While everyone else is downplaying expectations for the year-end Cancun climate summit, Mexican negotiators still believe there can be a “spectacular breakthrough.” After the failure of the recent Bonn climate talks to achieve any substantial progress, one has to wonder how Mexico is defining success in Cancun? And more importantly, how does it aim to facilitate that outcome?

Mexico has stopped short of pushing for comprehensive treaty to replace the Kyoto Protocol. Reluctantly acknowledging political reality after Bonn, Mexico’s chief delegate Fernando Tudela told Reuters earlier this week that “we will not be able to negotiate a new treaty in Cancun, that much is clear.” What they hope to come of their high profile summit is less clear.

Before the Bonn talks devolved into what one EU delegate referred to as “tit-for-tat” diplomacy, Mexico’s special representative for climate change Luis Alfonso de Alba had suggested the Cancun summit could result in three new treaties: “We are not just talking about one single legally binding instrument but a set of them.” As De Alba explained it to Nina Chestney of Reuters, one treaty could cover Annex I, developed country signatories to the Kyoto Protocol; another, developing countries; and a third treaty could be drafted in an attempt to codify the promised reductions made in Copenhagen by the US–the world’s richest unrepentant emitter of greenhouse gas.

Mexico’s foreign minister Patricia Espinosa is suggesting something entirely different: simply extend the Kyoto Protocol. Espinosa told The Hindu newspaper that “the existing legal framework is a good basis” for addressing climate change. “There is no need for a new treaty,” she said.

Under the Kyoto regime, developing countries–even large ones like China and India–are exempted from committing to carbon emissions reductions. As developing countries have come to produce an increasing share of greenhouse gases since 1997 when the Kyoto Protocol was initially adopted, that provision has become one of the biggest obstacles preventing American support for international climate agreements.

Espinosa’s proposal also faces logistical hurdles. The first commitment period for the Kyoto Protocol ends in 2012, but it most experts predict it would take years to authorize a second period leaving a regulatory gap between when Kyoto expires and comes back into force. Some worry that focusing on reauthorizing a contentious treaty will simply distract diplomats from the hard negotiating necessary to draft a more agreeable updated treaty (or treaties, as De Alba would have it).

Mexico is acutely aware that climate negotiators are running short on time to shape a post-Kyoto legal structure. “We have a window of opportunity that is closing,” said Mexico’s chief Bonn delegate Tudela. “What we want to do is rescue these negotiations.”

Since the conclusion of the Bonn talks, Mexican diplomats have been racing around the globe trying to do just that. Last week De Alba traveled to Stockholm and announced Mexico’s intentions to reach out to developing nations “that felt their views were not significantly taken into account” in Copenhagen. This week Foreign Minister Espinosa was in India, one of those emerging countries hurt by the last minute diplomatic push that produced the Copenhagen Accords. In New Delhi, she met with Prime Minister Manmohan Singh and Environment Minister Jairam Ramesh to deliver the message that, “an ambitious outcome [in Cancun] requires India’s sustained political guidance and support.”

Mexico’s efforts to keep developing nations happy may end up pleasing no one. Its quest for an inclusive summit risks further inflaming old debates on fundamental issues like whether developing nations should abide by emissions targets. While it may not have been fair or democratically produced, at least the Copenhagen Accords provided an road map–admittedly, a loophole-ridden one–to a lower carbon world. Stopping now to plot a new and even less certain course while carbon continues to accumulate in the earth’s atmosphere at unprecedented levels is even more dangerous.

A successful week of negotiations at the Tianjin talks in October, which builds consensus around differentiated treaties or extending Kyoto, would go a long way towards ensuring that diplomats emerge from the Cancun summit with the tools and strategies necessary to combat global warming. But as James Murray rightly observes at the Business Green blog, Mexico is employing “an absurdly high risk strategy.” Murray concludes that the “best option currently available is to agree [to] a treaty that does not go nearly far enough while hoping that it provides an economic framework that allows countries to overshoot their inadequate emission reduction targets.” Only time and the temperature will tell if Mexico’s gamble to stop global warming pays off.