Emissions Scenarios - IPCC

210 An Overview of Scenarios
additional scenario groups. Three of these (AlC, AIG, and
AIT) explore more extreme pattems of reliance on particular
resources and technologies compared to the more "balanced"
tendencies described in the AIB scenarios, including the AIB
marker. As discussed in Chapter 3 and Section 4.3.1, this
characteristic of the Al scenario family stems from the
interpretation of technological change and resource availability
as being cumulative and path dependent.
4.4.6.2. Al Scenario Groups
Besides the AIB marker scenario group, altemative pathways
unfold within the Al family, according to diverging technology
and resource assumptions (Figures 4-8 to 4-10). Two of these
groups (AlC and AIG) were merged into one fossil-intensive
group (AlFI) in the SPM. The more detailed information on
these two groups is presented here, in Chapter 5 and Appendix
Vll (see also footnote 1).
The coal-intensive scenario group AlC is restricted mainly to
conventional oil and gas, which results in the lowest
cumulative oil and gas use (15 to 19 ZJ) of all scenarios; it is
even slightly lower than in the B2 scenario, which has much
lower energy demand. As such, the scenario illustrates the
long-term GHG emission implications of quickly "running out
of conventional oil and gas" combined with rapid technological
progress in developing coal resources and clean coal winning
and conversion technologies. As a result, cumulative coal use is
very high - between 48 and 62 ZJ (median, 60 ZJ) between
1990 and 2100.
Conversely, oil and gas resources are assumed to be plentiful in
the world of scenario group AIG because of the assumed
development of economic extraction methods for
unconventional oil and gas, including methane clathrates.
Cumulative oil and gas extraction amounts to 76 to 88 ZJ,
about twice as high as in the AlC scenario group. Mainly this
reflects current perceptions that radical technological change
needs to оссш' to translate a more significant portion of the
resource base of unconventional oil and gas into potentially
recoverable reserves, a development evidentiy also crosschecked
by possible developments in non-fossil alternatives.
Cumulative coal extraction in AIG is relatively low at 15 to 38
ZJ (median, 19 ZJ) across the scenarios of this scenario group.
As a result of fast technological progress in post-fossil
altematives in the technology-dynamic AIT scenario group, the
call on oil and gas resources is comparatively modest -
cumulative extraction to 2100 ranges between 36 and 46 ZJ,
quite similar to the AlC scenario group. The main difference is
that because of the improvements in non-fossil alternatives the
call on coal resources remains modest - cumulative coal use of 4
to 12 ZJ (median: 10 ZJ) in AIT is the lowest of all the scenarios.
4.4.6.3. A2 Scenarios
Resource availability assumptions for the A2-ASF world are
generally rather conservative, essentially that current
conventional estimates of petroleum resource availability are
not expanded.^^ Unconventional hydrocarbons, such as
methane clathrates and heavy oils, do not come into large-scale
use. As a result, coal resource use is the highest among the
SRES marker scenarios. The ASF marker scenario
quantification of oil, natural gas, and coal resource availability
reflects the Rogner (1997) estimates for conventional oil and
coal resource availability and the recent IGU (1997) estimates
for conventional gas reserves (optimistic scenario, see Chapter
3). Resource extraction costs in the ASF depend on the
resource "grade" and vary from US$2.6 to 5.2 per GJ for oil (in
1990 dollars), from US$1.2 to 4.6 per GJ for gas, and US$0.7
to 6.0 per GJ for coal.
4.4.6.4. Harmonized and Other A2 Scenarios
The primary energy structure of the A2 family scenaiios is also
reflected in the cumulative fossil fuel resource use,
characterized by an increasing reliance on coal resources (see
Figures 4-8 to 4-10). The cumulative oil use varies by a factor
of two across the A2-family, between 11 and 24 ZJ (median, 18
ZJ; A2 marker, 17 ZJ). Cumulative gas use ranges between 20
and ZJ 36 (median, 23 ZJ; A2 marker, 25 ZJ). The higher end
of the range of gas resource use occurs in the A2G-1MAGE
scenarios, which explored the scenario sensitivity to assuming
that a significant fraction of methane hydrate occurrences
become technically and economically recoverable in an A2
world. Given the regional orientation of the A2 scenario
storyline and the resultant quest for energy independence, the
possibihty of tapping even currently "exotic" fossil resources
certainly merits such a scenario sensitivity analysis. The
opposite end of the resource availability spectmm is explored
in the MiniCAM scenarios of the A2 scenario family. First,
methane clathrates are assumed not to become available. As a
result, the call on resources focuses on coal (A2-MiniCAM) or,
in a scenario sensitivity analysis, more on unconventional oil
and gas (A2-A1-MiniCAM). The range of reliance on coal
resources is thus an inverse image of the range of oil and gas
resource availability. Cumulative coal extraction varies
between 22 and 53 ZJ (median, 35 ZJ; A2 marker, 47 ZJ)
across the scenarios of the A2 scenario family. This picture
mainly represents what used to be termed "conventional
wisdom" in much of the scenario literature (including the
previous IS92 scenario series). Importantly, while the
probabilities of alternative developments of fossil and nonfossil
resource availability cannot be assessed at present, the
multi-model, multi-scenario approach described here
demonstrates that the uncertainties in fossil resource
Even with this "conservative" assumption cumulative oil extraction
in the A2 marker scenario totals 16 ZJ, or 2.7 times currently
identified, recoverable oil reserves (6 ZJ or 143.3 billion tons; BP,
1999). Thus, the A2 scenario also assumes that in future it will be
possible to continue the historical trend in which large quantities of
(undiscovered or presently uneconomic) oil resources are transferred
into recoverable reserves. Some analysts consider such a future trend
as definitely optimistic (see the literature review in Chapter 3).