M
itigating greenhouse gas (GHG) emissions will require a thorough overhaul of our transportation systems, since they depend heavily on burning petroleum-based fuels (especially gasoline, diesel, jet fuel and bunker oil). From 1990 to 2019, transportation sector GHG emissions rose from 5.0 to 8.7 GtCO2eq, accounting for 23% of global emissions now. 70% of GHG emissions (6 Gt CO2eq) come from road vehicles. 1% comes from rail, 11% from marine shipping and 12% from aviation, with shipping and aviation growing most rapidly.
All illustrations from the IPCC 6th Assessment Report, Vol. 3, Chap. 10. Global transport sector greenhouse gas (GHG) emission trends.
Low carbon transportation-related energy pathways.
The transportation sector is under scrutiny because of its reliance on fossil fuels. Gasoline, diesel, jet fuel and other liquids areeasily portable and have enough energy density (Megajoules per kilogram: gasoline, 44 MJ/kg; diesel, 45 MJ/kg; crude oil, 46 MJ/kg; natural gas, 55 MJ/kg) to sustain transport for hours in the air or across land, or for weeks at sea. Electrifying land transport and employing biofuels and hydrogen for shipping and air transport are obvious, though difficult, ways to mitigate emissions.
Commercial readiness of various low energy strategies.
Transportation life cycle GHG emissions intensity. [ICEV = Internal Combustion Engine Vehicles; HEV = Hybrid Electric Vehicles; BEV = Battery Electric Vehicles; FCV = Fuel Cell Vehicles]
Reconfiguring urban transport, particularly around public forms, which can be more easily electrified, could reduce urban GHG emissions related to transportation by 25%. Electric vehicles (EVs) have lower life cycle GHG emission than internal combustion engine (ICE) vehicles, when charged with low-carbon sources. As with other sectors, overlapping mitigation efforts will have mutual and cascading effects on global emissions. Turning to sustainable energy sources will improve the transportation sector as it electrifies.
Emissions intensity by vehicle type and mass. [ICEV = Internal Combustion Engine Vehicles; HEV = Hybrid Electric Vehicles; BEV = Battery Electric Vehicles]
GHG emissions intensity, buses [ICEV = Internal Combustion Engine Vehicles; HEV = Hybrid Electric Vehicles; BEV = Battery Electric Vehicles; FCV = Fuel Cell Vehicles]
Battery technology is improving and becoming less expensive,
making not only light-duty personal transport, but heavy-duty truck transport
increasingly viable (especially when, in heavy trucks, combined with hydrogen
fuel). Along with the still-evolving battery technology, lack of infstructure
to support EVs and hydrogen fuels is a main obstacle to their use.
GHG emissions intensity, medium-duty trucks [ICEV = Internal Combustion Engine Vehicles; HEV = Hybrid Electric Vehicles; BEV = Battery Electric Vehicles; FCV = Fuel Cell Vehicles]
Aviation emissions trends, 1950-2020.
Without aggressive intervention, transport-related GHG emissions could increase from 16-50% by 2050, making it an urgent target for decarbonizing. This will require efforts at all levels, from individual consumer choices, to private enterprise developing more efficient technologies and governmental initiatives and research programs.
Trends and projected GHG emissions from the aviation sector to 2050.
Projected emissions from the aviation sector to 2100.
Tomorrow: industry.
Be brave, be steadfast, and be well.
Transportation-related GHG emissions by sector, region and scenario.
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