Emissions Scenarios - IPCC

212 An Overview of Scenarios
Table 4-11: Summary of technology improvements for extraction, distribution, and conversion technologies assumed for the
SRES scenarios. The classification reviews technology dynamics across the four marker scenarios and the four Al scenario
groups relative to each other Illustrative, scenario-specific technology assumptions are discussed in the text. AlC and AIG
have been combined into one fossil-intensive group AlFI in the SPM (see also footnote 1 ).
Technology Improvement Rates
Scenario Coal Oil Gas Non-fossil
AIB High High High High
A2^ Medium Low Low Low
Bib Medium Medium Medium Moderate-high
B2'= Low Low-medium Moderate-high Medium
AIG Low Very high Very high Medium
AlC High Low Low Low
AIT Low High High Very high
" Technology improvement rates in the A2 scenario are heterogeneous among the world regions.
Bl: The assumed time-dependent leaming coefficients range from 0.9 (i.e. a 10% reductionin the capitahoutput ratío on a doubling of
cumulated production) for oil, 0.9-0.95 for gas, and 0.9-0.95 for surface coal mining to about 0.94-0.96 for non-fossil electric power
generation options and 0.9-0.95 for commercial biofuels.
In the specific model implementations, "inconvenience costs" of energy-end use, including social externalities costs, are expected to be
particularly important for tradhional coal technologies (e.g., underground mining, cooking with coal stoves).
4.4.7.1. Al Scenarios
The AIB marker scenario represents the "balanced"
technology development group of Al scenarios; it assumes
significant innovations in energy technologies, which improve
energy efficiency and reduce the cost of energy supply.
Consistent with the A1 scenario storyline, such improvements
occur across the board and neither favor nor penalize particular
groups of technologies. Al assumes, in particular, drastic
reductions in power-generation costs, through the use of solar,
wind, and other modem renewable energies, and significant
progress in gas exploration, production, and transport. For a
different view, altemative scenario groups embedded within
the overall Al scenario family explore pathways of cumulative
technological change; that is, path-dependent scenarios in
which technologies evolve on mutually largely exclusive
development paths. In general this has been the historical
experience, in which the success of particular energy
technologies (the steam engine in the 19"' century, or intemal
combustion in the 20'*') have "locked out" other technological
altematives. These scenario groups explore altemative spectra
of technology dynamics in the domains of unconventional oil
and gas, coal, as well as post-fossil technologies. Salient
technology assumptions are described below.
Keeping in mind the very different degrees of technological
detail and the mechanisms for technology improvements
represented in the different models, a consistent inter-scenario
comparison of technology assumptions is best achieved within
the framework of one particular model. An overview of
different technology developments for the scenario groups of
the Al scenario is given in Box 4-8 for the AIM model, which
was also used to develop the AIB marker scenario. (A
comparison with die MARIA model indicated that technology
cost assumptions and their dynamics are quite congruent.) To
illustrate differences in technology chai-acteristics that drive the
four different SRES scenario families, conesponding scenariospecific
data based on MESSAGE data are presented at the end
of this Section.
4.4.7.2. Al Scenario Groups
As outlined above, besides the marker, three different groups
of Al scenarios were developed by the different modeling
groups (combined into two in the SPM, see also footnote 1). hi
total, nine altemative runs are clustered in thi'ee scenario
groups based on the AIM, MARIA, MESSAGE, and
MiniCAM models.
In the AIG scenario group, technological change enables a
larger fraction of the large occurrences of unconventional oil
and gas, including oil shales, tar sands, and especially methane
hydrates (clathrates) to be tapped. High technological leaming
and cost reduction effects could lower unconventional oil and
gas extraction costs by approximately 1% per year and
conversion technology costs by about factor of two (AIG-
MESSAGE, see Roehrl and Riahi, 2000). As mentioned in
Section 4.4.6, ahhough these assumptions yield higher
extractions of unconventional oil and gas resources, they are
not sufficient to tap significant fractions of unconventional
resources such as gas clathrates. Future scenario studies might
reassess the current state of knowledge on possible technology
development of these "exotic" fossil-fuel occurrences and the
conditions under which they could become a major future
source of unconventional hydrocarbon supply (and a massive
source of carbon emissions). For the AIG scenario group,
substantial improvements and extensions of the present
pipeline grids and entirely new natural gas pipelines systems