Emissions Scenarios - IPCC

88 An Overview of the Scenario Literature
Table 2-2: Database minimum, maximum, and median CO^ emissions levels in the year 2100 (in GtC). Data source: Morita
and Lee, 1998.
Number of scenarios Minimum Maximum Median
Intervention scenarios 62 -2.1 14.4 6.0
Non-intervention scenarios 88 1.2 59.4 21.3
Non-classified scenarios 40 -0.4 32.4 15.2
Total sample 190 -2.1 59.4 15.7
than the total sample - 21 GtC in 2100 compared with the 15.7
GtC median found in the total sample. The lower median of the
total sample may result from downward pressure exerted by the
inclusion of some intervention scenarios in the total sample.
However, it could also result from the influence of IS92a-like
scenarios (upward pressure) in the non-intervention sample
(see also Figure 2-10-
Figure 2-Id likewise depicts spaghetti curves for the intervention
scenarios. The entire range for the intervention scenarios is small
compared to those of the no policy scenarios and the total set of
scenarios. In 2100 the maximum (14.4 GtC) and the median (6
GtC) of this sample are significantly lower than maximum and
median values of the full and non-intervention sets.
Figure 2-le shows the range for scenarios that could not be
classified into these two groups because of insufficient
infonnation in the database. The range of scenarios in this
category is similar to that of the total sample in that it is very
broad. The median of this set in 2100 is also similar to that of
the total sample (15.7 GtC) and follows a similar trajectory.
Finally, the IS92a scenario (Leggett et ai, 1992; Pepper et al,
1992) appears to have influenced subsequent emissions scenarios
in the literature. The median population, gross world product, and
primary energy consumption trends in many scenarios in the
literature track very closely the developments in the IS92a
scenario (Morita and Lee, 1998). This is because IS92a
constituted a reference baseline that was emulated by different
60
Total database range
s
о
S
.-S
50
40
.9 Г. и 30
о
в
л
и
я 20
и
"я
о
10
5
1900
Statistics for 2100
N= 62 (75 in 1990)
95% = 10.5 GtC
75% = 7.2 GtC
Median = 6.0 GtC
25% = 4.5 GtC
5%= I.SGfC
1990 range
1950 2000 2050 ^2100
95%
75%
Median
25%
5%
Figure 2-Id: Global energy-related and industrial CO2 emissions for 75 intervention scenarios identified from the SRES
database. Historical development and future scenarios are shown as absolute values in GtC. Median (50*), 5*, 25*, 75*, and
95* percentiles of the frequency distribution are shown. The statistics associated with scenarios from the literature do not
imply probability of occurrence. The emissions paths for intervention scenarios show a more limited range of future emissions
than do those for the non-intervention scenarios (see Figure 2-Ic). The actual coverage of COj emissions sources may vary
across the 75 scenarios from the database included in the figure. The scenario samples used vary across the time steps (for
1990 75 scenarios; for 2100 62 scenarios were analyzed). Data sources: Morita and Lee, 1998; Nakicenovic et a/.,1998a.