Emissions Scenarios - IPCC

222 An Overview of Scenarios
Figure 4-11 also gives an overview of the evolution of the
global energy system between 1990 and 2100 as reflected in
the SRES scenarios. The four marker scenarios are shown as
thick lines. In addition, for each scenario family the area
sparmed by all the SRES scenarios in that family is marked in
the same color as the trajectory for the respective marker. The
SRES scenarios cover a wider range of energy structures than
the previous IS92 scenario series, reflecting advances in
knowledge on the uncertainty ranges of future fossil resource
availability and technological change. Scenarios Bl, B2, AIT,
and to some extent AIB follow a trend toward increasing
shares of zero-carbon options in the long term. AIG more or
less follows an oil-gas isoshare line that perpetuates the current
dominance of oil and gas in the global energy balance far into
the 2V^ century. Scenarios in group AlC indicate a near
doubling of coal's share in primary energy use. Also of interest
is the trajectory of the A2 marker scenario, which returns in its
energy stracture by 2100 (over 50% coal share) to the situation
that prevailed almost 200 years before (i.e., around 1900).
However, even with similar fuel shares, the technologies, enduse
fuels, and applications projected in the A2 scenario are
radically different from those of the past.
4.4.8.1. Al Scenarios
The most significant change in the long-term primary energy
mix in the AlB-AIM marker scenario is the fast market
penetration of (new) renewable energy. Its share increases from
Renewables/Nuclear
Figure 4-11: Global primary energy structure, shares (%) of oil and gas, coal, and non-fossil (zero-carbon) energy sources -
historical development from 1850 to 1990 and in SRES scenarios. Each comer of the triangle corresponds to a hypothetical
situation in which all primary energy is supplied by a single source - oil and gas, coal at the left, and non-fossil sources
(renewables and nuclear) to the right. Constant market shares of these energies are denoted by their respective isoshare lines.
Historical data from 1850 to 1990 are based on Nakicenovic et al. (1998). For 1990 to 2100, altemative trajectories show the
changes in the energy systems structures across SRES scenarios. They are grouped by shaded areas for the scenaiio families
Al, A2, Bl, and B2 with respective markers shown as lines. In addition, the four scenario groups within the Al family (AI,
Aie, AIG, and AIT) that explore different technological developments in the energy systems are shaded individually. The
AlC and AIG scenario groups have been merged into one fossil-intensive AlFI scenario group in the SPM (see footnote 1).
For comparison the IS92 scenario series are also shown, clustering along two trajectories (lS92c,d and IS92a,b,e,f). For model
results that do not include non-commercial energies, the corresponding estimates from the emulations of the various marker
scenarios by the MESSAGE model were added to the original model outputs.