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.
