This looks a very interesting project that mirrors my own thoughts. Take the UNIPCC “projections” of a future catastrophe – including all the nonsense about falling crop yields in Africa, collapsing polar ice caps, etc. – and you still have not got anything like the justification for policy.
If you then add the additional costs of ineffectual implementation, poor policy-making and other “policy” that economists would not recommend (e.g. bio-fuels) then the 50 to 1 ratio balloons. If the “science” turns out to be too extreme. If for instance a doubling of CO2 leads to just 1.5 degrees of temperature rise instead of 3 degrees, then the catastrophic consequences will not just halve, but be many times smaller. If the catastrophic consequences of a given amount of warming have been overstated, (such as storms not becoming more extreme, but less – as Hansen and Lindzen now agree) then it becomes worse still. If it turns out that a small amount of warming of net benefit to the planet (as it will be in Northern Europe) and/or that higher CO2 levels are of net benefit to the planet, then the whole exercise turns from incurring costs to prevent the future consequences of another lot of costs to incurring costs to prevent a benefit from happening.