One of the only good things that happened as a result of the pandemic and travel bans was a reduction pollution from flying. So we wondered just how much global carbon dioxide (CO2) emissions typically comes from flying.
That answer was easy. Aviation accounts for around 2.5% CO2 emissions. However if you are someone who does fly, air travel will make up a much larger share of your personal carbon footprint.
As the website World in Data explains, “The fact that aviation is relatively small for global emissions as a whole, but of large importance for individuals that fly is due to large inequalities in the world. Most people in the world do not take flights. There is no global reliable figure, but often cited estimates suggest that more than 80% of the global population have never flown.”
How do emissions from aviation vary across the world? Where do people have the highest footprint from flying?
The first and most straightforward comparison is to look at emissions from domestic aviation – that is, flights that depart and arrive in the same country.
This is easiest to compare because domestic aviation is counted in each country’s inventory of greenhouse gas emissions. International flights, on the other hand, are not attributed to specific countries – partly because of contention as to who should take responsibility (should it be the country of departure or arrival? What about layover flights?).
In the chart here we see the average per capita emissions from domestic flights in 2018. This data is sourced from the International Council on Clean Transportation – we then used UN population estimates to calculate per capita figures.2,3
We see large differences in emissions from domestic flights across the world. In the United States the average person emits around 386 kilograms of CO2 each year from internal flights. This is followed by Australia (267 kg); Norway (209 kg); New Zealand (174 kg); and Canada (168 kg). Compare this with countries at the bottom of the table – many across Africa, Asia, and Eastern Europe in particular emit less than one kilogram per person – just 0.8 kilograms; or 0.14 kilograms in Rwanda. For very small countries where there are no internal commercial flights, domestic emissions are of course, zero.
There are some obvious factors that explain some of these cross-country differences. Firstly, countries that are richer are more likely to have higher emissions because people can afford to fly. Second, countries that have a larger land mass may have more internal flights – and indeed we see a correlation between land area and domestic flight emissions; in small countries people are more likely to travel by other means such as car or train. And third, countries that are more geographically-isolated – such as Australia and New Zealand – may have more internal travel.
But of course domestic travel is only part of the overall equation.
Allocating emissions from international flights is more complex. International databases report these emissions separately as a category termed ‘bunker fuels’. The term ‘bunker fuel’ is used to describe emissions which come from international transport – either aviation or shipping.
Because they are not counted towards any particular country these emissions are also not taken into account in the goals that are set by countries in international treaties like the Kyoto protocol or the Paris Agreement.4
But if we wanted to allocate them to a particular country, how would we do it? Who do emissions from international flights belong to: the country that owns the airline; the country of departure; the country of arrival?
Let’s first take a look at how emissions would compare if we allocated them to the country of departure. This means, for example, that emissions from any flight that departs from Spain are counted towards Spain’s total. In the chart here we see international aviation emissions in per capita terms.
Some of the largest emitters per person in 2018 were Iceland (3.5 tonnes of CO2per person); Qatar (2.5 tonnes); United Arab Emirates (2.2 tonnes); Singapore (1.7 tonnes); and Malta (992 kilograms).
Again, we see large inequalities in emissions across the world – in many lower-income countries per capita emissions are only a few kilograms: 6 kilograms in India, 4 kilograms in Nigeria; and only 1.4 kilograms in the Democratic Republic of Congo.
As we can see wealthier nations tend to use a much bigger photo print than poorer ones. But when you adjust the data to reflect tourism, the differences become even more stark.
The above allocation of international aviation emissions to the country of departure raises some issues. It is not an accurate reflection of the local population of countries that rely a lot on tourism, for example. Most of the departing flights from these countries are carrying visiting tourists rather than locals.
One way to correct for this is to adjust these figures for the ratio of inbound to outbound travellers. This approach was applied in an analysis by Sola Zheng for the International Council on Clean Transportation. This attempts to distinguish between locals traveling abroad and foreign visitors traveling to that country on the same flight.5 For example, if we calculated that Spain had 50% more incoming than outgoing travellers, we would reduce its per capita footprint from flying by 50%. If the UK had 75% more outgoing travellers than incoming, we’d increase its footprint by 75%.
We have replicated this approach and applied this adjustment to these figures by calculating the inbound:outbound tourist ratio based on flight departures and arrival data from the World Bank.
How does this affect per capita emissions from international flights? The adjusted figures are shown in the chart here.
As we would expect, countries which are tourist hotspots see the largest change. Portugal’s emissions, for example, fall from 388 to just 60 kilograms per person. Portugese locals are responsible for much fewer travel emissions than outgoing tourists. Spanish emissions fall from 335 to 77 kilograms per person.
On the other hand, countries where the locals travel elsewhere see a large increase. In the UK, they almost double from 422 to 818 kilograms.
