Climate report a key to world emissions agreement in Bali

Sometimes warnings pack more punch when they come in a concentrated form – and at the right moment.

That's the hope United Nations officials have expressed after the weekend release of the last of four reports this year on global warming and options for trying to bring it under control.

The report reflects rising scientific confidence – and remaining uncertainties – in describing current and projected effects of global warming. That, plus the report's condensed size and terse talking points, virtually ensure it will play a key role in adding urgency to negotiations that begin on Dec. 3 in Nasu Dua, on the island of Bali in Indonesia.

The aim of next month's meeting is to gain consensus on a formal framework for reaching a new emissions-reduction pact over the next two years. A new pact would pick up where the 1997 Kyoto Protocol leaves off. Currently it only requires industrial countries to reduce their greenhouse-gas emissions by an average 5.5 percent below 1990 levels between 2008 and 2012.

Over the weekend, delegates from 140 nations meeting in Valencia, Spain, adopted the Intergovernmental Panel on Climate Change's (IPCC) "synthesis report." It's a thin volume distilled from three larger tomes the UN-sponsored group of scientists, economists, and other experts released earlier this year. It draws no new conclusions. But it does insist that some effects of global warming, such as sea-level rise, are inevitable and will continue for centuries, even if all heat-trapping greenhouse-gas emissions stopped tomorrow. Heading off the worst of the effects means moving aggressively to curb rising greenhouse gases, mainly carbon dioxide from burning fossil fuels, the report suggests.

The message "could not be simpler," says UN Secretary-General Ban Ki Moon. "Global, sweeping, concerted action is needed now; there is no time to waste."

The synthesis report reiterates that the warming of Earth's climate is "unequivocal" and that the scientists involved express "very high confidence" that human activities have warmed the climate since 1750. It also indicates that human influence on climate has contributed to rising sea levels, shifting storm tracks, increasing temperature extremes, and raising the risk of heat waves, droughts, and heavy rains.

The synthesis report uses sea levels to illustrate what many see as unavoidable long-term effects, depending on the rate of warming.

Even the most aggressive scenario to curb greenhouse-gas emissions – with emissions peaking by 2015 and falling to between 50 and 80 percent of 2000 levels by 2050 – would still warm the planet enough to ensure that over the next millennium, global average sea level would rise by up to 4.6 feet. The least aggressive scenario, which yields the largest warming, would raise sea levels by up to 12 feet. These increases come merely from heating the oceans, which expand when warmed. The scenarios don't take into account meltwater that icecaps in Greenland or Antarctica would contribute as the global average temperatures rise.

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