There is widespread acceptance that the climate is changing. Although the United Nations Framework Convention on Climate Change warns that the increase in global temperature should be below 2°C to avoid severe impacts, projections based on current emission trends point to much more substantial warming, with possible increases of 4°C or more in the long-term unless there is radical action to cut emissions.
Despite the increasing plausibility of these high-end scenarios, there are few studies that assess their potential impacts and the options available for reducing the risks. Existing modelling tools and methods fail to account for potential tipping points, the need to cope with radical rather than gradual change, the complex interactions between sectors and the synergies and trade-offs between adaptation and mitigation actions. It is vital that decision-makers have access to reliable scientific information on these uncertain, but potentially high-risk, scenarios of the future, so that they can make effective adaptation and mitigation plans.