My bad, I over reached.....of course scientists should participate in the policy debate, but they have no special claim to extraordinary credibility in that arena. We've seen several examples of that in the posts associated with this article: "I'm a PhD so listen to me"......the type that can kill any cocktail party within 50 paces.

And - granted - there are lots of clever ideas out there for mitigating antropogenic CO2 mediated climate change (more on this below), so the question becomes: what are the costs and benefits of the whole range of options, including the option of doing nothing? The predonderance of evidence points to doing nothing as the best cost benefit proposition: predictions of future climate states differ wildly (UK in the deep freeze, UK like Morocco in the summer), so the costs are just not known with any certainty; and, the existing cost calculations assume that individuals will just sit around and not adapt on their own as the climate changes (i.e., human behaviour as per usual is assumed out of the cost equation).

The only fly in the ointment is the risk of a major discontinuity - e.g. Gulf Stream shuts down over the space of a few decades or years - but the chances of this would seem to be about the same as a major meteorite strike. Both will definitely happen at some point in the future - the Gulf Stream has not, and will not persist forever, regardless of antrogenic CO2 mediated climate change - but the chances of occurence within a relevant timeframe are small, and - likely - we would get some kind of warning which would permit the attempt of emergency preventive measures.

But then again perhaps it's all too late. Isn't the mainstream prediction that the climate is heading for a major change even if today we completely stopped all antropogenic CO2 emissions? If so, then let's focus on adaptation: e.g., discourage reconconstruction of New Orleans, discourage construction in wildfire vulnerable areas, build a dyke around New York, and/or Bangladesh (coupled with development & governance to improve resilience to the tropical storms to which they have always been subject).

If the world restricted itself to the per capita carbon footprint of Europe - reasonable level of propserity, wind/solar/whatever, dense settlement, extensive public transit, below-replacement birthrates - we'd still be emitting far more CO2 than today. Even then, the very large scale viability of wind/solar/whatever is not clear, and do we want our landscape so blighted? Not to mention that there's a reason the European birthrate is so low: it's a depressing place to live......but nice to visit ;)

A serious and credible advocacy for reducing antropogenic CO2 while maintaining and building upon the quality of civilization, would be for massive investments in fission reactors (using the power to spilt Hydrogen out of water), coupled with massive investments in fusion research so that it's viable in time for the depletion of uranium (something like 150 years).