DURBAN: Veteran watchers of the UN climate process differ in their predictions for talks opening in Durban on Monday, but all foresee an outcome falling short of a major breakthrough.

A cascade of alarming news from scientists underscores the urgent need to slash CO2 emissions if humanity is to have a fighting chance of capping the rise in global temperature at two degrees Celsius, a goal enshrined at last year's climate forum in Cancun, Mexico.

But negotiators in Durban are still rattled by the near-collapse of the over-reaching 2009 Copenhagen Summit – have set their sights lower, analysts say.

The talks, under the 194-nation UN Framework Convention on Climate Change (UNFCCC), run through December 9.

“There are three scenarios that people are talking about for Durban,” said Alden Meyer of the Washington-based Union for Concerned Scientists, outlining results ranging from modest progress to complete deadlock.

The key to all of them lies in the fate of the UNFCCC's Kyoto Protocol, the world only legally binding agreement to curb greenhouse gases, Meyer and other experts say.

While the treaty itself is not threatened, its first five-year roster of commitments – under which rich nations must cut carbon emissions by about five per cent, compared to a 1990 benchmark – closes at the end of 2012.

The developing world, exempt from such constraints, wants advanced economies to renew their Kyoto vows.

But many – including Japan, Canada and Russia – have bluntly refused to do so as long as the world's top polluters remain unconstrained by international law.

After playing a major role in drafting Kyoto, the United States opted out in 2001.

Number One emitter China has set its own goals for improved energy efficiency, but refuses to take on carbon-cutting targets under a global regime, as do emerging giants India and Brazil.

Rich countries under the Protocol, adopted in 1997, accounted for 64 per cent of carbon emissions in 1990.

Today they emit less than a third.