In the Tällberg event we talked a lot about the deal we need, without really defining what was meant by that. I think it has at least four dimensions:
Technical
What science drives the goal? Is it 350ppm? 450ppm? 550ppm? 2C?
Social
What regions or sectors will move first, and what transfers will the rich or the winners use to induce the poor or the losers to play along? Do transfers consist of money, intellectual property, or both?
Implementation
What form will commitments take, who will make them, and how will they be implemented? Will the mechanism favor taxes or trading, for example? Will standards be expressed as intensities or absolute emissions or … ? How will goals and mechanisms adapt as we learn about uncertainties?
Coalition
We don’t have a deal now because we don’t have the coalition needed to make it happen. Some combination of the public, politicians, media, religion, education, etc. needs to come together to create critical mass behind a policy. We have fragments (the EU, California) but not a whole. I rather doubt that there is a quick, transformative solution (unless catastrophe drives us to one, which I’d rather not contemplate).
I say “critical mass” deliberately, because what we’re all implicitly searching for is a reinforcing feedback that will grow policy out of its current dysfunctional state. The question is, what is that loop? My guess is that it involves starting gradually. Don’t shoot for the moon and fail. Instead, take a little medicine at first. Impose a modest carbon tax. Observe that the economy doesn’t collapse, and efficiency is cheap or even profitable. Greentech gets a little more profitable, and the more numerous low-carbon voters grow to enjoy their tax rebates. Enlisting their support allows the tax to be ratcheted up further, and soon you’re rolling toward real emissions controls. But is the gain on that loop high enough to yield emissions reductions in time to avoid catastrophe?