sectoral economic costs and benefits of ghg mitigation - IPCC

Transport
The rapid expansion in the demand for transportation services, which underlies the growth in
energy demand, can be expected to continue over the next two decades as per-capita income
continues to grow. Growth will be especially rapid among low- and middle-income countries
outside the OECD in which income growth rates and income elasticity of private vehicle
ownership are expected to be high. However, among the OECD countries, the transportation
sector in Japan has been increasing the fastest (16.3%) compared to USA (6%) and Germany
(9%).
Policy framework to mitigate emissions
In developing countries, air quality management is an emerging priority, and the main motivator
is the health effect. Accordingly, the control of local air pollutants emitted by motor vehicles in
developing country cities is awarded priority over GHGs responsible for global climate change
concerns. Major local air pollutants emitted by motor vehicles include nitrogen oxides (NO x ),
hydrocarbons (HCs), carbon monoxide (CO), sulphur oxides (SO x ), particulate matter less than
10 microns in diametre (PM 10 ), and lead (Pb). From an air quality management principle, their
relative weighting based on toxicity levels of each pollutant is associated with uncertainty and
professional debate in locally motivated air pollution control programmes. Among these the
problems and priorities will – and should – differ from one city to another. For instance, in a
World Bank study, based on accepted health considerations, the approximate toxicity weighting
factor of CO is estimated to be 0.04, volatile organic compounds (VOCs) 1.8, NO x 4.7, SO x 1.4,
PM 10 2.3,and Pb 85, per emitted tonne of each pollutant (Wijetilleke and Karunaratne, 1995).
Present professional debate gives many reasons to believe that the relative weighting of PM 10
could be even higher than what is reflected above. But, in a World Bank study in Santiago both
Pb and CO were excluded in their analysis (Eskeland and Xie, 1998). Pb was excluded because
Pb content in gasoline was insignificant and it was already in the process of being phased out
completely, like most of the developing countries. CO was excluded because there are as yet no
quantified dose-response functions in the literature.
It is important to note that the gaseous and dust particles that are valued in a locally motivated
programme are not valued in terms of global warming potential (GWP) and vice versa. The GWP
is defined as a ratio of the global warming effect from one kilogram of a GHG relative to that
from one kilogram of CO 2 over a specified period of time. The hydrocarbons that are targeted for
emission control in air pollution control programme (VOCs or non-methane hydrocarbons) are
targeted precisely because of their reactivity. In contrast, the only hydrocarbon that is given a
value different from its terminal role as CO 2 is methane, which has a high discounted GWP
because it lives long in the atmosphere in a form with much higher spontaneous GWP than CO 2 .
When emissions of VOCs and CO are reduced in a locally motivated air pollution control
programme, the result is merely to increase the share of carbon atoms that are emitted directly as
CO 2 (more complete combustion). Such technical controls, therefore, have no significant effect
on global warming. When a technical option contributes to GHG emissions reduction, it is
typically because the option makes vehicles more fuel-efficient. Thus, there are less pollution
emissions per kilometres driven, but typically not per litre of fuel consumed.
In view of the above discussion, the strategy that needs to be adopted in any developing country
to reduce emission of local air pollutants and GHGs is discussed in the following two subsections.
Strategy to reduce local pollution
For reducing vehicular emissions of local air pollutants the following two approaches need to be
adopted simultaneously: (1) reducing emissions per vehicle kilometre (in short, mass emissions)
travelled and (2) reducing the total kilometres travelled.
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