Editing IPCC:AR6/WGIII/Chapter-2 (section)

==== 2.4.2.4 Transport Sector ====

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With a steady, average annual growth of +1.8% yr –1 between 2010 and 2019, global transport GHG emissions reached 8.9 GtCO 2 -eq in 2019 and accounted for 15% of all direct and indirect emissions (Figure 2.20). Road transport passenger and freight emissions represented by far the largest component and source of this growth (6.1 GtCO 2 -eq, 69% of all transport emissions in 2019) ( ''high confidence'' ). National plus international shipping and aviation emissions together accounted for 2.0 GtCO 2 -eq or 22% of the sector’s total in 2019. North America, Europe and Eastern Asia stand out as the main regional contributors to global transport emissions and together account for 50% of the sector’s total.

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'''Figure 2.20''' '''|''' '''Trends and drivers of global transport sector emissions (see Figure 2.16 caption for details) with energy measured as total final energy consumption.'''

The proportion of total final energy used in transport (28%) and its fast expansion over time weighs heavily on climate mitigation efforts, as 92% of transport energy comes from oil-based fuels ( [[#IEA--2020b|IEA 2020b]] ). These trends situate transport as one of the most challenging sectors for climate change mitigation – no country has so far been able to realise significant emissions reductions in the sector. North America’s absolute and per capita transport emissions are the highest amongst world regions, but those of South, South-East and East Asia are growing the fastest ( ''high confidence'' ) (between +4.6% and +5.2% yr –1 for CO 2 between 2010 and 2019) (Figure 2.20).

More so than any other sector, transport energy use has tracked GDP per capita growth (Figure 2.20), (Lamb et al. 2021). With the exception of road gasoline demand in OECD countries, the demand for all road fuels generally increases at least as fast as the rate at which GDP per capita increases ( [[#Liddle--2020|Liddle and Huntington 2020]] ). Developments since 1990 continue a historical trend of increasing travel distances and a shift from low- to high-speed transport modes that goes along with GDP growth ( [[#Schäfer--2009|Schäfer et al. 2009]] ; [[#Gota--2019|Gota et al. 2019]] ). Modest improvements in energy efficiency have been realised between 2010 and 2019, averaging –1.5% yr –1 in energy intensity globally, while carbon intensities of the transport sector have remained stable in all world regions (Figure 2.20). Overall, global increases in passenger and freight travel activity levels have outpaced energy efficiency and fuel economy improvements, continuing a long-term trend for the transport sector ( ''medium evidence'' , ''high agreement'' ) ( [[#Gucwa--2013|Gucwa and Schäfer 2013]] ; Grübler 2015; [[#McKinnon--2016|McKinnon 2016]] ).

Despite some policy achievements, energy use in the global transport system remains to the present deeply rooted in fossil fuels ( ''robust evidence'' , ''high agreement'' ) ( [[#Figueroa--2014|Figueroa et al. 2014]] ; [[#IEA--2019|IEA 2019]] ). In part this is due to the increasing adoption of larger, heavier combustion-based vehicles in some regions, which have tended to far outpace electric and hybrid vehicle sales (Chapter 10). Yet, stringent material efficiency and lightweight design of passenger vehicles alone would have the potential to cut cumulative global GHG emissions until 2060 by 16–39 GtCO 2 -eq ( [[#Pauliuk--2021|Pauliuk et al. 2021]] ).

While global passenger activity has expanded in all world regions, great disparities exist between low- and high-income regions, and within countries between urban and rural areas ( [[#ITF--2019|ITF 2019]] ). While private car use is dominant in OECD countries ( [[#EC--2019|EC 2019]] ), the growth of passenger-km (the product of number of travellers and distance travelled) has considerably slowed there, down to an increase of just 1% yr –1 between 2000 and 2017 ( [[#SLoCaT--2018|SLoCaT 2018]] ) (Chapter 10). Meanwhile, emerging economies in the Global South are becoming more car-dependent, with rapidly growing motorisation, on-demand private transport services, urban sprawl, and the emergence of local automotive production, while public transport struggles to provide adequate services ( [[#Dargay--2007|Dargay et al. 2007]] ; [[#Hansen--2017|Hansen and Nielsen 2017]] ; [[#Pojani--2017|Pojani and Stead 2017]] ).

Freight travel activity grew across the globe by 68% in the last two decades, driven by global GDP increases, together with the proliferation of online commerce and rapid (i.e., same-day and next-day) delivery ( [[#SLoCaT--2018|SLoCaT 2018]] ). Growth has been particularly rapid in heavy-duty road freight transport.

While accounting for a small share of total GHG emissions, domestic and international aviation have been growing faster than road transport emissions, with average annual growth rates of +3.3% and +3.4%, respectively, between 2010 and 2019 ( [[#Crippa--2021|Crippa et al. 2021]] ; [[#Minx--2021|Minx et al. 2021]] ;). Energy efficiency improvements in aviation were considerably larger than in road transport, but were outpaced by even larger increases in activity levels ( [[#SLoCaT--2018|SLoCaT 2018]] ; [[#Lee--2021|Lee et al. 2021]] ) (Chapter 10).

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