What share of global CO₂ emissions come from aviation?

Aviation accounts for 2.5% of global CO₂ emissions. But it has contributed around 4% to global warming to date.

Flying is one of the most carbon-intensive activities — yet it contributes just 2.5% of the world’s carbon emissions. How does this add up? Well, almost everyone in the world does not fly. Studies estimate that just 10% of the world flies in most years.¹ But as incomes rise, this will change.

A combination of increased demand and technological improvements has driven the change in aviation emissions over the last half-century. Total CO₂ emissions are often explained through the “Kaya identity” — how many people there are, their income, the energy efficiency of economies, and the carbon intensity of energy. We can use a similar framework to understand the drivers of aviation emissions.

In this article, I look at historical changes in aviation demand, efficiency, and its contribution to climate change. Most of this work is based on an excellent paper by Candelaria Bergero and colleagues and another by David Lee and colleagues. Bergero’s paper also looks at future trajectories of aviation demand and emissions; if you’re interested, it’s worth digging into more detail.

Metrics for Calculating Aviation Carbon Emissions

• Aviation demand: How many passenger and freight kilometers;
• Energy efficiency: How much energy is used per kilometer;
• Carbon intensity: What fuel is being used, which tells us the carbon emitted per unit of energy.

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

In the chart below, I’ve shown trends in these relevant metrics since 1990. These come from the paper by Candelaria Bergero and colleagues, published in Nature Sustainability.²

You’ll see that there is a blip in 2020 and 2021. That’s the sudden drop in international and domestic transport during the COVID-19 pandemic. Demand is rebounding quickly, and is expected to reach pre-pandemic levels again this year. For now, let’s ignore the unique period of the pandemic and focus on the trends up to 2019.

Between 1990 and 2019, both passenger and freight demand has approximately quadrupled. More people are flying, and more stuff is being moved around. In 2019, passengers traveled more than 8 trillion kilometers: that’s about the same as a light year.³

At the same time, flying has become more than twice as energy efficient. Traveling one passenger-kilometer in 1990 used 2.9 megajoules (MJ) of energy. By 2019, this had more than halved to 1.3 MJ. This efficiency has come from improved design and technology, larger planes that can carry more passengers, and a higher ‘passenger load factor’. Empty seats are less common than in the past.

The carbon intensity of that fuel — how much CO₂ is emitted per unit — has not changed at all. We used standard jet fuel in 1990 and are using the same stuff today. It

SDGs, Targets, and Indicators

1. SDG 13: Climate Action

   • Target 13.2: Integrate climate change measures into national policies, strategies, and planning.
   • Indicator 13.2.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning into their national policies, strategies, and planning.

2. SDG 9: Industry, Innovation, and Infrastructure

   • Target 9.4: Upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes.
   • Indicator 9.4.1: CO₂ emissions per unit of value added in manufacturing industries and construction.

Analysis

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The issues highlighted in the article are connected to SDG 13: Climate Action and SDG 9: Industry, Innovation, and Infrastructure.

2. What specific targets under those SDGs can be identified based on the article’s content?

• Under SDG 13: Climate Action, the specific target is Target 13.2: Integrate climate change measures into national policies, strategies, and planning.
• Under SDG 9: Industry, Innovation, and Infrastructure, the specific target is Target 9.4: Upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, there are indicators mentioned in the article that can be used to measure progress towards the identified targets:

• Indicator 13.2.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning into their national policies, strategies, and planning (related to SDG 13).
• Indicator 9.4.1: CO₂ emissions per unit of value added in manufacturing industries and construction (related to SDG 9).

Table: SDGs, Targets, and Indicators

Behold! This splendid article springs forth from the wellspring of knowledge, shaped by a wondrous proprietary AI technology that delved into a vast ocean of data, illuminating the path towards the Sustainable Development Goals. Remember that all rights are reserved by SDG Investors LLC, empowering us to champion progress together.

Source: ourworldindata.org

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