In 2019, transport accounted for nearly 30% of global final energy use and 23% of total energy sector direct CO2 emissions. Reducing oil use and CO2 emissions in long-distance transport modes – heavy-duty trucking, maritime shipping and aviation, the focus of this chapter – is particularly difficult because of their energy and power density requirements: technically viable alternative fuel technologies are not yet very advanced and are also likely to initially cost more than oil-based fuels. 

Global CO2 emissions in transport by mode in the Sustainable Development Scenario, 2000-2070


Each of the three sub-sectors have been hit hard by the Covid‑19 pandemic; aviation most of all with passenger volumes in 2020 expected to be half of 2019 levels. In the longer term, however, rising incomes and population growth are expected to continue to drive up demand, exacerbating the decarbonisation challenge.

In the Sustainable Development Scenario, operational and technical innovations unlock energy efficiency gains in the short to medium term, while switching to low-carbon fuels and electric powertrains drives emissions reductions in the long term. Yet none of the three sub-sectors is decarbonised by 2070 when collectively they emit 1.0 GtCO2.

In trucking, electricity and hydrogen dominate the fuel mix in 2070, powering vehicles that no longer rely on internal combustion engines. This hinges on rapid developments in batteries and fuel cells, as well as massive investment in new infrastructure, including hydrogen refuelling stations, fast chargers for electric trucks and electric road systems (which power vehicles as they drive).

In maritime shipping, biofuels, ammonia and hydrogen meet more than 80% of fuel needs in 2070, using around 13% of the world’s hydrogen production. Energy efficiency also makes a significant contribution. These changes require further tightening of efficiency targets and low-carbon fuel standards to close the price gap with fossil fuels and de-risk investment.

Global energy consumption and CO2 emissions in international shipping in the Sustainable Development Scenario, 2019-2070


In aviation, where technical fuel requirements are most stringent, biofuels and synthetic fuels account for three-quarters of the fuel demand in 2070. Synthetic fuels, which do not face the same supply constraints as biofuels, increase from about 2030 to meet almost half of demand by 2070. Policies will need to manage demand growth and promote new aircraft and engine technologies.

Global cumulative CO2 emissions reductions in aviation by technology readiness level in the Sustainable Development Scenario relative to the Stated Policies Scenario, 2019-2070


Global CO2 emissions reductions in aviation by abatement measure in the Sustainable Development Scenario relative to the Stated Policies Scenario, 2019-2070


The decarbonisation of these sub-sectors will require long-term planning and government support. R&D of alternative powertrains and fuels is needed to reduce costs and improve performance, and measures to develop associated infrastructure. More than 60% of the emissions reductions in 2070 come from technologies that are not commercially available today.