The transport sector [that includes both transport of goods and people] is one of the crucial drivers for the increase in global greenhouse gas (GHG) emissions. Although global CO2 emissions increased by 13% from 1990 to 2000, CO2 emissions from road transport and aviation each grew by 25%. (1) In Eastern Asia, the NOx and CO2 emissions from road transport doubled from 1990 to 2000. In the European Union, most sectors decreased their GHG emissions from 1990 to 2001, but emissions from transport increased by nearly 21% (2). The increase in GHG emissions from transportation is expected to persist. In 2050, 30–50% of total CO2 emissions are predicted to come from transport (3), compared with today’s 20–25%.
There are four main processes by which emissions from transport affect climate (1):
- by emission of direct greenhouse gases, principally CO2;
- by emission of indirect greenhouse gases, i.e., precursors of tropospheric Ozone and NOx, CO;
- by the direct effect of emission of aerosols;
- by the indirect effect of aerosols, which trigger changes in the distribution and properties of clouds.
Since preindustrial periods, transport contributed of 15% of total man-made CO2 [with peaks of 26% in heavily motorised countries] and of 31% Ozone forcing. The dominating contributor to climate change is CO2, followed by tropospheric Ozone. By subsector, road transport is the largest contributor (1). Overall, the transport sector accounts for 22% of CO2 emissions from energy use. Transport also contributes to global NO2 and CH4 (methane) emissions (4).
Transports have an impact on three major areas beyond being one of the major factors of the growth of greenhouse gases and therefore contributing to climate change (4):
Air pollution. Among the different environmental pollution problems, air pollution causes the greatest damage to health and loss of welfare from environmental causes, especially in Asian countries, where we can assist at the combination of local atmospheric conditions, rapid industrial and urban transport development. Air pollution is expected to increase considerably in most countries of the Asia-Pacific region over the next three decades. In addition, acid deposition is becoming increasingly problematic. Under business-as-usual conditions, regional emissions of sulphur dioxide are expected to increase fourfold by 2030 over those of 1990; emission of nitrogen oxides is expected to increase threefold. Vehicular emissions have become a major source of air pollution in many cities.
- Noise pollution. Acoustic nuisance is a serious problem, particularly in densely populated areas. 10% to 20% of the inhabitants in Western Europe and up to 50% of the inhabitants in some Central and Eastern European cities experience noise levels that exceed the maximum acceptable levels of 65 dBA. Noise associated with shipping has the potential to cause disturbance to marine animals, including the marine mammals, fish and birds. In aviation, standards and policy positions regarding aircraft noise have long existed and the issue of aircraft noise has been a driving issue in the location and operational parameters of airports and in the design of newer generation aircraft.
Infrastructure development. The development of roads and highways is associated with a number of major environmental issues such as those associated with loss of land resources through construction of infrastructure, pollutants (hydrocarbons, heavy metals, de-icing chemicals) that impact on surface and ground water resources as well as biodiversity impacts such as species loss and habitat fragmentation. Rail infrastructure route selection also poses environmental challenges with the creation a significant barriers within the landscape, causing fragmentation of local communities, wildlife habitats and farmland. Moreover, railways and related infrastructure have significant visual impact on rural and urban landscape.
- Fuglestvedt, J., T. xBerntsen, et al. (2008). “Climate forcing from the transports sectors.” PNAS 105(2): 454-458.
- European Environment Agency (2004) Analysis of Greenhouse Gas Emissions Trends and Projections in Europe 2003 (Eur Environ Agency, Copenhagen).
- Nakicenovic N, Alcamo J, Davis G, de Vries B, Fenhann J, Gaffin S, Gregory K, Gru ̈ bler A, Jung TY, Kram T, et al. (2000) Special Report on Emissions Scenarios (Cambridge Univ Press, Cambridge, UK).
- UNESCAP (2007). Meeting the needs of the environment.