Maritime shipping and commercial aviation contribute significantly to the global economy, making up about 16% and 4% of global GDP, respectively. Ships move 80-90% of the world's goods, and aviation transported 4.5 billion passengers annually at its peak before COVID-19 in 2019. However, both modes contribute a growing share of CO2 emissions.

Without urgent action, aviation and shipping will contribute a growing proportion of GHGs.

Aviation is currently responsible for about 3% of global energy-related CO2 emissions (about 1 gigaton — roughly equal to the annual emissions of Japan). This share is projected to rise to 4.5% by 2050 (2 gigatons) as the demand for air travel recovers from its COVID-19 slump and continues to increase. In addition to CO2 emissions, aviation also contributes to climate change via the warming effects of water vapor in contrails.

The use of passenger aviation is incredibly concentrated, too — in 2018, only 2 to 4% of the global population flew internationally. High-income countries are responsible for the largest share of aviation emissions — the U.S. alone contributes about 23%. The next largest emitter is China, at just over 10%.

In 2019, short-haul, medium-haul and long-haul flights all emitted equal shares of CO2 emissions. Where possible, it is ideal to replace short-haul flights with bus or rail trips.

Maritime shipping accounts for almost 3% of global GHG emissions. Roughly 85% of these emissions come from international shipping — the transport of goods by container ships, bulk carrier ships and tankers. 

Although shipping has become more energy-efficient since 2012, emissions from the sector could increase by up to 30% above 2008 emissions by 2050, due to increased demand for international goods. Notably, if we succeed in reducing demand for fossil fuels, the decreased trade in fossil fuels may cut this demand growth.

Several new options for zero-emission aviation and shipping are emerging, but they need to be deployed at scale as soon as possible.

Shipping and aviation in a 1.5 degrees C world will constitute an efficient, well-run movement of people and goods with minimal CO2 emissions. To accomplish this, the world must decrease travel via planes using fossil fuel and ships using heavy fuel oil. 

This includes reducing demand for travel, making operational and efficiency changes, and shifting air and sea travel to vessels using zero-emission options. Electricity, green hydrogen, ammonia, and, in some limited cases, advanced biofuels all hold potential. But because these solutions are either nascent or have not yet had commercial breakthroughs, additional public and private research and investment will be necessary to meet our climate goals.

Data Insights

What targets are most important to reach in the future?

Systems Change Lab has identified 2 targets to track progress. Click a chart to explore the data.

What factors may enable and prevent change?

Systems Change Lab has identified 8 factors of change that may catalyze or impede progress. Click a chart to explore the data.

Progress toward targets

Systems Change Lab has identified 2 targets target to track progress. Explore the data below.

Share of zero-emission fuels in marine shipping fuel supply

Scenarios aligned with a 1.5 degrees C pathway suggest that 84–93% of fuel used in maritime shipping will need to be zero-emission by 2050.

Zero-emission fuels (ZEF) for shipping include synthetic carbon-based fuels made from green hydrogen and captured carbon dioxide (CO2), such as e-methanol and Fischer-Tropsch Liquids, and direct use of green hydrogen and ammonia. Zero-emission fuels have not yet entered the maritime shipping fuel supply. 

Scenarios aligned with a 1.5 degrees C pathway suggest that 517% of fuel used in maritime shipping will need to be zero-emission by 2030 and 84–93% of fuel by 2050. These fuels have not yet entered the market, but they are being tested and piloted for deployment in the near future.

As of the beginning of 2022, there were over 200 pilot and demonstration projects to develop zero-emission shipping fuels. Given the lack of deployment but the signs of progress, we have categorized this indicator as going in the right direction but “well off track.” ZEF deployment is likely to follow an S-curve and the technology is in the emergence stage of adoption, so if the projects in development move to market and the policy levers are aligned, we may see quick growth in the uptake of these fuels.

Battery electric options are also in development for short-distance maritime shipping and travel, but are not included in this indicator. Biofuels such as biomethanol may provide some CO2 reductions compared to traditional heavy fuel oil or marine diesel oil, but they do not meet the definition of zero-emissions fuels.

Share of sustainable aviation fuels in global aviation fuel supply

There is not enough historical data to establish how much the rate of change would need to accelerate for the share of sustainable aviation fuels to reach 13-18% in 2030, but there are signs that supply and use is beginning to grow, albeit slowly for now.

The share of sustainable aviation fuels (SAF) — including fuels made from biomass, alcohol or electricity — in the global aviation fuel supply was less than 0.1% in 2020, the only historical data point currently available. If overall jet fuel demand rises with expected passenger growth in the coming decades, the absolute amount of SAF produced must also increase just to maintain share levels.

To stay on track for a 1.5 degree C scenario, the share of SAF needs to reach 1318% in 2030 and 78-100% in 2050. There are signs that SAF supply and use are beginning to grow, and airlines have secured purchase agreements for 21 million metric tons of SAF, with delivery timelines ranging from six months to 20 years. About 70% of the 21 million metric tons were agreed to in 2021 or 2022. Additionally, companies with large aviation footprints are working with airlines to purchase SAF (see, for example, Deloitte and Microsoft). 

SAF deployment is likely to follow an S-curve and the technology is in the emergence stage of adoption. If we begin to see more promising developments pick up, in addition to blending mandates like the European Union’s ReFuel EU proposal, the share of SAF in the global aviation fuel supply could begin to increase exponentially.

Enablers and barriers

We monitor momentum by tracking a set of 8 factors factor that can enable or prevent progress. Explore the data and learn about key actions driving progress.

Number of companies investing in zero-emission fuel storage infrastructure

Innovation
As of the end of 2021, 32 signatories to the Call to Action for Shipping Decarbonization were developing bunkering infrastructure for zero-emission fuels.

Using zero-carbon fuels for marine shipping will require new shoreside infrastructure to deliver the fuels to the ships. This is referred to as bunkering infrastructure. Many ports around the world have invested in new bunkering infrastructure in recent years, but this has typically been for liquefied natural gas (LNG).

Bunker infrastructure for LNG was available at 141 ports at the end of 2021. However, the role of LNG in decarbonizing shipping is in question because of concerns about methane leakage (both upstream and in use on vessels) increasing emissions and because a lot of energy is needed in the liquefaction process. Also, although LNG releases less carbon dioxide (CO2) at combustion than heavy fuel oil, it is not a zero-carbon fuel and its emissions would need to be accounted for. Because existing bunker infrastructure for LNG can only be converted to contain a few types of zero-emission fuels, most new construction will require a different kind of infrastructure.

In 2021, 237 companies across the maritime shipping value chain signed onto the Call to Action for Shipping Decarbonization, which called on world leaders to commit to decarbonizing shipping and provide funding and policy support along the way. As of the end of 2021, 32 signatories to the Call to Action were developing bunkering infrastructure for zero-emission fuels. Most of the entities developing bunkering infrastructure are ports, and this work is occurring on every inhabited continent. This indicator is a proxy for the broader investments in bunkering infrastructure, for which there is no publicly available data.

Number of companies committed to procuring zero-emission ships

Leadership
As of the end of 2021, 63 companies had signed deals to procure zero-emissions ships, which are expected to be commercialized in the 2030s.

Using zero-emission fuels in combustion engine ships will help lower emissions. So will developing new ship designs that allow for the use of 100% zero-emission fuels, electricity with batteries, green hydrogen, or other zero-emission solutions. 

The most straightforward way to understand the state of demand for zero-emission ships is to measure the number of companies committed to procuring these vessels for use in their shipping activities. In 2021, 237 companies across the maritime shipping value chain signed onto the Call to Action for Shipping Decarbonization, which called on world leaders to commit to decarbonizing shipping and provide funding and policy support along the way. As of the end of 2021, 63 of those 237 companies had signed deals to procure zero-emission ships

Because the zero-emission fuels that these ships will use are nascent, demand is low, but it is reasonable to expect that it will increase as more options emerge. Zero-emission ships are currently in the concept stage and are expected to be commercialized in the 2030s. It is likely that these commitments will provide certainty to manufacturers that demand exists, and as more options emerge and shipping companies understand that the technology is ready, it is reasonable to expect that commitments will increase. The number of signatories to the Call to Action is a proxy for the broader private sector commitment to procure zero-emission ships, for which there is no comprehensive, publicly available data.

Global research and development spending on zero-emission shipping

Innovation
Because zero-emission solutions for shipping, including fuels and ship design, are not commercially viable yet, more work must be done to develop, prove and scale them.

Because zero-emission solutions for shipping, including fuels and ship design, are not commercially viable yet, more work must be done to develop, prove and scale them. 

Measuring spending on research and development (R&D) helps us understand how much effort is being put into developing new solutions in a particular industry, and there is a positive relationship between R&D spending and the number of patents for new technologies. 

There is currently no publicly available information on global spending on R&D for zero-emission shipping fuels and ship design.

Number of major freight demanding companies committing to use zero-carbon shipping fuels by 2040

Leadership
In 2021, the Aspen Institute brought together nine major companies with large shipping demands. These companies committed to, among other things, leveraging their freight demand to support only shipping services powered by zero-emission fuels by 2040.

A key step in developing zero-emission fuels is proving that demand for the fuel exists: it unlocks financing, draws more players to the field, and, ultimately, ensures that the fuel makes it into real-world use. 

The most straightforward way to understand the state of demand for zero-emission shipping fuels is to measure the number of companies committed to running vessels on these fuels. In 2021, the Aspen Institute brought together nine major companies with large shipping demands, including Amazon, Ikea and Unilever. These nine companies committed to, among other things, leveraging their freight demand to support only shipping services powered by zero-emission fuels by 2040. 

Because zero-emission shipping fuels are nascent, demand is low, but it is reasonable to expect that it will increase as more options emerge. The number of companies in this coalition is a proxy for the broader private sector commitment to source zero-emission shipping fuels, for which there is no publicly available data.

Number of governments in Mission Innovation's Zero-Emission Shipping Mission

Leadership
Mission Innovation, an effort by major global economies to increase R&D spending on critical advancements in clean energy, established the Zero-Emission Shipping Mission in 2021. Ten countries are currently participating.

Although governments typically are not involved in the production of ships, they set the policies and regulations that govern maritime shipping. Governments can set policies, establish strategic pathways, and put in place requirements that provide signposts and regulatory certainty for the companies that supply and procure ships. 

Mission Innovation, an effort by major global economies to increase R&D spending on critical advancements in clean energy, established the Zero-Emission Shipping Mission in 2021. There are currently 10 governments participating in this effort: Denmark, France, Ghana, India, Morocco, Norway, Singapore, South Korea, the United Kingdom and the United States. These governments have pledged to work with the private sector to develop zero-emission ships, fuels and fueling infrastructure. 

Because this effort was established in 2021, there is no historical data to establish a trend. This indicator is a proxy for broader government commitment to zero-emission shipping decarbonization, for which there is no publicly available data.

Global research and development spending on zero-emission aviation

Innovation
Measuring spending on research and development (R&D) helps us understand how much effort is being put into developing new solutions in a particular industry, and there is a positive relationship between R&D spending and the number of patents for new technologies.

Because zero-emission solutions for aviation fuels and plane design are still nascent, more work must be done to develop, prove and scale them. Most attention is focused on liquid fuels and hydrogen, although recent advancements may allow for new options in electric aviation in the coming decades. 

Measuring spending on research and development (R&D) helps us understand how much effort is being put into developing new solutions in a particular industry, and there is a positive relationship between R&D spending and the number of patents for new technologies. There is currently no publicly available information on global spending on R&D for zero-emission aviation fuels and plane design.

Number of companies committing to accelerate sustainable aviation fuel

Leadership
The most straightforward way to understand the state of demand for SAFs is to measure the number of companies committed to procuring these fuels for their planes. As of 2020, 71 companies were members of the Clean Skies for Tomorrow coalition.

A key step in developing sustainable aviation fuels (SAFs) is proving to producers that demand for the fuel exists: it unlocks financing, draws more players to the field, and, ultimately, ensures that the fuel makes it into real-world use. The supply of aviation fuels typically comes from petroleum producers and refiners, and the SAFs that exist currently come from specialized producers and refiners as well. Demand for fuels typically comes from airlines and airports, but logistics companies also participate.

The most straightforward way to understand the state of demand for SAFs is to measure the number of companies committed to procuring these fuels for their planes. As of 2020, 71 companies were members of the Clean Skies for Tomorrow coalition. These companies include producers such as Shell and SkyNRG, airplane manufacturers such as Boeing, airport owners such as Dubai Airports and Corporación América Airports, airlines such as Lufthansa and Southwest, government agencies such as the Indian Renewable Energy Development Agency, and funders such as BlackRock and the Indian National Bank for Agriculture and Rural Development. 

Because SAFs are nascent, demand is low, but it is reasonable to expect that it will increase as more options emerge. This indicator is a proxy for the broader private sector commitment to decarbonize aviation, for which there is no publicly available data.

Number of jurisdictions with policies supporting the development of advanced biofuels

Regulation and Incentives
Advanced biofuels are still in their development phase and will require vastly greater levels of investment to help decarbonize hard-to-abate sectors like aviation and shipping. Only nine countries were identified as having policies supporting advanced biofuel development.

Advanced biofuels are those produced from non-food or non-feed inputs such as algae or waste organic matter. They provide a more sustainable alternative to conventional biofuels that compete with food production, drive global food prices higher, and take up arable land that contributes to deforestation. Conventional biofuel production is also water-intensive, with one liter of ethanol requiring up to 63 liters of water to produce. 

Advanced biofuels are still in their development phase and will require vastly greater levels of investment to help decarbonize hard-to-abate sectors like aviation and shipping. They could also play a key role in decarbonizing the large number of fossil fuel cars that will remain on our roads into the future. 

Only nine countries were identified as having policies supporting advanced biofuel development, with all but two, the United States and India, in Europe.