World governments begin another attempt Monday to overcome the disconnect between rich and poor nations on fighting global warming, with evidence mounting that the Earth's climate already is changing in ways that will affect both sides of the wealth divide.
During two weeks of talks in Cancun, Mexico, the 193-nation United Nations conference hopes to conclude agreements that will clear the way to mobilize billions of dollars for developing countries and give them green technology to help them shift from fossil fuels affecting climate change.
After a disappointing summit last year in Copenhagen, no hope remains of reaching an overarching deal this year setting legal limits on how much major countries would be allowed to pollute. Such an accord was meant to describe a path toward slashing greenhouse gas emissions by mid-century, when scientists say they should be half of today's levels.
Eighty-five countries have made specific pledges to reduce emissions or constrain their growth, but those promises amount to far less than required to keep temperatures from rising to potentially dangerous levels.
The recriminations that followed the Danish summit have raised questions over whether the unwieldy UN negotiations, which require at least tacit agreement from every nation, can ever work.
But Christiana Figueres, the top UN climate official, said world capitals are aware of both a growing environmental and political urgency. "Governments need to prove that the intergovernmental process can deliver," she said Sunday.
"They know that they can do it. They know that they need to compromise. I'm not saying it's a done deal. It's still going to be a heavy lift," she said.
About 15,000 negotiators, environmental activists, businessmen and journalists are convening at a resort complex under elaborate security precautions, including naval warships a few hundred metres offshore in the Gulf of Mexico.
While delegates haggle over the wording, timing and dollar figures involved in any agreement, scientists and political activists at the conference will be offering the latest indications of the planet's warming. Some 250 presentations are planned on the sidelines of the negotiations.
Meteorologists are likely to report that 2010 will end up tied for the hottest year globally since records began 131 years ago.
The UN scientific body that won the 2007 Nobel Peace Prize for its climate change report, which called global warming "unequivocal" and almost certainly caused by human activity, is expected to tell the conference its findings and warnings of potential disasters are hopelessly out of date.
Agronomists are due to report on shifting weather patterns that are destabilizing the world's food supply and access to clean water, and that could lead to mass migrations as farmers flee drought or flood-prone regions.
As often during the three-year process, attention will focus on the United States and China, key protagonists representing the industrialized and developing world.
U.S. negotiators may feel further constrained from showing flexibility toward the Chinese after the Republican swing in this month's congressional elections, which brought dozens of new legislators who doubt the seriousness of climate change.
The U.S. has insisted it will agree to binding pollution limits only if China also accepts legal limitations. China, now the world's biggest polluter but also the biggest investor in renewable energy, rejects international limits, saying it still needs to overcome widespread poverty and bears no historic responsibility for the problem.
But Figueres, the Costa Rican diplomat who became head of the UN climate secretariat in July, said the public argument may appear more bitter than it really is. At the most recent round of talks last October, "they were working very constructively with each other inside the negotiations," she said.