Emissions Scenarios - IPCC

132 Scenario Driving Forces
electricity generated by fossil fuels. Conversely, if biomass use
was previously on an unsustainable basis, the shift toward
commercial fuels can lower carbon intensities. The trend
toward replacement of biomass fuels by commercial fuels is
expected to continue in developing countries (lEA, 1995).
In addition to the energy use in buildings, Tiwari and Parikh
(1995) drew attention to energy use for buildings construction,
which accounts for 17% of India's carbon emissions in tenns
of embodied energy in steel, cement, glass, bricks, etc.
Typically, this embodied buildings energy is accounted for as
industrial energy use in energy statistics. Tiwari and Parikh
(1995) found that in India alternative construction methods
could save 23% of energy use at 0.03% increase in costs.
3.4.2.4. Transport
The transport sector consumed slightly over 63 EJ, or about
20% of global primary energy, in 1990. Transport sector
primary energy use grew at a relatively rapid average annual
rate of 2.8% between 1971 and 1990, slowing to 1.7% per year
between 1990 and ¡995. Industrialized countries clearly
dominate energy consumption in this sector, using 62% of the
world's transport energy in 1990, followed by REF (16%),
ALM (12%), and ASIA (10%) regions. The most rapid growth
was seen in the ASIA countries (5.9% per year) and the ALM
region (4.6% per year). Transport energy use dropped
dramatically in the REF region after 1990; by 1995 this region
only consumed 11% of global transport energy use. Growth in
transpoit primary energy use also declined slightly in the IND
region, dropping from an average of 2.2% per year between
1971 and 1990 to 1.9% per year between 1990 and 1995. High
growth continued in the ASIA and ALM regions, with the
ASIA countries increasing to an average of 7.6% per year
between 1990 and 1995 (BR 1997; lEA, 1997a; lEA, 1997b).
Influences on GHG emissions from the transport sector are
often divided into those that affect activity levels (travel and
freight movements) and those that affect technology (energy
efficiency, carbon intensity of fuel, emission factors for nitrous
oxide (NjO), etc.). The various driving forces and their effects
are reviewed in detail in the IPCC Working Group II (WGII)
Second Assessment Report (SAR) (Michaelis et al., 1996).
In aggregate, transport patterns are closely related to economic
activity, infrastructure, settlement pattems, and prices of fuels
and vehicles. They are also related to communication links. At
the household level, travel is affected by transport costs,
income, household size, local settlement patterns, the
occupation of the head of the household, household make-up,
and location (Jansson, 1989; Hensher et al., 1990; Walls et al.,
1993). People in higher-skilled occupations that require higher
levels of education are more price- and income-responsive in
their transport energy demand than people in lower-skilled
occupations (Greening and Jeng, 1994; Greening et al., 1994).
Urban layout both affects and is affected by the predominant
transport systems. It is also strongly influenced by other factors
such as people's preference for living in low-density areas,
close to parks or other green spaces, away from industry, and
close to schools and other services. Travel pattems may be
influenced by many factors, including the size of the
settlements, proximity to other settlements, location of
workplaces, provision of local facilities, and car ownership. A
survey of cities around the world (Newman and Kenworthy,
1990) found that population density strongly and inversely
correlates with transport energy use.
Many studies have examined the response of car travel and
gasoline demand to gasoline price, and are reviewed, for
example, in Michaelis (1996) and Michaelis et al. (1996). Such
studies typically find a measurable reduction in fuel demand,
distance traveled, car sales, and energy intensity in response to
fuel price increases. Studies of freight transport found
relatively small short-term impacts of diesel price increases,
and often produced results that were inconclusive or
statistically insignificant. Over the longer term, price
responsiveness is generally assumed to be larger because of
possible technology responses.
An important influence on future travel may be the
development of telecommunication technologies. In some
instances, improved communication can substitute for travel
as people can work at home or shop via the intemet. In others,
communication can help to increase travel by enabling
friendships and working relationships to develop over long
distances, and by permitting people to stay in touch with their
homes and offices while traveling. To the extent that
improvements in telecommunication technology stimulate the
economy, they are likely to result in increased freight
transport.
Energy intensity in the transport sector is measured as energy
used per passenger-km for passenger transport and per ton-km
for freight transport. Transport energy projections typically
incorporate a reduction in fleet energy intensity in the range 0.5
to 2% per year (Grübler et al, 1993b; lEA, 1993; Walsh,
1993). On-road energy intensity (fuel consumption per
kilometer driven) of Hght-duty passenger vehicles in North
America fell by nearly 2% per year between 1970 and 1990, to
about 13 to 14 liters per 100 kilometers, but it is now stationary
or rising. In other industrialized countries, changes in on-road
fuel consumption from 1970 to the present were quite small.
The average on-road energy intensity in North America was
85% higher than that in Europe in 1970, but only 25 to 30%
higher by the mid-1990s (Schipper, 1996).
In some countries, such as Italy and France, where fleet
average energy intensity has fallen during the past 20 years, the
energy intensity of car travel (MJ/passenger-km) has increased
as a result of declining car occupancy and the increasing use of
more efficient diesel vehicles (Schipper et al, 1993). However,
conversion to diesel has been encouraged by low duties on
diesel fuel relative to those on gasoline. The lower costs of
driving diesel vehicles may have acted as a significant stimulus
to travel by diesel car owners, and so offset much of the energy