Like cat-herding, the negotiations will be time-consuming, frustrating and unpredictable, for vast economic interests are at stake.

What the scientists say is this: time is fast running out for preventing bad, even catastrophic damage to the world's climate system from fossil-fuel pollution.

By some estimates, to reduce the overall rise in temperature to 2 C (3.6 F) by the end of this century compared with 1900 -- an increase assumed to be relatively safe, although no-one knows for sure -- the world has to halve its emissions by 2050 compared with Kyoto's 1990 benchmark.

So Kyoto's second commitment period, running from 2013-2017, has to start ratcheting the cuts in GHGs, for the present pledges are not even braking the annual surge in carbon dioxide (CO2) spewed into the atmosphere.

To achieve this, Kyoto 2 will have to not only tighten the screw on emissions by industrialised countries that were the first to burn oil, gas and coal and thus bear historical responsibility for today's crisis.

It will also have to somehow coax promises out of China and India that they will slow or reverse the massive growth in their pollution that has occurred in the past decade, as their surging economies voraciously burned fossil fuels.

But at Nairobi, the world's two most populous countries spelt out in capital letters that they will block any attempt to lure them into binding curbs on their emissions. Under the present Kyoto format, only industrialised countries are required to make these targeted cuts.

Emissions reductions carry an economic burden because of the cost of converting to more efficient, low-carbon energy use, although as conference scientific coordinator Halldor Thorgeisson observed, "delaying action is more expensive than doing something."

Indian Environment Minister Namo Narain Meena slammed as "surreal" those who were demanding that developing countries take on GHG-cutting pledges post-2012.

"India's emissions of CO2 are but three percent of the world's total, while we have 17 percent of the global population," Meena said.

"Even with eight percent annual growth, which we have accomplished for some years, and which is absolutely essential to sustain if we are to succeed in eliminating mass poverty in our lifetime, it will be many decades before India's GHG emissions approach anything like the current world average."

China, now the world's second biggest polluter, also said it was not ready to make targeted emissions pledges, and rounded on industrialised countries for failing to do more to transfer clean technology to developing nations.

Yet the developing-country dilemma is only one of the nightmarish tasks facing the 2013-2017 review.

It must also somehow define closer cooperation between Kyoto members and the United States, the world's No. 1 carbon culprit.

The United States almost wrecked Kyoto in 2001 when President George W. Bush said he would never ask the US Senate to ratify the treaty, contending it was too costly for the American economy and unfair because of the developing-country question.

Bush leaves office in January 2009 and the assumption is that he will not experience some miraculous pro-Kyoto conversion by then. That means there will be no time for his successor to steer the United States back into the Kyoto fold in time to shape the 2013-2017 negotiations.

Not all is lost on this score, for the Democrats' crushing victory in the mid-term Congressional polls is building pressure for the US to adopt mandatory caps on pollution and establish a carbon market.

Adding complexity to the equation are many spoiling factors, with individual countries pushing national interests, such as the notorious counting of forests in carbon quotas that so bedevilled completion of the first Kyoto period and demands for funds to help poor countries adapt to climate change.

There is time pressure, as well. A deal is needed by the end of 2009, as it will take a couple of years for the amended protocol to be ratified. Any delay will mean a gap between the two commitment periods, which would cripple confidence in the carbon markets.

The labyrinthine complexity and slowness of the Kyoto process contrasts starkly with the growing urgency of climate change.

But, as Catherine Pearce of Friends of the Earth International says, "We don't have the time or the opportunity to negotiate anything else."

And, she argues, "the existing architecture can work."

Fear, though, may concentrate minds.

Early next year, the world's top scientists are due to deliver their latest assessment on climate change, and it is likely to be quite as terrifying as Britain's Stern Report. "It's going to shock a lot of people," predicts WWF's Hans Verolme.

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