|Aviation and the Global Atmosphere|
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9.6.5. Infrastructure and Fuel Availability Assumptions
All of the long-term scenarios reviewed in this chapter were developed with the implicit assumption that sufficient system infrastructure and capacity will be available to handle the demand in an unconstrained fashion (infrastructure and capacity are defined for airports as runways, terminals, gates and aprons, roads, etc., and for airways as air navigation services, air traffic control, etc.). However, lack of infrastructure development may well impede future aviation growth. Lack of infrastructure will result in congestion and delay, additional fuel burn (in the air and on the ground), higher operating costs, higher ticket prices, and reduced service.
In some parts of the world, particularly in North America and Europe, the airway and airports system is currently operating under constraints that limit its ability to provide service. These constraints are likely to become more acute in the future as the demand for aviation services continues to grow. Congestion resulting from capacity constraints impairs the economic and environmental performance of airlines and the entire aviation system. To accommodate future demand, physical and technological infrastructure must be upgraded and expanded. In many areas, however, strong local pressures (especially related to noise created by aircraft movements) have constrained development of new airports and capacity improvements at existing airports. It is therefore important to note that the traffic forecasts reviewed in this chapter are all unconstrained forecasts that do not evaluate system capacity constraints when estimating future traffic growth.
Aviation also depends on petroleum fuels. For the past 50 years, known reserves of petroleum have continued to expand to satisfy 20-30 years of predicted demand. Over the short-term future, little change in the demand/supply situation is expected. Oil companies predict continued supply of their raw material, and kerosene supplies should have similar availability as the present day. Despite the forecast for increasing demand, oil prices are projected to rise only moderately over the next 20 years (Hutzler and Andersen, 1997).
Over the period of these scenarios (to 2050), estimates of availability are less clear, but there is a general view that the oil industry will continue to meet demand (Rogner, 1997). There are, however, less optimistic views for oil production, with some predictions of a production decline occurring within the next decade (Campbell and Laherrere, 1998). The long-term scenarios assessed for this report implicitly assume continued availability of fuel at moderate prices. This is a key assumption for all scenarios because large increases in the price of fuel and/or shortages in supply would act to restrain demand for passenger and cargo air transport.
All of the scenarios ignore (in their baseline assumptions) possible changes in service patterns or infrastructure that a future HSCT might require. The effects of an HSCT fleet are considered in Section 9.5.
Although none of the long-term scenarios reviewed here is considered impossible, some may be more plausible than others. We devised three simple checks to assess plausibility. The first estimated the fleet size required to carry projected traffic in 2050; the second examined implications for airport and infrastructure; and the third examined implications for kerosene demand. These plausibility checks represent an initial examination of the implications of the scenarios and are intended to illustrate possible consequences of traffic estimates resulting from the different scenarios. It must be emphasized that the fleet numbers produced by this analysis are approximate and are provided for comparative purposes only.
The fleet sizes implied by five of the scenarios were determined from the DTI traffic and fleet forecast model (see Section 9.3.2), which was developed primarily to project demand for new aircraft implied by 25-year traffic forecasts. The DTI model requires an annual traffic growth rate as an input; for this assessment purpose, this value was assumed to be a constant annual rate calculated from the base year traffic and the model's projection for 2050. The model assumes the fleet to comprise a range of jet aircraft types, described by seat capacity as follows: 80-99, 100-124, 125-159, 160-199, 200-249, 250-314, 315-399, 400-499, 500-624, and 625-799. The larger aircraft sizes have yet to be produced but are assumed to enter service beginning about 2005. Regional variations in fleet composition are reflected in the global fleet, based on current trends. This analysis does not capture the effects of compositional change that could be created as new markets develop. Average aircraft size growth is assumed (reflecting the historical trend of greater seating capacity for individual aircraft types over time). The future fleet required to satisfy the scenario demand estimates is derived through an iterative process by matching capacity to traffic demand, based on assumptions regarding aircraft unit productivity in capacity terms. Other model assumptions are as follows:
The assumption regarding lack of constraints requires comment. Today's civil aviation market is constrained only by the practical limitations of airport capacity and access restrictions, airspace restrictions, and economic restraint resulting from taxation, charges, and so forth that affect ticket price. Any constraints in the future, whether to address environmental problems or as a result of government policy, will affect or limit demand and therefore affect the emissions burden from civil aviation. In contrast, measures such as the introduction of advanced air traffic control systems may improve the efficiency of traffic management (see Chapter 8) but could lead to a traffic increase, with the consequence of increasing emissions from aircraft. Neither the scenarios nor the analysis of their impact have examined such possibilities because there would be too many permutations of possibilities to define a scenario acceptable to all.
Table 9-24 summarizes the estimated traffic in RPK x 109 for five of the scenarios. The global fleets (numbers of aircraft of all types) appropriate for each traffic estimate are also given.
In addition, it is necessary to consider the extent to which the freighter fleet might grow. An independent study was performed using figures for the current inventory of freighters and extrapolating the Boeing freighter forecast from 2015 at two growth rates-5.1% (high) and 2.5% (low). Assuming the high growth rate, the freighter fleet could grow to approximately 19,000 aircraft by 2050. The low-growth rate would require 8,000 freighter aircraft (Campbell-Hill Aviation Group, 1998). This calculation results in the adjusted commercial fleet profile given in Table 9-25.
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