Bronte Wells
Air travel is one of the fastest-growing sources of pollution, with the aviation sector accounting for about 2-3.5% of global emissions. Planes emit a large amount of carbon dioxide (CO2) and non-CO2 emissions, including nitrogen oxides (NOx), soot, water vapour, and sulfate aerosols, which all have an impact on the climate. The number of people travelling by air has increased significantly, from 100 million passengers in 1960 to 4.56 billion in 2019, and the demand for air travel is expected to continue rising. This increase in air traffic has outpaced improvements in technology and fuel efficiency, resulting in a higher overall carbon footprint for the aviation industry. While some people choose to reduce their carbon footprint by opting for ground transportation or flying less frequently, the most effective solution to curb aviation's contribution to climate change is a transition to carbon-neutral fuels.
| Characteristics | Values |
|---|---|
| CO2 emissions | 2-3.5% of global emissions, 1 billion tons of CO2 per year |
| Fuel consumption | 3.16 kg of CO2 per 1 kg of fuel consumed |
| Water vapour | 30% of jet fuel exhaust |
| Non-CO2 emissions | Nitrogen oxides (NOx), soot, sulfate aerosols |
| Energy efficiency | 2.9 MJ in 1990 to 1.3 MJ in 2019 |
| Passenger count | 100 million in 1960 to 4.56 billion in 2019 |
| Early action | Electrification, biofuels, hydrogen |
| Annual decrease | 2.5% decrease in air traffic |
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What You'll Learn
Aviation's contribution to global warming
Firstly, it is worth noting that aviation accounts for a notable proportion of global CO2 emissions. While estimates vary, it is suggested that aviation is responsible for around 2.5% of global CO2 emissions, with some sources stating it could be as high as 2.8%. This may not seem like a large percentage, but when considering the total emissions, it equates to around one billion tonnes of CO2. Additionally, aviation's contribution to global warming is not solely due to CO2 emissions. Aircraft also emit other greenhouse gases, such as water vapour, soot, and sulfur aerosols, which have a warming effect on the atmosphere. When taking these factors into account, aviation's contribution to global warming increases, with some studies estimating it to be around 3.5% to 4%.
The impact of aviation on global warming is influenced by several factors. One key factor is the increasing demand for air travel. Since 1990, both passenger and freight demand has approximately quadrupled, with more people flying and more goods being transported by air. This increase in demand has resulted in a corresponding increase in emissions. Additionally, the carbon intensity of the fuel used in aviation has not improved, and the industry still relies primarily on jet fuel, which emits a significant amount of CO2. While aircraft have become more energy-efficient, with improvements in design and technology, the carbon efficiency of travelling per kilometre has also increased.
Another factor to consider is the altitude at which aircraft emit greenhouse gases. The release of water vapour and other pollutants at high altitudes can significantly enhance their warming impact. This is because the greenhouse gases and pollutants emitted by aircraft can remain in the atmosphere for extended periods, trapping heat and contributing to the greenhouse effect. Furthermore, contrails—water vapour from aircraft exhausts—have a significant warming effect and are responsible for a large share of aviation's contribution to global warming.
To mitigate the impact of aviation on global warming, the industry will need to transition from jet fuel to more sustainable alternatives. Biofuels, hydrogen, electrification, and sustainable aviation fuel (SAF) are all potential options that could reduce the industry's carbon footprint. Additionally, as new aircraft from Boeing and Airbus already meet CO2 emission requirements, the gradual replacement of older aircraft with these newer, more efficient models will help to improve overall fleet performance. However, aviation remains one of the hardest sectors to decarbonise, and the implementation of these alternatives may be challenging.
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The impact of jet fuel
In addition to the direct warming effects of CO2, jet fuel combustion also produces non-CO2 climate forcers such as NOx and contrails-cirrus, which have a significant impact on climate change. Contrail cirrus alone can account for up to 57% of the total impact of aviation on global warming. These long, cloudy strips form when moisture in ice-saturated air freezes around soot particles released by burning jet fuel. The chemical composition of jet fuel, particularly the level of aromatics, influences the amount of soot produced during combustion and therefore the level of non-CO2 climate effects.
The use of jet fuel has health implications as well. Airport personnel are at risk of exposure to jet engine emissions, which include volatile organic compounds and particulate matter. Diesel exhaust, which has similar components to jet engine emissions, is classified as carcinogenic, and the particulate matter has been linked to adverse health effects, including cancer. Jet engine emissions contain large amounts of nano-sized particles, which can easily reach the lower airways upon inhalation.
To reduce the environmental and health impacts of jet fuel, the aviation industry needs to transition from jet fuel to more sustainable alternatives, such as electrification, biofuels, or hydrogen. While new aircraft are becoming more energy-efficient and some already meet or exceed CO2 emission requirements, the industry as a whole must adopt more sustainable practices to mitigate its contribution to climate change. Sustainable Aviation Fuels (SAFs), for example, have a lower aromatic content than fossil fuels, and their increased production could help reduce the climate impact of jet fuel. Additionally, policies such as the European Commission's ReFuelEU Aviation policy aim to provide better fuel for aviation, reducing the aromatic content of jet fuel.
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Alternatives to air travel
Air travel is a major contributor to global warming and climate change. Planes emit carbon dioxide (CO2) from burning fuel, as well as other atmospheric gases and pollutants such as ozone, methane, water vapour, soot, and sulphur aerosols. The warming effect of these emissions is stronger than the cooling effect, and aviation is estimated to have accounted for about 3.5% of effective radiative forcing to date. With the demand for air travel and freight quadrupling between 1990 and 2019, and projected to continue growing, aviation will make up an increasingly large share of global emissions.
- Private Jet Charters: Private jet charters have gained popularity since the pandemic, offering convenience, privacy, and a passenger-first approach. They can fly into smaller regional airports and allow passengers to determine their departure times. Companies like Elite Jets offer door-to-door chauffeur services, personalised temperature controls, leather massaging seats, high-speed Wi-Fi, and a fully-stocked bar.
- Rail Travel: Trains are a more energy-efficient mode of transport compared to planes, especially for shorter distances. Amtrak, for example, offers an extensive network of routes across the United States.
- Bus Travel: Coach buses or intercity buses can be a more sustainable alternative to air travel, especially for shorter distances. Companies like Green Tortoise and Megabus offer express coach services to various destinations.
- Bicycle Touring: For those who enjoy active travel, bicycle touring is a carbon-free way to explore a region. Adventure Cycling provides maps, routes, and guided tours for bicycle travel in North America.
- Electric Vehicles: For trips that can be accomplished by car, consider switching to electric vehicles (EVs) or hybrid vehicles, which produce fewer emissions than traditional cars. Carpooling or ridesharing can also reduce the environmental impact by spreading the emissions across multiple passengers.
While these alternatives may not always be feasible for long-distance or international travel, they can significantly reduce your carbon footprint for shorter trips or when combined with other sustainable practices.
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The role of new aircraft
The aviation industry has seen rapid growth in the past few decades, with the number of passengers travelling by air increasing from 100 million in 1960 to 4.56 billion in 2019. This growth is expected to continue, with the number of passengers projected to rise to 8.2 billion in the next 15 years. As a result, aviation emissions have been growing faster than any other mode of transport, and have more than doubled between 1990 and 2019. The aviation sector is responsible for approximately 3.5% of effective radiative forcing, which measures the difference between incoming and outgoing energy, resulting in a warming effect on the atmosphere.
To address the issue of increasing aviation emissions, new aircraft from manufacturers such as Boeing and Airbus have been introduced that meet or exceed the carbon emission standards set by the International Civil Aviation Organization (ICAO). These new aircraft are estimated to be around 10% more efficient than the standard, thanks to improved design and technology, larger planes, and higher passenger load factors. However, it is important to note that the carbon intensity of jet fuel has not changed, and biofuels and alternative fuels only make up a tiny fraction of global demand.
While more efficient aircraft can help to dampen the growth in emissions, they cannot eliminate them completely. The industry will need to transition from jet fuel to electrification, biofuels, hydrogen, or a combination of these alternatives to achieve net-zero emissions. In the meantime, other measures such as reducing corporate travel, improving flight paths, and investing in emissions offsets can also help to reduce aviation emissions.
Looking ahead, zero-emissions aircraft, such as hydrogen or electric planes, have the potential to significantly decrease aviation emissions for shorter ranges. However, they will require significant funding and are not expected to be in operation until the mid-2030s. As the climate crisis continues to loom, it is crucial for the aviation industry, governments, and international organizations to work together to adopt more ambitious policies and measures to reduce the sector's carbon footprint and limit the impact of global warming.
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The future of aviation emissions
Aviation accounts for a small share of global emissions—approximately 2.5% of global CO2 emissions—but it is one of the most challenging sectors to decarbonize. While efficiency improvements in aircraft design and technology, larger planes, and higher passenger load factors have helped, they cannot eliminate emissions.
In addition to fuel transitions, technology innovation in aircraft and engine design and operational optimization will play a crucial role. New aircraft are already more efficient and meet emission requirements, but the growth in air travel demand has historically outpaced efficiency improvements. Passenger and freight demand has quadrupled since 1990, and projections for 2050 estimate over 10 billion air passenger journeys.
To curb emissions growth, demand restraint solutions will be necessary. This includes implementing fiscal and regulatory policies to promote sustainable aviation fuels and encourage airlines to improve their fleet performance. International agreements, such as the International Civil Aviation Organization's pledge for net-zero emissions by 2050, provide a framework for action.
The aviation industry has a complex impact on climate change, affecting the concentration of atmospheric gases and pollutants beyond just CO2. While some of these impacts have a cooling effect, the overall warming effect is stronger. Addressing aviation emissions is crucial to mitigating the industry's contribution to global warming.
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Frequently asked questions
Planes emit CO2 as well as non-CO2 emissions, including nitrogen oxides (NOx), soot, water vapour, and sulfate aerosols. Aviation accounts for about 2-3.5% of global emissions.
Airplanes emit around 100 times more CO2 per hour than a shared bus or train ride.
Very small regional jets or very large aircraft with four engines are less fuel-efficient than typical single-aisle or small twin-aisle aircraft.
Taking a direct flight without layovers can help cut down on emissions.
The most effective solution is to fly less.
