(Agencies)
Updated: 2007-11-17 10:31

It summarises three massive documents issued this year covering the evidence for climate change; the present and possible future impacts of it; and the options for tackling the peril.

After Saturday, attention shifts to a key meeting in Bali, Indonesia, where governments must set down a "roadmap" for negotiations culminating in a deal to slash carbon emissions and help developing nations cope with climate change.

The IPCC experts agreed that the rise in Earth's temperature observed in the past few decades was principally due to human causes, not natural ones, as "climate sceptics" often aver.

The impacts of climate change are already visible, in the form of retreating glaciers and snow loss in alpine regions, thinning Arctic summer sea ice and thawing permafrost, according to the three IPCC reports issued earlier this year.

But sometimes sharp disagreement emerged during the five days of negotiations in Valencia to hammer out the summary, even though the main findings remained untouched.

US delegates in particular said references to "irreversible" climate change and impacts were imprecise.

They argued, for example, that the melting of glaciers or ice sheets -- which could raise ocean levels by several meters -- was not "irreversible" as ice could eventually reform.

"But we are not dealing with geological time scales of tens of thousands of years," said one delegate, irked by this reasoning. "We are talking about dire consequences to humans and the environment in the coming decades."

By 2100, global average surface temperatures could rise by between 1.1 C (1.98 F) and 6.4 C (11.52 F) compared to 1980-99 levels, while sea levels will rise by between 18 and 59 centimetres (7.2 and 23.2 inches), according to the IPCC's forecast.

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