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256 Third IMO GHG Study 2014
Analysis of historical transport work data
Introduction
Historical data on seaborne trade from a number of different cargo types from 1970 to 2012 have been used
to project future trade in terms of three different types of cargo, and total seaborne trade (TST) to 2050 using a
non-linear regression model. The model used is a Verhulst model of the sigmoid curve type, which simulates
the three typical phases of economic markets: emergence, maturation and saturation.
Methodology
Global data on seaborne transport are produced on a routine basis by the United Nations Conference on
Trade and Development (UNCTAD) as part of their annual Review of Maritime Transport, which has been
produced since 1968 (e.g. UNCTAD, 2013). The UNCTAD secretariat kindly provided annual data back to
1970. These data were in tonne-miles, which are more satisfactory than transport volume in tonnes (although
highly correlated) since this is a better measure of transport work performed.
The data included the following cargo types: crude oil, other oil products, iron ore, coal, grain, bauxite and
alumina, phosphate and other dry cargos. By interpretation, these categories can be usefully combined into
total oil, coal, total (non-coal) bulk dry goods and total dry goods, which approximate into three different ship
types – tankers, bulk raw material ships and container (and other) ships – but discriminating between fossil fuel
transport and non-fossil fuel transport.
Data for bauxite and alumina and for phosphate were only available from 1987 onwards, so have been
backfilled in a simplistic manner; bauxite and alumina from a simple linear trend, and phosphate as an average
of the 1987 to 2008 data, as the time series appears to be stationary.
Figure 33: Transport work for all categories of cargo, provided by UNCTAD,
from 1970 to 2012 in billion tonne-miles; also illustrated with global GDP
(right-hand axis) in US$ billion (constant 2005 prices)
From Figure 33 it is apparent why previous studies (Eyring et al., 2005; Eide et al, 2007; Buhaug et al., 2009)
have used TST data from 1985 on only; there is an extreme excursion of TST over the period 1970 to 1985,
which is entirely caused by crude oil seaborne trade and was driven by a number of political and economic
factors, some of which are connected with the political situation over oil prices during this period. Moreover,
the tanker sector was extremely volatile over this period (Stopford, 2009), with an oversupply of ships that in
some cases led to ships being scrapped straight after being produced, and some being laid up uncompleted.