2. General Trends Controlling Transport Growth and Demand
It should also be noted that, since the middle of the last century, there has been a move in developed countries towards suburbanization and counter-urbanization. This trend was accommodated by the development of a more adequate transportation infrastructure. Suburbanization began in earnest in the 1950s in the United States of America, following the construction of the interstate highway system and private vehicles being more affordable for middle class families. In the 1990s, another trend emerged (‘ex-urbanization’), when higher income urban dwellers started to move out of the inner cities and suburbs to high-end housing in the countryside. In addition to these changes, there have been also changes in the education levels, the income levels/inequality as well as changes in the geospatial distribution of the populations due to, for example, population movement towards the coastal areas. All these trends have been influencing transport needs and patterns, and related energy use and greenhouse gas emission patterns (e.g. Dodson and Sipe, 2006).
2.3
Environmental Trends and Implications for Inland Transport The transport sector is instrumental in many economic and social functions. At the same time, transport infrastructure/services have a significant environmental footprint at different spatio-temporal scales. Transport can even affect the global climate through its substantial emissions (see below) as well as be affected by the Climate Variability and Change (see also Chapter 7). Global Climate Variability and Change is controlled by the planet’s heat inflows and outflows and its storage dynamics in the various constituents of the earth’s system. There is now sufficient evidence to suggest a long-term, increasing temperature trend, with the global average air temperature having increased by about 0.8 °C since the 1850s and the upper 75 m of ocean increasing by 0.11 °C per decade over the last 40 years (IPCC, 2013). Atmospheric temperature increases of between 1.0 and 3.7 °C have been projected for 2100, depending on the scenario. Precipitation has also changed, but in a more complex manner, with some regions becoming wetter and others dryer; such trends are predicted to remain steady or even increase in pace in the future (IPCC, 2013). One of the most damaging side-effects of the temperature increases is rising mean sea levels, due to ocean thermal expansion, the melting of the Greenland and Antarctic ice sheets and the glacier and ice caps, the glacio-isostatic adjustment and changes in the terrestrial water storage (Hanna et al., 2013). Since the 1860s, sea levels have risen by about 0.2 m, with satellite information showing a progressive increase rate (to up to 3.1 mm/yr-1) since the 1990s (Church and White, 2011). Changes in the average climate conditions can also lead to fluctuations in the frequency, intensity, spatial coverage, duration, and timing of extreme weather and climate events, which can, in turn, modify the distributions of future climatic conditions. Extreme events (e.g. storms and storm surges, floods, droughts and heat waves), as well as changes in the patterns of particular climatic systems such as the monsoons (SREX, 2012), can have more severe impacts on transport than changes in the mean variables when concentrated in smaller areas over a limited period. One of the clearest trends appears to be the increasing frequency and intensity of heavy downpours. Climate models project the continuation of this trend; for example, the 1 in 20 year (heaviest) downpours of North America have been projected to occur every 4 to 15 years by 2100, depending on the location (Karl et al., 2009). River floods also appear to present significant hazards and evidence suggests increases in the frequency and intensity of heat waves—of extended periods of abnormally hot weather, as well as of severe droughts in some regions (EEA 2012; UNECE, 2013).
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