Transport CO₂ Emissions
Transport produces roughly a fifth of global CO₂ emissions — about 24% if you count only energy-related CO₂ — and reached nearly 8 Gt in 2022. Road vehicles dominate at around three-quarters of the total, while aviation and shipping each add a few percent of global emissions. These figures combine IEA energy data with mode-by-mode estimates from Our World in Data and ICCT.
Key Transport Emissions Insights
Road transport dominates
Road vehicles produce around three-quarters of all transport CO₂ — roughly 45% from passenger cars, motorcycles and buses and about 29% from trucks and freight. Road transport alone is close to 12% of total global CO₂ emissions.
Aviation punches above its size
Aviation reached almost 950 Mt CO₂ in 2023, about 2.5% of global energy-related CO₂. Direct flight emissions grew an average of 2.2% per year from 1990 to 2019, and the IEA expects them to pass their 2019 peak by 2025.
Shipping carries the world's trade
International shipping accounts for about 2% of global energy-related CO₂. It moves around 80% of world trade by volume yet still relies on heavy fuel oil, with alternative fuels under 0.5% of its energy use.
Hard to decarbonise
Aviation and shipping are 'hard-to-abate': batteries are too heavy for long flights and ocean voyages, so they depend on scarce sustainable fuels. The IEA says low-carbon fuels must rise from under 1% today to around 15% of their energy by 2030.
Transport CO₂ by Mode
Share of transport-sector CO₂ emissions split by mode, separating road passenger from road freight.
Key Finding: Road transport produces about 75% of transport CO₂ (≈45% passenger, ≈29% freight); aviation and shipping each contribute roughly 11%.
Transport CO₂ Emissions Over Time
Global transport CO₂ emissions in gigatonnes, showing long-run growth and the COVID-19 dip.
Key Finding: Transport CO₂ grew at about 1.7% per year from 1990 to 2022, reaching nearly 8 Gt after rebounding from the 2020 pandemic low.
Each Mode's Share of Global CO₂
How much of total global CO₂ emissions each transport mode is responsible for.
Key Finding: Road transport alone is about 12% of all global CO₂, while aviation (1.9%), shipping (1.7%) and rail (0.4%) are far smaller.
Aviation CO₂ Emissions
Direct CO₂ from aviation fuel combustion in megatonnes, including the pandemic crash and recovery.
Key Finding: Aviation CO₂ fell from over 1,000 Mt in 2019 to under 600 Mt in 2020, then recovered to almost 950 Mt by 2023.
Aviation vs Shipping: Global Share
Aviation's and international shipping's shares of global energy-related CO₂ emissions.
Key Finding: Aviation (≈2.5%) and shipping (≈2%) are each only a few percent of global energy CO₂, but their international 'bunker' emissions sit outside national climate targets.
Understanding Transport Emissions Data
Tailpipe vs lifecycle emissions
Most figures here count direct tailpipe and exhaust CO₂ — the carbon released when fuel is burned in engines. They generally exclude upstream emissions from extracting, refining and distributing the fuel, or from manufacturing the vehicles. A full lifecycle accounting would raise the totals and changes the relative ranking of options like electric vehicles, whose emissions depend on the power grid that charges them.
International bunkers sit outside national totals
Fuel loaded for international flights and voyages is recorded as international aviation and marine bunkers. Under UN climate reporting these emissions are not attributed to any single country's national inventory, which is why aviation and shipping are often regulated separately through ICAO and the IMO rather than national net-zero pledges. Comparing 'national' and 'global' transport figures can therefore double-count or omit these bunkers if you are not careful.
Why aviation and shipping are hard to abate
Long-distance flights and ocean voyages need energy-dense fuels; today's batteries are far too heavy for the range required. Decarbonising them depends on sustainable aviation fuels, green hydrogen, ammonia or e-fuels that are currently scarce and expensive — under 0.5% of shipping energy and under 1% of aviation energy. This is why these sectors are labelled hard-to-abate even though each is only a few percent of global CO₂.
Caveats and differing years
Mode-by-mode shares draw on Our World in Data estimates (around 2016–2018) while sector totals and recent trends come from the IEA (through 2022–2023). Because sources use different base years, methods and boundaries, the percentages will not sum perfectly and should be read as indicative shares rather than exact accounting. Transport's headline share varies between roughly 21% of all CO₂ and 24% of energy-only CO₂ depending on the denominator used.