By Jeff Tollefson

The ivory-colored beaches of Cancún promise tourists a chance to forget their worries. But there is no such assurance for the international negotiators who will flock to the Mexican resort next week to attend the sixteenth gathering of the United Nations Framework Convention on Climate Change.

One year after the near-collapse of climate talks in Copenhagen, participants will be hard-pressed to map a viable path forward. Global climate negotiations began in 1992 at the United Nations Earth Summit in Rio de Janeiro, Brazil, and led to the 1997 Kyoto Protocol, in which industrialized countries agreed to curb their emissions. But the protocol was intended as a first step, and countries have been struggling to agree on a follow-up treaty ever since. Jairam Ramesh, India's environment minister, says that Cancún is the "last chance" for such talks.

Given China's continued opposition to a hard target for cuts in greenhouse-gas emissions, and the failure of the United States to pass climate legislation, there is virtually no hope of a binding global emissions treaty at the Cancún meeting, which will run from November 29 to December 10. But the door remains open for progress on forestry, adaptation and technology transfer, agreements on which were close to fruition in Copenhagen but were ultimately held back by the principal dispute over emissions. This time, negotiators hope to take a bottom-up approach by settling on a package of smaller agreements that could serve as a starting point for real--albeit limited--action, even as broader treaty negotiations continue. Christiana Figueres, who took office as United Nations climate chief in May, says that Cancún can be successful if parties are willing to compromise and "balance their expectations" about the outcome.

"It's a question of trying to get some incremental gains," says Saleemul Huq, a senior fellow at the International Institute for Environment and Development (IIED) in London. "The approach of all-or-nothing that we took in Copenhagen blew up in our faces, and we can't just sit back and do nothing at all."

World leaders descended on Denmark in December 2009 to extend the Kyoto agreement, which is set to go dormant after the current commitment period expires in 2012. The goal was a new deal that included the United States--which has never signed the Kyoto Protocol--and the largest emerging economies, where emissions are growing at an alarming rate. After days of fruitless wrangling, a last-minute agreement brokered between the United States, China, India, Brazil and South Africa offered a way forward, but the effort buckled when a handful of developing countries who had no say in the crafting of the deal objected that commitments from industrialized nations to reduce carbon emissions did not go far enough. The accord failed to gain unanimous support, and negotiators returned home with no clarity on how to proceed.

Countries have spent the past year arguing over the details of the Copenhagen Accord, but the world's largest greenhouse-gas emitters, China and the United States, are at odds. The United States wants to see "measurable" and "verifiable" commitments from developing countries--as stated in the accord--whereas China and others question how the United States will meet its own commitment without legislative support from Congress.

"The reality is that until there is some kind of movement from the largest economy in the world, it is unrealistic for others to show their hand," says Shyam Saran, who stepped down this year as India's chief climate negotiator. Negotiators are currently marking time on the big issue and focusing on a more piecemeal approach, in the hope that these smaller initiatives will eventually "add up to something significant,",he says.

There has been considerable progress on initiatives that would funnel money from industrialized nations to developing countries, and help them to reduce emissions from deforestation and adapt to the changing climate. Negotiators also seem to be converging on the creation of a network of innovation centers to help developing countries to cope with climate and reduce emissions, although disputes over intellectual property could hamper technology transfer. But these agreements ultimately depend on financing.

In the Copenhagen Accord, which has now been endorsed by most nations, rich countries agreed to provide money for programs to help the developing world: a total of $30 billion by 2012, increasing to $100 billion a year by 2020. An analysis by the IIED has identified roughly $28.5 billion that has been pledged for short-term financing so far, but it is not always clear whether these pledges represent new money or existing aid repackaged as climate finance. Nor is it clear how countries will live up to the longer-term commitment. Nations are discussing a multitude of financing mechanisms, from direct appropriations to levies and carbon taxes on international transport.

At the Cancún talks, Mexico will have a strategic role in pulling these agreements together, both as the host nation and as an emerging economy that has been willing to engage with developed countries and talk about climate commitments from developing countries. The Mexican delegation will convene key parties in an effort to guide the process and keep everybody on track. They will also have a hand in guiding parallel--but separate--talks over extending the Kyoto Protocol, although little progress is expected on that front.

Meanwhile, thousands of professional negotiators assigned to specific aspects of a collective climate deal will be working to remove bracketed language--representing areas of disagreement--and assemble a single text that can be unanimously approved by the conference. The parties will also try to establish a new deadline for further decisions, either next year at talks in Cape Town, South Africa, or in 2012, when countries will mark the twentieth anniversary of the start of the climate talks.

But there are no guarantees that old ghosts won't come back to haunt Cancún, making it hard to reach any significant agreement. U.S. negotiators have warned that the Copenhagen Accord is a package deal, meaning that the financing it has already promised is contingent on developing countries living up to their part of the deal. And that means that disputes about emissions commitments could once again hold up progress in other areas.

"I don't think you make progress on any of these issues without some progress on all of them," says Eileen Claussen, president of the Pew Center on Global Climate Change in Arlington, Va. She anticipates two possible climate outcomes: in the positive scenario, countries will make incremental progress in negotiations and continue to implement climate policies at home, opening the way to a more comprehensive treaty a few years down the road. "The negative scenario," she says, "is that it all blows up."