3.2 Baseline scenarios
3.2.1 Drivers of emissions
Trajectories of future emissions are determined by complex dynamic processes that are influenced by factors such as demographic and socio-economic development, as well as technological and institutional change. An often-used identity to describe changes in some of these factors is based on the IPAT identity (Impact = Population x Affluence x Technology – see Holdren, 2000; Ehrlich and Holdren, 1971) and in emissions modelling is often called the ‘Kaya identity’ (see Section 18.104.22.168 and Yamaji et al., 1991). These two relationships state that energy-related emissions are a function of population growth, GDP per person, changes in energy intensity, and carbon intensity of energy consumption. These factors are discussed in Section 3.2.1 to describe new information published on baseline scenarios since the TAR. There are more than 800 emission scenarios in the literature, including almost 400 baseline (non-intervention) scenarios. Many of these scenarios were collected during the IPCC SRES and TAR processes (Morita and Lee, 1998) and made available through the Internet. Systematic reviews of the baseline and mitigation scenarios were reported in the SRES (Nakicenovic et al., 2000) and the TAR (Morita et al., 2001), respectively. The corresponding databases have been updated and extended recently (Nakicenovic et al., 2006; Hanaoka et al., 2006). The recent scenario literature is discussed and compared with the earlier scenarios in this section.