Scenarios

Scenarios are unfolding sequences of interrelated events stemming from prior and ongoing decisions. With regard to climate change and carbon emissions, the outputs of climate and carbon cycle models under different scenarios of population growth, economic development, and fossil and other fuel use have proved to be useful in exploring possible policy options for mitigation of climate change due to greenhouse gas emissions. Owing to the contingent nature of historical evolution, economic and technological development may in fact be unknowable in advance. Nevertheless, the scenario approach is useful because it allows asking “what if?” questions. A variety of scenarios have been published by several research groups. There is, of course, an infinite variety of scenarios that will lead, say, to keeping the future level of CO2 below a certain level. One of the earliest sets is that presented in the first of the scientific reports from the Intergovernmental Panel on Climate Change (IPCC). Subsequent scenarios have been suggested by Wigley et al. (1996) and by Nakicenovic et al. (1998).

The Intergovernmental Panel on Climate Change (IPCC) scenarios

The authors of the IPCC report point out that scenarios are not predictions of the future, but merely illustrate the effects of a range of economic, demographic, and policy assumptions. In Climate Change 1992 the IPCC examined six scenarios, including the one called IS92a, which has become known as the Business as Usual scenario (BAU).