How will Copenhagen overcome the collective action problem?

I’m not asking about climate science here, I’m asking about collective action problems in international law and policy. How is this exercise different from previous failures? Even if new states are persuaded to say yes on paper, on what grounds does anyone think that these commitments will be fulfilled this time, particularly given the record of Kyoto? The article linked here from the AP talks about “momentum building” and “legally binding agreements.” What does that mean and how? Legally binding to prevent defection down the road, how? This is not an attempt to get snarky, but complete puzzlement on my part. How is this different from earlier attempts?

The one thing that might be different, so far as I can tell, is that the meeting might make moves toward the global fund for the developing world. Which would suggest, however, that the world has largely accepted that it won’t really do anything about the problem on the front end, but might do things to address concrete damage in the developing world. Or perhaps will simply hand out the money as a sort of buy-off and global welfare transfer payment. That seems to me to be the most likely outcome of Copenhagen, at most, and maybe or maybe not an agreement that, on the basis of past experience, will be invoked in op-ed pages and law review articles and politely sidelined as discussions get underway for the next round of agreements. Copenhagen (apart from the speeches and expressions of concern and photo ops and opportunity for the Secretary General to re-cast himself as a little bit of a rock star) appears to me mostly about the fund. It might have similar collective action problems in collecting for it, but that is a lot easier as a tradeoff than actually doing any of the stuff that might be proposed or even agreed to on the issue of climate change itself.