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MODELING THE GLOBAL SOCIETY-BIOSPHERE-CLIMATE SYSTEM: PART 2: COMPUTED
SCENARIOS
J. Alcamo, G.J. van den Born, A.F. Bouwman, B.J. de Haan, K.
Klein Goldewijk, O. Klepper, J. Krabec, R. Leemans, J.G.J.
Olivier, A.M.C. Toet, H.J.M. de Vries, H.J. van der Woerd
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As described earlier, the Conventional Wisdom scenario assumes
that biofuels will make a significant contribution to the world's
future energy consumption. Indeed, this is the conventional
wisdom of current
energy studies (see, for example, World Energy
Council, 1993). In the "No Biofuels" scenario, we investigate the
sensitivity of the climate system to biofuel use. For this
scenario, we remove the biofuels specified in the Conventional
Wisdom scenario
(other than fuelwood). We further assume that oil
will be used if biofuels are not available. This is a fairly good
assumption for the transport sector where oil and other liquid
fuels are the major energy carriers. For other sectors, however,
it is rather
difficult to decide on the fuel that would be used
in place of biofuels. For example, coal can be used as well as
oil in power generation. Consequently, the use of oil is simply a
default assumption for this sensitivity study. We note that the
total
supply of oil, required by this scenario over the next
century does not exhaust the presently known oil reserves.
All
other assumptions are the same as the Conventional Wisdom
scenario.
Removing biofuels from the energy system results in an increase
in CO2 emissions of 1.8 Pg C a-1 in year 2050, and 5.2 Pg C a-1
in year 2100 over the Conventional Wisdom scenario (Table 7).
This is because biofuel combustion is assumed to have zero net C
emissions (because an equal amount of CO2 is assumed to be
assimilated by regrown biomass). The difference is relatively
small in 2050 as
compared to 2100 because the Conventional Wisdom
scenario assumes that biofuel use will increase greatly in Africa
and Asia in the second half of next century. Following the rise
in emissions, atmospheric concentrations of CO2 are also larger
in this
scenario as compared to the Conventional Wisdom scenario;
the concentration is 17 ppm greater in 2050, and 80 ppm in 2100.
Methane emissions and atmospheric concentrations, on the other
hand, decrease relative to the Conventional Wisdom scenario
because
unit emissions of CH4 from biofuels are higher than from
oil (Figure 13). This is a crucial
result and depends on the
implicit assumption of how biofuels are burned. If they are
gasified, for example, most of the
CH4 would be utilized rather
than emitted to the atmosphere. However, scenario assumptions
imply that it is combusted without gasification. Lower emissions
of CH4 lead to lower concentrations of this substance in the
atmosphere. This also applies to CO and
NOx, two other important
precursors of tropospheric ozone. The lower concentrations of O3
precursors leads to lower concentrations of tropospheric ozone.
The net effect of these changes on radiative forcing are
important. The increase in CO2
concentration tends to increase
radiative forcing, while the decrease in CH4 and tropospheric O3
tends to decrease it. The net effect is a very small difference
in the change of surface temperature between this and the
Conventional Wisdom scenario (Figure
15
and Table 7).
Synopsis of Results of No Biofuels Scenario
Summing up, emissions
from biofuels result in lower atmospheric levels of CO2, but
higher levels of CH4 and O3. The net result is a small difference
in climate change between scenarios with and without biofuels.
These results point out the importance of taking into account all
emissions as well as the composition of the atmosphere.
However,
as noted above, these conclusions also depend on assumptions
about biomass utilization. These results also raise interesting
questions -- How sensitive are scenario results to the assumed
mix of fuels that are used instead of biofuels? How does
the
effect of biofuels on tropospheric ozone depend on the background
atmospheric concentration of ozone precursors? What influence
does the timing of introduction of biofuels have on the rate of
climate change?
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Sources
Alcamo, Joseph (ed.). 1994. IMAGE 2.0: Integrated Modeling of Global
Climate Change. Dordrecht, The Netherlands: Kluwer Academic
Publishers.
Suggested Citation
Consortium for International
Earth Science Information Network (CIESIN). 1995. IMAGE 2.0 Model
Guide [online]. University Center, Mich.
CIESIN URL: http://sedac.ciesin.org/mva/image-2.0/image-2.0-toc.html
Acknowledgement
This work, including access to the data and technical assistance, is
provided by CIESIN, with funding from the National Aeronautics and
Space Administration under Contract NAS5-32632 for the Development and
Operation of the Socioeconomic Data and Applications Center (SEDAC).
Data Errors, Corrections and Disclaimer
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