Figure SPM.1: Comparison
of reference and stabilization scenarios. The figure is divided into six parts,
one for each of the reference scenario groups from the Special Report on Emissions
Scenarios (SRES, see Box SPM.1). Each part of the figure shows the range of total
global CO2 emissions (gigatonnes of carbon (GtC)) from all anthropogenic
sources for the SRES reference scenario group (shaded in grey) and the ranges
for the various mitigation scenarios assessed in the TAR leading to stabilization
of CO2 concentrations at various levels (shaded in colour). Scenarios
are presented for the A1 family subdivided into three groups (the balanced A1B
group (Figure SPM.1a), non-fossil fuel A1T (Figure SPM.1b) and the fossil intensive
A1FI (Figure SPM.1c)) with stabilization of CO2 concentrations at 450,
550, 650 and 750 ppmv; for the A2 group with stabilization at 550 and 750 ppmv
in Figure SPM.1d, the B1 group with stabilization at 450 and 550 ppmv in Figure
SPM.1e, and the B2 group with stabilization at 450, 550 and 650 ppmv in Figure
SPM.1f. The literature is not available to assess 1000 ppmv stabilization scenarios.
The figure illustrates that the lower the stabilization level and the higher the
baseline emissions, the wider the gap. The difference between emissions in different
scenario groups can be as large as the gap between reference and stabilization
scenarios within one scenario group. The dotted lines depict the boundaries of
the ranges where they overlap.
