Emissions Scenarios - IPCC

150 Scenario Driving Forces
fuel mix and also control measures for large point sources. This
pattern emerges also from the literature on environmental
Kuznets curves (e.g., World Bank, 1992; IIASA-WEC, 1995)
and is corroborated by both longitudinal and cross-sectional
empirical data reviewed in detail in Grübler (1998c).
Historically, the decline in sulfur pollution levels was achieved
simply by dispersion of pollutants (tall stacks policy).
Subsequently, the actual emissions also started to decline, as a
result of both structural change (substitution of solids by gas
and electricity as end-use fuels) and sulfur reduction measures
(oil product desulfurization and scrubbing of large point
sources).
Emissions for 1990 reported in the scenarios reviewed in
Chapter 2 and in Grübler (1998c) indicate a range from 55 to
91 MtS. The upper range is explained largely by a lack of
complete coverage of SO2 emission sources in long-term
scenario studies and models. Lower values coirespond to
studies drat include only the dominant energy sector emissions
(range of 59.7 to 65.4 MtS), and higher estimates also include
other sources, most notably metallurgical and from biomass
burning. None of the long-term scenario studies appears to
include SO2 emissions from intemational bunker (shipping)
fuels, estimated at 3 + 1 MtS in 1990 (Olivier et al., 1996;
Corbett et al, 1999; Smith et ai, 2000). Historical global
sulfur emissions estimates are given in Dignon and Hameed
(1989).
Grübler (1998c) also argues that SO2 control and intervention
policies in many rapidly industrializing countries (particularly
those with high population densities) are highly likely to be
phased in more quickly than the historical experience of
Europe, North America, Japan, or Korea. This analysis is
supported by existing policies and trends in Brazil, China, and
India (Shukla et al., 1999; Rosa and Schechtman, 1996; Qian
and Zhang, 1998). Most recent SO2 emission inventory data
suggest that since 1990 SO2 emission growth has significantly
slowed in East Asia compared to earlier forecasts, in response
to the first SOj control measures implemented in China, South
Korea and Thailand (Streets and Waldhoff 2000). Dadi et al.
(1998) estimate that in 1995 about 11% (1.5 MtS of a total of
13.5 MtS gross emissions) of China's SO2 emissions were
removed through various control measures.
The evaluation of the IS92 scenarios (Alcamo et al, 1995)
concluded that the projected SOj emissions in the IS92
scenarios do not reflect recent changes in sulfur-related
environmental legislation, in particular the amendments to the
Clean Air Act in the USA, and the Second European Sulfur
Protocol. Increasingly, many developing countries are adopting
sulfur control legislation that ranges from reduction of sulfur
contents in oil products (e.g. China, Thailand, and India; see
Streets et al., 2000), through a maximum sulfur content in coal
(e.g. in China; see Streets and Waldhoff, 2000), to SO2 controls
at coal-fired power plants (e.g. China, South Korea, Thailand;
for a review see lEA, 1999). For instance, an estimated 3575
MW of coal-fired electricity China is generated by plants
already equipped with sulfur control devices (lEA, 1999).
Since publication of the IS92 scenarios a number of important
new sulfur impact studies have become available, and analyzed
in particular:
• Implications of acidic deposition levels of high SOj
emissions scenarios such as IS92a (Amann et al., 1995;
Posch etal, 1996).
• Aggregate ecosystems impacts, especially whether
critical loads for acidification are exceeded given
deposition levels and different buffering capacities of
soils (Amann et al., 1995; Posch et al, 1996).
• Direct vegetation damage, particularly on food crops
(Fischer and Rosenzweig, 1996).
These studies provide further infomation on the impacts of
high concentrations and deposition of SO2 emissions, beyond
the well-documented impacts on human health, ecosystems
productivity, and material damages (for reviews see Cratzen
and Graedel, 1986; WHO and UNEP, 1993; WMO, 1997).
These studies are particularly important because they
document environmental changes of high-emission scenarios
by using detailed representations of the numerous non-linear
dose-response relationships between emissions, atmospheric
concentrations, deposition, ecosystems sensitivity thresholds,
and impacts. All recent studies agree that unabated high SOj
emissions along the Hues of IS92a or even above would yield
high impacts not only for natural ecosystems and forests, but
also for economically important food crops and human health,
especially in Asia where emissions growth is projected to be
particularly high.
A representative result (based on Amann et al, 1995) is shown
in Figure 3-17, which contrasts 1990 European sulfur
deposition levels with those of Asia by 2050 in a high SO2
emission scenario (very close to IS 92a). Typically, in such
scenarios, SO, emissions in Asia alone could surpass current
global levels as early as 2020 (Amann et al, 1995; Posch et al,
1996). Sulfur deposition above 5 g/m^ per year occurred in
Europe in 1990 in the area of the borders of the Czech
Republic, Poland, and Germany (the former GDR), often
referred to as the "black triangle." In view of its ecological
impacts it was officially designated by UNEP as an "ecological
disaster zone." In a scenario such as IS92a (or even higher
emissions), similar high sulfur deposition would occur by
around 2020 over more than half of Eastern China, large parts
of southern Korea, and some smaller parts of Thailand and
southern Japan.
Fischer and Rosenzweig (1996) assessed the combined impacts
of climate change and acidification of agricultural crops in
Asia for such a scenario. Their overall conclusion was that the
projected likely regional climate change would largely benefit
agricultural output in China, whereas it would lower
agricultural productivity on the Indian subcontinent (the
combined effect of projected temperature and precipitation
changes would have differential impacts across various crops
and subrogions). However, projected high levels of acidic
deposition in China would reduce agricultural output to an