Environmental Engineering Reference
In-Depth Information
Growth factors embedded in mobile source energy and emissions models appear to
capture this economic-driven growth in freight transportation (EIA, 2003; EPA et al.,
2004; EPA, 1998; 2003). Importantly, some trend reports claim that freight energy growth
will slow over the next two decades (Mantzos and Capros, 2006), although these analyses
seem inconsistent with global trade economic projections for imported goods. A basic
insight when adopting growth patterns based on the economic drivers of freight is that
growth rates in GDP and trade volumes are coupled. In other words, if growth in GDP
and trade volumes is compounded as forecast by economic and transportation demand
studies, then growth in energy requirements cannot be linear without decoupling (changes
in energy intensity). Even with e
ciency improvements, compounding increases in trade
volumes are likely to outstrip energy conservation e
ff
orts unless a technological or oper-
ational breakthrough in goods movement emerges.
Previous studies have described global growth rates for maritime shipping, based on
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eet size, trade growth and/or cargo tkm, mostly calibrated to linear or conservative
extrapolations of historic data. The
IMO Study on Greenhouse Gas Emissions from Ships
and other studies (Skjølsvik et al., 2000; EC and ENTEC UK, 2002) used
eet growth
rates based on two market forecast principles, validated by historical seaborne trade pat-
terns: (1) world economic growth will continue; and (2) demand for shipping services will
follow the general economic growth. The IMO study correctly stated that growth in
demand for shipping services was driven by both increased cargo (tonnage) and increased
cargo movements (ton-miles), and considered that these combined factors made extrap-
olation from historic data di
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cult. None the less, their forecast for future seaborne
trade (combined cargoes in terms of tonnage) was between 1.5% and 3% annually.
The IMO study applied these rates of growth in trade to represent growth in energy
requirements.
Eyring et al. (2005b) estimated 'future world seaborne trade in terms of volume in
million tons for a speci
t to past
data. Except for the Eyring et al. work, these linear extrapolations appear to present
growth rates slower than the economy. Linear extrapolations are likely biased on the low
side, because shipping growth rates have actually grown faster than the economy. Studies
for Southern California (San Pedro Bay) ports con
fi
c ship tra
c scenario in a future year' using a linear
fi
rm that growth in cargo volumes
equivalent to 6-7% compounding annual growth rates is expected for some major ports
(NNI Task Force, 2005; Mercator Transportation Group et al., 2005; Meyer Mohaddes
Associates, 2004; Parsons Transportation Group, 2004). However, increased cargo
throughput may not produce a corresponding increase in port calls, as some studies
suggest (Mercator Transportation Group et al., 2005). Historic data on port calls to San
Pedro Bay have shown that the number of ship calls remained between 5000 and 7000 calls
per year since the 1950s (Port of Los Angeles et al., 1994). Furthermore, proportional
relationships between environmental impacts and goods movement trends are re
fi
ected in
recent port and regional studies of economic activity and goods transportation, particu-
larly those focused on Southern California ports (NNI Task Force, 2005; California Air
Resources Board, 2006; Southern California Association of Governments, 2006; Port of
Los Angeles, 2006).
Forecasting of environmental impact from shipping is constrained by the quality of
shipping and trade forecasts (Stopford, 1997). At the global scale, we evaluate available
trends in energy use and/or emissions from published literature with the seaborne cargo
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