Peter – I’m reluctant to engage in an extended discussion of anthropogenic vs natural climate variability. It’s an enormous topic – far too broad to do justice to here. I think it would be more useful for me to repeat a point I made above – if you want to convince individuals with a strong background in climate science that you have a valid economic point to make, you will need to base it on the expectation that continued anthropogenic carbon emissions are likely to exert significant adverse effects (even if their magnitude is controversial), and that substantially reducing carbon emissions will substantially reduce the severity of those effects.
I could devote much space to detailing the evidentiary basis for those conclusions, and provoke many arguments from blogosphere partisan warriors in the process. Whether the conclusions are right or wrong, though, doesn’t in my view change the fact that if you depend on their being wrong for your arguments, your arguments will be seen as unpersuasive by the majority of those who know the science very well. I also assume you genuinely want to arrive at a position that is accurate rather than to merely win arguments. In that case, you’ll have to try to evaluate as objectively as you can how likely those scientific conclusions are to be wrong. Blogs are probably not very helpful for that purpose, but I don’t know if there’s any quick way to get an accurate perspective on climate science without running into personal biases. Perhaps consulting a wide diversity of expert sources would be helpful.