UN chief Kofi Annan has criticised a "frightening lack of leadership" in tackling global warming, at a major UN climate summit in Nairobi.
Annan said global warming was one of the gravest threats to the world
Mr Annan told delegates the phenomenon was as grave a threat as conflict, poverty and the spread of weapons.
He said sceptics were "out of step, out of arguments and out of time".
Mr Annan announced a plan by six UN agencies to help Africa receive funds for clean development projects, such as renewable energy and forestry.
The BBC News website's environment correspondent, Richard Black, says the full details of the scheme have still to emerge.
But he says what did become clear was Mr Annan's scorn for climate sceptics - people who do not accept that emissions of greenhouse gasses are warming the planet's surface.
Our correspondent says it was strong language for a UN secretary general, particularly when the most politically important adherents of the sceptical position hold power in the White House in Washington.
Mr Annan, who is due to step down from his post at the end of December, warned that ignoring global warming would be to the world's detriment.
"It is increasingly clear that it will cost far less to cut emissions now than to deal with the consequences later," he told the 189-nation meeting in Kenya's capital.
The UN chief said climate change was also a threat to peace and security.
"Changing patterns of rainfall, for example, can heighten competition for resources, setting in motion potentially destabilising tensions and migrations...
"There is evidence that some of this is already occurring; more could well be in the offing."
Over the past week and a half, delegates have been trying to agree a timetable for the completion of discussions on globally binding emissions cuts beyond the existing Kyoto Protocol targets.
Our correspondent says there was never a chance of the targets themselves being negotiated at the conference.
But many observers maintain that unless a clear timetable emerges, there will not be enough time to get new targets into place before 2012, when those agreed at Kyoto expire.
One outstanding issue which has for now been resolved concerns the management of the Adaptation Fund, designed to help the poorest countries protect themselves against the impact of climate change.
A bloc of richer countries had been arguing for the fund to be administered by the Global Environment Facility (Gef), a UN affiliate which already manages many environmental funds.
Some developing countries argued that Gef constraints were too stringent.
Reports warn Africa is the most vulnerable place to climate change
Our correspondent says for the moment they have got their way in a compromise deal which will see the fund governed by a new body with a guaranteed majority of developing country delegates, though Gef might still be called in to manage it under this new body.
"The fund is how we [the richer developing countries] share the benefits of clean development with the poorest countries, the countries which produce least greenhouse gases and so have few options for mitigating their emissions," said Bernaditas Muller, head of the Philippines delegation, who spoke for the G-77 bloc during negotiations.
"It can't be treated like donor money - it's our money, a solidarity fund."
Over the next three days, ministers can revisit any of the areas which appear to have been agreed, and lengthy negotiations are anticipated.