Treaty success

So basically, I'm interested in how states succeed in making treaties. That presumes, of course, that I'm able to tell the difference between a successful and an unsuccessful attempt to make a treaty. Which, of course, I'm totally not. What defines a successful treaty-making attempt? Is it successful if you get ratification? Not necessarily; you might end up getting ratification of a totally worthless aspirational agreement that ultimately has no effect. How do you tell the difference (particularly given that there's a real branch of political science that argues that treaties are, by definition, epiphenomenal and therefore NEVER matter)?

Or you might get ratification of a more authentic treaty, only to have it collapse afterward. Is it successful if it lasts for only 2 years? 10? 25?

There's also the question of, success for who? Is it success if the two drivers of a treaty effort are the US and the USSR, and one of them gets what they want but the other doesn't? Is it successful if you get ratification of a carbon emissions treaty but the US, the largest emitter in the world at the time, doesn't sign?

The last question is particularly relevant to me at the moment, because I'm looking at the Law of the Sea negotiations, which are largely judged successful, from what I've seen, even though the US never actually signed (but which signed some subsequent stuff, and mostly - I believe - abides by the treaty anyway) in spite of the fact that it was a major driver of negotiations. So was the treaty a success immediately even though the US didn't sign, because enough other people did, even though the US is the world's largest maritime power? Was it not initially a success, or impossible to judge, but became a success because in practice it seems to have held? How do I treat that in a rigorous manner?

The Copenhagen round is widely judged to have obviously been a failure, because nobody got what they went in wanting and negotiations very visibly fell apart. On the one hand, this judgment is made even though there ultimately was a document, approved by all but one participant, containing voluntary emissions mitigation pledges from a much higher number of nations than committed to mitigations under Kyoto - including the US and China. Should that lead us to call it a success? On the other hand, those pledges are all voluntary, while Kyoto's pledges were binding; does that confirm that Copenhagen was a relative failure? On the third hand, Kyoto's binding pledges haven't, in practice, uniformly led to actual achievement of real cuts - so are voluntary pledges really that much worse? Could we call that a success? On the fourth hand, though all but one of the nations at Copenhagen accepted the document, one - Bolivia! - refused, and since the Convention on Climate Change works by consensus, this means the document is not formally adopted into the Convention - failure! And on the fifth hand, nations have continued to add their pledges in over time, months after the Bolivian-dictated failure to add it to the Convention. Does the fact that countries cared enough to keep adding to it months afterward suggest that it has been something of a success after all?

Whew.