Over the next five days, delegates to the 27th session of the Intergovernmental Panel on Climate Change (IPCC) will synthesize the information gathered by the Panel's various working groups into one succinct report that will form the basis of future policy action on climate change.

The Fourth Assessment Report - to be released on Saturday - will guide participants at a major summit next month in Bali, Indonesia, as they seek to try to hammer out a successor agreement to the Kyoto Protocol, which contains binding targets for reducing emissions but expires in 2012.

"What is produced here in Valencia is the guide that every one of the thousands of delegates attending the crucial Climate Convention meeting in Bali will be packing in their suitcases and slipping in their back pockets," said Achim Steiner, the head of the UN Environment Programme (UNEP), in his address to the opening of the session.

"It is the final full stop behind the question as to whether climate change is happening and the likely impacts - many of which will happen in the time-frame of people alive today, not in some far distant future," Steiner said.

Mr. Steiner added that "the momentum on climate change in 2007 has been nothing short of breathtaking," hailing the work of the IPCC and its scientists - the recipients of this year's Nobel Peace Prize, along with Al Gore. It was the IPCC that earlier this year issued a report confirming global warming to be likely driven by human activities.

He said the landscapes on Antarctica are "rare and wonderful," but also deeply disturbing as the ice continues melting at a fast pace.

"All this may be gone, and not in the distant future, unless we act, together, now," he warned. "It is all floating ice, one-fifth of the entire continent. If it broke up, sea levels could rise by 6 meters, or 18 feet," he noted, pointing out that 138 tons of ice already are being lost every year.

"It is here where our work, together, comes into focus," Mr. Ban said in a statement issued on Friday. "We see Antarctica's beauty - and the danger global warming represents, and the urgency that we do something about it."

Mr. Ban, who has made a climate change a priority issue since he became Secretary-General, received a briefing from scientists at a Chilean Air Force base in Antarctica before visiting the Collins Glaciers and then the Sejong Research Center.

On Sunday, Mr. Ban traveled to Brazil to meet with President Luis Inácio Lula da Silva.

He also visited an ethanol plant to show how biofuels have both potentially beneficial and harmful effects and that governments must be careful to balance the costs and benefits of developing them as energy sources.

Mr. Ban next will travel to Tunisia to attend an international counter-terrorism conference organized by the UN, the Tunisian Government and the Organization of the Islamic Conference. From there, he heads to Valencia, Spain, to participate in launching the latest report of the Intergovernmental Panel on Climate Change.