A new round of climate talks opened this week in Bonn, Germany, with the ambitious goal of reaching a comprehensive legal agreement “applicable to all Parties” by 2015.

Countries agreed to launch the new round last December in Durban, South Africa, as part of a package deal that also keeps the Kyoto Protocol alive, at least for now. The so-called Durban Platform negotiations offer governments the chance to consider new approaches and—one can hope—commit themselves to meaningful action.

Since the start of the U.N. Framework Convention on Climate Change (UNFCCC) 15 years ago, there’s been tension between two competing models—binding targets-and-timetables vs. voluntary pledge-and-review. And in actuality, parties have now constructed both: the first in the 1997 Kyoto Protocol, the second in the parallel framework that emerged in Copenhagen in 2009 and was further developed in Cancún and Durban.

Quite clearly, neither approach is delivering the strong action we need. But over the next three and a half years, negotiators will have plenty of opportunity to weigh the relative merits of the two, and perhaps see if there’s a third way that borrows the best of both.

For the moment, their focus is primarily procedural—choosing a chair, deciding on a work plan, etc. But as they take up these questions, parties are laying down markers for the more substantive negotiations to come.

The Durban Platform does three things:

• First, it sets a 2015 deadline for an agreement to take effect in 2020.
• Second, it requires that the agreement be an amendment, a protocol or otherwise have “legal force.” To many, though not all, this means it must be legally binding.
• Third, it says the agreement will be “applicable to all Parties.” This would appear to obliterate the strict binary differentiation between developed and developing countries embedded in the Kyoto Protocol. But beyond that, it really offers no hint of an alternative approach to the ever-present issue of equity.

Indeed, the Durban Platform is more or less a blank slate. Which means parties have all the latitude they need to think creatively about alternative pathways—or to meander in endless circles.

Pre-meeting submissions from the United States, China, and the European Union give a flavor for how positions are beginning to line up.

Neither the U.S. nor China appears eager to rush things. The U.S. says this is a year for “brainstorming” and there’s no need to agree now on all the issues to be considered.  China stresses the importance of future inputs, such as the Fifth Assessment of the Intergovernmental Panel on Climate Change, and declares the fulfillment of past commitments by developed countries on finance and technology “the fundamental basis … to make any progress.”

Not surprisingly, they offer somewhat different takes on how Durban speaks to equity. China underscores the UNFCCC principle of “common but differentiated responsibilities,” and insists that Durban’s aim is “by no means to renegotiate or rewrite the Convention.” The U.S., on the other hand, believes a reinterpretation is long overdue and insists “the new agreement will have legal force with respect to all Parties, developed and developing countries alike.”

The EU, meanwhile, already has a vision of what the 2015 agreement should look like and isn’t shy about putting it forward. Among other things, the EU calls for “those countries with the greatest responsibilities and capabilities” (i.e., including the United States, which is not in Kyoto, as well as China and other major emerging economies) to have legally-binding commitments for absolute economy-wide emission reductions. In this respect, at least, something along the lines of Kyoto-enlarged.

The Bonn talks runs through the end of next week. Parties may also meet for a week in Bangkok in September before the year-end Conference of the Parties in Doha, Qatar.  It’s not a year for big breakthroughs, but hopefully a reasonable start on what promises to be a challenging path.

It’s worth remembering, though, that what’s possible within the negotiations by 2015 is fundamentally a function of what’s happening outside the negotiations—the political will, policies and action that can be mustered at the national level. So while it’s important to move the talks along, the real work right now is back at home.