ABSTRACT
The interrelated environmental, social and economic challenges imposed by global climate change will make it one of the most important political issues in the coming century. While there are still large uncertainties concerning the sensitivity of the climate system, the Intergovernmental Panel on Climate Change (IPCC) has concluded that most of the observed global warming since the mid-twentieth century is very likely due to human activities (IPCC 2007). This conclusion is well supported also in other parts of the scientifi c community. For example, all scientifi c bodies in the United States agree as well as the vast majority of papers published in refereed scientifi c journals (Oreskes 2004).
