I’ve spent the last week at the Bali Climate Conference, so my choice is heavily influenced by that experience. My preference is Jeffrey Frankel’s Proposal One: For Fairness, Use Formulas. If it turns out during the process of negotiation that Proposal One is not achievable because it is too ambitious or too complex, Proposal Three might be a fallback position.
The Bali conference has shown that stopping global warming is not only a question of policy models - it is a question of leadership and vision. In the dramatic days and hours leading up to a watered-down compromise, our leaders have shown that they are not up to the task (yet). What they suggest so far will not get the job done. Science tells us that more dramatic steps are necessary than the ones that the Bali negotiators suggest (and might, after further watering them down, put into a treaty with binding commitments in 2009). It seems to me that most people are more aware of the urgency and the magnitude of the problem than their leaders are.