Emissions Scenarios - IPCC

306 Summary Discussions and Recommendations
1900 1950 2000 2050 2100
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1900 1950 2000 2025 2050 2100
Figure 6-6: Global COj emissions from energy and industry in Figure 6-6a and from land-use change in Figure 6-6b -
historical development from 1900 to 1990 and in 40 SRES scenarios from 1990 to 2100, shown as an index (1990 = 1). The
range is large in the base year 1990, as indicated by an "error" bar, but is excluded from the indexed future emissions paths.
The dashed time-paths depict individual SRES scenarios and the shaded area the range of scenarios from the literature (as
documented in the SRES database). The median (50*), 5"', and 95* percentiles of the frequency distribution are shown. The
statistics associated with the distribution of scenarios do not imply probability of occurrence (e.g., the frequency distribution о
the scenarios in the literature may be influenced by the use of IS92a as a reference for many subsequent studies). The 40 SREI
scenarios are classified into seven groups that constitute four scenario families. Jointly the scenarios span most of the range of
the scenarios in the literature. The emissions profiles are dynamic, ranging from continuous increases to those that curve
through a maximum and then decline. The colored vertical bars indicate the range of the four SRES scenario families in 2100,
Also shown as vertical bars on the right of Figure 6-6a are the ranges of emissions in 2100 of IS92 scenarios and of scenarios
from the literature that apparently include additional climate initiatives (designated as "intervention" scenarios emissions
range), those that do not ("non-intervention"), and those that caimot be assigned to either of these two categories ("nonclassified").
This classification is based on a subjective evaluation of the scenarios in the database by the members of the
writing team and is explained in Chapter 2. It was not possible to develop an equivalent classification for land-use emissions
scenarios. Three vertical bars in Figure 6-6b indicate the range of IS92 land-use emissions in 2025, 2050 and 2100.
Classification of land-use change emission scenarios similar to that for energy and industry emissions was not possible.