Experts warn of 'abrupt' warming

The IPCC says more heatwaves are very likely in the future

A UN panel has agreed a landmark report declaring that climate change is "unequivocal" and may bring "abrupt and irreversible" impacts.

After arduous talks in Valencia, Spain, scientists agreed a document they hope will shape debate on the next phase of the fight against climate change.

Among their conclusions are that carbon dioxide emissions are rising faster than they were a decade ago.

The text will be officially launched by UN chief Ban Ki-moon on Saturday.

Delegates to the Intergovernmental Panel on Climate Change (IPCC) summarised thousands of pages of scientific analysis, bringing together elements of the three reports already released this year, on the science of climate change, impacts and adaptation, and options for mitigating the problem.

"This is the strongest report yet by the IPCC - but says that there is still time to act," Bill Hare, an Australian climate scientist and one of the authors, told Reuters.

Among the report's top-line conclusions are that climate change is "unequivocal", that humankind's emissions of greenhouse gases are more than 90% likely to be the main cause, and that impacts can be reduced at reasonable cost.

The synthesis summary finalised late on Friday strengthens the language of those earlier reports with a warning that climate change may bring "abrupt and irreversible" impacts.

Such impacts could include the fast melting of glaciers and species extinctions.

"Approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5C (relative to the 1980-1999 average)," the summary concludes.

Other potential impacts highlighted in the text include:

• between 75m and 250m people projected to have scarcer fresh water supplies than at present
• yields from rain-fed agriculture could be halved
• food security likely to be further compromised in Africa
• widespread impacts on coral reefs

Writing in the International Herald Tribune ahead of the report's release, Ban Ki-moon said the world may be nearing a tipping-point on climate change.

"We all agree. Climate change is real, and we humans are its chief cause. Yet even now, few people fully understand the gravity of the threat, or its immediacy.

"Now I believe we are on the verge of a catastrophe if we do not act."

Local witnesses

His comments were endorsed by environmental groups on the fringes of the IPCC gathering.

IPCC PROJECTIONS Probable temperature rise between 1.8C and 4C Possible temperature rise between 1.1C and 6.4C Sea level most likely to rise by 28-43cm Arctic summer sea ice disappears in second half of century Increase in heatwaves very likely Increase in tropical storm intensity likely

"Climate change is here, it's impacting our lives and our economies, and we need to do something about it," commented Hans Verolme, director of the climate change programme with the environmental group WWF.

"After this report, there are no politicians left who can argue they don't know what climate change is or they don't know what to do about it."

At a news conference, the WWF presented testimonies from "climate change witnesses" in various parts of the world.

Speaking by video link, Australian scientists and fishermen spoke of the changes they were seeing on the Great Barrier Reef.

And Olav Mathis Eira, a Sami reindeer herder from Norway, said that his communities are seeing weather patterns unprecedented in their oral history.

"Winter is one-and-a-half months later than it used to be," he said. "We observed birds and insects that do not have a name in Sami."

The IPCC findings will feed into the next round of negotiations on the UN climate convention and Kyoto Protocol, which open in Bali on 3 December.