Emissions Scenarios - IPCC

Scenario Driving Forces 151
(a)
Sulfur deposition (g/yr/m^)
0 - 1 1-5 H i > 5
199A) are projected to rise above that level. Interestingly, all
long-term sulfur scenarios published since 1995 do not judge
this to be a likely (not to mention environmentally desirable)
possibility. Representative sulfur-emissions control and
intervention scenarios (Amann et al., 1995; Posch et al., 1996;
Nakicenovic et ah, 1998a) suggest instead an upper range of
global emissions below 100 MtS by 2050 and below 120 MtS by
2100, a range covered in the two low variants IS92c and IS92d
only. These patterns were also confiimed by Pepper et al. (1998)
in a recent re-analysis of the previous IS92 scenarios. Using the
same methodology as deployed in developing the IS92
scenarios, the revised scenarios have maximum global SO,
emissions below 142 MtS by 2020, and 56 MtS by 2100 (EPA3
and EPA5 scenarios, respectively). The median from the more
recent scenario hterature analyzed in Grübler (1998c) indicates
near-constant global SO2 emissions - 77 MtS by 2020, 68 MtS
by 2060, and 57 MtS by 2100. This global stability, however,
masks decisive regional differences (discussed above).
Emissions in the OECD countries will continue their declining
trends in line with their sulfur reduction policies. Emissions
outside OECD will rise initially with increasing energy demand,
but sulfur controls will be progressively phased in to mitigate
against impacts of high unabated SO, emissions on health,
agriculture, ecosystems, and tourism.
Figure 3-17: Current sulfur deposition in Europe (a) and
projections for a high growth, coal-intensive scenario similar
to IS92a for Asia in 2020 (b), in gS/ml Source: Grübler,
1998c, based on Amann et al., 1995.
extent that would more than offset any possible beneficial
impacts of regional climate change. This is primarily because
sulfur (and nitrogen) deposition, while acting as fertilizer for
plant growth at lower deposition levels, negatively affects plant
growth at higher deposition levels. Projections in a scenario
such as IS92a are that the threshold levels will be surpassed
between 2020 and 2050 for all major Asian food crops.
The review of recent literature on acidification impact studies
given in Grubler (1998c) concludes that the impacts on human
health, on economically important food crops, and on
ecosystems are so substantial as to lender any scenario with
SOj emissions as high as, or higher than, IS92a very unlikely.
Grübler (1998c) canied out a detailed comparison of SOj
emissions scenarios at the global and regional level. He
concluded that the range of future SOj emissions spanned by
the previous high-demand IPCC scenarios (all IS92 scenarios
except IS92c and IS92d) corresponded well with scenarios
available in the literature that do not include any direct sulfuremissions
control or indirect intervention measures and policies
(Figure 3-18). Typically, in such scenarios, global SOj
emissions could rise to between 130 and 250 MtS by 2100, and
in some older scenarios (Matsuoka et al., 1994; Morita et al..
The need to abate local air pollution, including SO, emissions,
is not only environmental, but also economic. For example,
according to the World Bank (1997c, I997d) the current
damage by environmental pollution is about 8% of GDP in
China (and up to 20% of production in urban areas), while
abatement costs would be between I and 2.5% of GDP.
According to one World Bank (1997c) report, the costs are '"so
high under the business-as-usual scenario that it is hardly
necessary to consider the amenity and ecosystem benefits of
cleaner air to justify action." Therefore, it is no surprise that in
several developing regions, policies are already being
developed and implemented to abate SOj emissions, in China,
by 1995 coal-cleaning technology had been developed, and
de-sulfurizing technology introduced and applied
(Government of People's Republic of China, 1996). The SO2
emissions target set by the Chinese government is 12.3 MtS by
2000 as compared to 11.9 MtS in 1995. Economic
instruments, such as pollution charges, pricing policy,
favorable terms of investment for environmental technology,
market creation, and ecological compensation fees, are being
introduced in China now (UNEP, 1999). By June 1997, some
64,000 enteфrises with heavy pollutant emissions had been
closed for refurbishment or had ceased production. As a
consequence, ambient concentrations of sulfur have been
relatively stable in medium-size and small cities, and they
have actually decreased in large cities. This change is
occurring at significantly lower levels of income as compared
to income levels in the USA and Europe at the time when their
sulfur abatement started.
In India, several sulfur policies are being introduced currently,
including mandatory washing of coal used 500 km away from
the mine mouth, a policy that is expected to significantly