From the Climategate 2.0 collection, to a European Peoples Party officials who is trying to eliminate skepticism from the EPP’s position paper on climate, Phil Jones describes the origin of the 2o limit:
"The 2 deg C limit is talked about by a lot within Europe. It is never defined though what it means. Is it 2 deg C for the globe or for Europe? Also when is/was the base against which the 2 deg C is calculated from? I know you don’t know the answer, but I don’t either! I think it is plucked out of thin air. I think it is too high as well. If it is 2 deg C globally, this could be more in Europe – especially the northern part. A better limit might be maintaining some summer Arctic sea ice!"