The transport sector is the fastest growing contributor to climate emissions. Growth in energy use is higher for the transport sector than any other end-use sector. The main drivers of global transport energy growth are land transport, mostly light-duty vehicles, such as cars, as well as freight transport.
Transport’s contribution to climate change include:
- long-lived carbon dioxide (CO2) emissions and;
- short-lived black carbon generated primarily by diesel vehicles.
Transport accounted for about 23% of global carbon dioxide emissions in 2010 and 27% of end-use energy emissions with urban transport accounting for about 40% of end-use energy consumption. Carbon dioxide persists in the atmosphere for over a century, with long-term warming effects (IPCC, 2014).
Short-lived climate pollutants (SLCPs)
Black carbon, a short-lived climate pollutant, is the second highest contributor to global warming after CO2. Black carbon has a warming effect many times more powerful than carbon dioxide, but it persists in the atmosphere for only a few weeks – so measures to reduce black carbon can also have an immediate effect on slowing the pace of climate change.
Diesel transport is one of the world’s major sources of black carbon (along with household biomass cookstoves). Not only does black carbon have a significant warming effect, but it is also a major component of particulate matter, the air pollutant most closely associated with increased air-pollution related mortality and morbidity.
Ground-level ozone is another short-lived climate pollutant stimulated by transport pollution. Ozone is created by a mix of are pollutants, including oxides of nitrogen (NOx) produced by vehicle engines and methane emissions from other sources (e.g. landfills and animal waste). Ozone contributes to chronic respiratory diseases, particularly childhood asthma.