Bronte Wells
Aviation's contribution to global carbon emissions is about 2%, according to the International Air Transport Association (IATA). However, with the world moving towards greener energy sources, aviation's proportion of total emissions is expected to rise. The impact of flying on the environment has been highlighted by climate activists like Greta Thunberg, who chose to sail to a UN climate conference instead of flying. The debate around flying versus driving centres on the carbon footprint of each mode of transport. While planes emit more carbon per passenger over long distances, driving solo in a car produces more carbon emissions than flying. However, when multiple people are travelling together, the gap closes, and driving can become the more environmentally friendly option.
| Characteristics | Values |
|---|---|
| Aviation emissions growth compared to other transport | Aviation emissions are growing faster than any other mode of transport and have more than doubled between 1990 and 2019. |
| Aviation's contribution to global carbon emissions | Aviation contributes about 2% of the world's global carbon emissions. |
| Comparison of car and plane emissions over equivalent distances | A car pollutes just as much, and often even more than a plane over equivalent distances. |
| Impact of number of passengers on emissions | Carpooling can make driving less energy-intensive than flying, while higher occupancy rates in planes have helped spread emissions over more people. |
| Impact of travel class on emissions | Carbon emissions per passenger per kilometre travelled are about three times higher for business class and four times higher for first class due to more space per seat. |
| Alternatives to flying | Taking the train, bus, or ferry can reduce emissions compared to flying or driving alone. |
| Non-CO2 effects of aviation emissions | Aviation emissions have strong warming non-CO2 effects due to nitrogen oxides, vapour trails, water vapour, black carbon, and sulphur oxide, contributing twice as much to global warming as aircraft CO2. |
What You'll Learn
- Aviation emissions are growing faster than other transport modes
- Planes burn fossil fuels and release CO2 emissions
- Non-CO2 emissions from planes contribute twice as much to global warming
- Longer flights are more efficient, but taking off uses more fuel
- Carpooling makes driving less energy-intensive than flying
Aviation emissions are growing faster than other transport modes
The growth in air travel and freight is a significant factor in the increase in aviation emissions. The number of annual worldwide passengers has increased from 100 million in 1960 to 4.56 billion in 2019. The rebound of international travel post-COVID-19 has also played a role, with aviation emissions in 2022 reaching almost 80% of pre-pandemic levels.
Several factors contribute to the high emissions from aviation. Airplanes burn fossil fuels, releasing CO2 emissions and causing strong warming non-CO2 effects due to nitrogen oxides (NOx), vapour trails, and cloud formation at high altitudes. These non-CO2 effects contribute twice as much to global warming as aircraft CO2 emissions and were responsible for two-thirds of aviation's climate impact in 2018.
To address the growing aviation emissions, various measures have been proposed, including the use of sustainable aviation fuels, improvements in airframes and engines, operational optimisations, and a shift to less emission-intensive modes of transport, such as trains. Flying less, reducing corporate travel, and teleconferencing instead of attending business meetings can also help reduce aviation emissions.
While aviation emissions are growing faster than other transport modes, it is important to note that the comparison between aviation and car pollution is complex. Recent studies suggest that a car can pollute just as much, or even more, than a plane over equivalent distances. The number of occupants in a car or plane and technical improvements in engine technology also impact the emissions comparison.
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Planes burn fossil fuels and release CO2 emissions
Aviation emissions are a significant contributor to climate change. Airplanes burn fossil fuels, releasing CO2 emissions and causing strong warming non-CO2 effects due to nitrogen oxides (NOx), vapour trails, and cloud formation at high altitudes. Aviation emissions have been increasing faster than those from any other mode of transport and could more than double by 2050 if left unchecked.
Aviation contributes about 2% of global carbon emissions, with long-haul flights and higher passenger capacities in business and first class resulting in higher emissions per passenger per kilometre. Aircraft engine emissions include water vapour, black carbon, nitrous oxide, and sulphur oxide, which contribute to the greenhouse effect and heat trapping. CO2 is the largest component of aircraft emissions, accounting for around 70% of exhaust, and has the same direct warming impact as emissions from other fossil fuel sources.
The burning of jet fuel (kerosene) releases various gases and particulates, including water vapour, which makes up about 30% of the exhaust. While water vapour has a minimal direct warming impact, it contributes to the formation of contrails and contrail-induced cirrus clouds, which can amplify the warming effect up to three times that of CO2.
To address aviation's impact on climate change, the International Civil Aviation Organization (ICAO) established CO2 emission standards for new aircraft, with efficiency requirements mandating a 4% reduction in cruise fuel consumption compared to 2015 performance. Additionally, the European Union adopted ReFuelEU Aviation, promoting sustainable aviation fuel (SAF) blend-in shares through 2050. These initiatives aim to curb the growth of aviation emissions and reduce their environmental footprint.
While aviation emissions are a concern, it's important to consider the overall fuel efficiency of the vehicle when comparing flying to driving. Carpooling with three or more people in a fuel-efficient vehicle can make driving less energy-intensive than flying, even accounting for increased weight. Additionally, flying less and opting for more sustainable travel options, such as trains or teleconferencing for business meetings, can help reduce the climate impact of air travel.
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Non-CO2 emissions from planes contribute twice as much to global warming
Aviation accounts for around 2-2.5% of global CO2 emissions. However, its overall contribution to climate change is higher due to non-CO2 emissions. These non-CO2 emissions from planes, such as water vapour, soot, nitrous oxides, and contrails, contribute twice as much to global warming as aircraft CO2 emissions.
Non-CO2 emissions from planes have a strong warming effect due to their impact on other atmospheric gases and pollutants. For example, water vapour from jet fuel consumption can contribute to the formation of contrails, which trap heat at flight altitude. Similarly, nitrogen oxides in the exhaust form ozone, a potent greenhouse gas with a warming effect. While some non-CO2 emissions, such as soot and sulphates, have a cooling effect by eliminating methane, the overall warming impact is greater.
The warming effect of non-CO2 emissions from planes is significant, especially when considering the rapid growth in aviation. Between 1990 and 2019, emissions from aviation more than doubled, and they are projected to double again by 2050 if left unmitigated. The increase in passenger numbers and demand for air travel contributes to this growth, with aviation becoming more accessible and affordable for more people worldwide.
While aviation has become more energy-efficient, with improved technology and larger planes, the carbon intensity of jet fuel has not improved. The gains in efficiency have only partially offset the emissions from increased demand. Additionally, the use of biofuels and alternative fuels remains a small fraction of global demand, making it challenging to reduce the carbon intensity of aviation.
To address the impact of aviation on global warming, individuals can choose more sustainable modes of transport, such as trains or coaches, or opt for destinations reachable by less climate-intensive means. Flying less and opting for video conferencing instead of business trips can also help reduce aviation's contribution to global warming. Additionally, choosing airlines with newer, more efficient aircraft and economy tickets can lower emissions per passenger.
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Longer flights are more efficient, but taking off uses more fuel
Aviation contributes about 2% of the world's global carbon emissions, according to the International Air Transport Association (IATA). However, emissions from aviation are growing faster than any other mode of transport.
The Intergovernmental Panel on Climate Change highlights that aviation emissions include water vapour, which creates clouds, and releases black carbon, nitrous oxide, and sulphur oxide. These emissions contribute to the greenhouse effect and the trapping of heat.
When comparing the efficiency of longer flights to shorter ones, it is important to consider the impact of aerodynamic drag. During a long-haul flight, an aircraft reaches its cruising altitude and then flies level before beginning its descent. The climb and descent segments account for nearly 15% of the total flight time, and these high-drag conditions increase carbon emissions.
Longer flights are generally more fuel-efficient than shorter ones. This is because cruising requires less fuel than taking off and climbing, and longer flights have a higher proportion of cruising time compared to shorter flights. Additionally, better aerodynamics, reduced weight, and improved engine efficiency can further enhance fuel efficiency.
However, it is important to note that longer flights may require more fuel overall due to the need for additional fuel to extend the range. As a result, long-haul flights may have to limit the number of seats to compensate for the extra fuel weight. Therefore, while longer flights are more efficient in terms of fuel consumption per mile, they may still contribute more to pollution due to the total amount of fuel burned.
To reduce the environmental impact of air travel, individuals can consider alternative modes of transport, such as trains, or opt for longer individual holidays instead of multiple short trips. Additionally, carpooling can be a more fuel-efficient option than flying, as the presence of multiple passengers reduces the energy intensity per person.
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Carpooling makes driving less energy-intensive than flying
The debate around the environmental impact of airplanes and cars is a complex one, with various factors influencing the overall pollution levels of each mode of transport. While aviation contributes about 2% of global carbon emissions, according to the International Air Transport Association (IATA), the impact of flying goes beyond CO2 emissions. Non-CO2 effects, such as nitrogen oxides (NOx) and vapour trails, contribute twice as much to global warming as aircraft CO2 emissions. These effects are short-lived, and addressing them could quickly reduce aviation's contribution to climate change.
In terms of energy intensity, flying has become more efficient than driving, particularly in the United States. According to an analysis by the University of Michigan's Transportation Research Institute, transporting one person a mile by aircraft consumed 2,465 British thermal units (BTUs) in 2012, compared to 4,211 BTUs for moving one person a mile by car. When adjusted for cargo, flying consumed just 2,033 BTUs per person-mile. This trend is supported by researcher Michael Sivak's findings, which showed that driving consumed 71% more energy per person-mile than flying in 2012.
However, the comparison between flying and driving is not straightforward. The number of occupants in a car or an aircraft can significantly impact the pollution levels per person. Carpooling, for example, can reduce the energy intensity of driving by having multiple passengers share the ride. Similarly, seat occupancy rates in aircraft can affect the pollution levels per passenger. Additionally, the distance of the journey and the class of travel in an aircraft can also influence the pollution levels.
While flying has become more energy-efficient, it is important to consider the overall impact of aviation on the environment. Reducing corporate travel and choosing more sustainable modes of transport, such as trains or ferries, can help lower aviation emissions. By cutting corporate travel to 50% of pre-COVID levels, Europe could reduce CO2 emissions by 32.6 MtCO2 by 2030, which is equivalent to taking 16 million polluting cars off the road.
In conclusion, carpooling can indeed make driving less energy-intensive than flying, especially when considering the number of occupants in a vehicle. However, the environmental impact of aviation extends beyond energy intensity and CO2 emissions, and addressing these issues through measures such as clean fuels and reduced corporate travel can help mitigate aviation's contribution to climate change.
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Frequently asked questions
Airplanes burn fossil fuels, which release CO2 emissions and have a warming effect due to nitrogen oxides, vapour trails, and cloud formation. Aviation contributes about 2% of global carbon emissions, and these emissions have been growing faster than any other mode of transport. However, the impact per passenger-hour travelled is 6 to 47 times higher for aviation than car travel due to the short-term effects of contrails and clouds. Overall, the mode of transport with the lowest carbon footprint depends on various factors such as the number of passengers, distance, and fuel efficiency.
When travelling alone, driving a car would result in higher emissions than air travel. However, if there are multiple passengers, the emissions per person decrease in a car while they increase in a plane. For example, a cross-country flight from New York to Los Angeles for one person emits 0.62 tons of CO2, while the same trip in a car emitting 21.6 miles per gallon would release 1.26 tons of carbon emissions. But with three people, the car becomes the better option.
Longer flights are generally more efficient than shorter ones as cruising requires less fuel, and the impact of the take-off and landing phases is reduced over more kilometres. Similarly, for cars, fuel consumption increases over longer distances. Therefore, for longer distances, choosing a plane may result in a lower carbon footprint, especially if there are multiple passengers.
Yes, the class of air travel impacts pollution levels. For long-haul flights, carbon emissions per passenger per kilometre are about three times higher for business class and four times higher for first class than for economy class. This is because there is more space per seat, so each person accounts for a larger amount of the plane's pollution.
Yes, there are more sustainable alternatives to flying or driving long distances. For example, you could take a train or ferry, or opt for teleconferencing instead of attending business meetings in person. These options can help reduce your carbon footprint and contribute to mitigating climate change.
