This section is concerned with the impact of mitigation on the construction industry, rather than with the options for mitigating energy use in buildings, which are considered in Chapter 3. One of the main products of the construction sector are buildings which require energy for a number of services such as lighting, space heating and cooling, and electricity for equipment. Energy consumption in buildings reaches nearly one-third of total primary energy consumption in the US, and hence their importance for GHG emission reductions. Mitigation will lead to changes in the materials used, and in design and heat control, all tending to increase the quantity (output) and improve the quality of buildings. Most renewable energy investments, such as hydropower and electricity from biomass, also require inputs from the construction sector.

Multisectoral modelling suggests that carbon tax and permit policies will have little impact on construction output and employment; this finding is established in the literature, but incomplete. Table 9.1 shows that according to three different macroeconomic models (Garbaccio et al. 1999; Jorgenson et al., 1999; and Barker, 1999) construction will increase its output by about +1%. Two other models in the same table (Bertram et al., 1993; Cambridge Econometrics, 1998) find 0% variation in the construction output.

Transport energy use has been growing steadily worldwide, with the largest increases occurring in Asia, the Middle East and North Africa, and it is projected to grow more rapidly than energy use in other sectors through at least until 2020 (Michaelis and Davidson, 1996; IEA, 1997b; Schafer, 1998; Nakicenovic et al., 2000). There are few options available to reduce transport energy use which do not involve significant economic, social or political costs. Governments presently find it difficult to implement measures to reduce overall demand for mobility (IEA, 1997b). Singapore is an exception to this general rule as a result of a comprehensive set of policies dating from 1975 to limit traffic (Michaelowa, 1996).

Almost all transport energy is supplied from oil, and the growing demand for transport seems inconsistent with macroeconomic studies that project decreased demand for oil as the result of GHG mitigation policies. Further research is needed to resolve this apparent inconsistency (Bernstein and Pan, 2000).

Local concerns, traffic congestion and air pollution, are currently the key drivers for transport policy (Bernstein and Pan, 2000). Measures to reduce traffic congestion also reduce CO₂ emissions, since they involve either reducing the number of vehicles on the road or increasing the average speed and fuel efficiency at which vehicles travel through urban areas. Policies to reduce traffic congestion include: improvements in mass transit, incentives for car pooling, and fees for entering city centres (Bose, 2000), as well as employer-based transport management, parking management, park-and-ride programmes, and road use pricing. One approach has been to assess the external (social) costs of transport, including contribution to global warming, as a guide to the level of taxes or user charges by transport modes that would internalize these costs, and hence improve the efficiency of the system (ECMT, 1998).

Figure 9.5: Historical trends in transport and communication volume indices for France (Source: Gruebler, 1998: Chapter 7).

An “information society” based on a digital information network is sometimes projected to replace a substantial proportion of physical travel. However, historical data show that the telegraph and telephone did not affect the steady growth of transportation in France (see Figure 9.5). Mokhtarian et al. (1995) conclude that telecommuting, one aspect of the information society, does reduce transportation energy use. However, the reductions are smaller than often assumed, because they are partially offset by increased household energy use, and because some telecommuters do so only for part of their working day. Care must be taken in extrapolating future reductions from the limited case studies currently available; the behaviour of early-adapters may be different from that of later telecommuters. In the medium term, macro view, information technologies appear to be complementary to transportation (Gruebler, 1998); but in the longer term an “information society” could significantly replace travel and associated impacts, although this remains speculative.

9.2.8.1 Aviation

In 1999, in response to a request from the International Civil Aviation Organization (ICAO), the IPCC prepared a Special Report, Aviation and the Global Atmosphere, which included a comprehensive review of the potential impacts of aviation on the climate system (Penner et al., 1999). The demand for air travel, as measured in revenue passenger-kilometres, is projected to grow by 5%/year for the next 15 years, but improvements in efficiency and operations are projected to hold the growth in CO₂ emissions to 3%/year. Aircraft also emit water vapour, NO_x, SO_x and soot, and trigger the formation of condensation trails (contrails) and may increase cirrus cloudiness – all of which contribute to climate change (Penner et al., 1999).

Penner et al. present several growth scenarios for aviation that provide a basis for sensitivity analysis for climate modelling. These scenarios, which assume the scope for switching from air travel to other modes of travel is limited, show radiative forcing resulting from subsonic aircraft emissions growing from the 1992 level of 0.05Wm^-2 to between 0.13 and 0.56Wm^-2 by 2050. The scenario with economic growth equal to the IS92a reference scenario indicates that aviation may contribute 0.19 Wm^-2, or about 5% of anthropogenic radiative forcing, by 2050. More supersonic aircraft would substantially increase this contribution, although there is considerable uncertainty whether any such fleet will be developed. The growth scenarios do not consider air space and infrastructure limitations; however, recent experience in both Europe and North America indicates that the air traffic system is reaching saturation. Penner et al. assume that by 2050 all currently identified improvements in aircraft efficiency and operations will be implemented. However, turnover time in the aviation industry is long. Individual aircraft will be operated by commercial airlines for 25 years or more, and a successful product, including its derivatives, will be produced for possibly 25 years or longer. Thus, the overall life of an aircraft type can exceed 50 years.

Penner et al. (1999) conclude:
“Although improvements in aircraft and engine technology and in the efficiency of the air traffic control system will bring environmental benefits, these will not fully offset the effects of increased emissions from the projected growth in aviation. Policy options to reduce emissions further include more stringent aircraft emissions regulations, removal of subsidies and incentives that have negative environmental consequences, market-based options such as environmental levies (charges and taxes) and emissions trading, voluntary agreements, research programmes, and substitution of aviation by rail and coach. Most of these options would lead to increased airline costs and fares. Some of these approaches have not been fully investigated or tested in aviation and their outcomes are uncertain (Penner et al., 1999, p. 11).”

The need for further research in this area is explored at the end of the chapter.

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