MEXICO CITY, Mexico — Climate change conferences have an inauspicious history filled with political squabbling and little concrete progress. There is limited hope that this year's conference in Cancun will be any different.

Nearly 200 national delegates and thousands of support staff, scientists and NGO workers arrived Monday to again try to work toward accords that would limit the output of greenhouse gases.

But some say it's all a matter of expectations — and that you can't define success in Cancun by whether it results in a binding agreement on climate change.

Instead, it's possible to view the conference in Cancun as a forerunner to next year's conference in Durban, South Africa. In which case, success should be judged by incremental progress, not by an all-encompassing solution, say some activists.

There are four main themes on the table: developing ways to adapt to changing climate and weather patterns; transferring knowledge and green technologies to help poorer nations adapt; increasing regulation to prevent tropical deforestation; and creating a plan for how all of this will be financed.

But delegates are up against almost universally low expectations, and leaders around the world have expressed disdain for the conference, known as COP 16.

Ethiopian President Meles Zenawi, this year’s spokesman for the African Union, declared in October the event “would flop.” Many have echoed remarks by Indian Environmental Minister Jairam Pranesh that “Cancun is headed nowhere.” Observers everywhere have commented that no agreements are likely until next year’s conference at the earliest.

These sentiments are fueled by the general consensus that last year’s event in Copenhagen ended in failure.

But despite massive shortcomings, Copenhagen yielded some positive results.

It marked the first international recognition of a scientific rationale for ensuring global temperatures did not rise more than 2 degrees Celsius. And Western governments pledged to reduce their own emissions and provide assistance to developing nations predicted to be hit hardest by climate change.

However, since no binding agreements were made and political squabbling tends to stall talks, action toward reducing emissions remains slow.

The European Union has long been the most progressive body on climate change, and its national leaders will again be a vocal proponent for the argument that emission levels can be reduced without dire economic consequences.

With an increasingly powerful environmental lobby, India has been particularly outspoken on climate change in recent years, and Brazil released important data Thursday showing that it had reduced tropical deforestation by 14 percent, which could help provide confidence that significant progress can be made in preserving forests.

While island nations such as the Maldives, Tuvalu and Nauru may be politically and economically weak, they illustrate perhaps the strongest moral reason for action: largely, "we will disappear."

Mexico is an unlikely host country, with roughly 30 percent of its public sector revenue derived from PEMEX, the national oil company, and few large scale sustainable projects. However, national leaders seem at least moderately sincere about making improvements, and certainly want Cancun — hardly a model city of sustainability — to leave a very different legacy than its predecessor.

Blame for the failure of international agreements to materialize has fallen squarely on two major players: the United States and China. At the lead-up to Cancun in Tianjin, China, the two butted heads again, hurling diplomatic mud at one another through thinly veiled words. China derides the United States for its lack of action to reduce emissions, while the United States claims China continues to renege on agreements in Copenhagen.

The battle between the two largest emitters is viewed by many as the main blockade to progress.

But not everyone is so pessimistic. Doug Boucher, director of climate research and analysis at the U.S.-based Union of Concerned Scientists, believes there's an opportunity to look beyond these two nations and move forward on the central topics.

Though progressive binding agreements would be preferable, Boucher does not regard them as the only measure of success, and sees value in progress toward more concrete future agreements.

Gustavo Ampugnani, coordinator for Greenpeace Mexico’s climate and energy campaign, describes this year as a crucial stepping stone.

“Cancun is a middle point between the failure of Copenhagen, and the future possible success of South Africa,” he said. “And for Cancun, for it to be this middle point, on the path to the right destination, it needs to lay the seeds for global agreements that we want to see in South Africa.”