From the above discussions it is clear that mitigating climate change is a key challenge for humanity. The IPCC (2007b) has put emphasis on the fact that global emissions should decline in the near future to avoid ‘dangerous interference with the climate system’, as outlined in the United Nations Framework Convention on Climate Change. To achieve this, a global average maximum level of warming has been identified at 2 ºC by 2100 compared to 1990, beyond which largely negative impacts for ecosystems and socioeconomic systems are likely to occur (Hansen et al. 2006; Anderson and Bows 2008; Parry et al. 2008; Meinshausen et al. 2009).