former World Bank chief economist singled out China and India -- but also the United States -- as powerhouse nations whose backing is crucial for a global solution.

Commissioned by the British government and backed by Prime Minister Tony Blair, the Stern review estimates that worldwide inaction could cost the equivalent of between five and 20 percent of global gross domestic product every year, forever.

By contrast, the cost of action is equivalent to one percent of GDP, a "manageable" increase equivalent to a one-off one percent goods price increase, Stern said.

Experts have warned that global warning will have the largest impact on Africa, a continent of 800 million people, highlighted by unpredictable climate changes like floods and droughts.

Other issues due for discussion is the creation of an Adaptation Fund designed to help poor nations cope with climate change.

"The worst impacts of climate change can be prevented only if governments act now," said Steve Sawyer, Greenpeace International policy advisor.

"Future generations will not forgive us if we delay. The legal, moral and political obligations of the rich are clear: they must dramatically reduce their emissions ... "

Copyright © 2006 Agence France Presse

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