What share of world CO₂ emissions come from aviation?

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Aviation accounts for two.5% of world CO₂ emissions. But it surely has contributed round 4% to international warming to this point.

Flying is among the most carbon-intensive actions — but it contributes simply 2.5% of the world’s carbon emissions. How does this add up? Nicely, nearly everybody on the planet doesn’t fly. Research estimate that simply 10% of the world flies in most years.1 However as incomes rise, this can change.

A mix of elevated demand and technological enhancements has pushed the change in aviation emissions over the past half-century. Whole CO2 emissions are sometimes defined by the “Kaya identification” — how many individuals there are, their earnings, the vitality effectivity of economies, and the carbon depth of vitality. We are able to use an analogous framework to know the drivers of aviation emissions.

On this article, I take a look at historic modifications in aviation demand, effectivity, and its contribution to local weather change. Most of this work is predicated on an glorious paper by Candelaria Bergero and colleagues and one other by David Lee and colleagues. Bergero’s paper additionally appears at future trajectories of aviation demand and emissions; in case you’re , it’s value digging into extra element.

To calculate carbon emissions from aviation, we have to know three metrics:

  • Aviation demand: What number of passenger and freight kilometers;
  • Vitality effectivity: How a lot vitality is used per kilometer;
  • Carbon depth: What gas is getting used, which tells us the carbon emitted per unit of vitality.

Multiply these metrics collectively, and we get carbon dioxide (CO2) emissions.

Within the chart under, I’ve proven tendencies in these related metrics since 1990. These come from the paper by Candelaria Bergero and colleagues, revealed in Nature Sustainability.2

You’ll see that there’s a blip in 2020 and 2021. That’s the sudden drop in worldwide and home transport through the COVID-19 pandemic. Demand is rebounding shortly, and is predicted to achieve pre-pandemic ranges once more this yr. For now, let’s ignore the distinctive interval of the pandemic and give attention to the tendencies as much as 2019.

Between 1990 and 2019, each passenger and freight demand has roughly quadrupled. Extra persons are flying, and extra stuff is being moved round. In 2019, passengers traveled greater than 8 trillion kilometers: that’s about the identical as a lightweight yr.3

On the identical time, flying has turn into greater than twice as vitality environment friendly. Touring one passenger-kilometer in 1990 used 2.9 megajoules (MJ) of vitality. By 2019, this had greater than halved to 1.3 MJ. This effectivity has come from improved design and expertise, bigger planes that may carry extra passengers, and the next ‘passenger load issue’. Empty seats are much less frequent than prior to now.

The carbon depth of that gas — how a lot CO2 is emitted per unit — has not modified in any respect. We used commonplace jet gas in 1990 and are utilizing the identical stuff at this time. It has not gotten any cleaner. Biofuels and different alternate options are only a tiny fraction of world demand.

Click on to open interactive model

If flying has turn into greater than twice as vitality environment friendly, and the carbon emitted per unit of vitality has not modified, then it follows that the carbon effectivity of touring one kilometer can also be greater than twice as excessive. In 1990, one passenger-kilometer would emit 357 grams of CO2. By 2019, this had greater than halved to 157 grams.

How have the modifications in demand and expertise affected CO2 emissions?

Nicely, if demand has quadrupled, however aviation has turn into twice as environment friendly, then emissions will double. The beneficial properties in effectivity have partly counteracted the emissions from elevated demand.

In 1990, international aviation emitted round 0.5 billion tonnes. In 2019, that was round 1 billion.

World CO2 emissions from aviation have quadrupled for the reason that Sixties

I used to be curious to see a longer-term perspective. To attain this I prolonged the latest knowledge again to 1940, utilizing knowledge from a paper by David Lee and colleagues.4 That is proven within the chart under. Emissions have quadrupled for the reason that mid-Sixties.

Line chart showing the rise of global CO2 emissions from aviation.

I’ve calculated aviation’s share of world emissions utilizing the time collection above and whole CO2 emissions knowledge from the World Carbon Mission.5

You may see the leads to the chart under. In 2019, aviation accounted for two.5% of CO2 emissions from fossil sources and land use. This share has fluctuated from 2% to 2.5% for the reason that mid-Nineties however with a marked improve since 2010.

Click on to open interactive model

Whereas aviation accounts for round 2.5% of world CO2 emissions, its general contribution to local weather change is increased.

Together with emitting CO2 from burning gas, planes additionally have an effect on the focus of different atmospheric gases and pollution. They generate a short-term improve however a long-term lower in ozone and methane, and elevated emissions of water vapor, soot, sulfur aerosols, and water contrails. Whereas a few of these impacts end in warming, others induce a cooling impact. However general, the warming impact is stronger.

David Lee et al. (2020) quantified the general impact of aviation on international warming when all of those impacts had been included. To do that, they calculated the so-called “radiative forcing”. Radiative forcing measures the distinction between incoming vitality and the vitality radiated again to house. If extra vitality is absorbed than radiated, the environment turns into hotter.

Taking all of those results under consideration, the authors estimate that aviation has accounted for about 3.5% of efficient radiative forcing to this point. One other examine estimates that it has been answerable for 4% of world temperature rise since pre-industrial instances.6

Though CO2 will get a lot of the consideration, it accounts for lower than half of this warming. Two-thirds come from non-CO2 forcings. Contrails — water vapor from plane exhausts — account for the most important share. This explains why aviation contributes 2.5% of annual CO2 emissions however extra in terms of its whole impression on warming.

Aviation is among the hardest sectors to decarbonize. Electrical energy can turn into low-carbon by the deployment of renewables and nuclear; street transport and heating by electrification. Even “hard-to-abate” industries comparable to cement and metal have rising low-carbon alternate options.7

Aviation is, by comparability, behind the curve. World demand will probably develop within the coming many years as populations get richer. Due to this fact, the rise in emissions will likely be decided by whether or not aviation can preserve enhancements in vitality effectivity and swap to low-carbon fuels. To this point, the sector has made nearly no progress on the latter.

Whereas extra environment friendly planes can dampen a number of the progress in emissions, they will’t remove them utterly. To do this, the business might want to transfer from jet gas to electrification, biofuels, hydrogen, or a mixture. Till it makes this swap, aviation will make up an ever-increasing share of world emissions.

Acknowledgements

Many due to Max Roser, Edouard Mathieu and Candelaria Bergero for his or her precious suggestions and feedback on this text.

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Hannah Ritchie (2024) - “What share of world CO₂ emissions come from aviation?” Revealed on-line at OurWorldInData.org. Retrieved from: 'https://ourworldindata.org/global-aviation-emissions' [Online Resource]

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@article{owid-global-aviation-emissions,
    writer = {Hannah Ritchie},
    title = {What share of world CO₂ emissions come from aviation?},
    journal = {Our World in Knowledge},
    yr = {2024},
    be aware = {https://ourworldindata.org/global-aviation-emissions}
}
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